Hydroformylation of methyl oleate catalyzed by rhodium complexes

International Nuclear Information System (INIS)

Mendes, Ana Nery Furlan; Rosa, Ricardo Gomes da; Gregorio, Jose Ribeiro

2012-01-01

In this work, we describe the hydroformylation of methyl oleate catalyzed by several rhodium complexes. Parameters including total pressure, phosphorous/rhodium and CO/H 2 ratio, temperature and phosphorous ligands were scanned. Total conversion of the starting double bonds was achieved while maintaining excellent selectivity in aldehydes. (author)

Rhodium enalcarbenoids: direct synthesis of indoles by rhodium(II)-catalyzed [4+2] benzannulation of pyrroles.

Science.gov (United States)

Dawande, Sudam Ganpat; Kanchupalli, Vinaykumar; Kalepu, Jagadeesh; Chennamsetti, Haribabu; Lad, Bapurao Sudam; Katukojvala, Sreenivas

2014-04-14

Disclosed herein is the design of an unprecedented electrophilic rhodium enalcarbenoid which results from rhodium(II)-catalyzed decomposition of a new class of enaldiazo compounds. The synthetic utility of these enalcarbenoids has been successfully demonstrated in the first transition-metal-catalyzed [4+2] benzannulation of pyrroles, thus leading to substituted indoles. The new benzannulation has been applied to the efficient synthesis of the natural product leiocarpone as well as a potent adipocyte fatty-acid binding protein inhibitor. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhodium(III)-Catalyzed Amidation of Unactivated C(sp(3) )-H Bonds.

Science.gov (United States)

Wang, He; Tang, Guodong; Li, Xingwei

2015-10-26

Nitrogenation by direct functionalization of C-H bonds represents an important strategy for constructing C-N bonds. Rhodium(III)-catalyzed direct amidation of unactivated C(sp(3) )-H bonds is rare, especially under mild reaction conditions. Herein, a broad scope of C(sp(3) )-H bonds are amidated under rhodium catalysis in high efficiency using 3-substituted 1,4,2-dioxazol-5-ones as the amide source. The protocol broadens the scope of rhodium(III)-catalyzed C(sp(3) )-H activation chemistry, and is applicable to the late-stage functionalization of natural products. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Iridium‐Catalyzed Dehydrogenative Decarbonylation of Primary Alcohols with the Liberation of Syngas

DEFF Research Database (Denmark)

Olsen, Esben Paul Krogh; Madsen, Robert

2012-01-01

A new iridium‐catalyzed reaction in which molecular hydrogen and carbon monoxide are cleaved from primary alcohols in the absence of any stoichiometric additives has been developed. The dehydrogenative decarbonylation was achieved with a catalyst generated in situ from [Ir(coe)2Cl]2 (coe=cyclooct......A new iridium‐catalyzed reaction in which molecular hydrogen and carbon monoxide are cleaved from primary alcohols in the absence of any stoichiometric additives has been developed. The dehydrogenative decarbonylation was achieved with a catalyst generated in situ from [Ir(coe)2Cl]2 (coe...... to excellent yields. Ethers, esters, imides, and aryl halides are stable under the reaction conditions, whereas olefins are partially saturated. The reaction is believed to proceed by two consecutive organometallic transformations that are catalyzed by the same iridium(I)–BINAP species. First, dehydrogenation...

Ruthenium-Catalyzed Dehydrogenative Decarbonylation of Primary Alcohols

DEFF Research Database (Denmark)

Mazziotta, Andrea; Madsen, Robert

2017-01-01

Dehydrogenative decarbonylation of a primary alcohol involves the release of both dihydrogen and carbon monoxide to afford the one-carbon shorter product. The transformation has now been achieved with a ruthenium-catalyzed protocol by using the complex Ru(COD)Cl2 and the hindered monodentate ligand...... P(o-tolyl)3 in refluxing p-cymene. The reaction can be applied to both benzylic and long chain linear aliphatic alcohols. The intermediate aldehyde can be observed during the transformation, which is therefore believed to proceed through two separate catalytic cycles involving first dehydrogenation...... of the alcohol and then decarbonylation of the resulting aldehyde....

Silver-Catalyzed Dehydrogenative Synthesis of Carboxylic Acids from Primary Alcohols

DEFF Research Database (Denmark)

Ghalehshahi, Hajar Golshadi; Madsen, Robert

2017-01-01

A simple silver-catalyzed protocol has been developed for the acceptorless dehydrogenation of primary alcohols into carboxylic acids and hydrogen gas. The procedure uses 2.5 % Ag2 CO3 and 2.5-3 equiv of KOH in refluxing mesitylene to afford the potassium carboxylate which is then converted...... into the acid with HCl. The reaction can be applied to a variety of benzylic and aliphatic primary alcohols with alkyl and ether substituents, and in some cases halide, olefin, and ester functionalities are also compatible with the reaction conditions. The dehydrogenation is believed to be catalyzed by silver...

Rhodium-Catalyzed Linear Codimerization and Cycloaddition of Ketenes with Alkynes

Directory of Open Access Journals (Sweden)

Teruyuki Kondo

2010-06-01

Full Text Available A novel rhodium-catalyzed linear codimerization of alkyl phenyl ketenes with internal alkynes to dienones and a novel synthesis of furans by an unusual cycloaddition of diaryl ketenes with internal alkynes have been developed. These reactions proceed smoothly with the same rhodium catalyst, RhCl(PPh33, and are highly dependent on the structure and reactivity of the starting ketenes.

Rhodium-catalyzed regioselective olefination directed by a carboxylic group.

Science.gov (United States)

Mochida, Satoshi; Hirano, Koji; Satoh, Tetsuya; Miura, Masahiro

2011-05-06

The ortho-olefination of benzoic acids can be achieved effectively through rhodium-catalyzed oxidative coupling with alkenes. The carboxylic group is readily removable to allow ortho-olefination/decarboxylation in one pot. α,β-Unsaturated carboxylic acids such as methacrylic acid also undergo the olefination at the β-position. Under the rhodium catalysis, the cine-olefination of heteroarene carboxylic acids such as thiophene-2-carboxylic acid proceeds smoothly accompanied by decarboxylation to selectively produce the corresponding vinylheteroarene derivatives. © 2011 American Chemical Society

Rhodium(iii)-catalyzed ortho-olefination of aryl phosphonates.

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Chary, Bathoju Chandra; Kim, Sunggak

2013-09-25

Rhodium(iii)-catalyzed C-H olefination of aryl phosphonic esters is reported for the first time. In this mild and efficient process, the phosphonic ester group is utilized successfully as a new directing group. In addition, mono-olefination for aryl phosphonates is observed using a phosphonic diamide directing group.

Synthesis of benzimidazoles via iridium-catalyzed acceptorless dehydrogenative coupling.

Science.gov (United States)

Sun, Xiang; Lv, Xiao-Hui; Ye, Lin-Miao; Hu, Yu; Chen, Yan-Yan; Zhang, Xue-Jing; Yan, Ming

2015-07-21

Iridium-catalyzed acceptorless dehydrogenative coupling of tertiary amines and arylamines has been developed. A number of benzimidazoles were prepared in good yields. An iridium-mediated C-H activation mechanism is suggested. This finding represents a novel strategy for the synthesis of benzimidazoles.

Rhodium-catalyzed C-H alkynylation of arenes at room temperature.

Science.gov (United States)

Feng, Chao; Loh, Teck-Peng

2014-03-03

The rhodium(III)-catalyzed ortho C-H alkynylation of non-electronically activated arenes is disclosed. This process features a straightforward and highly effective protocol for the synthesis of functionalized alkynes and represents the first example of merging a hypervalent iodine reagent with rhodium(III) catalysis. Notably, this reaction proceeds at room temperature, tolerates a variety of functional groups, and more importantly, exhibits high selectivity for monoalkynylation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Iridium-Catalyzed Regioselective Borylation of Substituted Biaryls

KAUST Repository

Chotana, Ghayoor; Asghar, Soneela; Shahzadi, Tayyaba; Alazmi, Meshari; Gao, Xin; Emwas, Abdul-Hamid M.; Saleem, Rahman; Batool, Farhat

2018-01-01

Biarylboronic esters are generally prepared by directed ortho­ -metalation or by Miyaura borylation and hence rely on the presence of a directing group or pre-functionalization. In this paper, the preparation of biarylboronic esters by direct C

Mechanism of intermolecular hydroacylation of vinylsilanes catalyzed by a rhodium(I) olefin complex: a DFT study.

Science.gov (United States)

Meng, Qingxi; Shen, Wei; Li, Ming

2012-03-01

Density functional theory (DFT) was used to investigate the Rh(I)-catalyzed intermolecular hydroacylation of vinylsilane with benzaldehyde. All intermediates and transition states were optimized completely at the B3LYP/6-31G(d,p) level (LANL2DZ(f) for Rh). Calculations indicated that Rh(I)-catalyzed intermolecular hydroacylation is exergonic, and the total free energy released is -110 kJ mol(-1). Rh(I)-catalyzed intermolecular hydroacylation mainly involves the active catalyst CA2, rhodium-alkene-benzaldehyde complex M1, rhodium-alkene-hydrogen-acyl complex M2, rhodium-alkyl-acyl complex M3, rhodium-alkyl-carbonyl-phenyl complex M4, rhodium-acyl-phenyl complex M5, and rhodium-ketone complex M6. The reaction pathway CA2 + R2 → M1b → T1b → M2b → T2b1 → M3b1 → T4b → M4b → T5b → M5b → T6b → M6b → P2 is the most favorable among all reaction channels of Rh(I)-catalyzed intermolecular hydroacylation. The reductive elimination reaction is the rate-determining step for this pathway, and the dominant product predicted theoretically is the linear ketone, which is consistent with Brookhart's experiments. Solvation has a significant effect, and it greatly decreases the free energies of all species. The use of the ligand Cp' (Cp' = C(5)Me(4)CF(3)) decreased the free energies in general, and in this case the rate-determining step was again the reductive elimination reaction.

Rhodium-catalyzed C-H functionalization with N-acylsaccharins.

Science.gov (United States)

Wu, Hongxiang; Liu, Tingting; Cui, Ming; Li, Yue; Jian, Junsheng; Wang, Hui; Zeng, Zhuo

2017-01-18

A rhodium-catalyzed C-H functionalization with activated amides by decarbonylation has been developed. Notably, this is the first C-H arylation employing N-acylsaccharins as coupling partners to give biaryls in good to excellent yields. The highlight of the work is the high tolerance of functional groups such as formyl, ester, and vinyl and the use of a removable directing group.

Aerobic Asymmetric Dehydrogenative Cross-Coupling between Two C(sp3)-H Groups Catalyzed by a Chiral-at-Metal Rhodium Complex.

Science.gov (United States)

Tan, Yuqi; Yuan, Wei; Gong, Lei; Meggers, Eric

2015-10-26

A sustainable C-C bond formation is merged with the catalytic asymmetric generation of one or two stereocenters. The introduced catalytic asymmetric cross-coupling of two C(sp3)-H groups with molecular oxygen as the oxidant profits from the oxidative robustness of a chiral-at-metal rhodium(III) catalyst and exploits an autoxidation mechanism or visible-light photosensitized oxidation. In the latter case, the catalyst serves a dual function, namely as a chiral Lewis acid for catalyzing enantioselective enolate chemistry and at the same time as a visible-light-driven photoredox catalyst. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhodium(II)-catalyzed enantioselective synthesis of troponoids.

Science.gov (United States)

Murarka, Sandip; Jia, Zhi-Jun; Merten, Christian; Daniliuc, Constantin-G; Antonchick, Andrey P; Waldmann, Herbert

2015-06-22

We report a rhodium(II)-catalyzed highly enantioselective 1,3-dipolar cycloaddition reaction between the carbonyl moiety of tropone and carbonyl ylides to afford troponoids in good to high yields with excellent enantioselectivity. We demonstrate that α-diazoketone-derived carbonyl ylides, in contrast to carbonyl ylides derived from diazodiketoesters, undergo [6+3] cycloaddition reactions with tropone to yield the corresponding bridged heterocycles with excellent stereoselectivity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhodium-catalyzed chemo- and regioselective decarboxylative addition of β-ketoacids to alkynes.

Science.gov (United States)

Li, Changkun; Grugel, Christian P; Breit, Bernhard

2016-04-30

A highly efficient rhodium-catalyzed chemo- and regioselective addition of β-ketoacids to alkynes is reported. Applying a Rh(i)/(S,S)-DIOP catalyst system, γ,δ-unsaturated ketones were prepared with exclusively branched selectivity under mild conditions. This demonstrates that readily available alkynes can be an alternative entry to allyl electrophiles in transition-metal catalyzed allylic alkylation reactions.

Electrooxidative Rhodium-Catalyzed C-H/C-H Activation: Electricity as Oxidant for Cross-Dehydrogenative Alkenylation.

Science.gov (United States)

Qiu, Youai; Kong, Wei-Jun; Struwe, Julia; Sauermann, Nicolas; Rogge, Torben; Scheremetjew, Alexej; Ackermann, Lutz

2018-04-06

Rhodium(III) catalysis has enabled a plethora of oxidative C-H functionalizations, which predominantly employ stoichiometric amounts of toxic and/or expensive metal oxidants. In contrast, we describe the first electrochemical C-H activation by rhodium catalysis that avoids hazardous chemical oxidants. Thus, environmentally-benign twofold C-H/C-H functionalizations were accomplished with weakly-coordinating benzoic acids and benzamides, employing electricity as the terminal oxidant with H2 as the sole byproduct. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhodium-catalyzed redox-neutral coupling of phenidones with alkynes.

Science.gov (United States)

Fan, Zhoulong; Lu, Heng; Li, Wei; Geng, Kaijun; Zhang, Ao

2017-07-21

A switchable synthesis of N-substituted indole derivatives from phenidones via rhodium-catalyzed redox-neutral C-H activation has been achieved. In this protocol, we firstly disclosed that the reactivity of Rh(iii) catalysis could be enhanced through employing palladium acetate as an additive. Some representative features include external oxidant-free, applicable to terminal alkynes, short reaction time and operational simplicity. The utility of this method is further showcased by the economical synthesis of potent anticancer PARP-1 inhibitors.

Intramolecular Hydroamination of Unbiased and Functionalized Primary Aminoalkenes Catalyzed by a Rhodium Aminophosphine Complex

Science.gov (United States)

Julian, Lisa D.; Hartwig, John F.

2010-01-01

We report a rhodium catalyst that exhibits high reactivity for the hydroamination of primary aminoalkenes that are unbiased toward cyclization and that possess functional groups that would not be tolerated in hydroaminations catalyzed by more electrophilic systems. This catalyst contains an unusual diaminophosphine ligand that binds to rhodium in a κ3-P,O,P mode. The reactions catalyzed by this complex typically proceed at mild temperatures (room temperature to 70 °C), occur with primary aminoalkenes lacking substituents on the alkyl chain that bias the system toward cyclization, occur with primary aminoalkenes containing chloride, ester, ether, enolizable ketone, nitrile, and unprotected alcohol functionality, and occur with primary aminoalkenes containing internal olefins. Mechanistic data imply that these reactions occur with a turnover-limiting step that is different from that of reactions catalyzed by late transition metal complexes of Pd, Pt, and Ir. This change in the turnover-limiting step and resulting high activity of the catalyst stem from favorable relative rates for protonolysis of the M-C bond to release the hydroamination product vs reversion of the aminoalkyl intermediate to regenerate the acyclic precursor. Probes for the origin of the reactivity of the rhodium complex of L1 imply that the aminophosphine groups lead to these favorable rates by effects beyond steric demands and simple electron donation to the metal center. PMID:20839807

Chemo- and regioselective homogeneous rhodium-catalyzed hydroamidomethylation of terminal alkenes to N-alkylamides.

Science.gov (United States)

Raoufmoghaddam, Saeed; Drent, Eite; Bouwman, Elisabeth

2013-09-01

A rhodium/xantphos homogeneous catalyst system has been developed for direct chemo- and regioselective mono-N-alkylation of primary amides with 1-alkenes and syngas through catalytic hydroamidomethylation with 1-pentene and acetamide as model substrates. For appropriate catalyst performance, it appears to be essential that catalytic amounts of a strong acid promoter, such as p-toluenesulfonic acid (HOTs), as well as larger amounts of a weakly acidic protic promoter, particularly hexafluoroisopropyl alcohol (HOR(F) ) are applied. Apart from the product N-1-hexylacetamide, the isomeric unsaturated intermediates, hexanol and higher mass byproducts, as well as the corresponding isomeric branched products, can be formed. Under optimized conditions, almost full alkene conversion can be achieved with more than 80% selectivity to the product N-1-hexylamide. Interestingly, in the presence of a relatively high concentration of HOR(F) , the same catalyst system shows a remarkably high selectivity for the formation of hexanol from 1-pentene with syngas, thus presenting a unique example of a selective rhodium-catalyzed hydroformylation-hydrogenation tandem reaction under mild conditions. Time-dependent product formation during hydroamidomethylation batch experiments provides evidence for aldehyde and unsaturated intermediates; this clearly indicates the three-step hydroformylation/condensation/hydrogenation reaction sequence that takes place in hydroamidomethylation. One likely role of the weakly acidic protic promoter, HOR(F) , in combination with the strong acid HOTs, is to establish a dual-functionality rhodium catalyst system comprised of a neutral rhodium(I) hydroformylation catalyst species and a cationic rhodium(III) complex capable of selectively reducing the imide and/or ene-amide intermediates that are in a dynamic, acid-catalyzed condensation equilibrium with the aldehyde and amide in a syngas environment. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hydroformylation of methyl oleate catalyzed by rhodium complexes; Hidroformilacao do oleato de metila catalisada por complexos de rodio

Energy Technology Data Exchange (ETDEWEB)

Mendes, Ana Nery Furlan [Universidade Federal do Espirito Santo (UFES), Sao Mateus, ES (Brazil). Centro Universitario Norte do Espirito Santo. Dept. de Ciencias Naturais; Rosa, Ricardo Gomes da; Gregorio, Jose Ribeiro, E-mail: jrg@iq.ufrgs.br [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Inst. de Quimica

2012-07-01

In this work, we describe the hydroformylation of methyl oleate catalyzed by several rhodium complexes. Parameters including total pressure, phosphorous/rhodium and CO/H{sub 2} ratio, temperature and phosphorous ligands were scanned. Total conversion of the starting double bonds was achieved while maintaining excellent selectivity in aldehydes. (author)

Asymmetric Synthesis of Hydrocarbazoles Catalyzed by an Octahedral Chiral-at-Rhodium Lewis Acid.

Science.gov (United States)

Huang, Yong; Song, Liangliang; Gong, Lei; Meggers, Eric

2015-12-01

A bis-cyclometalated chiral-at-metal rhodium complex catalyzes the Diels-Alder reaction between N-Boc-protected 3-vinylindoles (Boc = tert-butyloxycarbonyl) and β-carboxylic ester-substituted α,β-unsaturated 2-acyl imidazoles with good-to-excellent regioselectivity (up to 99:1) and excellent diastereoselectivity (>50:1 d.r.) as well as enantioselectivity (92-99% ee) under optimized conditions. The rhodium catalyst serves as a chiral Lewis acid to activate the 2-acyl imidazole dienophile by two-point binding and overrules the preferred regioselectivity of the uncatalyzed reaction. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

PipPhos and MorfPhos : Privileged monodentate phosphoramidite ligands for rhodium-catalyzed asymmetric hydrogenation

NARCIS (Netherlands)

Bernsmann, Heiko; van den Berg, M; Hoen, Robert; Minnaard, AJ; Mehler, G; Reetz, MT; De Vries, JG; Feringa, BL

2005-01-01

A library of 20 monodentate phosphoramidite ligands has been prepared and applied in rhodium-catalyzed asymmetric hydrogenation. This resulted in the identification of two ligands, PipPhos and MorfPhos, that afford excellent and in several cases unprecedented enantioselectivities in the

Rhodium Catalyzed Annulation of N-Benzoylsulfonamide with Isocyanide via C-H Activation

Science.gov (United States)

Zhu, Chen; Xie, Weiqing; Falck, John R.

2012-01-01

Isocyanide insertion: the first rhodium-catalyzed annulation of N-benzoylsulfonamide incorporating with isocyanide via C-H activation is described. The transformation is broadly compatible with N-benzoylsulfonamides bearing various electron-properties as well as isocyanides. From practical point of view, this methodology provides the most straightforward approach to a series of 3-(imino)isoindolinones. PMID:21972033

Rhodium-catalyzed triarylphosphine synthesis via cross-coupling of aryl iodides and acylphosphines

Directory of Open Access Journals (Sweden)

Jiefang Yang

2018-01-01

Full Text Available Rhodium(I-catalyzed C–P cross-coupling reaction with aryl iodides and acylphosphines was disclosed for a straight forward synthesis of triarylphosphines. The acylphosphines were successfully employed as both the phosphorus source and the ligand to the Rh(I catalyst. The triarylphosphines could be afforded in a yield up to 98% with good toleration of wide functional groups.

Experimental and Theoretical Mechanistic Investigation of the Iridium-Catalyzed Dehydrogenative Decarbonylation of Primary Alcohols

DEFF Research Database (Denmark)

Olsen, Esben Paul Krogh; Singh, Thishana; Harris, Pernille

2015-01-01

The mechanism for the iridium-BINAP catalyzed dehydrogenative decarbonylation of primary alcohols with the liberation of molecular hydrogen and carbon monoxide was studied experimentally and computationally. The reaction takes place by tandem catalysis through two catalytic cycles involving...... cycles. One carbon monoxide ligand was shown to remain coordinated to iridium throughout the reaction, and release of carbon monoxide was suggested to occur from a dicarbonyl complex. IrH2Cl(CO)(rac-BINAP) was also synthesized and detected in the dehydrogenation of benzyl alcohol. In the same experiment......, IrHCl2(CO)(rac-BINAP) was detected from the release of HCl in the dehydrogenation and subsequent reaction with IrCl(CO)(rac-BINAP). This indicated a substitution of chloride with the alcohol to form a square planar iridium alkoxo complex that could undergo a beta-hydride elimination. A KIE of 1...

Regioselective syntheses of 1,2-benzothiazines by rhodium-catalyzed annulation reactions.

Science.gov (United States)

Cheng, Ying; Bolm, Carsten

2015-10-12

Rhodium-catalyzed directed carbene insertions into aromatic CH bonds of S-aryl sulfoximines lead to intermediates, which upon dehydration provide 1,2-benzothiazines in excellent yields. The domino-type process is regioselective and shows a high functional-group tolerance. It is scalable, and the only by-products are dinitrogen and water. Three illustrative transformations underscore the synthetic value of the products. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhodium-catalyzed asymmetric hydrogenation of unprotected NH imines assisted by a thiourea.

Science.gov (United States)

Zhao, Qingyang; Wen, Jialin; Tan, Renchang; Huang, Kexuan; Metola, Pedro; Wang, Rui; Anslyn, Eric V; Zhang, Xumu

2014-08-04

Asymmetric hydrogenation of unprotected NH imines catalyzed by rhodium/bis(phosphine)-thiourea provided chiral amines with up to 97% yield and 95% ee. (1)H NMR studies, coupled with control experiments, implied that catalytic chloride-bound intermediates were involved in the mechanism through a dual hydrogen-bonding interaction. Deuteration experiments proved that the hydrogenation proceeded through a pathway consistent with an imine. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhodium-Catalyzed Regioselective C7-Olefination of Indazoles Using an N-Amide Directing Group.

Science.gov (United States)

Guo, Lei; Chen, Yanyu; Zhang, Rong; Peng, Qiujun; Xu, Lanting; Pan, Xianhua

2017-02-01

A rhodium-catalyzed regioselective C-H olefination of indazole is described. This protocol relies on the use of an efficient and removable N,N-diisopropylcarbamoyl directing group, which offers facile access to C7-olefinated indazoles with high regioselectivity, ample substrate scope and broad functional group tolerance. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Excess Substrate is a Spectator Ligand in a Rhodium-Catalyzed Asymmetric [2+2+2] Cycloaddition of Alkenyl Isocyanates with Tolanes

Science.gov (United States)

Oinen, Mark Emil; Yu, Robert T.; Rovis, Tomislav

2009-01-01

Excess substrate has been identified as an unintended spectator ligand affecting enantioselectivity in the [2+2+2] cycloaddition of alkenyl isocyanates with tolanes. Replacement of excess substrate with an exogenous additive affords products with consistent and higher ee’s. The increase in enantioselectivity is the result of a change in composition of a proposed rhodium(III) intermediate on the catalytic cycle. The net result is a rational probe of a short-lived rhodium(III) intermediate, and gives insight that may have applications in many rhodium catalyzed reactions. PMID:19803471

Intermolecular rhodium-catalyzed [2 + 2 + 2] carbocyclization reactions of 1,6-enynes with symmetrical and unsymmetrical alkynes†

Science.gov (United States)

Andrew Evans, P.; Sawyer, James R.; Lai, Kwong Wah; Huffman, John C.

2006-01-01

The crossed intermolecular rhodium-catalyzed [2 + 2 + 2] carbocyclization of carbon and heteroatom tethered 1,6-enynes can be accomplished with symmetrical and unsymmetrical alkynes, to afford the corresponding bicyclohexadienes in an efficient and highly selective manner. PMID:16075089

Rhodium-catalyzed chemo-, regio-, and enantioselective addition of 2-pyridones to terminal allenes.

Science.gov (United States)

Li, Changkun; Kähny, Matthias; Breit, Bernhard

2014-12-08

A rhodium-catalyzed chemo-, regio-, and enantioselective addition of 2-pyridones to terminal allenes to give branched N-allyl 2-pyridones is reported. Preliminary mechanistic studies support the hypothesis that the reaction was initiated from the more acidic 2-hydroxypyridine form, and the initial kinetic O-allylation product was finally converted into the thermodynamically more stable N-allyl 2-pyridones. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Efficient Synthesis of Spirobarbiturates and Spirothiobarbiturates Bearing Cyclopropane Rings by Rhodium(II)-Catalyzed Reactions of Cyclic Diazo Compounds

International Nuclear Information System (INIS)

Wang, Xue; Lee, Yong Rok

2013-01-01

Rhodium(II)-catalyzed reactions of cyclic diazo compounds derived from barbituric acid and thiobarbituric acid with a variety of styrene moieties were examined. These reactions provide rapid synthetic routes to the preparations of spirobarbiturates and spirothiobarbiturates bearing cyclopropane rings

Efficient Synthesis of Spirobarbiturates and Spirothiobarbiturates Bearing Cyclopropane Rings by Rhodium(II)-Catalyzed Reactions of Cyclic Diazo Compounds

Energy Technology Data Exchange (ETDEWEB)

Wang, Xue; Lee, Yong Rok [Yeungnam Univ., Gyeongsan (Korea, Republic of)

2013-06-15

Rhodium(II)-catalyzed reactions of cyclic diazo compounds derived from barbituric acid and thiobarbituric acid with a variety of styrene moieties were examined. These reactions provide rapid synthetic routes to the preparations of spirobarbiturates and spirothiobarbiturates bearing cyclopropane rings.

Rhodium(III)-catalyzed three-component reaction of imines, alkynes, and aldehydes through C-H activation.

Science.gov (United States)

Huang, Ji-Rong; Song, Qiang; Zhu, Yu-Qin; Qin, Liu; Qian, Zhi-Yong; Dong, Lin

2014-12-15

An efficient rhodium(III)-catalyzed tandem three-component reaction of imines, alkynes and aldehydes through CH activation has been developed. High stereo- and regioselectivity, as well as good yields were obtained in most cases. The simple and atom-economical approach offers a broad scope of substrates, providing polycyclic skeletons with potential biological properties. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Functional Group Interconversion: Decarbonylative Borylation of Esters for the Synthesis of Organoboronates

KAUST Repository

Guo, Lin

2016-09-26

A new and efficient nickel-catalyzed decarbonylative borylation reaction of carboxylic acid esters with bis(pinacolato)-diboron has been developed. This transformation allows access to structurally diverse aryl as well as alkenyl and alkyl boronate esters with high reactivity, broad substrate scope, and excellent functional-group tolerance. Further experiments show that this protocol can be carried out on a gram scale and applied to orthogonal synthetic strategies.

Functional Group Interconversion: Decarbonylative Borylation of Esters for the Synthesis of Organoboronates

KAUST Repository

Guo, Lin; Rueping, Magnus

2016-01-01

A new and efficient nickel-catalyzed decarbonylative borylation reaction of carboxylic acid esters with bis(pinacolato)-diboron has been developed. This transformation allows access to structurally diverse aryl as well as alkenyl and alkyl boronate esters with high reactivity, broad substrate scope, and excellent functional-group tolerance. Further experiments show that this protocol can be carried out on a gram scale and applied to orthogonal synthetic strategies.

Rhodium(I) catalysis in olefin photoreactions

International Nuclear Information System (INIS)

Salomon, R.G.; El Sanadi, N.

1975-01-01

The photorearrangement (254 nm) of 1,5-cyclooctadiene (1) in the presence of rhodium(I) chloride to give 1,4-cyclooctadiene (4) was found by deuterium labeling to involve an intramolecular [1,3] shift of hydrogen. A rate-determining cleavage of an allylic C--H bond is indicated by a deuterium isotope effect, k/sub H//k/sub D/ = 1.55 +- 0.03 for the 1 → 4 rearrangement. The acyclic 1,5-diene, 3,3-dimethyl-1,5-hexadiene (8), rearranges in the presence of rhodium(I) chloride upon uv irradiation (254 nm) to give cis-3,3-dimethyl-1,4-hexadiene (10) and the trans isomer 11 in a 1:4 ratio, respectively. This observation supports a mechanism for the photorearrangement of olefins catalyzed by rhodium(I) involving an initial photodissociation of one of two rhodium(I) coordinated carbon-carbon double bonds. This results in an increase in the coordinative unsaturation of rhodium(I) and enhances the proclivity of this d/sub s/ metal atom toward oxidative addition of an allylic C--H bond. A eta 3 -allylrhodium hydride intermediate then gives rearranged olefin by reductive elimination. Lastly, a novel photochemical, rhodium(I) catalyzed hydrogen transfer is reported which gives cyclooctene (7) from cyclooctadienes under unprecedentedly mild conditions. (auth)

Direct Synthesis of 5-Aryl Barbituric Acids by Rhodium(II)-Catalyzed Reactions of Arenes with Diazo Compounds**

Science.gov (United States)

Best, Daniel; Burns, David J; Lam, Hon Wai

2015-01-01

A commercially available rhodium(II) complex catalyzes the direct arylation of 5-diazobarbituric acids with arenes, allowing straightforward access to 5-aryl barbituric acids. Free N—H groups are tolerated on the barbituric acid, with no complications arising from N—H insertion processes. This method was applied to the concise synthesis of a potent matrix metalloproteinase (MMP) inhibitor. PMID:25959544

Enantioselective synthesis of chiral 3-aryl-1-indanones through rhodium-catalyzed asymmetric intramolecular 1,4-addition.

Science.gov (United States)

Yu, Yue-Na; Xu, Ming-Hua

2013-03-15

Enantioselective synthesis of potentially useful chiral 3-aryl-1-indanones was achieved through a rhodium-catalyzed asymmetric intramolecular 1,4-addition of pinacolborane chalcone derivatives using extraordinary simple MonoPhos as chiral ligand under relatively mild conditions. This novel protocol offers an easy access to a wide variety of enantioenriched 3-aryl-1-indanone derivatives in high yields (up to 95%) with excellent enantioselectivities (up to 95% ee).

Rhodium-catalyzed [(3+2)+2] carbocyclization of alkynylidenecyclopropanes with substituted allenes: stereoselective construction of tri- and tetrasubstituted exocyclic olefins.

Science.gov (United States)

Evans, P Andrew; Negru, Daniela E; Shang, Deju

2015-04-13

The development of the stereoselective rhodium-catalyzed [(3+2)+2] carbocyclization of alkynylidenecyclopropanes (ACPs) with substituted allenes is described. This work demonstrates that activated and unactivated allenes preferentially undergo carbometalation at the distal terminus to generate tri- and tetrasubstituted exocyclic olefins with a neutral rhodium catalyst. In addition, this method provides a strategy for the total synthesis of the guaiane family of sesquiterpenes, which are not directly accessible using alkynes as exogenous π-components. Finally, the preparation of the bicyclo[5.4.0]undecane ring system using a homologated ACP tether serves to further illustrate the versatility of this approach. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhodium-Catalyzed Decarbonylation of Aldoses

DEFF Research Database (Denmark)

Monrad, Rune; Madsen, Robert

2007-01-01

A catalytic procedure is described for decarbonylation of unprotected aldoses to afford alditols with one less carbon atom. The reaction is performed with the rhodium complex Rh(dppp)2Cl in a refluxing diglyme - DMA solution. A slightly improved catalyst turnover is observed when a catalytic amount...

Rhodium-catalyzed annulation of arenes with alkynes through weak chelation-assisted C-H activation.

Science.gov (United States)

Yang, Yudong; Li, Kaizhi; Cheng, Yangyang; Wan, Danyang; Li, Mingliang; You, Jingsong

2016-02-18

The purpose of this article is to give a brief review of weak chelation-assistance as a powerful means for the rhodium-catalyzed annulation of arenes with alkynes. The use of commonly occurring functional groups (e.g., ketones, aldehydes, carboxylic acids and alcohols) as the directing groups enriches the versatility of auxiliary ligands and extends the scope of products. This short article offers an overview on emerging procedures, highlights their advantages and limitations, and covers the latest progress in the rapid synthesis of organic functional materials and natural products.

Rhodium-Catalyzed Insertion Reaction of PhP Group of Pentaphenylcyclopentaphosphine with Acyclic and Cyclic Disulfides.

Science.gov (United States)

Arisawa, Mieko; Sawahata, Kyosuke; Yamada, Tomoki; Sarkar, Debayan; Yamaguchi, Masahiko

2018-02-16

Organophosphorus compounds with a phosphorus atom attached to a phenyl group and two organothio/organoseleno groups were synthesized using the rhodium-catalyzed insertion reaction of the PhP group of pentaphenylcyclopentaphosphine (PhP) 5 with acyclic disulfides and diselenides. The method was applied to the synthesis of heterocyclic compounds containing the S-P-S group by the reaction of (PhP) 5 and cyclic disulfides such as 1,2-dithietes, 1,2-dithiocane, 1,4,5-dithiopane, and 1,2-dithiolanes.

Regio- and enantioselective synthesis of N-substituted pyrazoles by rhodium-catalyzed asymmetric addition to allenes.

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Haydl, Alexander M; Xu, Kun; Breit, Bernhard

2015-06-08

The rhodium-catalyzed asymmetric N-selective coupling of pyrazole derivatives with terminal allenes gives access to enantioenriched secondary and tertiary allylic pyrazoles, which can be employed for the synthesis of medicinally important targets. The reaction tolerates a large variety of functional groups and labelling experiments gave insights into the reaction mechanism. This new methodology was further applied in a highly efficient synthesis of JAK 1/2 inhibitor (R)-ruxolitinib. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhodium(III)-Catalyzed [3+2]/[5+2] Annulation of 4-Aryl 1,2,3-Triazoles with Internal Alkynes through Dual C(sp2)-H Functionalization.

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Yang, Yuan; Zhou, Ming-Bo; Ouyang, Xuan-Hui; Pi, Rui; Song, Ren-Jie; Li, Jin-Heng

2015-05-26

A rhodium(III)-catalyzed [3+2]/[5+2] annulation of 4-aryl 1-tosyl-1,2,3-triazoles with internal alkynes is presented. This transformation provides straightforward access to indeno[1,7-cd]azepine architectures through a sequence involving the formation of a rhodium(III) azavinyl carbene, dual C(sp(2))-H functionalization, and [3+2]/[5+2] annulation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhodium(I)-catalyzed cyclization of allenynes with a carbonyl group through unusual insertion of a C-O bond into a rhodacycle intermediate.

Science.gov (United States)

Oonishi, Yoshihiro; Yokoe, Takayuki; Hosotani, Akihito; Sato, Yoshihiro

2014-01-20

Rhodium(I)-catalyzed cyclization of allenynes with a tethered carbonyl group was investigated. An unusual insertion of a CO bond into the C(sp(2) )-rhodium bond of a rhodacycle intermediate occurs via a highly strained transition state. Direct reductive elimination from the obtained rhodacyle intermediate proceeds to give a tricyclic product containing an 8-oxabicyclo[3.2.1]octane skeleton, while β-hydride elimination from the same intermediate gives products that contain fused five- and seven-membered rings in high yields. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Predictable and Regioselective Insertion of Internal Unsymmetrical Alkynes in Rhodium-Catalyzed Cycloadditions with Alkenyl Isocyanates

Science.gov (United States)

Friedman, Rebecca Keller; Rovis, Tomislav

2009-01-01

A regioselective, rhodium-catalyzed cycloaddition between a variety of internal, unsymmetrical alkynes is described. We document the impact of both steric and electronic properties of the alkyne on reaction course, efficiency and enantioselectivity. The substituent that better stabilizes a positive charge or the larger group, all else being equal, inserts distal to the carbonyl moiety in a predictable and controllable fashion. The reaction scope is broad and the enantioselectivities are high, providing an ‘instruction manual’ for substrate choice when utilizing this reaction as a synthetic tool. PMID:19569692

Manganese-catalyzed Dehydrogenative Alkylation or α-Olefination of Alkyl-N-Heteroaromatics by Alcohols.

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Kempe, Rhett; Zhang, Guoying; Irrgang, Torsten; Dietel, Thomas; Kallmeier, Fabian

2018-05-02

Catalysis involving earth-abundant transition metals is an option to help save our rare noble metal resources and is especially interesting if novel reactivity or selectivity patterns are observed. We report here on a novel reaction: the dehydrogenative alkylation or α-olefination of alkyl-N-heteroaromatics by alcohols. Manganese complexes developed in our laboratory catalyze the reaction efficiently. Fe and Co complexes stabilized by such ligands are essentially inactive. Hydrogen is liberated during the reaction and bromo or iodo functional groups and olefins can be tolerated. A variety of alkyl-N-heteroaromatics can be functionalized, and benzyl and aliphatic alcohols undergo the reaction. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhodium-catalyzed Asymmetric Hydrogenation of α-Dehydroamino Ketones: A General Approach to Chiral α-amino Ketones.

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Gao, Wenchao; Wang, Qingli; Xie, Yun; Lv, Hui; Zhang, Xumu

2016-01-01

Rhodium/DuanPhos-catalyzed asymmetric hydrogenation of aliphatic α-dehydroamino ketones has been achieved and afforded chiral α-amino ketones in high yields and excellent enantioselectives (up to 99 % ee), which could be reduced further to chiral β-amino alcohols by LiAlH(tBuO)3 with good yields. This protocol provides a readily accessible route for the synthesis of chiral α-amino ketones and chiral β-amino alcohols. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The divergent synthesis of nitrogen heterocycles by rhodium(II)-catalyzed cycloadditions of 1-sulfonyl 1,2,3-triazoles with 1,3-dienes.

Science.gov (United States)

Shang, Hai; Wang, Yuanhao; Tian, Yu; Feng, Juan; Tang, Yefeng

2014-05-26

The first rhodium(II)-catalyzed aza-[4+3] cycloadditions of 1-sulfonyl 1,2,3-triazoles with 1,3-dienes have been developed, and enable the efficient synthesis of highly functionalized 2,5-dihydroazepines from readily available precursors. In some cases, the reaction pathway could divert to formal aza-[3+2] cycloadditions, thus leading to 2,3-dihydropyrroles. In this context, the titled reaction represents a capable tool for the divergent synthesis of two types of synthetically valuable aza-heterocycles from common rhodium(II) iminocarbene intermediates. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Initial Stages in the Rhodium(III)-Catalyzed C-H Bond Activation of Primary Alcohols in Aqueous Solution

DEFF Research Database (Denmark)

Eriksen, J.; Monsted, L.; Monsted, O.

2010-01-01

The mechanism of the catalytic HID exchange in primary alcohol substrates derived from aldopentoses, promoted by a macrocyclic rhodium(III) complex, has been shown to occur by a reversible redox reaction that gives aldehyde and a rhodium hydride complex. Hydride exchange in the latter complex...... promotes the introduction of solvent hydrogen in the primary alcohol formed by the reverse reaction. The hydride complex has been crystallographically characterized as a trifluoromethanesulfonate salt that contains the trans-[Rh(cycb)(H)(OH2)](2+) (cycb = rac-5,5,7,12,12,14-hexamethyl-1......,4,8,11-tetraazacyclotetradecane) cation. The hydride complex is stable for extended periods of time in acidic solution in the absence of oxidants. In basic solutions a series of base-catalyzed reactions take place to yield ultimately the same mixture of [Rh(cycb)(OH)(2)](+) isomers as produced by base hydrolysis of the trans...

Rhodium-catalyzed enantioselective intramolecular C-H silylation for the syntheses of planar-chiral metallocene siloles.

Science.gov (United States)

Zhang, Qing-Wei; An, Kun; Liu, Li-Chuan; Yue, Yuan; He, Wei

2015-06-01

Reported herein is the rhodium-catalyzed enantioselective C-H bond silylation of the cyclopentadiene rings in Fe and Ru metallocenes. Thus, in the presence of (S)-TMS-Segphos, the reactions took place under very mild conditions to afford metallocene-fused siloles in good to excellent yields and with ee values of up to 97%. During this study it was observed that the steric hindrance of chiral ligands had a profound influence on the reactivity and enantioselectivity of the reaction, and might hold the key to accomplishing conventionally challenging asymmetric C-H silylations. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chiral Cu(II-catalyzed enantioselective β-borylation of α,β-unsaturated nitriles in water

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Lei Zhu

2015-10-01

Full Text Available The promising performance of copper(II complexes was demonstrated for asymmetric boron conjugate addition to α,β-unsaturated nitriles in water. The catalyst system, which consisted of Cu(OAc2 and a chiral 2,2′-bipyridine ligand, enabled β-borylation and chiral induction in water. Subsequent protonation, which was accelerated in aqueous medium, led to high activity of this asymmetric catalysis. Both solid and liquid substrates were suitable despite being insoluble in water.

Dehydrogenative Synthesis of Imines from Alcohols and Amines Catalyzed by a Ruthenium N-Heterocyclic Carbene Complex

DEFF Research Database (Denmark)

Maggi, Agnese; Madsen, Robert

2012-01-01

A new method for the direct synthesis of imines from alcohols and amines is described where hydrogen gas is liberated. The reaction is catalyzed by the ruthenium N-heterocyclic carbene complex [RuCl2(IiPr)(p-cymene)] in the presence of the ligand DABCO and molecular sieves. The imination can...... be applied to a variety of primary alcohols and amines and can be combined with a subsequent addition reaction. A deuterium labeling experiment indicates that the catalytically active species is a ruthenium dihydride. The reaction is believed to proceed by initial dehydrogenation of the alcohol...

Rhodium Phosphine-π-Arene Intermediates in the Hydroamination of Alkenes

Science.gov (United States)

Liu, Zhijian; Yamamichi, Hideaki; Madrahimov, Sherzod T.; Hartwig, John F.

2011-01-01

A detailed mechanistic study of the intramolecular hydroamination of alkenes with amines catalyzed by rhodium complexes of a biaryldialkylphosphine are reported. The active catalyst is shown to contain the phosphine ligand bound in a κ1, η6 form in which the arene is π-bound to rhodium. Addition of deuterated amine to an internal olefin showed that the reaction occurs by trans addition of the N-H bond across the C=C bond, and this stereochemistry implies that the reaction occurs by nucleophilic attack of the amine on a coordinated alkene. Indeed, the cationic rhodium fragment binds the alkene over the secondary amine, and the olefin complex was shown to be the catalyst resting state. The reaction was zero-order in substrate, when the concentration of olefin was high, and a primary isotope effect was observed. The primary isotope effect, in combination with the observation of the alkene complex as the resting state, implies that nucleophilic attack of the amine on the alkene is reversible and is followed by turnover-limiting protonation. This mechanism constitutes an unusual pathway for rhodium-catalyzed additions to alkenes and is more closely related to the mechanism for palladium-catalyzed addition of amide N-H bonds to alkenes. PMID:21309512

Highly enantioselective rhodium(I)-catalyzed carbonyl carboacylations initiated by C-C bond activation.

Science.gov (United States)

Souillart, Laetitia; Cramer, Nicolai

2014-09-01

The lactone motif is ubiquitous in natural products and pharmaceuticals. The Tishchenko disproportionation of two aldehydes, a carbonyl hydroacylation, is an efficient and atom-economic access to lactones. However, these reaction types are limited to the transfer of a hydride to the accepting carbonyl group. The transfer of alkyl groups enabling the formation of CC bonds during the ester formation would be of significant interest. Reported herein is such asymmetric carbonyl carboacylation of aldehydes and ketones, thus affording complex bicyclic lactones in excellent enantioselectivities. The rhodium(I)-catalyzed transformation is induced by an enantiotopic CC bond activation of a cyclobutanone and the formed rhodacyclic intermediate reacts with aldehyde or ketone groups to give highly functionalized lactones. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fe(II)/Fe(III)-Catalyzed Intramolecular Didehydro-Diels-Alder Reaction of Styrene-ynes.

Science.gov (United States)

Mun, Hyeon Jin; Seong, Eun Young; Ahn, Kwang-Hyun; Kang, Eun Joo

2018-02-02

The intramolecular didehydro-Diels-Alder reaction of styrene-ynes was catalyzed by Fe(II) and Fe(III) to produce various naphthalene derivatives under microwave heating conditions. Mechanistic calculations found that the Fe(II) catalyst activates the styrenyl diene in an inverse-electron-demand Diels-Alder reaction, and the consecutive dehydrogenation reaction can be promoted by either Fe(II)-catalyzed direct dehydrogenation or an Fe(III)-catalyzed rearomatization/dehydrogenation pathway.

Direct Synthesis of 5-Aryl Barbituric Acids by Rhodium(II)-Catalyzed Reactions of Arenes with Diazo Compounds.

Science.gov (United States)

Best, Daniel; Burns, David J; Lam, Hon Wai

2015-06-15

A commercially available rhodium(II) complex catalyzes the direct arylation of 5-diazobarbituric acids with arenes, allowing straightforward access to 5-aryl barbituric acids. Free N-H groups are tolerated on the barbituric acid, with no complications arising from N-H insertion processes. This method was applied to the concise synthesis of a potent matrix metalloproteinase (MMP) inhibitor. © 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Rhodium catalyzed regioselective arene homologation of aryl urea via double C-H bond activation and migratory insertion of alkyne

Institute of Scientific and Technical Information of China (English)

Yan Wang; Hao Zhou; Ke Xu; Mei-Hua Shen; Hua-Dong Xu

2017-01-01

A convenient rhodium catalyzed oxidative arene homologation of aniline derivatives with symmetrical or unsymmetrical alkynes using Cu(OAc)2 as oxidant is described.Urea group is shown to be effective as a directing group for initial ortho C-H activation.Two migratory insertion events of alkyne into Rh-C bond occur successively,both with complete regioselectivity.This method is particularly useful for synthesis of polyarenes with different substituents,which has not been reported with conventional protocol.A mechanism has been proposed to explain the observed data.

Redox-neutral rhodium-catalyzed C-H functionalization of arylamine N-oxides with diazo compounds: primary C(sp(3))-H/C(sp(2))-H activation and oxygen-atom transfer.

Science.gov (United States)

Zhou, Bing; Chen, Zhaoqiang; Yang, Yaxi; Ai, Wen; Tang, Huanyu; Wu, Yunxiang; Zhu, Weiliang; Li, Yuanchao

2015-10-05

An unprecedented rhodium(III)-catalyzed regioselective redox-neutral annulation reaction of 1-naphthylamine N-oxides with diazo compounds was developed to afford various biologically important 1H-benzo[g]indolines. This coupling reaction proceeds under mild reaction conditions and does not require external oxidants. The only by-products are dinitrogen and water. More significantly, this reaction represents the first example of dual functiaonalization of unactivated a primary C(sp(3) )H bond and C(sp(2) )H bond with diazocarbonyl compounds. DFT calculations revealed that an intermediate iminium is most likely involved in the catalytic cycle. Moreover, a rhodium(III)-catalyzed coupling of readily available tertiary aniline N-oxides with α-diazomalonates was also developed under external oxidant-free conditions to access various aminomandelic acid derivatives by an O-atom-transfer reaction. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhodium(III)-Catalyzed Activation of C(sp3)-H Bonds and Subsequent Intermolecular Amidation at Room Temperature.

Science.gov (United States)

Huang, Xiaolei; Wang, Yan; Lan, Jingbo; You, Jingsong

2015-08-03

Disclosed herein is a Rh(III)-catalyzed chelation-assisted activation of unreactive C(sp3)-H bonds, thus enabling an intermolecular amidation to provide a practical and step-economic route to 2-(pyridin-2-yl)ethanamine derivatives. Substrates with other N-donor groups are also compatible with the amidation. This protocol proceeds at room temperature, has a relatively broad functional-group tolerance and high selectivity, and demonstrates the potential of rhodium(III) in the promotive functionalization of unreactive C(sp3)-H bonds. A rhodacycle having a SbF6(-) counterion was identified as a plausible intermediate. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhodium-Catalyzed Denitrogenative [3+2] Cycloaddition: Access to Functionalized Hydroindolones and the Framework of Montanine-Type Amaryllidaceae Alkaloids.

Science.gov (United States)

Yang, Hongjian; Hou, Shengtai; Tao, Cheng; Liu, Zhao; Wang, Chao; Cheng, Bin; Li, Yun; Zhai, Hongbin

2017-09-18

Rhodium-catalyzed denitrogenative [3+2] cycloaddition of 1-sulfonyl-1,2,3-triazoles with cyclic silyl dienol ethers has been developed for the synthesis of functionalized hydroindolones or their corresponding silyl ethers. The present method has been employed to construct synthetically valuable bicyclo[3.3.1]alkenone derivatives and pyrrolidine-ring-containing bicyclic indole compounds. As a further synthetic application, a stereoselective synthesis of 5,11-methanomorphanthridin-3-one, which shares a key skeleton with montanine-type Amaryllidaceae alkaloids has been achieved by using this chemistry. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

An N-Linked Bidentate Phosphoramidite Ligand (N-Me-BIPAM for Rhodium-Catalyzed Asymmetric 1,4-Addition of Arylboronic Acids to α,β-Unsaturated Ketones

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Norio Miyaura

2012-12-01

Full Text Available A new bidentate phosphoramidite (N-Me-BIPAM based on Shibasaki’s N-linked BINOL was synthesized. This ligand appears to be highly effective for rhodium-catalyzed asymmetric conjugated addition of arylboronic acids to α,β-unsaturated enones. The reaction of ortho-substituted arylboronic acid with acyclic and cyclic enones provides the corresponding products in good yields and enantioselectivities.

Forging Unsupported Metal-Boryl Bonds with Icosahedral Carboranes.

Science.gov (United States)

Saleh, Liban M A; Dziedzic, Rafal M; Khan, Saeed I; Spokoyny, Alexander M

2016-06-13

In contrast to the plethora of metal-catalyzed cross-coupling methods available for the installation of functional groups on aromatic hydrocarbons, a comparable variety of methods are currently not available for icosahedral carboranes, which are boron-rich three-dimensional aromatic analogues of aryl groups. Part of this is due to the limited understanding of the elementary steps for cross-coupling involving carboranes. Here, we report our efforts in isolating metal-boryl complexes to further our understanding of one of these elementary steps, oxidative addition. Structurally characterized examples of group 10 M-B bonds featuring icosahedral carboranes are completely unknown. Use of mercurocarboranes as a reagent to deliver M-B bonds saw divergent reactivity for platinum and palladium, with a Pt-B bond being isolated for the former, and a rare Pd-Hg bond being formed for the latter. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhodium(I)-Complexes Catalyzed 1,4-Conjugate Addition of Arylzinc Chlorides to N-Boc-4-pyridone.

Science.gov (United States)

Guo, Fenghai; McGilvary, Matthew A; Jeffries, Malcolm C; Graves, Briana N; Graham, Shekinah A; Wu, Yuelin

2017-05-01

Rhodium(I)-complexes catalyzed the 1,4-conjugate addition of arylzinc chlorides to N -Boc-4-pyridone in the presence of chlorotrimethylsilane (TMSCl). A combination of [RhCl(C₂H₄)₂]₂ and BINAP was determined to be the most effective catalyst to promote the 1,4-conjugate addition reactions of arylzinc chlorides to N -Boc-4-pyridone. A broad scope of arylzinc reagents with both electron-withdrawing and electron-donating substituents on the aromatic ring successfully underwent 1,4-conjugate addition to N -Boc-4-pyridone to afford versatile 1,4-adducts 2-substituted-2,3-dihydropyridones in good to excellent yields (up to 91%) and excellent ee (up to 96%) when ( S )-BINAP was used as chiral ligand.

Theoretical investigation of the mechanism of tritiated methane dehydrogenation reaction using nickel-based catalysts

Energy Technology Data Exchange (ETDEWEB)

Dong, Liang; Li, Jiamao; Deng, Bing; Yang, Yong; Wang, Heyi [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Li, Weiyi [School of Physics and Chemistry, Xihua University, Chengdu 610065 (China); Li, Shuo, E-mail: lishuo@cqut.edu.cn [School of Chemical Engineering, Chongqing University of Technology, Chongqing 400054 (China); Tan, Zhaoyi, E-mail: tanzhaoyi@caep.cn [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China)

2015-06-15

Graphical abstract: - Highlights: • Four-step dehydrogenation of CT{sub 4} catalyzed by Ni to form Ni–C by releasing T{sub 2}. • The process of Ni + CT{sub 4} → NiCT{sub 2} + T{sub 2} is more achievable than that of NiCT{sub 2} → NiC + T{sub 2}. • TNiCT → T{sub 2}NiC step is the RDS with the rate constant of k = 2.8 × 10{sup 13} exp(−313,136/RT). • The hydrogen isotope effect value of k{sub H}/k{sub T} is 2.94, and k{sub D}/k{sub T} is 1.39. • CH{sub 4} and CD{sub 4} dehydrogenations are likely to occur, accompanied by the CT{sub 4} cracking. - Abstract: The mechanism of tritiated methane dehydrogenation reaction catalyzed by nickel-based catalyst was investigated in detail by density functional theory (DFT) at the B3LYP/[6-311++G(d, p), SDD] level. The computational results indicated that the dehydrogenation of tritiated methane is endothermic. The decomposition of tritiated methane catalyzed by Ni to form Ni-based carbon (Ni–C) after a four-step dehydrogenation companied with releasing tritium. After the first and second dehydrogenation steps, Ni + CT{sub 4} formed NiCT{sub 2}. After the third and fourth dehydrogenation steps, NiCT{sub 2} formed NiC. The first and second steps of dehydrogenation occurred on both the singlet and triplet states, and the lowest energy route is Ni + CT{sub 4} → {sup 1}COM → {sup 1}TS1 → {sup 3}IM1 → {sup 3}TS2 → {sup 3}IM2. The third and fourth steps of dehydrogenation occurred on both the singlet and quintet states, and the minimum energy reaction pathway appeared to be IM3 → {sup 1}TS4 → {sup 5}IM4 → {sup 5}TS5 → {sup 5}IM5 → {sup 5}pro + T{sub 2}. The fourth step of dehydrogenation TNiCT → T{sub 2}NiC was the rate-determining step of the entire reaction with the rate constant of k{sub 2} = 2.8 × 10{sup 13} exp(−313,136/RT) (in cm{sup 3} mol{sup −1} s{sup −1}), and its activation energy barrier was calculated to be 51.8 kcal/mol. The Ni-catalyzed CH{sub 4} and CD{sub 4} cracking

Theoretical investigation of the selective dehydration and dehydrogenation of ethanol catalyzed by small molecules.

Science.gov (United States)

Wang, Yanqun; Tang, Yizhen; Shao, Youxiang

2017-09-01

Catalytic dehydration and dehydrogenation reactions of ethanol have been investigated systematically using the ab initio quantum chemistry methods The catalysts include water, hydrogen peroxide, formic acid, phosphoric acid, hydrogen fluoride, ammonia, and ethanol itself. Moreover, a few clusters of water and ethanol were considered to simulate the catalytic mechanisms in supercritical water and supercritical ethanol. The barriers for both dehydration and dehydrogenation can be reduced significantly in the presence of the catalysts. It is revealed that the selectivity of the catalytic dehydration and dehydrogenation depends on the acidity and basicity of the catalysts and the sizes of the clusters. The acidic catalyst prefers dehydration while the basic catalysts tend to promote dehydrogenation more effectively. The calculated water-dimer catalysis mechanism supports the experimental results of the selective oxidation of ethanol in the supercritical water. It is suggested that the solvent- and catalyst-free self-oxidation of the supercritical ethanol could be an important mechanism for the selective dehydrogenation of ethanol on the theoretical point of view. Copyright © 2017 Elsevier Inc. All rights reserved.

THE LATEST ADVANCEMENTS IN THE ACYLATION REACTIONS VIA CROSS-DEHYDROGENATIVE COUPLING AND/OR METAL CATALYSTS

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Soykan Ağar

2017-12-01

Full Text Available There are quite many examples in the scientific literature regarding the acylation reactions, especially the metal-catalyzed acylation reactions, metal-free acylation reactions, metal-catalyzed acylation via cross-dehydrogenative coupling (CDC reactions and metal-free acylation via cross-dehydrogenative coupling (CDC reactions. In this review paper, the most important examples of these domains were brought together and their mechanisms were exhibited in a clear, chronological format. Following these, the best example study towards green chemistry with a metal-free and high-yielding route was mentioned and discussed to demonstrate what has achieved in this field regarding the new acylation reaction mechanisms using the advantages of cross-dehydrogenative coupling (CDC reactions. The most prominent studies regarding these domains have been examined thoroughly and the latest progress in this field was explained in detail.

Rhodium(II)-Catalyzed and Thermally Induced Intramolecular Migration of N-Sulfonyl-1,2,3-triazoles: New Approaches to 1,2-Dihydroisoquinolines and 1-Indanones.

Science.gov (United States)

Sun, Run; Jiang, Yu; Tang, Xiang-Ying; Shi, Min

2016-04-11

New rhodium(II)-catalyzed or thermally induced intramolecular alkoxy group migration of N-sulfonyl-1,2,3-triazoles has been developed, affording divergent synthesis of 1,2-dihydroisoquinoline and 1-indanone derivatives according to different conditions. N-Sulfonyl keteneimine is the key intermediate for the synthesis of dihydroisoquinoline, whereas the aza-vinyl carbene intermediate results in the formation of 1-indanone. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhodium-catalyzed C-H bond activation for the synthesis of quinonoid compounds: Significant Anti-Trypanosoma cruzi activities and electrochemical studies of functionalized quinones.

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Jardim, Guilherme A M; Silva, Thaissa L; Goulart, Marilia O F; de Simone, Carlos A; Barbosa, Juliana M C; Salomão, Kelly; de Castro, Solange L; Bower, John F; da Silva Júnior, Eufrânio N

2017-08-18

Thirty four halogen and selenium-containing quinones, synthesized by rhodium-catalyzed C-H bond activation and palladium-catalyzed cross-coupling reactions, were evaluated against bloodstream trypomastigotes of T. cruzi. We have identified fifteen compounds with IC 50 /24 h values of less than 2 μM. Electrochemical studies on A-ring functionalized naphthoquinones were also performed aiming to correlate redox properties with trypanocidal activity. For instance, (E)-5-styryl-1,4-naphthoquinone 59 and 5,8-diiodo-1,4-naphthoquinone 3, which are around fifty fold more active than the standard drug benznidazole, are potential derivatives for further investigation. These compounds represent powerful new agents useful in Chagas disease therapy. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Regioconvergent and Enantioselective Rhodium-Catalyzed Hydroamination of Internal and Terminal Alkynes: A Highly Flexible Access to Chiral Pyrazoles.

Science.gov (United States)

Haydl, Alexander M; Hilpert, Lukas J; Breit, Bernhard

2016-05-04

The rhodium-catalyzed asymmetric N-selective coupling of pyrazole derivatives with internal and terminal alkynes features an utmost chemo-, regio-, and enantioselective access to enantiopure allylic pyrazoles, readily available for incorporation in small-molecule pharmaceuticals. This methodology is distinguished by a broad substrate scope, resulting in a remarkable compatability with a variety of different functional groups. It furthermore exhibits an intriguing case of regio-, position-, and enantioselectivity in just one step, underscoring the sole synthesis of just one out of up to six possible products in a highly flexible approach to allylated pyrazoles by emanating from various internal and terminal alkynes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Elucidation of structural isomers from the homogeneous rhodium-catalyzed isomerization of vegetable oils.

Science.gov (United States)

Andjelkovic, Dejan D; Min, Byungrok; Ahn, Dong; Larock, Richard C

2006-12-13

The structural isomers formed by the homogeneous rhodium-catalyzed isomerization of several vegetable oils have been elucidated. A detailed study of the isomerization of the model compound methyl linoleate has been performed to correlate the distribution of conjugated isomers, the reaction kinetics, and the mechanism of the reaction. It has been shown that [RhCl(C8H8)2]2 is a highly efficient and selective isomerization catalyst for the production of highly conjugated vegetable oils with a high conjugated linoleic acid (CLA) content, which is highly desirable in the food industry. The combined fraction of the two major CLA isomers [(9Z,11E)-CLA and (10E,12Z)-CLA] in the overall CLA mixture is in the range from 76.2% to 93.4%. The high efficiency and selectivity of this isomerization method along with the straightforward purification process render this approach highly promising for the preparation of conjugated oils and CLA. Proposed improvements in catalyst recovery and reusability will only make this method more appealing to the food, paint, coating, and polymer industries in the future.

Rhodium-catalyzed [5 + 2 + 1] cycloaddition of ene-vinylcyclopropanes and CO: reaction design, development, application in natural product synthesis, and inspiration for developing new reactions for synthesis of eight-membered carbocycles.

Science.gov (United States)

Wang, Yi; Yu, Zhi-Xiang

2015-08-18

Practical syntheses of natural products and their analogues with eight-membered carbocyclic skeletons are important for medicinal and biological investigations. However, methods and strategies to construct the eight-membered carbocycles are limited. Therefore, developing new methods to synthesize the eight-membered carbocycles is highly desired. In this Account, we describe our development of three rhodium-catalyzed cycloadditions for the construction of the eight-membered carbocycles, which have great potential in addressing the challenges in the synthesis of medium-sized ring systems. The first reaction described in this Account is our computationally designed rhodium-catalyzed two-component [5 + 2 + 1] cycloaddition of ene-vinylcyclopropanes (ene-VCPs) and CO for the diastereoselective construction of bi- and tricyclic cyclooctenones. The design of this reaction is based on the hypothesis that the C(sp(3))-C(sp(3)) reductive elimination of the eight-membered rhodacycle intermediate generated from the rhodium-catalyzed cyclopropane cleavage and alkene insertion, giving Wender's [5 + 2] cycloadduct, is not easy. Under CO atmosphere, CO insertion may occur rapidly, converting the eight-membered rhodacycle into a nine-membered rhodacycle, which then undergoes an easy C(sp(2))-C(sp(3)) reductive elimination process and furnishes the [5 + 2 + 1] product. This hypothesis was supported by our preliminary DFT studies and also served as inspiration for the development of two [7 + 1] cycloadditions: the [7 + 1] cycloaddition of buta-1,3-dienylcyclopropanes (BDCPs) and CO for the construction of cyclooctadienones, and the benzo/[7 + 1] cycloaddition of cyclopropyl-benzocyclobutenes (CP-BCBs) and CO to synthesize the benzocyclooctenones. The efficiency of these rhodium-catalyzed cycloadditions can be revealed by the application in natural product synthesis. Two eight-membered ring-containing natural products, (±)-asterisca-3(15),6-diene and (+)-asteriscanolide, have been

Aerobic, Metal-Free, and Catalytic Dehydrogenative Coupling of Heterocycles: En Route to Hedgehog Signaling Pathway Inhibitors.

Science.gov (United States)

Bering, Luis; Paulussen, Felix M; Antonchick, Andrey P

2018-04-06

The nitrosonium ion-catalyzed dehydrogenative coupling of heteroarenes under mild reaction conditions is reported. The developed method utilizes ambient molecular oxygen as a terminal oxidant, and only water is produced as byproduct. Dehydrogenative coupling of heteroarenes translated into the rapid discovery of novel hedgehog signaling pathway inhibitors, emphasizing the importance of the developed methodology.

Enantioselective Rhodium-Catalyzed [2+2+2] Cycloadditions of Terminal Alkynes and Alkenyl Isocyanates: Mechanistic Insights Lead to a Unified Model that Rationalizes Product Selectivity

Science.gov (United States)

Dalton, Derek M.; Oberg, Kevin M.; Yu, Robert T.; Lee, Ernest E.; Perreault, Stéphane; Oinen, Mark Emil; Pease, Melissa L.; Malik, Guillaume; Rovis, Tomislav

2009-01-01

This manuscript describes the development and scope of the asymmetric rhodium-catalyzed [2+2+2] cycloaddition of terminal alkynes and alkenyl isocyanates leading to the formation of indolizidine and quinolizidine scaffolds. The use of phosphoramidite ligands proved crucial for avoiding competitive terminal alkyne dimerization. Both aliphatic and aromatic terminal alkynes participate well, with product selectivity a function of both the steric and electronic character of the alkyne. Manipulation of the phosphoramidite ligand leads to tuning of enantio- and product selectivity, with a complete turnover in product selectivity seen with aliphatic alkynes when moving from Taddol-based to biphenol-based phosphoramidites. Terminal and 1,1-disubstituted olefins are tolerated with nearly equal efficacy. Examination of a series of competition experiments in combination with analysis of reaction outcome shed considerable light on the operative catalytic cycle. Through a detailed study of a series of X-ray structures of rhodium(cod)chloride/phosphoramidite complexes, we have formulated a mechanistic hypothesis that rationalizes the observed product selectivity. PMID:19817441

Stereoselective hydrogenation of olefins using rhodium-substituted carbonic anhydrase--a new reductase.

Science.gov (United States)

Jing, Qing; Okrasa, Krzysztof; Kazlauskas, Romas J

2009-01-01

One useful synthetic reaction missing from nature's toolbox is the direct hydrogenation of substrates using hydrogen. Instead nature uses cofactors like NADH to reduce organic substrates, which adds complexity and cost to these reductions. To create an enzyme that can directly reduce organic substrates with hydrogen, researchers have combined metal hydrogenation catalysts with proteins. One approach is an indirect link where a ligand is linked to a protein and the metal binds to the ligand. Another approach is direct linking of the metal to protein, but nonspecific binding of the metal limits this approach. Herein, we report a direct hydrogenation of olefins catalyzed by rhodium(I) bound to carbonic anhydrase (CA-[Rh]). We minimized nonspecific binding of rhodium by replacing histidine residues on the protein surface using site-directed mutagenesis or by chemically modifying the histidine residues. Hydrogenation catalyzed by CA-[Rh] is slightly slower than for uncomplexed rhodium(I), but the protein environment induces stereoselectivity favoring cis- over trans-stilbene by about 20:1. This enzyme is the first cofactor-independent reductase that reduces organic molecules using hydrogen. This catalyst is a good starting point to create variants with tailored reactivity and selectivity. This strategy to insert transition metals in the active site of metalloenzymes opens opportunities to a wider range of enzyme-catalyzed reactions.

A Mixed-Ligand Chiral Rhodium(II) Catalyst Enables the Enantioselective Total Synthesis of Piperarborenine B.

Science.gov (United States)

Panish, Robert A; Chintala, Srinivasa R; Fox, Joseph M

2016-04-11

A novel, mixed-ligand chiral rhodium(II) catalyst, Rh2(S-NTTL)3(dCPA), has enabled the first enantioselective total synthesis of the natural product piperarborenine B. A crystal structure of Rh2(S-NTTL)3(dCPA) reveals a "chiral crown" conformation with a bulky dicyclohexylphenyl acetate ligand and three N-naphthalimido groups oriented on the same face of the catalyst. The natural product was prepared on large scale using rhodium-catalyzed bicyclobutanation/ copper-catalyzed homoconjugate addition chemistry in the key step. The route proceeds in ten steps with an 8% overall yield and 92% ee. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhodium(II)-Catalyzed Asymmetric Sulfur(VI) Reduction of Diazo Sulfonylamidines

OpenAIRE

Selander, Nicklas; Fokin, Valery V.

2012-01-01

Diazo sulfonylamidines readily undergo enantioselective oxygen transfer from sulfur to carbon atom in the presence of chiral rhodium(II) carboxylates resulting in chiral sulfinylamidines. This unusual asymmetric atom transfer “reduction” occurs rapidly under mild conditions, and sulfinylamidines are obtained in excellent yield.

Copper-catalyzed recycling of halogen activating groups via 1,3-halogen migration.

Science.gov (United States)

Grigg, R David; Van Hoveln, Ryan; Schomaker, Jennifer M

2012-10-03

A Cu(I)-catalyzed 1,3-halogen migration reaction effectively recycles an activating group by transferring bromine or iodine from a sp(2) to a benzylic carbon with concomitant borylation of the Ar-X bond. The resulting benzyl halide can be reacted in the same vessel under a variety of conditions to form an additional carbon-heteroatom bond. Cross-over experiments using an isotopically enriched bromide source support intramolecular transfer of Br. The reaction is postulated to proceed via a Markovnikov hydrocupration of the o-halostyrene, oxidative addition of the resulting Cu(I) complex into the Ar-X bond, reductive elimination of the new sp(3) C-X bond, and final borylation of an Ar-Cu(I) species to turn over the catalytic cycle.

The isomerization of allylrhodium intermediates in the rhodium-catalyzed nucleophilic allylation of cyclic imines.

Science.gov (United States)

Hepburn, Hamish B; Lam, Hon Wai

2014-10-20

Allylrhodium species generated from potassium allyltrifluoroborates can undergo isomerization by 1,4-rhodium(I) migration to give more complex isomers, which then react with cyclic imines to provide products with up to three new stereochemical elements. High enantioselectivities are obtained using chiral diene-rhodium complexes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Amphoteric Borylketenimines: Versatile Intermediates in the Synthesis of Borylated Heterocycles.

Science.gov (United States)

Kaldas, Sherif J; O'Keefe, Kowan T V; Mendoza-Sanchez, Rodrigo; Yudin, Andrei K

2017-07-21

We report the first synthesis of amphoteric borylketenimines from ethynyl N-methyliminodiacetic acid (MIDA) boronate and sulfonyl azides via copper catalysis. In situ trapping of these intermediates with various nucleophiles provided access to novel borylated azetidimines, iminocoumarins, amides, iminooxetanes, and amidines. The described strategy based on borylketenimines offers high levels of chemo- and regioselectivity, enabling the synthesis of unprecedented borylated molecules. This work highlights the unexplored utility of borylketenimines in the synthesis of potentially bioactive molecules. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tandem rhodium catalysis: exploiting sulfoxides for asymmetric transition-metal catalysis.

Science.gov (United States)

Kou, K G M; Dong, V M

2015-06-07

Sulfoxides are uncommon substrates for transition-metal catalysis due to their propensity to inhibit catalyst turnover. In a collaborative effort with Ken Houk, we developed the first dynamic kinetic resolution (DKR) of allylic sulfoxides using asymmetric rhodium-catalyzed hydrogenation. A detailed mechanistic analysis of this transformation using both experimental and theoretical methods revealed rhodium to be a tandem catalyst that promoted both hydrogenation of the alkene and racemization of the allylic sulfoxide. Using a combination of deuterium labelling and DFT studies, a novel mode of allylic sulfoxide racemization via a Rh(III)-π-allyl intermediate was identified.

Rhodium-catalyzed Chemo- and Regioselective Cross-dimerization of Two Terminal Alkynes

Science.gov (United States)

Xu, Hua-Dong; Zhang, Ren-Wei; Li, Xiaoxun; Huang, Suyu; Tang, Weiping; Hu, Wen-Hao

2013-01-01

Cross-dimerization of terminal arylacetylenes and terminal propargylic alcohols/amides has been achieved in the effect of a rhodium catalyst. This method features high chemo- and regioselectivities rendering convenient and atom economical access to functionalized enynes. PMID:23356993

Ring Expansion and Rearrangements of Rhodium(II) Azavinyl Carbenes

Science.gov (United States)

Selander, Nicklas; Worrell, Brady T.

2013-01-01

An efficient, regioselective and convergent method for the ring expansion and rearrangement of 1-sulfonyl-1,2,3-triazoles under rhodium(II)-catalyzed conditions is described. These denitrogenative reactions form substituted enaminone and olefin-based products, which in the former case can be further functionalized to unique products rendering the sulfonyl triazole traceless. PMID:23161725

Easy access to nucleophilic boron through diborane to magnesium boryl metathesis

Science.gov (United States)

Pécharman, Anne-Frédérique; Colebatch, Annie L.; Hill, Michael S.; McMullin, Claire L.; Mahon, Mary F.; Weetman, Catherine

2017-04-01

Organoboranes are some of the most synthetically valuable and widely used intermediates in organic and pharmaceutical chemistry. Their synthesis, however, is limited by the behaviour of common boron starting materials as archetypal Lewis acids such that common routes to organoboranes rely on the reactivity of boron as an electrophile. While the realization of convenient sources of nucleophilic boryl anions would open up a wealth of opportunity for the development of new routes to organoboranes, the synthesis of current candidates is generally limited by a need for highly reducing reaction conditions. Here, we report a simple synthesis of a magnesium boryl through the heterolytic activation of the B-B bond of bis(pinacolato)diboron, which is achieved by treatment of an easily generated magnesium diboranate complex with 4-dimethylaminopyridine. The magnesium boryl is shown to act as an unambiguous nucleophile through its reactions with iodomethane, benzophenone and N,N'-di-isopropyl carbodiimide and by density functional theory.

Redox-Neutral Rh(III)-Catalyzed Olefination of Carboxamides with Trifluoromethyl Allylic Carbonate.

Science.gov (United States)

Park, Jihye; Han, Sangil; Jeon, Mijin; Mishra, Neeraj Kumar; Lee, Seok-Yong; Lee, Jong Suk; Kwak, Jong Hwan; Um, Sung Hee; Kim, In Su

2016-11-18

The rhodium(III)-catalyzed olefination of various carboxamides with α-CF 3 -substituted allylic carbonate is described. This reaction provides direct access to linear CF 3 -allyl frameworks with complete trans-selectivity. In particular, a rhodium catalyst provided Heck-type γ-CF 3 -allylation products via the β-O-elimination of rhodacycle intermediate and subsequent olefin migration process.

Green synthesis of Ni-Nb oxide catalysts for low-temperature oxidative dehydrogenation of ethane

KAUST Repository

Zhu, Haibo; Rosenfeld, Devon C.; Anjum, Dalaver H.; Caps, Valerie; Basset, Jean-Marie

2015-01-01

The straightforward solid-state grinding of a mixture of Ni nitrate and Nb oxalate crystals led to, after mild calcination (T<400°C), nanostructured Ni-Nb oxide composites. These new materials efficiently catalyzed the oxidative dehydrogenation (ODH

Mechanistic studies of copper(I)-catalyzed 1,3-halogen migration.

Science.gov (United States)

Van Hoveln, Ryan; Hudson, Brandi M; Wedler, Henry B; Bates, Desiree M; Le Gros, Gabriel; Tantillo, Dean J; Schomaker, Jennifer M

2015-04-29

An ongoing challenge in modern catalysis is to identify and understand new modes of reactivity promoted by earth-abundant and inexpensive first-row transition metals. Herein, we report a mechanistic study of an unusual copper(I)-catalyzed 1,3-migration of 2-bromostyrenes that reincorporates the bromine activating group into the final product with concomitant borylation of the aryl halide bond. A combination of experimental and computational studies indicated this reaction does not involve any oxidation state changes at copper; rather, migration occurs through a series of formal sigmatropic shifts. Insight provided from these studies will be used to expand the utility of aryl copper species in synthesis and develop new ligands for enantioselective copper-catalyzed halogenation.

Direct C-H alkylation and indole formation of anilines with diazo compounds under rhodium catalysis.

Science.gov (United States)

Mishra, Neeraj Kumar; Choi, Miji; Jo, Hyeim; Oh, Yongguk; Sharma, Satyasheel; Han, Sang Hoon; Jeong, Taejoo; Han, Sangil; Lee, Seok-Yong; Kim, In Su

2015-12-18

The rhodium(III)-catalyzed direct functionalization of aniline C-H bonds with α-diazo compounds is described. These transformations provide a facile construction of ortho-alkylated anilines with diazo malonates or highly substituted indoles with diazo acetoacetates.

Rhodium-Catalyzed Enantioselective Cyclopropanation of Olefins with N-Sulfonyl 1,2,3-Triazoles

Science.gov (United States)

Chuprakov, Stepan; Kwok, Sen Wai; Zhang, Li; Lercher, Lukas; Fokin, Valery V.

2009-01-01

N-Sulfonyl 1,2,3-triazoles readily form rhodium(II) azavinyl carbenes, which react with olefins to produce cyclopropanes with excellent diastereo- and enantioselectivity and in high yield. PMID:19928917

Rhodium(III)-catalyzed [3+2] annulation of 5-aryl-2,3-dihydro-1H-pyrroles with internal alkynes through C(sp²)-H/alkene functionalization.

Science.gov (United States)

Zhou, Ming-Bo; Pi, Rui; Hu, Ming; Yang, Yuan; Song, Ren-Jie; Xia, Yuanzhi; Li, Jin-Heng

2014-10-13

This study describes a new rhodium(III)-catalyzed [3+2] annulation of 5-aryl-2,3-dihydro-1H-pyrroles with internal alkynes using a Cu(OAc)2 oxidant for building a spirocyclic ring system, which includes the functionalization of an aryl C(sp(2))-H bond and addition/protonolysis of an alkene C=C bond. This method is applicable to a wide range of 5-aryl-2,3-dihydro-1H-pyrroles and internal alkynes, and results in the assembly of the spiro[indene-1,2'-pyrrolidine] architectures in good yields with excellent regioselectivities. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reactivity of rhodium during co-deposition of rhodium and carbon

International Nuclear Information System (INIS)

Marot, Laurent; Steiner, Roland; De Temmerman, Gregory; Oelhafen, Peter

2009-01-01

The detailed characterizations of rhodium/carbon films prepared by co-deposition using a dual magnetron sputtering have been carried out on silicon substrates at room temperature. Effects of the carbon incorporated in the film on the chemical bonding state, optical reflectivity and crystallinity were investigated using XPS, reflectivity measurements, XRD and SEM. The incorporation of carbon changes the films' crystallinity and thus producing amorphous films. The reflectivity of the films decreases linearly as the rhodium concentration decreases. It is important to note that no chemical bonding was observed between rhodium and carbon whatever the deposition conditions, even at high deposition temperature. Concerning the reactivity of rhodium films with oxygen, after long term storage in air the rhodium surface is covered with a thin rhodium oxide (few nanometers). However, for these films no variation of the optical reflectivity was observed after long air storage.

Rhodium thioacetate complexes

International Nuclear Information System (INIS)

Baranovskij, I.B.; Golubnichaya, M.A.; Mazo, G.Ya.

1976-01-01

Thioacetato-complexes of rhodium(II) were prepared by the reaction of thioacetic acid with rhodium(II) carboxylates. Diamagnetic compounds of the type Rh 2 (CH 3 COS) 4 2A, where A=H 2 O, Py, N 2 H 4 .HCl, Thio, KNCS, DMSO, CH 3 CN, CsCl, or CH 3 COSH, were isolated. Their infrared spectra were recorded, and the principal vibrational wavenumbers assigned. The X-ray electron spectra confirm that rhodium is divalent. The thioacetato-complexes are dimeric, with a metal-metal bond. [Rh(NH 3 ) 5 (CH 3 COS)]I 2 was prepared, and its properties studied. The significant decrease in the strength of the bonds formed by the axial ligands with rhodium is due to the strong trans-influence of the covalent rhodium-rhodium sigma-bond

Ortho lithiation-in situ borylation of substituted morpholine benzamides

DEFF Research Database (Denmark)

Cederbalk, Anna; Lysén, Morten; Kehler, Jan

2017-01-01

Morpholine amides are cheap and safe alternative to Weinreb amides as acylating agents of organometallic species. Herein, the in-situ lithiation/borylation of 18 ortho- meta- and para-substituted morpholine benzamides has been investigated. 10 of the 18 substrates provided the desired boronic est...

BCl3‐Induced Annulative Oxo‐ and Thioboration for the Formation of C3‐Borylated Benzofurans and Benzothiophenes

Science.gov (United States)

Warner, Andrew J.; Churn, Anna; McGough, John S.

2016-01-01

Abstract BCl3‐induced borylative cyclization of aryl‐alkynes possessing ortho‐EMe (E=S, O) groups represents a simple, metal‐free method for the formation of C3‐borylated benzothiophenes and benzofurans. The dichloro(heteroaryl)borane primary products can be protected to form synthetically ubiquitous pinacol boronate esters or used in situ in Suzuki–Miyaura cross couplings to generate 2,3‐disubstituted heteroarenes from simple alkyne precursors in one pot. In a number of cases alkyne trans‐haloboration occurs alongside, or instead of, borylative cyclization and the factors controlling the reaction outcome are determined. PMID:27897368

Non-isothermal synergetic catalytic effect of TiF{sub 3} and Nb{sub 2}O{sub 5} on dehydrogenation high-energy ball milled MgH{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Zhang, Tiebang, E-mail: tiebangzhang@nwpu.edu.cn; Hou, Xiaojiang; Hu, Rui; Kou, Hongchao; Li, Jinshan

2016-11-01

MgH{sub 2}-M (M = TiF{sub 3} or Nb{sub 2}O{sub 5} or both of them) composites prepared by high-energy ball milling are used in this work to illustrate the dehydrogenation behavior of MgH{sub 2} with the addition of catalysts. The phase compositions, microstructures, particle morphologies and distributions of MgH{sub 2} with catalysts have been evaluated. The non-isothermal synergetic catalytic-dehydrogenation effect of TiF{sub 3} and Nb{sub 2}O{sub 5} evaluated by differential scanning calorimetry gives the evidences that the addition of catalysts is an effective strategy to destabilize MgH{sub 2} and reduce hydrogen desorption temperatures and activation energies. Depending on additives, the desorption peak temperatures of catalyzed MgH{sub 2} reduce from 417 °C to 341 °C for TiF{sub 3} and from 417 °C to 336 °C for Nb{sub 2}O{sub 5}, respectively. The desorption peak temperature reaches as low as 310 °C for MgH{sub 2} catalyzed by TiF{sub 3} coupling with Nb{sub 2}O{sub 5}. The non-isothermal synergetic catalytic effect of TiF{sub 3} and Nb{sub 2}O{sub 5} is mainly attributed to electronic exchange reactions with hydrogen molecules, which improve the recombination of hydrogen atoms during dehydrogenation process of MgH{sub 2}. - Highlights: • Catalytic surface for MgH{sub 2} is achieved by high-energy ball milling. • Non-isothermal dehydrogenation behavior of MgH{sub 2} with TiF{sub 3} and/or Nb{sub 2}O{sub 5} is illustrated. • Dehydrogenation activation energies of synergetic catalyzed MgH{sub 2} are obtained. • Synergetic catalytic-dehydrogenation mechanism of TiF{sub 3} and Nb{sub 2}O{sub 5} is proposed.

Enantioselective Rhodium Enolate Protonations. A New Methodology for the Synthesis of β2-Amino Acids

Science.gov (United States)

Sibi, Mukund P.; Tatamidani, Hiroto; Patil, Kalyani

2008-01-01

Rhodium catalyzed conjugate addition of an aryl boronic acid to α-methylamino acrylates followed by enantioselective protonation of the oxa-π-allylrhodium intermediate provides access to aryl substituted β2-amino acids. The impact of the different variables of the reaction on the levels of enantioselectivity has been assessed. PMID:15957893

Elucidation of Mechanisms and Selectivities of Metal-Catalyzed Reactions using Quantum Chemical Methodology.

Science.gov (United States)

Santoro, Stefano; Kalek, Marcin; Huang, Genping; Himo, Fahmi

2016-05-17

Quantum chemical techniques today are indispensable for the detailed mechanistic understanding of catalytic reactions. The development of modern density functional theory approaches combined with the enormous growth in computer power have made it possible to treat quite large systems at a reasonable level of accuracy. Accordingly, quantum chemistry has been applied extensively to a wide variety of catalytic systems. A huge number of problems have been solved successfully, and vast amounts of chemical insights have been gained. In this Account, we summarize some of our recent work in this field. A number of examples concerned with transition metal-catalyzed reactions are selected, with emphasis on reactions with various kinds of selectivities. The discussed cases are (1) copper-catalyzed C-H bond amidation of indoles, (2) iridium-catalyzed C(sp(3))-H borylation of chlorosilanes, (3) vanadium-catalyzed Meyer-Schuster rearrangement and its combination with aldol- and Mannich-type additions, (4) palladium-catalyzed propargylic substitution with phosphorus nucleophiles, (5) rhodium-catalyzed 1:2 coupling of aldehydes and allenes, and finally (6) copper-catalyzed coupling of nitrones and alkynes to produce β-lactams (Kinugasa reaction). First, the methodology adopted in these studies is presented briefly. The electronic structure method in the great majority of these kinds of mechanistic investigations has for the last two decades been based on density functional theory. In the cases discussed here, mainly the B3LYP functional has been employed in conjunction with Grimme's empirical dispersion correction, which has been shown to improve the calculated energies significantly. The effect of the surrounding solvent is described by implicit solvation techniques, and the thermochemical corrections are included using the rigid-rotor harmonic oscillator approximation. The reviewed examples are chosen to illustrate the usefulness and versatility of the adopted methodology in

Synthesis of Polycyclic Ring Systems Using Transition Metal Catalyzed Cyclizations of Diazo Alkynyl Ketones

Directory of Open Access Journals (Sweden)

Albert Padwa

2000-12-01

Full Text Available The rhodium(II-catalyzed reaction of α-diazo ketones bearing tethered alkyne units represents a new and useful method for the construction of a variety of substituted cyclopentenones. The process proceeds by addition of the rhodium-stabilized carbenoid onto the acetylenic π-bond to give a vinyl carbenoid intermediate. The resulting rhodium complex undergoes a wide assortment of reactions including cyclopropanation, 1,2-hydrogen migration, CH-insertion, addition to tethered alkynes and ylide formation. When 2-alkynyl-2-diazo-3-oxobutanoates were treated with a Rh(II-catalyst, furo[3,4-c]furans were formed in excellent yield.

Enantioselective rhodium enolate protonations. A new methodology for the synthesis of beta2-amino acids.

Science.gov (United States)

Sibi, Mukund P; Tatamidani, Hiroto; Patil, Kalyani

2005-06-23

[reaction: see text] Rhodium-catalyzed conjugate addition of an aryl boronic acid to alpha-methylamino acrylates followed by enantioselective protonation of the oxa-pi-allylrhodium intermediate provides access to aryl-substituted beta(2)-amino acids. The impact of the different variables of the reaction on the levels of enantioselectivity has been assessed.

Catalytic dehydrogenation of alcohol over solid-state molybdenum sulfide clusters with an octahedral metal framework

Energy Technology Data Exchange (ETDEWEB)

Kamiguchi, Satoshi, E-mail: kamigu@riken.jp [Advanced Catalysis Research Group, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako City, Saitama 351-0198 (Japan); Organometallic Chemistry Laboratory, RIKEN, 2-1 Hirosawa, Wako City, Saitama 351-0198 (Japan); Okumura, Kazu [School of Advanced Engineering, Kogakuin University, Nakano-machi, Hachioji City, Tokyo 192-0015 (Japan); Nagashima, Sayoko; Chihara, Teiji [Graduate School of Science and Engineering, Saitama University, Shimo-Okubo, Sakura-ku, Saitama City, Saitama 338-8570 (Japan)

2015-12-15

Graphical abstract: - Highlights: • Solid-state molybdenum sulfide clusters catalyzed the dehydrogenation of alcohol. • The dehydrogenation proceeded without the addition of any oxidants. • The catalytic activity developed when the cluster was activated at 300–500 °C in H{sub 2}. • The Lewis-acidic molybdenum atom and basic sulfur ligand were catalytically active. • The clusters function as bifunctional acid–base catalysts. - Abstract: Solid-state molybdenum sulfide clusters with an octahedral metal framework, the superconducting Chevrel phases, are applied to catalysis. A copper salt of a nonstoichiometric sulfur-deficient cluster, Cu{sub x}Mo{sub 6}S{sub 8–δ} (x = 2.94 and δ ≈ 0.3), is stored in air for more than 90 days. When the oxygenated cluster is thermally activated in a hydrogen stream above 300 °C, catalytic activity for the dehydrogenation of primary alcohols to aldehydes and secondary alcohols to ketones develops. The addition of pyridine or benzoic acid decreases the dehydrogenation activity, indicating that both a Lewis-acidic coordinatively unsaturated molybdenum atom and a basic sulfur ligand synergistically act as the catalytic active sites.

Hydroformylation of olefins and reductive carbonylation of aryl halides with syngas formed ex situ from dehydrogenative decarbonylation of hexane-1,6-diol

DEFF Research Database (Denmark)

Christensen, Stig Holden; Olsen, Esben Paul Krogh; Rosenbaum, Jascha

2014-01-01

A variety of primary alcohols have been investigated as convenient substrates for the ex situ delivery of carbon monoxide and molecular hydrogen in a two-chamber reactor. The gaseous mixture is liberated in one chamber by an iridium-catalysed dehydrogenative decarbonylation of the alcohol...... and then consumed in the other chamber in either a rhodium-catalysed hydroformylation of olefins or a palladium-catalysed reductive carbonylation of aryl halides. Hexane-1,6-diol was found to be the optimum alcohol for both reactions where moderate to excellent yields were obtained of the product aldehydes...

Nb effect in the nickel oxide-catalyzed low-temperature oxidative dehydrogenation of ethane

KAUST Repository

Zhu, Haibo

2012-01-01

A method for the preparation of NiO and Nb-NiO nanocomposites is developed, based on the slow oxidation of a nickel-rich Nb-Ni gel obtained in citric acid. The resulting materials have higher surface areas than those obtained by the classical evaporation method from nickel nitrate and ammonium niobium oxalate. These consist in NiO nanocrystallites (7-13 nm) associated, at Nb contents >3 at.%., with an amorphous thin layer (1-2 nm) of a niobium-rich mixed oxide with a structure similar to that of NiNb 2O 6. Unlike bulk nickel oxides, the activity of these nanooxides for low-temperature ethane oxidative dehydrogenation (ODH) has been related to their redox properties. In addition to limiting the size of NiO crystallites, the presence of the Nb-rich phase also inhibits NiO reducibility. At Nb content >5 at.%, Nb-NiO composites are thus less active for ethane ODH but more selective, indicating that the Nb-rich phase probably covers part of the unselective, non-stoichiometric, active oxygen species of NiO. This geometric effect is supported by high-resolution transmission electron microscopy observations. The close interaction between NiO and the thin Nb-rich mixed oxide layer, combined with possible restructuration of the nanocomposite under ODH conditions, leads to significant catalyst deactivation at high Nb loadings. Hence, the most efficient ODH catalysts obtained by this method are those containing 3-4 at.% Nb, which combine high activity, selectivity, and stability. The impact of the preparation method on the structural and catalytic properties of Nb-NiO nanocomposites suggests that further improvement in NiO-catalyzed ethane ODH can be expected upon optimization of the catalyst. © 2011 Elsevier Inc. All rights reserved.

Hydrolysis of Letrozole catalyzed by macrocyclic Rhodium (I) Schiff-base complexes.

Science.gov (United States)

Reddy, P Muralidhar; Shanker, K; Srinivas, V; Krishna, E Ravi; Rohini, R; Srikanth, G; Hu, Anren; Ravinder, V

2015-03-15

Ten mononuclear Rhodium (I) complexes were synthesized by macrocyclic ligands having N4 and N2O2 donor sites. Square planar geometry is assigned based on the analytical and spectral properties for all complexes. Rh(I) complexes were investigated as catalysts in hydrolysis of Nitrile group containing pharmaceutical drug Letrozole. A comparative study showed that all the complexes are efficient in the catalysis. The percent yields of all the catalytic reaction products viz. drug impurities were determined by spectrophotometric procedures and characterized by spectral studies. Copyright © 2014 Elsevier B.V. All rights reserved.

Synthesis of bis- and tris(indolylmethanes catalyzed by an inorganic nano-sized catalyst followed by dehydrogenation to hyperconjugated products

Directory of Open Access Journals (Sweden)

Khorshidi Alireza

2016-01-01

Full Text Available A set of bis- and tris(indolylmethanes were prepared and dehydrogenated to their hyperconjugated products in a one-pot fashion. Nano-sized-SO3H functionalized mesoporous KIT-6 coated on magnetite nanoparticles (Fe3O4@SiO2@KIT-6-OSO3H was used as an efficient catalyst in the first step of synthesis, and dehydrogenation was performed by using (NH42S2O8 after removal of the catalyst. The catalyst was fully characterized by Fourier transform infrared spectroscopy (FT-IR, transmission electron microscopy (TEM and X-ray powder diffraction (XRD, as well as nitrogen adsorption-desorption isotherms. The bis- and tris(indolylmethanes were studied by UV-Vis spectroscopy before and after dehydrogenation, and effect of the ambient parameters on their spectra was investigated. It was found that bis- and tris(indolylmethanes have no considerable absorption in the visible range and what makes them colorful is partial dehydrogenation due to exposure to air. Our catalyst as a new combination of known materials, showed superiority in terms of yield, time, and mild reaction conditions in comparison with previous reports.

Rhodium segregation in dilute silver-rhodium alloys

International Nuclear Information System (INIS)

Krolas, K.; Sternik, M.

1995-01-01

Segregation of Rh in Ag-based alloys has been studied using the perturbed angular correlation of γ-rays emitted in the nuclear decay of radioactive 111 In. The formation of impurity complexes, consisting of an 111 In probe atom and one or more Rh atoms, was observed as a function of annealing time and temperature. Rhodium atom aggregation starts at about 600 K. From the fraction of 111 In bound to isolated Rh atoms the solute rhodium atom concentration was determined. It increases with the nominal alloy concentration up to about 0.04 at.% and then it is essentially constant for the nominal Rh concentration varying between 0.1 and 0.5 at.%. The solute rhodium atom concentration is 3 times larger at the melting point than at 750 K

Manganese Catalyzed α-Olefination of Nitriles by Primary Alcohols.

Science.gov (United States)

Chakraborty, Subrata; Das, Uttam Kumar; Ben-David, Yehoshoa; Milstein, David

2017-08-30

Catalytic α-olefination of nitriles using primary alcohols, via dehydrogenative coupling of alcohols with nitriles, is presented. The reaction is catalyzed by a pincer complex of an earth-abundant metal (manganese), in the absence of any additives, base, or hydrogen acceptor, liberating dihydrogen and water as the only byproducts.

One-Step Borylation of 1,3-Diaryloxybenzenes Towards Efficient Materials for Organic Light-Emitting Diodes.

Science.gov (United States)

Hirai, Hiroki; Nakajima, Kiichi; Nakatsuka, Soichiro; Shiren, Kazushi; Ni, Jingping; Nomura, Shintaro; Ikuta, Toshiaki; Hatakeyama, Takuji

2015-11-09

The development of a one-step borylation of 1,3-diaryloxybenzenes, yielding novel boron-containing polycyclic aromatic compounds, is reported. The resulting boron-containing compounds possess high singlet-triplet excitation energies as a result of localized frontier molecular orbitals induced by boron and oxygen. Using these compounds as a host material, we successfully prepared phosphorescent organic light-emitting diodes exhibiting high efficiency and adequate lifetimes. Moreover, using the present one-step borylation, we succeeded in the synthesis of an efficient, thermally activated delayed fluorescence emitter and boron-fused benzo[6]helicene. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Unravelling The Mechanism of Basic Aqueous Methanol Dehydrogenation Catalyzed By Ru-PNP Pincer Complexes

DEFF Research Database (Denmark)

Alberico, Elisabetta; Lennox, Alastair J. J.; Vogt, Lydia K.

2016-01-01

Ruthenium PNP complex 1a (RuH(CO)Cl(HN(C2H4Pi-Pr2)2)) represents a state-of-the-art catalyst for low-temperature (methanol dehydrogenation to H2 and CO2. Herein, we describe an investigation that combines experiment, spectroscopy, and theory to provide a mechanistic rationale...

Atom-Economical Dimerization Strategy by the Rhodium-Catalyzed Addition of Carboxylic Acids to Allenes: Protecting-Group-Free Synthesis of Clavosolide A and Late-Stage Modification.

Science.gov (United States)

Haydl, Alexander M; Breit, Bernhard

2015-12-14

Natural products of polyketide origin with a high level of symmetry, in particular C2 -symmetric diolides as a special macrolactone-based product class, often possess a broad spectrum of biological activity. An efficient route to this important structural motif was developed as part of a concise and highly convergent synthesis of clavosolide A. This strategy features an atom-economic "head-to-tail" dimerization by the stereoselective rhodium-catalyzed addition of carboxylic acids to terminal allenes with the simultaneous construction of two new stereocenters. The excellent efficiency and selectivity with which the C2 -symmetric core structures were obtained are remarkable considering the outcome under classical dimerization conditions. Furthermore, this approach facilitates late-stage modification and provides ready access to potential new lead structures. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photocatalytic carbon dioxide reduction with rhodium-based catalysts in solution and heterogenized within metal-organic frameworks.

Science.gov (United States)

Chambers, Matthew B; Wang, Xia; Elgrishi, Noémie; Hendon, Christopher H; Walsh, Aron; Bonnefoy, Jonathan; Canivet, Jérôme; Quadrelli, Elsje Alessandra; Farrusseng, David; Mellot-Draznieks, Caroline; Fontecave, Marc

2015-02-01

The first photosensitization of a rhodium-based catalytic system for CO2 reduction is reported, with formate as the sole carbon-containing product. Formate has wide industrial applications and is seen as valuable within fuel cell technologies as well as an interesting H2 -storage compound. Heterogenization of molecular rhodium catalysts is accomplished via the synthesis, post-synthetic linker exchange, and characterization of a new metal-organic framework (MOF) Cp*Rh@UiO-67. While the catalytic activities of the homogeneous and heterogeneous systems are found to be comparable, the MOF-based system is more stable and selective. Furthermore it can be recycled without loss of activity. For formate production, an optimal catalyst loading of ∼10 % molar Rh incorporation is determined. Increased incorporation of rhodium catalyst favors thermal decomposition of formate into H2 . There is no precedent for a MOF catalyzing the latter reaction so far. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhenium-catalyzed dehydrogenative olefination of C(sp(3))-H bonds with hypervalent iodine(III) reagents.

Science.gov (United States)

Gu, Haidong; Wang, Congyang

2015-06-07

A dehydrogenative olefination of C(sp(3))-H bonds is disclosed here, by merging rhenium catalysis with an alanine-derived hypervalent iodine(III) reagent. Thus, cyclic and acyclic ethers, toluene derivatives, cycloalkanes, and nitriles are all successfully alkenylated in a regio- and stereoselective manner.

Monodisperse gold-palladium alloy nanoparticles and their composition-controlled catalysis in formic acid dehydrogenation under mild conditions.

Science.gov (United States)

Metin, Önder; Sun, Xiaolian; Sun, Shouheng

2013-02-07

Monodisperse 4 nm AuPd alloy nanoparticles with controlled composition were synthesized by co-reduction of hydrogen tetrachloroaurate(III) hydrate and palladium(II) acetylacetonate with a borane-morpholine complex in oleylamine. These NPs showed high activity (TOF = 230 h(-1)) and stability in catalyzing formic acid dehydrogenation and hydrogen production in water at 50 °C without any additives.

Line profile analyses of rhodium metal obtained by decomposition of rhodium carbonyl

International Nuclear Information System (INIS)

Chandra, D.; Mandalia, H.; Garner, M.L.; Blakely, M.K.; Lau, K.H.

1995-01-01

Metal carbonyls are important for chemical vapor deposition (CVD) of metals and alloys and formation of high surface area metallic particles which have potential applications as catalysts. Rhodium carbonyl [Rh 6 (CO) 16 ] produces high surface area metallic particles whose structure has been reported as monoclinic (I2/a) with lattice dimensions, a=17.00(±0.03)Angstrom, b=9.78(±0.02)Angstrom, c=17.53(±0.03)Angstrom and Β=121 degrees 45' ± 30' at room temperature. Generally, metal carbonyl crystals dissociate under vacuum as carbonyl gas and decompose to metallic crystals and carbon monoxide at higher temperatures. However, the behavior of rhodium carbonyl crystals is different; they decompose directly to metallic rhodium without the formation of rhodium carbonyl gas in vacuum. Several residual fine grains of rhodium metal are found after the decomposition in vacuum at relatively low temperatures. The metallic samples of rhodium were obtained from vapor pressure experiments using torsion Knudsen-effusion apparatus. X-ray diffraction analyses performed on these gains showed severely broadened Bragg reflections indicative of small particle size and/or lattice microgram. In this study, a comparison of lattice strains and domain sizes obtained by integral breadth and Fourier methods has been made. In addition a comparison of the lattice strains and domain sizes has been made between the Cauchy, Gaussian, Cauchy-Gaussian and Aqua integral breadth methods

Investigation into cathode polarization during deposition of rhodium-nickel and rhodium-indium alloys

International Nuclear Information System (INIS)

Evdokimova, N.V.; Byacheslavov, P.M.; Lokshtanova, O.G.

1979-01-01

The results of kinetic regularities experimental investigations during electrodeposition of rhodium-nickel and rhonium-indium alloys are presented. Methods of general and partial polarization curves have been used to show the nature of polarization during the rhonium-nickel and rhodium-indium alloys deposition. It is shown that indium into the rhodium-indium alloy and nickel into the rhodium-nickel alloy deposit with great depolarization ( PHIsub(In)sup(0)=-0.33B, PHIsub(Ni)sup(0)=-0.23B). Indium and nickel in pure form do not deposit from the electrolytes of the given composition (H 2 SO 4 - 50 g/l, HNH 2 SO 3 -10 g/l). The recalculation of partial polarization curve of indium precipitation into the rhodium-indium alloy in the mixed kinetics coordinates gives a straight line with 40 mV inclination angle. This corresponds to the delayed stage of the second electron addition with the imposition of diffusion limitations

One-pot synthesis of 2,5-dihydropyrroles from terminal alkynes, azides, and propargylic alcohols by relay actions of copper, rhodium, and gold.

Science.gov (United States)

Miura, Tomoya; Tanaka, Takamasa; Matsumoto, Kohei; Murakami, Masahiro

2014-12-01

Relay actions of copper, rhodium, and gold formulate a one-pot multistep pathway, which directly gives 2,5-dihydropyrroles starting from terminal alkynes, sulfonyl azides, and propargylic alcohols. Initially, copper-catalyzed 1,3-dipolar cycloaddition of terminal alkynes with sulfonyl azides affords 1-sulfonyl-1,2,3-triazoles, which then react with propargylic alcohols under the catalysis of rhodium. The resulting alkenyl propargyl ethers subsequently undergo the thermal Claisen rearrangement to give α-allenyl-α-amino ketones. Finally, a gold catalyst prompts 5-endo cyclization to produce 2,5-dihydropyrroles. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhodium platings – experimental study

OpenAIRE

Rudolf, R.; Budić, B.; Stamenković, D.; Čolić, M.; Ivanič, A.; Kosec, B.

2013-01-01

Modern rhodium plating solutions are based on either sulphate or phosphate. Although in theory there are four possible combinations, in practice only three different rhodium electrolytes are used. These are based on dilutions of rhodium sulphate or phosphate concentrates with added sulphuric or phosphoric acid. These processes are be discussed in this paper with a demonstration of Rh platings in the Slovenian firm Zlatarna Celje d.d.

Shale gas opportunities. Dehydrogenation of light alkanes

Energy Technology Data Exchange (ETDEWEB)

Patcas, F.C.; Dieterle, M.; Rezai, A.; Asprion, N. [BASF SE, Ludwigshafen (Germany)

2013-11-01

The discovery and use of shale gas in North America has become a game changer for the chemical industry by access to a cheaper feedstock compared to conventional oil. Increased number of ethane crackers spurred increasing interest in light alkanes dehydrogenation. Several companies have announced their interest in new propane dehydrogenation units in North America. BASF is developing light alkanes dehydrogenation technologies for two decades now. BASF developed jointly with Linde the isothermal C3 dehydrogenation process. The latest dehydrogenation catalyst development at BASF focused on a supported and steam resistant Pt-Sn catalyst which yielded excellent selectivity and activity. Intense research work both internally as well as in cooperation with universities contributed to the understanding of the relationship between the surface structure and catalyst performances like activity, selectivity and coking resistance. Using such type of catalysts BASF developed an autothermal propane dehydrogenation as well as a butane dehydrogenation process. The most recent catalyst development was a dehydrogenation catalyst coated on a honeycomb monolith to improve catalyst usage and pressure drop. This will probably be the first industrial usage of catalytic monoliths in a chemical synthesis process. (orig.) (Published in summary form only)

Rhodium platings – experimental study

Directory of Open Access Journals (Sweden)

R. Rudolf

2013-07-01

Full Text Available Modern rhodium plating solutions are based on either sulphate or phosphate. Although in theory there are four possible combinations, in practice only three different rhodium electrolytes are used. These are based on dilutions of rhodium sulphate or phosphate concentrates with added sulphuric or phosphoric acid. These processes are be discussed in this paper with a demonstration of Rh platings in the Slovenian firm Zlatarna Celje d.d.

Mechanism of Intramolecular Rhodium- and Palladium-Catalyzed Alkene Alkoxyfunctionalizations

KAUST Repository

Vummaleti, Sai V. C.

2015-11-13

Density functional theory calculations have been used to investigate the reaction mechanism for the [Rh]-catalyzed intramolecular alkoxyacylation ([Rh] = [RhI(dppp)+] (dppp, 1,3-bis(diphenylphosphino)propane) and [Pd]/BPh3 dual catalytic system assisted intramolecular alkoxycyanation ([Pd] = Pd-Xantphos) using acylated and cyanated 2-allylphenol derivatives as substrates, respectively. Our results substantially confirm the proposed mechanism for both [Rh]- and [Pd]/ BPh3-mediated alkoxyfunctionalizations, offering a detailed geometrical and energetical understanding of all the elementary steps. Furthermore, for the [Rh]-mediated alkoxyacylation, our observations support the hypothesis that the quinoline group of the substrate is crucial to stabilize the acyl metal complex and prevent further decarbonylation. For [Pd]/BPh3-catalyzed alkoxycyanation, our findings clarify how the Lewis acid BPh3 cocatalyst accelerates the only slow step of the reaction, corresponding to the oxidative addition of the cyanate O-CN bond to the Pd center. © 2015 American Chemical Society.

Mechanism of Intramolecular Rhodium- and Palladium-Catalyzed Alkene Alkoxyfunctionalizations

KAUST Repository

Vummaleti, Sai V. C.; Alghamdi, Miasser; Poater, Albert; Falivene, Laura; Scaranto, Jessica; Beetstra, Dirk J.; Morton, Jason G.; Cavallo, Luigi

2015-01-01

Density functional theory calculations have been used to investigate the reaction mechanism for the [Rh]-catalyzed intramolecular alkoxyacylation ([Rh] = [RhI(dppp)+] (dppp, 1,3-bis(diphenylphosphino)propane) and [Pd]/BPh3 dual catalytic system assisted intramolecular alkoxycyanation ([Pd] = Pd-Xantphos) using acylated and cyanated 2-allylphenol derivatives as substrates, respectively. Our results substantially confirm the proposed mechanism for both [Rh]- and [Pd]/ BPh3-mediated alkoxyfunctionalizations, offering a detailed geometrical and energetical understanding of all the elementary steps. Furthermore, for the [Rh]-mediated alkoxyacylation, our observations support the hypothesis that the quinoline group of the substrate is crucial to stabilize the acyl metal complex and prevent further decarbonylation. For [Pd]/BPh3-catalyzed alkoxycyanation, our findings clarify how the Lewis acid BPh3 cocatalyst accelerates the only slow step of the reaction, corresponding to the oxidative addition of the cyanate O-CN bond to the Pd center. © 2015 American Chemical Society.

Enantioselective Access to Spirocyclic Sultams by Chiral Cp(x) -Rhodium(III)-Catalyzed Annulations.

Science.gov (United States)

Pham, Manh V; Cramer, Nicolai

2016-02-12

Chiral spirocyclic sultams are a valuable compound class in organic and medicinal chemistry. A rapid entry to this structural motif involves a [3+2] annulation of an N-sulfonyl ketimine and an alkyne. Although the directing-group properties of the imino group for C-H activation have been exploited, the developments of related asymmetric variants have remained very challenging. The use of rhodium(III) complexes equipped with a suitable atropchiral cyclopentadienyl ligand, in conjunction with a carboxylic acid additive, enables an enantioselective and high yielding access to such spirocyclic sultams. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interstellar dehydrogenated PAH anions: vibrational spectra

Science.gov (United States)

Buragohain, Mridusmita; Pathak, Amit; Sarre, Peter; Gour, Nand Kishor

2018-03-01

Interstellar polycyclic aromatic hydrocarbon (PAH) molecules exist in diverse forms depending on the local physical environment. Formation of ionized PAHs (anions and cations) is favourable in the extreme conditions of the interstellar medium (ISM). Besides in their pure form, PAHs are also likely to exist in substituted forms; for example, PAHs with functional groups, dehydrogenated PAHs etc. A dehydrogenated PAH molecule might subsequently form fullerenes in the ISM as a result of ongoing chemical processes. This work presents a density functional theory (DFT) calculation on dehydrogenated PAH anions to explore the infrared emission spectra of these molecules and discuss any possible contribution towards observed IR features in the ISM. The results suggest that dehydrogenated PAH anions might be significantly contributing to the 3.3 μm region. Spectroscopic features unique to dehydrogenated PAH anions are highlighted that may be used for their possible identification in the ISM. A comparison has also been made to see the size effect on spectra of these PAHs.

Highly selective formation of imines catalyzed by silver nanoparticles supported on alumina

DEFF Research Database (Denmark)

Mielby, Jerrik Jørgen; Poreddy, Raju; Engelbrekt, Christian

2014-01-01

The oxidative dehydrogenation of alcohols to aldehydes catalyzed by Ag nanoparticles supported on Al2O3 was studied. The catalyst promoted the direct formation of imines by tandem oxidative dehydrogenation and condensation of alcohols and amines. The reactions were performed under mild conditions......-2 in the gas phase. The use of an efficient and selective Ag catalyst for the oxidative dehydrogenation of alcohol in the presence of amines gives a new green reaction protocol for imine synthesis. (C) 2014, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B...... and afforded the imines in high yield (up to 99%) without any byproducts other than H2O. The highest activity was obtained over 5 wt% Ag/Al2O3 in toluene with air as oxidant. The reactions were also performed under oxidant-free conditions where the reaction was driven to the product side by the production of H...

Dehydrogenation of benzene on Pt(111) surface

Science.gov (United States)

Gao, W.; Zheng, W. T.; Jiang, Q.

2008-10-01

The dehydrogenation of benzene on Pt(111) surface is studied by ab initio density functional theory. The minimum energy pathways for benzene dehydrogenation are found with the nudge elastic band method including several factors of the associated barriers, reactive energies, intermediates, and transient states. The results show that there are two possible parallel minimum energy pathways on the Pt(111) surface. Moreover, the tilting angle of the H atom in benzene can be taken as an index for the actual barrier of dehydrogenation. In addition, the properties of dehydrogenation radicals on the Pt(111) surface are explored through their adsorption energy, adsorption geometry, and electronic structure on the surface. The vibrational frequencies of the dehydrogenation radicals derived from the calculations are in agreement with literature data.

Bipyridine- and phenanthroline-based metal-organic frameworks for highly efficient and tandem catalytic organic transformations via directed C-H activation

Energy Technology Data Exchange (ETDEWEB)

Manna, Kuntal [Univ. of Chicago, Chicago, IL (United States); Zhang, Teng [Univ. of Chicago, Chicago, IL (United States); Greene, Francis X. [Univ. of Chicago, Chicago, IL (United States); Lin, Wenbin [Univ. of Chicago, Chicago, IL (United States)

2015-02-16

We report here the synthesis of a series of robust and porous bipyridyl- and phenanthryl-based metal–organic frameworks (MOFs) of UiO topology (BPV-MOF, mBPV-MOF, and mPT-MOF) and their postsynthetic metalation to afford highly active single-site solid catalysts. While BPV-MOF was constructed from only bipyridyl-functionalized dicarboxylate linker, both mBPV- and mPT-MOF were built with a mixture of bipyridyl- or phenanthryl-functionalized and unfunctionalized dicarboxylate linkers. The postsynthetic metalation of these MOFs with [Ir(COD)(OMe)]₂ provided Ir-functionalized MOFs (BPV-MOF-Ir, mBPV-MOF-Ir, and mPT-MOF-Ir), which are highly active catalysts for tandem hydrosilylation of aryl ketones and aldehydes followed by dehydrogenative ortho-silylation of benzylicsilyl ethers as well as C–H borylation of arenes using B₂pin₂. Both mBPV-MOF-Ir and mPT-MOF-Ir catalysts displayed superior activities compared to BPV-MOF-Ir due to the presence of larger open channels in the mixed-linker MOFs. Impressively, mBPV-MOF-Ir exhibited high TONs of up to 17000 for C–H borylation reactions and was recycled more than 15 times. The mPT-MOF-Ir system is also active in catalyzing tandem dehydrosilylation/dehydrogenative cyclization of N-methylbenzyl amines to azasilolanes in the absence of a hydrogen acceptor. Importantly, MOF-Ir catalysts are significantly more active (up to 95 times) and stable than their homogeneous counterparts for all three reactions, strongly supporting the beneficial effects of active site isolation within MOFs. This work illustrates the ability to increase MOF open channel sizes by using the mixed linker approach and shows the enormous potential of developing highly active and robust single-site solid catalysts based on MOFs containing nitrogen-donor ligands for important organic transformations.

Dehydrogenative Diels-Alder reaction.

Science.gov (United States)

Ozawa, Takuya; Kurahashi, Takuya; Matsubara, Seijiro

2011-10-07

The dehydrogenative cycloaddition of dieneynes, which possess a diene in the form of a styrene moiety and a dienophile in the form of an alkyne moiety, produces naphthalene derivatives when heated. It was found that a key requirement of this process is the presence of a silyl group attached to the alkyne moiety, which forces a dehydrogenation reaction to occur. © 2011 American Chemical Society

Oxidative Olefination of Anilides with Unactivated Alkenes Catalyzed by an (Electron-Deficient η(5) -Cyclopentadienyl)Rhodium(III) Complex Under Ambient Conditions.

Science.gov (United States)

Takahama, Yuji; Shibata, Yu; Tanaka, Ken

2015-06-15

The oxidative olefination of sp(2) C-H bonds of anilides with both activated and unactivated alkenes using an (electron-deficient η(5) -cyclopentadienyl)rhodium(III) complex is reported. In contrast to reactions using this electron-deficient rhodium(III) catalyst, [Cp*RhCl2 ]2 showed no activity against olefination with unactivated alkenes. In addition, the deuterium kinetic isotope effect (DKIE) study revealed that the C-H bond cleavage step is thought to be the turnover-limiting step. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reaction pathways for reduction of nitrate ions on platinum, rhodium, and platinum-rhodium alloy electrodes

International Nuclear Information System (INIS)

Cunha, M.C.P.M. da; De Souza, J.P.I.; Nart, F.C.

2000-01-01

The reduction of nitrate ions on platinum, rhodium, and platinum-rhodium alloy electrodes has been investigated using differential electrochemical mass spectrometry and in situ FTIR measurements. For 3 M HNO 3 concentration it has been found that nitrate starts the reduction with partial N-O bond dissociation and N-N bond formation generating NO and N 2 O. At potentials lower than 0.2 V the reaction proceeds forming dissolved NH 4 + . For potentials lower than 0 V the reduction continues via a multiple pathway reaction leading to the nonselective production of N 2 , NH 2 OH, and N 2 H 2 . On the alloyed electrodes, the production of NO and N 2 O has been observed in both cathodic and anodic scans, while on pure platinum and rhodium electrodes the reaction has been observed only during the cathodic scan. Contrasting with the pure platinum and rhodium alloys, where the N-O bond break starts forming NO and N 2 O, on the alloys HNO 2 has been observed as the first reaction step. For alloys with higher rhodium composition, like Pt 75 Rh 25 , no N 2 has been detected for potentials lower than 0 V

Rh-Catalyzed Annulations of N-Methoxybenzamides and Ketenimines: Sterically and Electronically Controlled Synthesis of Isoquinolinones and Isoindolinones.

Science.gov (United States)

Zhou, Xiaorong; Zhang, Zhiyin; Zhao, Hongyang; Lu, Ping; Wang, Yanguang

2017-04-07

Rhodium-catalyzed C-H activation/annulation reactions of ketenimines with N-methoxybenzamides are reported. The outcome of reactions is dependent on the structure of ketenimines. The β-alkyl-substituted ketenimines furnish 3-iminoisoquinolin-1(2H)-ones in a formal [4 + 2] annulation manner, while the β-ester substituted ketenimines afford 3-aminoisoindolin-1-ones in a formal [4 + 1] annulation manner. The synthesized [4 + 2] products undergo an intramolecular Cu-catalyzed C-N coupling to be converted to benzo[4,5]imidazo[1,2-b]isoquinolin-11-ones, which can be directly prepared from ketenimines and N-methoxybenzamides by a one-pot Rh-catalyzed annulation/Cu-catalyzed C-N coupling sequence.

Sterically directed iridium-catalyzed hydrosilylation of alkenes in the presence of alkynes.

Science.gov (United States)

Muchnij, Jill A; Kwaramba, Farai B; Rahaim, Ronald J

2014-03-07

A selective iridium catalyzed hydrosilylation of alkenes in the presence of more reactive alkynes is described. By utilizing [IrCl(COD)]2 in the presence of excess COD, hydrosilylation of alkenes and alkynes with ethynylsilanes is achieved with good chemo- and regioselectivity. This approach goes against the traditional reactivity trends of platinum and rhodium catalysts and allows access to highly substituted silicon alkyne tethers.

Iodine-Catalyzed Direct Olefination of 2-Oxindoles and Alkenes via Cross-Dehydrogenative Coupling (CDC) in Air.

Science.gov (United States)

Huang, Hong-Yan; Wu, Hong-Ru; Wei, Feng; Wang, Dong; Liu, Li

2015-08-07

A direct intermolecular olefination of sp(3) C-H bond between 2-oxindoles and simple alkenes via a Cross-Dehydrogenative Coupling (CDC) strategy has been developed. In the absence of additional base, moderate to excellent yields have been obtained by using a catalytic amount of iodine with atmospheric oxygen as the reoxidant. Based on the observation of a radical capture experiment, the transformation is proposed to proceed via a radical process.

Distribution of Rhodium in Mice Submitted to Treatment With the Adduct of Rhodium Propionate and Sodium Isonicotinate

OpenAIRE

de Souza, Aparecido Ribeiro; Najjar, Renato; de Oliveira, Elizabeth; Zyngier, Szulim Ber

1997-01-01

The distribution of rhodium in Balb/c mice following intraperitoneal (ip) administration of a solution of adduct of rhodium propionate and sodium isonicotinate has been investigated. The metal concentration was determined in blood and in the following organ tissues: brain, heart, lung, liver, spleen, kidney, testes, and uterus/ovary, and the rhodium concentration was obtained by Inductively Coupled Argon Atomic Emission Spectroscopy (ICP-AES). The metal was detected in all organ tissues exami...

Rhodium-Catalyzed C-C Bond Formation via Heteroatom-Directed C-H Bond Activation

Energy Technology Data Exchange (ETDEWEB)

Colby, Denise; Bergman, Robert; Ellman, Jonathan

2010-05-13

Once considered the 'holy grail' of organometallic chemistry, synthetically useful reactions employing C-H bond activation have increasingly been developed and applied to natural product and drug synthesis over the past decade. The ubiquity and relative low cost of hydrocarbons makes C-H bond functionalization an attractive alternative to classical C-C bond forming reactions such as cross-coupling, which require organohalides and organometallic reagents. In addition to providing an atom economical alternative to standard cross - coupling strategies, C-H bond functionalization also reduces the production of toxic by-products, thereby contributing to the growing field of reactions with decreased environmental impact. In the area of C-C bond forming reactions that proceed via a C-H activation mechanism, rhodium catalysts stand out for their functional group tolerance and wide range of synthetic utility. Over the course of the last decade, many Rh-catalyzed methods for heteroatom-directed C-H bond functionalization have been reported and will be the focus of this review. Material appearing in the literature prior to 2001 has been reviewed previously and will only be introduced as background when necessary. The synthesis of complex molecules from relatively simple precursors has long been a goal for many organic chemists. The ability to selectively functionalize a molecule with minimal pre-activation can streamline syntheses and expand the opportunities to explore the utility of complex molecules in areas ranging from the pharmaceutical industry to materials science. Indeed, the issue of selectivity is paramount in the development of all C-H bond functionalization methods. Several groups have developed elegant approaches towards achieving selectivity in molecules that possess many sterically and electronically similar C-H bonds. Many of these approaches are discussed in detail in the accompanying articles in this special issue of Chemical Reviews. One approach

Synthesis and characterization of the Rhodium (II) citrate complex

International Nuclear Information System (INIS)

Najjar, R.; Santos, F.S. dos; Seidel, W.

1987-01-01

The preparation and characterization of the rhodium (II) citrate is described. Rhodium citrate was prepared by reacting citric acid trihydrated (3,4 g, 16 mmols) with anhydrous rhodium acetate (0,44 g, 1 mmol). Th electronic instruments, thermogravimetric curve and spectrum of rhodium (II) citrate are analysed. (M.J.C.) [pt

Automated Quantum Mechanical Predictions of Enantioselectivity in a Rhodium-Catalyzed Asymmetric Hydrogenation.

Science.gov (United States)

Guan, Yanfei; Wheeler, Steven E

2017-07-24

A computational toolkit (AARON: An automated reaction optimizer for new catalysts) is described that automates the density functional theory (DFT) based screening of chiral ligands for transition-metal-catalyzed reactions with well-defined reaction mechanisms but multiple stereocontrolling transition states. This is demonstrated for the Rh-catalyzed asymmetric hydrogenation of (E)-β-aryl-N-acetyl enamides, for which a new C 2 -symmetric phosphorus ligand is designed. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cu-catalyzed C(sp³)-H bond activation reaction for direct preparation of cycloallyl esters from cycloalkanes and aromatic aldehydes.

Science.gov (United States)

Zhao, Jincan; Fang, Hong; Han, Jianlin; Pan, Yi

2014-05-02

Cu-catalyzed dehydrogenation-olefination and esterification of C(sp(3))-H bonds of cycloalkanes with TBHP as an oxidant has been developed. The reaction involves four C-H bond activations and gives cycloallyl ester products directly from cycloalkanes and aromatic aldehydes.

Selective rhodium-catalyzed reduction of tertiary amides in amino acid esters and peptides.

Science.gov (United States)

Das, Shoubhik; Li, Yuehui; Bornschein, Christoph; Pisiewicz, Sabine; Kiersch, Konstanze; Michalik, Dirk; Gallou, Fabrice; Junge, Kathrin; Beller, Matthias

2015-10-12

Efficient reduction of the tertiary amide bond in amino acid derivatives and peptides is described. Functional group selectivity has been achieved by applying a commercially available rhodium precursor and bis(diphenylphosphino)propane (dppp) ligand together with phenyl silane as a reductant. This methodology allows for specific reductive derivatization of biologically interesting peptides and offers straightforward access to a variety of novel peptide derivatives for chemical biology studies and potential pharmaceutical applications. The catalytic system tolerates a variety of functional groups including secondary amides, ester, nitrile, thiomethyl, and hydroxy groups. This convenient hydrosilylation reaction proceeds at ambient conditions and is operationally safe because no air-sensitive reagents or highly reactive metal hydrides are needed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An operando FTIR spectroscopic and kinetic study of carbon monoxide pressure influence on rhodium-catalyzed olefin hydroformylation.

Science.gov (United States)

Kubis, Christoph; Sawall, Mathias; Block, Axel; Neymeyr, Klaus; Ludwig, Ralf; Börner, Armin; Selent, Detlef

2014-09-08

The influence of carbon monoxide concentration on the kinetics of the hydroformylation of 3,3-dimethyl-1-butene with a phosphite-modified rhodium catalyst has been studied for the pressure range p(CO)=0.20-3.83 MPa. Highly resolved time-dependent concentration profiles of the organometallic intermediates were derived from IR spectroscopic data collected in situ for the entire olefin-conversion range. The dynamics of the catalyst and organic components are described by enzyme-type kinetics with competitive and uncompetitive inhibition reactions involving carbon monoxide taken into account. Saturation of the alkyl-rhodium intermediates with carbon monoxide as a cosubstrate occurs between 1.5 and 2 MPa of carbon monoxide pressure, which brings about a convergence of aldehyde regioselectivity. Hydrogenolysis of the acyl intermediate is fast at 30 °C and low pressure of p(CO)=0.2 MPa, but is of minus first order with respect to the solution concentration of carbon monoxide. Resting 18-electron hydrido and acyl complexes that correspond to early and late rate-determining states, respectively, coexist as long as the conversion of the substrate is not complete. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Correction of rhodium detector signals for comparison to design calculations

International Nuclear Information System (INIS)

Judd, J.L.; Chang, R.Y.; Gabel, C.W.

1989-01-01

Rhodium detectors are used in many commercial pressurized water reactors PWRs [pressurized water reactor] as in-core neutron detectors. The signals from the detectors are the result of neutron absorption in 103 Rh and the subsequent beta decay of 104 Rh to 104 Pd. The rhodium depletes ∼1% per full-power month, so corrections are necessary to the detector signal to account for the effects of the rhodium depletion. These corrections result from the change in detector self-shielding with rhodium burnup and the change in rhodium concentration itself. Correction for the change in rhodium concentration is done by multiplication of the factor N(t)/N 0 , where N(t) is the rhodium concentration at time t and N 0 is the initial rhodium concentration. The calculation of the self-shielding factor is more complicated and is presented. A self-shielding factor based on the fraction of rhodium remaining was calculated with the CASMO-3 code. The results obtained from our comparisons of predicted and measured in-core detector signals show that the CASMO-3/SIMULATE-3 code package is an effective tool for estimating pin peaking and power distributions

Rh-Catalyzed annulations of N-methoxybenzamides with ketenimines: synthesis of 3-aminoisoindolinones and 3-diarylmethyleneisoindolinones with strong aggregation induced emission properties.

Science.gov (United States)

Zhou, Xiaorong; Peng, Zhixing; Zhao, Hongyang; Zhang, Zhiyin; Lu, Ping; Wang, Yanguang

2016-08-23

Rhodium-catalyzed C-H activation/annulation reactions of ketenimines with N-methoxybenzamides furnished 3-aminoisoindolin-1-ones and 3-(diarylmethylene)isoindolin-1-ones. The synthesized 3-(diarylmethylene)isoindolin-1-ones exhibited aggregation induced emissions in aqueous tetrahydrofuran solution and strong green-yellow emissions in solids.

Preparation of rhodium target for cyclone-30 accelerator

International Nuclear Information System (INIS)

Deng Xuesong; Li Dakang; Xie Xiangqian; Li Chao

2002-01-01

The rhodium target for Cyclone-30 accelerator is prepared by pulse electroplating method. The effects of pulse parameters, rhodium concentration, acidity and temperature on the properties of the target layer are studied, and the optimal process is determined. The rhodium target, mass thickness is more than 150 mg/cm 2 , adapts to producing 103 Pd on Cyclone-30 accelerator

Dehydrogenation in large ingot casting process

International Nuclear Information System (INIS)

Ubukata, Takashi; Suzuki, Tadashi; Ueda, Sou; Shibata, Takashi

2009-01-01

Forging components (for nuclear power plants) have become larger and larger because of decreased weld lines from a safety point of view. Consequently they have been manufactured from ingots requirement for 200 tons or more. Dehydrogenation is one of the key issues for large ingot manufacturing process. In the case of ingots of 200 tons or heavier, mold stream degassing (MSD) has been applied for dehydrogenation. Although JSW had developed mold stream degassing by argon (MSD-Ar) as a more effective dehydrogenating practice, MSD-Ar was not applied for these ingots, because conventional refractory materials of a stopper rod for the Ar blowing hole had low durability. In this study, we have developed a new type of stopper rod through modification of both refractory materials and the stopper rod construction and have successfully expanded the application range of MSD-Ar up to ingots weighting 330 tons. Compared with the conventional MSD, the hydrogen content in ingots after MSD-Ar has decreased by 24 percent due to the dehydrogenation rate of MSD-Ar increased by 34 percent. (author)

REGIOSELECTIVE OXIDATIONS OF EQUILENIN DERIVATIVES CATALYZED BY A RHODIUM (III) PORPHYRIN COMPLEX-CONTRAST WITH THE MANGANESE (III) PORPHYRIN. (R826653)

Science.gov (United States)

AbstractEquilenin acetate and dihydroequilenin acetate were oxidized with iodosobenzene and a rhodium(III) porphyrin catalyst. The selectivity of the reactions differs from that with the corresponding Mn(III) catalyst, or from that of free radical chain oxidation.

Design, Synthesis and Biological Activity of Novel Reversible Peptidyl FVIIa Inhibitors Rh-Catalyzed Enantioselective Synthesis of Diaryl Amines

DEFF Research Database (Denmark)

Storgaard, Morten

functional group tolerance. Unfortunately, these -aryl tetramic acids were too unreactive and ring opening toward the synthesis of the building block did not succeed. However, -aryl tetramic acids are still interesting compounds due to their potential biological activity. The building block 3.15 (P1......-catalyzed enantioselective synthesis of diaryl amines, which is an important class of compounds (Chapter 4). For example it is found in the third generation anti-histaminic agent levocetirizine. Development of efficient synthetic routes is therefore of considerably interest. The rhodium-catalyzed enantioselective synthesis...

Rh(iii)-catalyzed C-H olefination of N-pentafluoroaryl benzamides using air as the sole oxidant.

Science.gov (United States)

Lu, Yi; Wang, Huai-Wei; Spangler, Jillian E; Chen, Kai; Cui, Pei-Pei; Zhao, Yue; Sun, Wei-Yin; Yu, Jin-Quan

2015-03-01

The oxidative olefination of a broad array of arenes and heteroarenes with a variety of activated and unactivated olefins has be achieved via a rhodium(iii)-catalyzed C-H activation reaction. The use of an N -pentafluorophenyl benzamide directing group is crucial for achieving catalytic turnovers in the presence of air as the sole oxidant without using a co-oxidant.

The influence of rhodium burn-up on the sensitivity of rhodium self-powered neutron detectors

International Nuclear Information System (INIS)

Erben, O.

1980-01-01

Depression and self-shielding coefficients are presented for thermal and epithermal neutron flux densities. Functions are shown describing the distribution of beta particle sources on the emitter cross section for 0 to 50% rhodium burnup. The values are calculated of detector sensitivity to thermal and epithermal neutron flux densities for the said burnup for main types of rhodium SPN detectors made by SODERN. (J.B.)

Rh(III)-catalyzed oxidative olefination of N-(1-naphthyl)sulfonamides using activated and unactivated alkenes.

Science.gov (United States)

Li, Xuting; Gong, Xue; Zhao, Miao; Song, Guoyong; Deng, Jian; Li, Xingwei

2011-11-04

Rhodium(III)-catalyzed oxidative olefination of N-(1-naphthyl)sulfonamides has been achieved at the peri position. Three categories of olefins have been successfully applied. Activated olefins reacted to afford five-membered azacycles as a result of oxidative olefination-hydroamination. Unactivated olefins reacted to give the olefination product. 2-fold oxidative C-C and C-N coupling was achieved for allylbenzenes. © 2011 American Chemical Society

Pyridine synthesis by reactions of allyl amines and alkynes proceeding through a Cu(OAc)2 oxidation and Rh(III)-catalyzed N-annulation sequence.

Science.gov (United States)

Kim, Dong-Su; Park, Jung-Woo; Jun, Chul-Ho

2012-11-28

A new methodology has been developed for the synthesis of pyridines from allyl amines and alkynes, which involves sequential Cu(II)-promoted dehydrogenation of the allylamine and Rh(III)-catalyzed N-annulation of the resulting α,β-unsaturated imine and alkyne.

Antitumor effect and toxicity of free rhodium (II) citrate and rhodium (II) citrate-loaded maghemite nanoparticles in mice bearing breast cancer.

Science.gov (United States)

Carneiro, Marcella Lemos Brettas; Peixoto, Raphael C A; Joanitti, Graziela A; Oliveira, Ricardo G S; Telles, Luis A M; Miranda-Vilela, Ana L; Bocca, Anamélia L; Vianna, Leonora M S; da Silva, Izabel C R; de Souza, Aparecido R; Lacava, Zulmira G M; Báo, Sônia N

2013-02-16

Magnetic fluids containing superparamagnetic iron oxide nanoparticles represent an attractive platform as nanocarriers in chemotherapy. Recently, we developed a formulation of maghemite nanoparticles coated with rhodium (II) citrate, which resulted in in vitro cytotoxicity enhanced up to 4.6 times when compared to free rhodium (II) citrate formulation on breast carcinoma cells. In this work, we evaluate the antitumor activity and toxicity induced by these formulations in Balb/c mice bearing orthotopic 4T1 breast carcinoma. Mice were evaluated with regard to the treatments' toxicity through analyses of hemogram, serum levels of alanine aminotransferase, iron, and creatinine; DNA fragmentation and cell cycle of bone marrow cells; and liver, kidney and lung histology. In addition, the antitumor activity of rhodium (II) citrate and maghemite nanoparticles coated with rhodium (II) citrate was verified by tumor volume reduction, histology and immunohistochemistry. Regarding the treatments' toxicity, no experimental groups had alterations in levels of serum ALT or creatinine, and this suggestion was corroborated by the histopathologic examination of liver and kidney of mice. Moreover, DNA fragmentation frequency of bone marrow cells was lower than 15% in all experimental groups. On the other hand, the complexes rhodium (II) citrate-functionalized maghemite and free rhodium (II) citrate led to a marked growth inhibition of tumor and decrease in CD31 and Ki-67 staining. In summary, we demonstrated that both rhodium (II) citrate and maghemite nanoparticles coated with rhodium (II) citrate formulations exhibited antitumor effects against 4T1 metastatic breast cancer cell line following intratumoral administration. This antitumor effect was followed by inhibition of both cell proliferation and microvascularization and by tumor tissue injury characterized as necrosis and fibrosis. Remarkably, this is the first published report demonstrating the therapeutic efficacy of maghemite

Gold nanoparticles on OMS-2 for heterogeneously catalyzed aerobic oxidative α,β-dehydrogenation of β-heteroatom-substituted ketones.

Science.gov (United States)

Yoshii, Daichi; Jin, Xiongjie; Yatabe, Takafumi; Hasegawa, Jun-Ya; Yamaguchi, Kazuya; Mizuno, Noritaka

2016-12-06

In the presence of Au nanoparticles supported on manganese oxide OMS-2 (Au/OMS-2), various kinds of β-heteroatom-substituted α,β-unsaturated ketones (heteroatom = N, O, S) can be synthesized through α,β-dehydrogenation of the corresponding saturated ketones using O 2 (in air) as the oxidant. The catalysis of Au/OMS-2 is truly heterogeneous, and the catalyst can be reused.

Measurement of the hyperfine magnetic field on rhodium in chromium

International Nuclear Information System (INIS)

Peretto, P.; Teisseron, G.; Berthier, J.

1978-01-01

Hyperfine magnetic field of rhodium in a chromium matrix is studied. Anisotropy of rhodium 100 is + 0.17. Time dependence of angular correlation is given with a sample containing 145 ppm of rhodium despite the short life [fr

Rhodium complexes as therapeutic agents.

Science.gov (United States)

Ma, Dik-Lung; Wang, Modi; Mao, Zhifeng; Yang, Chao; Ng, Chan-Tat; Leung, Chung-Hang

2016-02-21

The landscape of inorganic medicinal chemistry has been dominated by the investigation of platinum, and to a lesser extent ruthenium, complexes over the past few decades. Recently, complexes based on other metal centers such as rhodium have attracted attention due to their tunable chemical and biological properties as well as distinct mechanisms of action. This perspective highlights recent examples of rhodium complexes that show diverse biological activities against various targets, including enzymes and protein-protein interactions.

Current-induced runaway vibrations in dehydrogenated graphene nanoribbons

DEFF Research Database (Denmark)

Christensen, Rasmus Bjerregaard; Lu, Jing Tao; Hedegard, Per

2016-01-01

We employ a semi-classical Langevin approach to study current-induced atomic dynamics in a partially dehydrogenated armchair graphene nanoribbon. All parameters are obtained from density functional theory. The dehydrogenated carbon dimers behave as effective impurities, whose motion decouples from...

Current-induced runaway vibrations in dehydrogenated graphene nanoribbons

DEFF Research Database (Denmark)

Christensen, Rasmus Bjerregaard; Lu, Jing Tao; Hedegard, Per

2016-01-01

We employ a semi-classical Langevin approach to study current-induced atomic dynamics in a partially dehydrogenated armchair graphene nanoribbon. All parameters are obtained from density functional theory. The dehydrogenated carbon dimers behave as effective impurities, whose motion decouples fro...

Synthesis of phenanthridines via palladium-catalyzed picolinamide-directed sequential C–H functionalization

Directory of Open Access Journals (Sweden)

Ryan Pearson

2013-05-01

Full Text Available We report a new synthesis of phenanthridines based on palladium-catalyzed picolinamide-directed sequential C–H functionalization reactions starting from readily available benzylamine and aryl iodide precursors. Under the catalysis of Pd(OAc2, the ortho-C–H bond of benzylpicolinamides is first arylated with an aryl iodide. The resulting biaryl compound is then subjected to palladium-catalyzed picolinamide-directed intramolecular dehydrogenative C–H amination with PhI(OAc2 oxidant to form the corresponding cyclized dihydrophenanthridines. The benzylic position of these dihydrophenanthridines could be further oxidized with Cu(OAc2, removing the picolinamide group and providing phenathridine products. The cyclization and oxidation could be carried out in a single step and afford phenathridines in moderate to good yields.

Desaturation reactions catalyzed by soluble methane monooxygenase.

Science.gov (United States)

Jin, Y; Lipscomb, J D

2001-09-01

Soluble methane monooxygenase (MMO) is shown to be capable of catalyzing desaturation reactions in addition to the usual hydroxylation and epoxidation reactions. Dehydrogenated products are generated from MMO-catalyzed oxidation of certain substrates including ethylbenzene and cyclohexadienes. In the reaction of ethylbenzene, desaturation of ethyl C-H occurred along with the conventional hydroxvlations of ethyl and phenyl C-Hs. As a result, styrene is formed together with ethylphenols and phenylethanols. Similarly, when 1,3- and 1,4-cyclohexadienes were used as substrates, benzene was detected as a product in addition to the corresponding alcohols and epoxides. In all cases, reaction conditions were found to significantly affect the distribution among the different products. This new activity of MMO is postulated to be associated with the chemical properties of the substrates rather than fundamental changes in the nature of the oxygen and C-H activation chemistries. The formation of the desaturated products is rationalized by formation of a substrate cationic intermediate, possibly via a radical precursor. The cationic species is then proposed to partition between recombination (alcohol formation) and elimination (alkene production) pathways. This novel function of MMO indicates close mechanistic kinship between the hydroxylation and desaturation reactions catalyzed by the nonheme diiron clusters.

Cyclopentadiene-mediated hydride transfer from rhodium complexes.

Science.gov (United States)

Pitman, C L; Finster, O N L; Miller, A J M

2016-07-12

Attempts to generate a proposed rhodium hydride catalytic intermediate instead resulted in isolation of (Cp*H)Rh(bpy)Cl (1), a pentamethylcyclopentadiene complex, formed by C-H bond-forming reductive elimination from the fleeting rhodium hydride. The hydride transfer ability of diene 1 was explored through thermochemistry and hydride transfer reactions, including the reduction of NAD(+).

Kinetic method of determination of rhodium trace amounts

International Nuclear Information System (INIS)

Kalinina, V.E.; Lyakushina, V.M.; Rybina, A.E.

1978-01-01

A catalytic action of rhodium compounds has been detected and studied in the reaction of copper (2) tellurate oxidation with hypobromite to ditelluratocuprate (3) in an alkaline medium. The relationships between the reaction rate and concentrations of copper, tellurate, and hypobromite have been established. The optimum concentrations of the used compounds have been found: Csub(Cu(2))=4x10 -5 g-ion/l; Csub(OHsup(-))=3.0 g-ion/l; Csub(Te)=1.4x10 -2 g-ion/l; Csub(NaBrO)=2.17x10 -3 M. It has been established for chloride, sulphate, and perchlorate solutions of rhodium (3) and (4) that the reaction sensitivity increases by 2-3-fold with a temperature rise from 25-60 deg C. The technique of determining rhodium traces has been developed based on its catalytic action. The low limit of determined rhodium amounts is about 10 -3 mkg/ml

The effects of primary beam filters on the analysis of rhodium and cadmium using a rhodium target x-ray tube

International Nuclear Information System (INIS)

Anzelmo, J.A.; Boyer, B.W.

1986-01-01

Since its introduction in 1964, the thin end-window rhodium target x-ray tube has been considered to be an excellent general purpose source of excitation. Heavy elements are efficiently excited by high Bremsstrahlung and the K lines of rhodium while the light elements are excited by the L lines of rhodium. The ability to efficiently excite both heavy and light elements is essential to special applications such as auto catalysts, which are composed of precious metals in a clay-like matrix. Close control of the light elements, including sodium, phosphorous, aluminum and silicon, and the heavy element precious metals, such as rhodium, are necessary to keep operating characteristics and manufacturing expense at desired levels. A quick survey of typical x-ray tube targets shows that some targets are more efficient for light elements while others are more efficient for heavy elements. The few general purpose x-ray tubes that are available have characteristic lines which overlap on elements to be determined. The rhodium target, which is a good excitation source for most of the elements mentioned, contains line overlaps on cadmium (RHKB) and rhodium (RHKA). When using a sequential wavelength dispersive XRF spectrometer, the characteristic lines of the tube scattered from the sample can be removed by a programmable primary beam filter having an absorption edge just higher in wavelength than the wavelengths to be removed. The thickness and composition of the filter, as well as the choice of KV and MA, will determine the operating parameter necessary to achieve the optimum precision and lowest limits of detection. For this study, synthetic samples are made up using Kaolin as the matrix

Electronic and magnetic properties of ultrathin rhodium nanowires

CERN Document Server

Wang Bao Lin; Ren-Yun; Sun Hou Qian; Chen Xiao Shuang; Zhao Ji Jun

2003-01-01

The structures of ultrathin rhodium nanowires are studied using empirical molecular dynamics simulations with a genetic algorithm. Helical multishell cylindrical and pentagonal packing structures are found. The electronic and magnetic properties of the rhodium nanowires are calculated using an spd tight-binding Hamiltonian in the unrestricted Hartree-Fock approximation. The average magnetic moment and electronic density of states are obtained. Our results indicate that the electronic and magnetic properties of the rhodium nanowires depend not only on the size of the wire but also on the atomic structure. In particular, centred pentagonal and hexagonal structures can be unusually ferromagnetic.

Rhodium mediated bond activation: from synthesis to catalysis

Energy Technology Data Exchange (ETDEWEB)

Ho, Hung-An [Iowa State Univ., Ames, IA (United States)

2012-01-01

alcohols have been investigated as well. The proposed mechanism is based on the stochiometric reactions of the possible metal and organic intermediates. Primary amines, hypothesized to undergo a similar reaction pathway, have been verified to give dehydrogenative coupling product, imines. In the end, the well-developed neutral tridentate Tpm coordinates to the rhodium bis(ethylene) dimer in the presence of TlPF₆ to give the cationic complex, [TpmRh(C₂H₄)₂][PF₆] (5.1). 5.1 serves as the first example of explicit determination of the solid state hapticity, evidenced by X-ray structure, among all the cationic Tpm^RM(C₂H₄)₂⁺ (Tpm^R = Tpm, Tpm*, M = Rh, Ir) derivatives. The substitution chemistry of this compound has been studied by treating with soft and hard donors. The trimethylphosphine-sbustituted complex activates molecular hydrogen to give the dihydride compound.

Base metal dehydrogenation of amine-boranes

Science.gov (United States)

Blacquiere, Johanna Marie [Ottawa, CA; Keaton, Richard Jeffrey [Pearland, TX; Baker, Ralph Thomas [Los Alamos, NM

2009-06-09

A method of dehydrogenating an amine-borane having the formula R.sup.1H.sub.2N--BH.sub.2R.sup.2 using base metal catalyst. The method generates hydrogen and produces at least one of a [R.sup.1HN--BHR.sup.2].sub.m oligomer and a [R.sup.1N--BR.sup.2].sub.n oligomer. The method of dehydrogenating amine-boranes may be used to generate H.sub.2 for portable power sources, such as, but not limited to, fuel cells.

Synthesis of Arylthiopyrimidines by Copper-catalyzed Aerobic Oxidative C-S Cross-coupling

Energy Technology Data Exchange (ETDEWEB)

Lee, Ok Suk; Kim, Hyeji; Sohn, Jeong-Hun [Chungnam National University, Daejeon (Korea, Republic of); Lee, Hee-Seung [KAIST, Daejeon (Korea, Republic of); Shin, Hyunik [Yonsung Fine Chemicals R and D Center, Suwon (Korea, Republic of)

2016-02-15

Copper-catalyzed C–S cross-coupling reactions have been considered as powerful tools in synthetic chemistry and utilized for diverse heterocycle syntheses. In the reactions, the aspects of no need of ligands has been particular advantage over other metal catalysis. We have developed a Cu-catalyzed cascade reaction for the synthesis of fully substituted 2-arylthiopyrimidines from 3,4-dihydropyrimidine-2(1H)-thiones (DHPMs) under aerobic conditions. This cascade reaction of DHPM with aryl iodide proceeds presumably via sequential tautomerization, C–S cross-coupling, and oxidative dehydrogenation (oxidation followed by elimination). Considering that DHPM substrates were easily synthesized by Biginelli three component coupling reaction of aryl aldehyde, β-ketoester, and thiourea, the present method provides a direct access toward diverse 2-arylthiopyrimidines which have been used as a prominent substructure of drug molecules.

The synthesis of benzimidazoles and quinoxalines from aromatic diamines and alcohols by iridium-catalyzed acceptorless dehydrogenative alkylation.

Science.gov (United States)

Hille, Toni; Irrgang, Torsten; Kempe, Rhett

2014-05-05

Benzimidazoles and quinoxalines are important N-heteroaromatics with many applications in pharmaceutical and chemical industry. Here, the synthesis of both classes of compounds starting from aromatic diamines and alcohols (benzimidazoles) or diols (quinoxalines) is reported. The reactions proceed through acceptorless dehydrogenative condensation steps. Water and two equivalents of hydrogen are liberated in the course of the reactions. An Ir complex stabilized by the tridentate P^N^P ligand N(2) ,N(6) -bis(di-isopropylphosphino)pyridine-2,6-diamine revealed the highest catalytic activity for both reactions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Size and Site Dependence of the Catalytic Activity of Iridium Clusters toward Ethane Dehydrogenation.

Science.gov (United States)

Ge, Yingbin; Jiang, Hao; Kato, Russell; Gummagatta, Prasuna

2016-12-01

This research focuses on optimizing transition metal nanocatalyst immobilization and activity to enhance ethane dehydrogenation. Ethane dehydrogenation, catalyzed by thermally stable Ir n (n = 8, 12, 18) atomic clusters that exhibit a cuboid structure, was studied using the B3LYP method with triple-ζ basis sets. Relativistic effects and dispersion corrections were included in the calculations. In the dehydrogenation reaction Ir n + C 2 H 6 → H-Ir n -C 2 H 5 → (H) 2 -Ir n -C 2 H 4 , the first H-elimination is the rate-limiting step, primarily because the reaction releases sufficient heat to facilitate the second H-elimination. The catalytic activity of the Ir clusters strongly depends on the Ir cluster size and the specific catalytic site. Cubic Ir 8 is the least reactive toward H-elimination in ethane: Ir 8 + C 2 H 6 → H-Ir 8 -C 2 H 5 has a large (65 kJ/mol) energy barrier, whereas Ir 12 (3 × 2 × 2 cuboid) and Ir 18 (3 × 3 × 2 cuboid) lower this energy barrier to 22 and 3 kJ/mol, respectively. The site dependence is as prominent as the size effect. For example, the energy barrier for the Ir 18 + C 2 H 6 → H-Ir 18 -C 2 H 5 reaction is 3, 48, and 71 kJ/mol at the corner, edge, or face-center sites of the Ir 18 cuboid, respectively. Energy release due to Ir cluster insertion into an ethane C-H bond facilitates hydrogen migration on the Ir cluster surface, and the second H-elimination of ethane. In an oxygen-rich environment, oxygen molecules may be absorbed on the Ir cluster surface. The oxygen atoms bonded to the Ir cluster surface may slightly increase the energy barrier for H-elimination in ethane. However, the adsorption of oxygen and its reaction with H atoms on the Ir cluster releases sufficient heat to yield an overall thermodynamically favored reaction: Ir n + C 2 H 6 + 1 / 2 O 2 → Ir n + C 2 H 4 + H 2 O. These results will be useful toward reducing the energy cost of ethane dehydrogenation in industry.

Asymmetric Chemoenzymatic Reductive Acylation of Ketones by a Combined Iron-Catalyzed Hydrogenation-Racemization and Enzymatic Resolution Cascade

KAUST Repository

El-Sepelgy, Osama

2017-02-28

A general and practical process for the conversion of prochiral ketones into the corresponding chiral acetates has been realized. An iron carbonyl complex is reported to catalyze the hydrogenation-dehydrogenation-hydrogenation of prochiral ketones. By merging the iron-catalyzed redox reactions with enantioselective enzymatic acylations a wide range of benzylic, aliphatic and (hetero)aromatic ketones, as well as diketones, were reductively acylated. The corresponding products were isolated with high yields and enantioselectivities. The use of an iron catalyst together with molecular hydrogen as the hydrogen donor and readily available ethyl acetate as acyl donor make this cascade process highly interesting in terms of both economic value and environmental credentials.

Total synthesis of fluoxetine and duloxetine through an in situ imine formation/borylation/transimination and reduction approach.

Science.gov (United States)

Calow, Adam D J; Fernández, Elena; Whiting, Andrew

2014-08-28

We report efficient, catalytic, asymmetric total syntheses of both (R)-fluoxetine and (S)-duloxetine from α,β-unsaturated aldehydes conducting five sequential one-pot steps (imine formation/copper mediated β-borylation/transimination/reduction/oxidation) followed by the specific ether group formation which deliver the desired products (R)-fluoxetine in 45% yield (96% ee) and (S)-duloxetine in 47% yield (94% ee).

Quantification of Rhodium in a Series of Inorganic and ...

African Journals Online (AJOL)

NICO

... such as rhodium hydridocarbonyl tristriphenylphosphine, [HRh(CO)(PPh3)3], .... The selection of the most suitable wavelengths for rhodium, yttrium and cobalt ... chloride ions were removed from the CRM samples as chlorine gas with the ...

Noble metal-catalyzed homogeneous and heterogeneous processes in treating simulated nuclear waste media with formic acid

International Nuclear Information System (INIS)

King, R.B.; Bhattacharyya, N.K.; Smith, H.D.

1995-09-01

Simulants for the Hanford Waste Vitrification Plant feed containing the major non-radioactive components Al, Cd, Fe, Mn, Nd, Ni, Si, Zr, Na, CO 3 2 -, NO 3 -, and NO 2 - were used to study reactions of formic acid at 90 degrees C catalyzed by the noble metals Ru, Rh, and/or Pd found in significant quantities in uranium fission products. Such reactions were monitored using gas chromatography to analyze the CO 2 , H 2 , NO, and N 2 O in the gas phase and a microammonia electrode to analyze the NH 4 +/NH 3 in the liquid phase as a function of time. The following reactions have been studied in these systems since they are undesirable side reactions in nuclear waste processing: (1) Decomposition of formic acid to CO 2 + H 2 is undesirable because of the potential fire and explosion hazard of H 2 . Rhodium, which was introduced as soluble RhCl 3 -3H 2 O, was found to be the most active catalyst for H 2 generation from formic acid above ∼ 80 degrees C in the presence of nitrite ion. The H 2 production rate has an approximate pseudo first-order dependence on the Rh concentration, (2) Generation of NH 3 from the formic acid reduction of nitrate and/or nitrite is undesirable because of a possible explosion hazard from NH 4 NO 3 accumulation in a waste processing plant off-gas system. The Rh-catalyzed reduction of nitrogen-oxygen compounds to ammonia by formic acid was found to exhibit the following features: (a) Nitrate rather than nitrite is the principal source of NH 3 . (b) Ammonia production occurs at the expense of hydrogen production. (c) Supported rhodium metal catalysts are more active than rhodium in any other form, suggesting that ammonia production involves heterogeneous rather than homogeneous catalysis

trans-[Pt(BCat')Me(PCy3)2]: an experimental case study of reductive elimination processes in Pt-Boryls through associative mechanisms.

Science.gov (United States)

Braunschweig, Holger; Bertermann, Rüdiger; Brenner, Peter; Burzler, Michael; Dewhurst, Rian D; Radacki, Krzysztof; Seeler, Fabian

2011-10-10

A stable trans-(alkyl)(boryl) platinum complex trans-[Pt(BCat')Me(PCy(3))(2)] (Cat'=Cat-4-tBu; Cy=cyclohexyl=C(6)H(11)) was synthesised by salt metathesis reaction of trans-[Pt(BCat')Br(PCy(3))(2)] with LiMe and was fully characterised. Investigation of the reactivity of the title compound showed complete reductive elimination of Cat'BMe at 80 °C within four weeks. This process may be accelerated by the addition of a variety of alkynes, thereby leading to the formation of the corresponding η(2) -alkyne platinum complexes, of which [Pt(η(2)-MeCCMe)(PCy(3))(2)] was characterised by X-ray crystallography. Conversion of the trans-configured title compound to a cis derivative remained unsuccessful due to an instantaneous reductive elimination process during the reaction with chelating phosphines. Treatment of trans-[Pt(BCat')Me(PCy(3))(2)] with Cat(2)B(2) led to the formation of CatBMe and Cat'BMe. In the course of further investigations into this reaction, indications for two indistinguishable reaction mechanisms were found: 1) associative formation of a six-coordinate platinum centre prior to reductive elimination and 2) σ-bond metathesis of B-B and C-Pt bonds. Mechanism 1 provides a straightforward explanation for the formation of both methylboranes. Scrambling of diboranes(4) Cat(2)B(2) and Cat'(2)B(2) in the presence of [Pt(PCy(3))(2)], fully reductive elimination of CatBMe or Cat'BMe from trans-[Pt(BCat')Me(PCy(3))(2)] in the presence of sub-stoichiometric amounts of Cat(2)B(2), and evidence for the reversibility of the oxidative addition of Cat(2)B(2) to [Pt(PCy(3))(2)] all support mechanism 2, which consists of sequential equilibria reactions. Furthermore, the solid-state molecular structure of cis-[Pt(BCat)(2)(PCy(3))(2)] and cis-[Pt(BCat')(2)(PCy(3))(2)] were investigated. The remarkably short B-B separations in both bis(boryl) complexes suggest that the two boryl ligands in each case are more loosely bound to the Pt(II) centre than in related bis(boryl

An Extended X-ray Absorption Fine Structure Study of Rhodium-Oxygen Bonds in a Highly Dispersed Rhodium/Aluminum Oxide Catalyst

NARCIS (Netherlands)

Koningsberger, D.C.; Zon, J.B.A.D. van; Blik, H.F.J. van 't; Visser, G.J.; Prins, R.; Mansour, A.N.; Sayers, D.E.; Short, D.R.

1985-01-01

Analysis of in situ EXAFS measurements on a 2.4 wt % Rh/A120, catalyst, reduced at 473 K after calcination at 623 K, shows the presence of two different rhodium-oxygen bonds (viz. 2.05 and 2.68 A). The oxygen neighbors of rhodium at a distance of 2.05 A disappear after reduction at 673 K. The

Manganese-Catalyzed Aminomethylation of Aromatic Compounds with Methanol as a Sustainable C1 Building Block.

Science.gov (United States)

Mastalir, Matthias; Pittenauer, Ernst; Allmaier, Günter; Kirchner, Karl

2017-07-05

This study represents the first example of a manganese-catalyzed environmentally benign, practical three-component aminomethylation of activated aromatic compounds including naphtols, phenols, pyridines, indoles, carbazoles, and thiophenes in combination with amines and MeOH as a C1 source. These reactions proceed with high atom efficiency via a sequence of dehydrogenation and condensation steps which give rise to selective C-C and C-N bond formations, thereby releasing hydrogen and water. A well-defined hydride Mn(I) PNP pincer complex, recently developed in our laboratory, catalyzes this process in a very efficient way, and a total of 28 different aminomethylated products were synthesized and isolated yields of up to 91%. In a preliminary study, a related Fe(II) PNP pincer complex was shown to catalyze the methylation of 2-naphtol rather than its aminomethylation displaying again the divergent behavior of isoelectronic Mn(I) and Fe(II) PNP pincer systems.

Dehydrogenation mechanism of LiBH{sub 4} by Poly(methyl methacrylate)

Energy Technology Data Exchange (ETDEWEB)

Huang, Jianmei [School of Materials Science and Engineering, and Key Laboratory of Advanced Energy Storage Materials of Guangdong Province, South China University of Technology, Guangzhou 510641 (China); China-Australia Joint Laboratory for Energy & Environmental Materials, South China University of Technology, Guangzhou 510641 (China); Yan, Yurong [School of Materials Science and Engineering, and Key Laboratory of Advanced Energy Storage Materials of Guangdong Province, South China University of Technology, Guangzhou 510641 (China); Ouyang, Liuzhang, E-mail: meouyang@scut.edu.cn [School of Materials Science and Engineering, and Key Laboratory of Advanced Energy Storage Materials of Guangdong Province, South China University of Technology, Guangzhou 510641 (China); China-Australia Joint Laboratory for Energy & Environmental Materials, South China University of Technology, Guangzhou 510641 (China); Key Laboratory for Fuel Cell Technology in Guangdong Province, South China University of Technology, Guangzhou 510641 (China); Wang, Hui [School of Materials Science and Engineering, and Key Laboratory of Advanced Energy Storage Materials of Guangdong Province, South China University of Technology, Guangzhou 510641 (China); China-Australia Joint Laboratory for Energy & Environmental Materials, South China University of Technology, Guangzhou 510641 (China); Zhu, Min, E-mail: memzhu@scut.edu.cn [School of Materials Science and Engineering, and Key Laboratory of Advanced Energy Storage Materials of Guangdong Province, South China University of Technology, Guangzhou 510641 (China); China-Australia Joint Laboratory for Energy & Environmental Materials, South China University of Technology, Guangzhou 510641 (China)

2015-10-05

Highlights: • LiBH{sub 4} is amorphous after modified with PMMA. • Dehydrogenation temperature of LiBH{sub 4} decreases by 120 °C after modifying with PMMA. • The LiBH{sub 4}@PMMA composite releases 10 wt.% hydrogen at 360 °C within 1 h. • C=O group of PMMA weakens the B−H bonds to lower dehydrogenation temperature. - Abstract: We investigated the dehydrogenation properties and mechanism of Poly(methyl methacrylate) (PMMA) confined LiBH{sub 4}. Thermal stability of LiBH{sub 4} was reduced by PMMA, with a decrease in dehydrogenation temperature by 120 °C. At 360 °C, the composite showed fast dehydrogenation kinetics with 10 wt.% of hydrogen released within 1 h. The improved dehydrogenation performance was mainly attributed to the reaction between LiBH{sub 4} and PMMA forming Li{sub 3}BO{sub 3} as a final product. Furthermore, the presence of electrostatic interaction between B atom of LiBH{sub 4} and O atom in the carbonyl group of PMMA may weaken the B−H bonding of [BH{sub 4}]{sup −} and lower the hydrogen desorption temperature.

First-principles study of hydrogen diffusion in transition metal Rhodium

International Nuclear Information System (INIS)

Bao, Wulijibilige; Cui, Xin; Wang, Zhi-Ping

2015-01-01

In this study, the diffuse pattern and path of hydrogen in transition metal rhodium are investigated by the first-principles calculations. Density functional theory is used to calculate the system energies of hydrogen atom occupying different positions in rhodium crystal lattice. The results indicate that the most stable position of hydrogen atom in rhodium crystal lattice locates at the octahedral interstice, and the tetrahedral interstice is the second stable site. The activation barrier energy for the diffusion of atomic hydrogen in transition metal rhodium is quantified by determining the most favorable path, i.e., the minimum-energy pathway for diffusion, that is the indirect octahedral-tetrahedral-octahedral (O-T-O) pathway, and the activation energy is 0.8345eV

Chemical Posttranslational Modification with Designed Rhodium(II) Catalysts.

Science.gov (United States)

Martin, S C; Minus, M B; Ball, Z T

2016-01-01

Natural enzymes use molecular recognition to perform exquisitely selective transformations on nucleic acids, proteins, and natural products. Rhodium(II) catalysts mimic this selectivity, using molecular recognition to allow selective modification of proteins with a variety of functionalized diazo reagents. The rhodium catalysts and the diazo reactivity have been successfully applied to a variety of protein folds, the chemistry succeeds in complex environments such as cell lysate, and a simple protein blot method accurately assesses modification efficiency. The studies with rhodium catalysts provide a new tool to study and probe protein-binding events, as well as a new synthetic approach to protein conjugates for medical, biochemical, or materials applications. © 2016 Elsevier Inc. All rights reserved.

Kalman filtering for rhodium self-powered neutron detectors

International Nuclear Information System (INIS)

Kantrowitz, M.L.

1988-01-01

Rhodium self-powered neutron detectors are utilized in many pressurized water reactors to determine the neutronic behavior within the core. In order to compensate for the inherent time delay associated with the response of these detectors, a dynamic compensation algorithm is currently used in Combustion Engineering plants to reconstruct the dynamic flux signal which is being sensed by the rhodium detectors. This paper describes a new dynamic compensation algorithm, based on Kalman filtering, which improves on the noise gain and response time characteristics of the algorithm currently used, and offers the possibility of utilizing the proven rhodium detector based fixed in-core detector system as an integral part of advanced core control and/or protection systems

Block copolymer lithography of rhodium nanoparticles for high temperature electrocatalysis.

Science.gov (United States)

Boyd, David A; Hao, Yong; Li, Changyi; Goodwin, David G; Haile, Sossina M

2013-06-25

We present a method for forming ordered rhodium nanostructures on a solid support. The approach makes use of a block copolymer to create and assemble rhodium chloride nanoparticles from solution onto a surface; subsequent plasma and thermal processing are employed to remove the polymer and fully convert the nanostructures to metallic rhodium. Films cast from a solution of the triblock copolymer poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) dissolved in toluene with rhodium(III) chloride hydrate were capable of producing a monolayer of rhodium nanoparticles of uniform size and interparticle spacing. The nanostructures were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. The electrocatalytic performance of the nanoparticles was investigated with AC impedance spectroscopy. We observed that the addition of the particles to a model solid oxide fuel cell anode provided up to a 14-fold improvement in the anode activity as evidenced by a decrease in the AC impedance resistance. Examination of the anode after electrochemical measurement revealed that the basic morphology and distribution of the particles were preserved.

The dehydrogenation performance and reaction mechanisms of Li{sub 3}AlH{sub 6} with TiF{sub 3} additive

Energy Technology Data Exchange (ETDEWEB)

Liu, Shu-Sheng [Materials and Thermochemistry Laboratory, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Graduate School of Chinese Academy of Sciences, Beijing 100049 (China); Zhang, Yao; Sun, Li-Xian; Zhang, Jian; Zhao, Jun-Ning [Materials and Thermochemistry Laboratory, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Xu, Fen [Faculty of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian 116029 (China); Huang, Feng-Lei [State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081 (China)

2010-05-15

For Li{sub 3}AlH{sub 6} prepared by mechanical milling method, the dissociation reaction enthalpy and activation energy are calculated to be 22.1 kJ mol{sup -1} H{sub 2} and 133.7 {+-} 2.7 kJ mol{sup -1}, respectively. The dehydrogenation performance of Li{sub 3}AlH{sub 6} is greatly enhanced by TiF{sub 3} additive, especially in the kinetic behaviors. For the Li{sub 3}AlH{sub 6} + 10 mol% TiF{sub 3} sample, the starting temperature of dehydrogenation is obviously decreased by 60 C from that of pure Li{sub 3}AlH{sub 6} (190 C), and 3.0 wt.% H{sub 2} may be released within 1000 s at 120 C under an initial vacuum. With the amount of TiF{sub 3} increasing, the starting temperature decreases and the kinetics improves due to the decrease in the activation energy. The X-ray diffraction (XRD) together with thermogravimetric analysis (TGA) results show that there are three mechanochemical reactions involved during milling: i) Li{sub 3}AlH{sub 6} + TiF{sub 3} {yields} 3 LiF + Al + Ti + 3H{sub 2}, ii) Ti + H{sub 2} {yields} TiH{sub 2}, iii) 3 Al + Ti {yields} Al{sub 3}Ti. The in-situ formed Ti species (TiH{sub 2} and Al{sub 3}Ti) co-catalyze the thermal dehydrogenation of Li{sub 3}AlH{sub 6}. (author)

Rhodium(I)-catalyzed cycloisomerization of benzylallene-alkynes through C-H activation.

Science.gov (United States)

Kawaguchi, Yasuaki; Yasuda, Shigeo; Kaneko, Akira; Oura, Yuki; Mukai, Chisato

2014-07-14

The efficient Rh(I)-catalyzed cycloisomerization of benzylallene-alkynes produced the tricyclo[9.4.0.0(3,8)]pentadecapentaene skeleton through a C(sp2)-H bond activation in good yields. A plausible reaction mechanism proceeds via oxidative addition of the acetylenic C-H bond to Rh(I), an ene-type cyclization to the vinylidenecarbene-Rh(I) intermediate, and an electrophilic aromatic substitution with the vinylidenecarbene species. It was proposed based on deuteration and competition experiments. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dinuclear ditertiary phosphite derivatives of rhodium

International Nuclear Information System (INIS)

Meintjies, E.

1981-08-01

The overall objective of the research described in this thesis was the design, synthesis, characterization and chemistry of dinuclear complexes of rhodium in which the metal atoms are held in close proximity to each other. Complexes of this nature are of considerable interest owing, in part, to their potential as models for multicentred metal catalysts, as well as to the highly novel and unusual chemistry already discovered for a number of them. A survey of dinuclear complexes of rhodium containing carbonyl and group V donor ligands has been presented as a background introduction to the research reported in this thesis. The coordination behaviour of the diphosphazane ligands, (RO) 2 PN(R')P(OR) 2 (R=Ph or Me, R' = Et; R = Et or Pr/i, R' = Me), and the ditertiary phosphite ligand, (EtO) 2 POP(OEt) 2 , towards certain rhodium precursors has been investigated. A number of highly unusual neutral dinuclear complexes of rhodium, in which these ligands bridge-bond the two rhodium atoms, have been synthesized. Two types of monocarbonyl decarbonylation products are observed for compounds of the type, [Rh 2 Cl 2 (CO) 2 (μ-diphosphazane) 2 ]. 1 H and 31 P[ 1 H] n.m.r. spectral studies have been carried out with the object of establishing the nature of the bridging halogen ligands in the tricarbonyl species. Asymetric zerovalent dinuclear species of the type, [Rh 2 (CO) 3 -[μ-(RO) 2 PN(R')P(OR) 2 ] 2 ] (R = Ph or Me, R' = Et; R = Pr/i, R' = Me), are obtained. A single crystal X-ray analysis has been carried out. Homoleptic cationic species are obtained by reaction of the alkoxydiphosphazane ligands with [Rh(C 8 H 12 )(solvent)(n)] + under the appropriate reaction conditions. The solution and solid-state infrared spectra and the 31 P[ 1 H] n.m.r. spectra of all new compounds synthesized in this study are discussed in terms of possible structures for these compounds. Where appropriate, the n.m.r. spectral data are also discussed in terms of fluxional behaviour

Green synthesis of Ni-Nb oxide catalysts for low-temperature oxidative dehydrogenation of ethane

KAUST Repository

Zhu, Haibo

2015-03-05

The straightforward solid-state grinding of a mixture of Ni nitrate and Nb oxalate crystals led to, after mild calcination (T<400°C), nanostructured Ni-Nb oxide composites. These new materials efficiently catalyzed the oxidative dehydrogenation (ODH) of ethane to ethylene at a relatively low temperature (T<300°C). These catalysts appear to be much more stable than the corresponding composites prepared by other chemical methods; more than 90% of their original intrinsic activity was retained after 50h with time on-stream. Furthermore, the stability was much less affected by the Nb content than in composites prepared by classical "wet" syntheses. These materials, obtained in a solvent-free way, are thus promising green and sustainable alternatives to the current Ni-Nb candidates for the low-temperature ODH of ethane.

Industrial tests of rhodium self-powered detectors: the Golfech 2 experimentation

International Nuclear Information System (INIS)

Mourlevat, J.L.; Janvier, D.; Warren, H.D.

2000-01-01

In co-operation with Electricite de France (EDF), FRAMATOME has been testing two in-core strings which are equipped with rhodium self-powered detectors (SPDs) in the Golfech Unit 2 reactor (1300 MW, 4L plant) since August 1997. The rhodium SPDs and the strings which support them were designed and built by the US FRAMATOME subsidiary FRAMATOME-COGEMA-FUEL (FCF). The rhodium signals and some other plant parameters are acquired through the use of a specific device designed by the CEA (Commissariat a l'Energie Atomique) and are processed off-line by FRAMATOME. This demonstration test is planned to last until mid-2000. The following presentation is focused on the results obtained during the first demonstration cycle (from 08/97 to 12/98). The tests that have been conducted consist of checking the rhodium depletion and of comparing the rhodium signals to the movable probes. In order to compensate for the delay in the rhodium signals, a deconvolution algorithm has also been tested. Up to now, the results are very satisfactory and a future large scale industrial application is being discussed with the EDF. The main objective of the next experimentation phase is to test - under industrial conditions - a prototype of an on-line monitoring unit known as the Partial In-Core Monitoring System (PIMS). This system will include 16 rhodium in-core strings and will use an on-line 3-D core model. (authors)

Iridium‐Catalyzed Condensation of Amines and Vicinal Diols to Substituted Piperazines

DEFF Research Database (Denmark)

Lorentz-Petersen, Linda Luise Reeh; Nordstrøm, Lars Ulrik Rubæk; Madsen, Robert

2012-01-01

is believed to involve dehydrogenation of the 1,2‐diol to the α‐hydroxy aldehyde, which condenses with the amine to form the α‐hydroxy imine. The latter rearranges to the corresponding α‐amino carbonyl compound, which then reacts with another amine followed by reduction of the resulting imine.......A straightforward procedure is described for the synthesis of piperazines from amines and 1,2‐diols. The heterocyclization is catalyzed by [Cp*IrCl2]2 and sodium hydrogen carbonate and can be achieved with either toluene or water as solvent. The transformation does not require any stoichiometric...

Low gravity containerless processing of immiscible gold rhodium alloys

Science.gov (United States)

Andrews, J. Barry

1986-01-01

Under normal one-g conditions immiscible alloys segregate extensively during solidification due to sedementation of the more dense of the immiscible liquid phases. However, under low-g conditions it should be possible to form a dispersion of the two immiscible liquids and maintain this dispersed structure during solidification. Immiscible (hypermonotectic) gold-rhodium alloys were processed in the Marshall Space Flight Center 105 meter drop tube in order to investigate the influence of low gravity, containerless solidification on their microstructure. Hypermonotectic alloys composed of 65 atomic % rhodium exhibited a tendency for the gold rich liquid to wet the outer surface of the containerless processed samples. This tendency led to extensive segregation in several cases. However, well dispersed microstructures consisting of 2 to 3 micron diameter rhodium-rich spheres in a gold-rich matrix were produced in 23.4 atomic % rhodium alloys. This is one of the best dispersions obtained in research on immiscible alloy-systems to data.

Free Rhodium (II) citrate and rhodium (II) citrate magnetic carriers as potential strategies for breast cancer therapy

Science.gov (United States)

2011-01-01

Background Rhodium (II) citrate (Rh2(H2cit)4) has significant antitumor, cytotoxic, and cytostatic activity on Ehrlich ascite tumor. Although toxic to normal cells, its lower toxicity when compared to carboxylate analogues of rhodium (II) indicates Rh2(H2cit)4 as a promising agent for chemotherapy. Nevertheless, few studies have been performed to explore this potential. Superparamagnetic particles of iron oxide (SPIOs) represent an attractive platform as carriers in drug delivery systems (DDS) because they can present greater specificity to tumor cells than normal cells. Thus, the association between Rh2(H2cit)4 and SPIOs can represent a strategy to enhance the former's therapeutic action. In this work, we report the cytotoxicity of free rhodium (II) citrate (Rh2(H2cit)4) and rhodium (II) citrate-loaded maghemite nanoparticles or magnetoliposomes, used as drug delivery systems, on both normal and carcinoma breast cell cultures. Results Treatment with free Rh2(H2cit)4 induced cytotoxicity that was dependent on dose, time, and cell line. The IC50 values showed that this effect was more intense on breast normal cells (MCF-10A) than on breast carcinoma cells (MCF-7 and 4T1). However, the treatment with 50 μM Rh2(H2cit)4-loaded maghemite nanoparticles (Magh-Rh2(H2cit)4) and Rh2(H2cit)4-loaded magnetoliposomes (Lip-Magh-Rh2(H2cit)4) induced a higher cytotoxicity on MCF-7 and 4T1 than on MCF-10A (p rhodium (II) citrate-loaded maghemite nanoparticles and magnetoliposomes induced more specific cytotoxicity on breast carcinoma cells than on breast normal cells, which is the opposite of the results observed with free Rh2(H2cit)4 treatment. Thus, magnetic nanoparticles represent an attractive platform as carriers in Rh2(H2cit)4 delivery systems, since they can act preferentially in tumor cells. Therefore, these nanopaticulate systems may be explored as a potential tool for chemotherapy drug development. PMID:21443799

Shaking table test study on seismic performance of dehydrogenation fan for nuclear power plants

International Nuclear Information System (INIS)

Liu Kaiyan; Shi Weixing; Cao Jialiang; Wang Yang

2011-01-01

Seismic performance of the dehydrogenation fan for nuclear power plants was evaluated based on the shaking table test of earthquake simulation. Dynamic characteristics including the orthogonal tri-axial fundamental frequencies and equivalent damping ratios were measured by the white noise scanning method. Artificial seismic waves were generated corresponding to the floor acceleration response spectra for nuclear power plants. Furthermore, five OBE and one SSE shaking table tests for dehydrogenation fan were performed by using the artificial seismic waves as the seismic inputs along the orthogonal axis simultaneity. Operating function of dehydrogenation fan was monitored and observed during all seismic tests, and performance indexes of dehydrogenation fan were compared before and after seismic tests. The results show that the structural integrity and operating function of the dehydrogenation fan are perfect during all seismic tests; and the performance indexes of the dehydrogenation fan can remain consistent before and after seismic tests; the seismic performance of the dehydrogenation fan can satisfy relevant technical requirements. (authors)

Local Electric Field Effects on Rhodium-Porphyrin and NHC-Gold Catalysts

Science.gov (United States)

2015-01-05

AFRL-OSR-VA-TR-2015-0023 (NII) - Local Electric Field Effects on Rhodium -Porphyrin and NHC-Gold Catalysts MATTHEW KANAN LELAND STANFORD JUNIOR UNIV...Effects on Rhodium -Porphyrin and NHC-Gold Catalysts Principal Investigator: Matthew W. Kanan Project Publications: 1. “An Electric Field–Induced Change...Stanford University Grant/Contract Title The full title of the funded effort. (NII)-Local Electric Field Effects on Rhodium -Porphyrin and NHC-Gold

Adsorption and dehydrogenation of tetrahydroxybenzene on Cu(111)

DEFF Research Database (Denmark)

Bebensee, Fabian; Svane, K.; Bombis, Christian

2013-01-01

Adsorption of tetrahydroxybenzene (THB) on Cu(111) and Au(111) surfaces is studied using a combination of STM, XPS, and DFT. THB is deposited intact, but on Cu(111) it undergoes gradual dehydrogenation of the hydroxyl groups as a function of substrate temperature, yielding a pure dihydroxy......-benzoquinone phase at 370 K. Subtle changes to the adsorption structure upon dehydrogenation are explained from differences in molecule–surface bonding....

Palladium-catalyzed aerobic regio- and stereo-selective olefination reactions of phenols and acrylates via direct dehydrogenative C(sp2)-O cross-coupling.

Science.gov (United States)

Wu, Yun-Bin; Xie, Dan; Zang, Zhong-Lin; Zhou, Cheng-He; Cai, Gui-Xin

2018-04-26

An efficient olefination protocol for the oxidative dehydrogenation of phenols and acrylates has been achieved using a palladium catalyst and O2 as the sole oxidant. This reaction exhibits high regio- and stereo-selectivity (E-isomers) with moderate to excellent isolated yields and a wide substrate scope (32 examples) including ethyl vinyl ketone and endofolliculina.

Microwave-assisted intramolecular dehydrogenative Diels-Alder reactions for the synthesis of functionalized naphthalenes/solvatochromic dyes.

Science.gov (United States)

Kocsis, Laura S; Benedetti, Erica; Brummond, Kay M

2013-04-01

Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to the preparation of new organic dyes. Although numerous strategies have been reported to access naphthalene scaffolds, many procedures still present limitations in terms of incorporating functionality, which in turn narrows the range of available substrates. The development of versatile methods for direct access to substituted naphthalenes is therefore highly desirable. The Diels-Alder (DA) cycloaddition reaction is a powerful and attractive method for the formation of saturated and unsaturated ring systems from readily available starting materials. A new microwave-assisted intramolecular dehydrogenative DA reaction of styrenyl derivatives described herein generates a variety of functionalized cyclopenta[b]naphthalenes that could not be prepared using existing synthetic methods. When compared to conventional heating, microwave irradiation accelerates reaction rates, enhances yields, and limits the formation of undesired byproducts. The utility of this protocol is further demonstrated by the conversion of a DA cycloadduct into a novel solvatochromic fluorescent dye via a Buchwald-Hartwig palladium-catalyzed cross-coupling reaction. Fluorescence spectroscopy, as an informative and sensitive analytical technique, plays a key role in research fields including environmental science, medicine, pharmacology, and cellular biology. Access to a variety of new organic fluorophores provided by the microwave-assisted dehydrogenative DA reaction allows for further advancement in these fields.

Electronic and magnetic properties of small rhodium clusters

Energy Technology Data Exchange (ETDEWEB)

Soon, Yee Yeen; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technology, Multimedia University, Melaka Campus, 75450 Melaka (Malaysia)

2015-04-24

We report a theoretical study of the electronic and magnetic properties of rhodium-atomic clusters. The lowest energy structures at the semi-empirical level of rhodium clusters are first obtained from a novel global-minimum search algorithm, known as PTMBHGA, where Gupta potential is used to describe the atomic interaction among the rhodium atoms. The structures are then re-optimized at the density functional theory (DFT) level with exchange-correlation energy approximated by Perdew-Burke-Ernzerhof generalized gradient approximation. For the purpose of calculating the magnetic moment of a given cluster, we calculate the optimized structure as a function of the spin multiplicity within the DFT framework. The resultant magnetic moments with the lowest energies so obtained allow us to work out the magnetic moment as a function of cluster size. Rhodium atomic clusters are found to display a unique variation in the magnetic moment as the cluster size varies. However, Rh{sub 4} and Rh{sub 6} are found to be nonmagnetic. Electronic structures of the magnetic ground-state structures are also investigated within the DFT framework. The results are compared against those based on different theoretical approaches available in the literature.

Tailored Cyclic and Linear Polycarbosilazanes by Barium-Catalyzed N-H/H-Si Dehydrocoupling Reactions.

Science.gov (United States)

Bellini, Clément; Orione, Clément; Carpentier, Jean-François; Sarazin, Yann

2016-03-07

Ba[CH(SiMe3 )2 ]2 (THF)3 catalyzes the fast and controlled dehydrogenative polymerization of Ph2 SiH2 and p-xylylenediamine to afford polycarbosilazanes. The structure (cyclic versus linear; end-groups) and molecular weight of the macromolecules can be tuned by adjusting the Ph2 SiH2 /diamine feed ratio. A detailed analysis of the resulting materials (mol. wt up to ca. 10 000 g mol(-1) ) is provided. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrochemical behavior of rhodium(III) in 1-butyl-3-methylimidazolium chloride ionic liquid

Energy Technology Data Exchange (ETDEWEB)

Jayakumar, M.; Venkatesan, K.A. [Fuel Chemistry Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Srinivasan, T.G. [Fuel Chemistry Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)], E-mail: tgs@igcar.gov.in

2008-02-15

Electrochemical behavior of rhodium(III) chloride in 1-butyl-3-methylimidazolium chloride was investigated by various electrochemical transient techniques at glassy carbon working electrode at different temperatures (343-373 K). Cyclic voltammogram of rhodium(III) in bmimCl consisted of a surge in reduction current occurring at a potential of -0.48 V (vs. Pd) is due to the reduction of Rh(III) to metallic rhodium and a very small oxidation wave occurring at -0.1 V. Increase of scan rate increases the peak current and remarkably shifts the cathodic peak potential (E{sub p}{sup c1}) in negative direction indicating the irreversibility of electroreduction of rhodium(III). The diffusion coefficient of rhodium(III) in bmimCl ({approx}10{sup -9} cm{sup 2}/s) was determined and the energy of activation ({approx}25 kJ/mol) was deduced from cyclic voltammograms at various temperatures. The cathodic ({tau}{sub r}) and anodic ({tau}{sub o}) transition times were measured from chronopotential transients and the ratio {tau}{sub o}/{tau}{sub r} was found to be 1:7. Electrowinning of rhodium from bmimCl medium results in a deposition of metallic rhodium with lower (20-25%) Faradaic efficiency. A separation factor of rhodium from co-existing noble metal fission product palladium in bmimCl was determined during electrodeposition.

Rhodium(III)- and iridium(III)-catalyzed C7 alkylation of indolines with diazo compounds.

Science.gov (United States)

Ai, Wen; Yang, Xueyan; Wu, Yunxiang; Wang, Xuan; Li, Yuanchao; Yang, Yaxi; Zhou, Bing

2014-12-22

A Rh(III)-catalyzed procedure for the C7-selective C-H alkylation of various indolines with α-diazo compounds at room temperature is reported. The advantages of this process are: 1) simple, mild, and pH-neutral reaction conditions, 2) broad substrate scope, 3) complete regioselectivity, 4) no need for an external oxidant, and 5) N2 as the sole byproduct. Furthermore, alkylation and bis-alkylation of carbazoles at the C1 and C8 positions have also been developed. More significantly, for the first time, a successful Ir(III)-catalyzed intermolecular insertion of arene C-H bonds into α-diazo compounds is reported. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhodium trichloride as a homogeneous catalyst for isotopic hydrogen exchange. Comparison with heterogeneous rhodium in the deuteriation of aromatic compounds and alkanes

Energy Technology Data Exchange (ETDEWEB)

Blake, M R; Garnett, J L; Gregor, I K; Hannan, W; Hoa, K; Long, M A [New South Wales Univ., Kensington (Australia)

1975-12-03

The use of rhodium trichloride as a homogeneous catalyst for the exchange of aromatic compounds and alkanes is described; comparison of the results with corresponding data from heterogeneous rhodium metal and other homogeneous systems, e.g., platinum and iridium, supports the proposal that specific type of ..pi..-complex mechanisms are common to all such exchange systems.

Thermal, Catalytic Conversion of Alkanes to Linear Aldehydes and Linear Amines.

Science.gov (United States)

Tang, Xinxin; Jia, Xiangqing; Huang, Zheng

2018-03-21

Alkanes, the main constituents of petroleum, are attractive feedstocks for producing value-added chemicals. Linear aldehydes and amines are two of the most important building blocks in the chemical industry. To date, there have been no effective methods for directly converting n-alkanes to linear aldehydes and linear amines. Here, we report a molecular dual-catalyst system for production of linear aldehydes via regioselective carbonylation of n-alkanes. The system is comprised of a pincer iridium catalyst for transfer-dehydrogenation of the alkane using t-butylethylene or ethylene as a hydrogen acceptor working sequentially with a rhodium catalyst for olefin isomerization-hydroformylation with syngas. The system exhibits high regioselectivity for linear aldehydes and gives high catalytic turnover numbers when using ethylene as the acceptor. In addition, the direct conversion of light alkanes, n-pentane and n-hexane, to siloxy-terminated alkyl aldehydes through a sequence of Ir/Fe-catalyzed alkane silylation and Ir/Rh-catalyzed alkane carbonylation, is described. Finally, the Ir/Rh dual-catalyst strategy has been successfully applied to regioselective alkane aminomethylation to form linear alkyl amines.

Ceria-Based Mixed Oxide Supported Nano-Gold as an Efficient and Durable Heterogeneous Catalyst for Oxidative Dehydrogenation of Amines to Imines Using Molecular Oxygen

Directory of Open Access Journals (Sweden)

Bashir Ahmad Dar

2012-06-01

Full Text Available The present work is intended to determine the catalytic activity of Mixed Oxide supported gold for aerobic oxidative dehydrogenation of amines to imines using Ceria as a main constituent of the each support. The model catalysts Au/CeO2:TiO2 Au/CeO2:SiO2, Au/CeO2:ZrO2 and Au/CeO2:Al2Os were prepared by deposition co-precipitation method and deposition of gold was determined by EDEX analysis. The supported nano-gold catalyzes the dehydrogenation of secondary amines to imines without loss of activity. On recycling good amount of product yield is obtained. Oxidation of secondary amines to imines is carried at 100˚C and almost 90 % conversion was obtained with >99% selectivity. © 2012 BCREC UNDIP. All rights reservedReceived: 26th December 2011; Revised: 7th June 2012; Accepted: 13rd June 2012[How to Cite: B.A. Dar, M. Sharma, B. Singh. (2012. Ceria-Based Mixed Oxide Supported Nano-Gold as an Efficient and Durable Heterogeneous Catalyst for Oxidative Dehydrogenation of Amines to Imines Using Molecular Oxygen. Bulletin of Chemical Reaction Engineering & Catalysis, 7(1: 79-84.  doi:10.9767/bcrec.7.1.1257.79-84][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.7.1.1257.79-84 ] | View in 

Rhodium self-powered neutron detector's lifetime for korean standard nuclear power plants

International Nuclear Information System (INIS)

Yoo, Choon Sung; Kim, Byoung Chul; Park, Jong Ho; Fero, Arnold H.; Anderson, S. L.

2005-01-01

A method to estimate the relative sensitivity of a self-powered rhodium detector for an upcoming cycle is developed by combining the rhodium depletion data from a nuclear design with the site measurement data. This method can be used both by nuclear power plant designers and by site staffs of Korean standard nuclear power plants for determining which rhodium detectors should be replaced during overhauls

Rhodium(II) Proximity-Labeling Identifies a Novel Target Site on STAT3 for Inhibitors with Potent Anti-Leukemia Activity.

Science.gov (United States)

Minus, Matthew B; Liu, Wei; Vohidov, Farrukh; Kasembeli, Moses M; Long, Xin; Krueger, Michael J; Stevens, Alexandra; Kolosov, Mikhail I; Tweardy, David J; Sison, Edward Allan R; Redell, Michele S; Ball, Zachary T

2015-10-26

Nearly 40 % of children with acute myeloid leukemia (AML) suffer relapse arising from chemoresistance, often involving upregulation of the oncoprotein STAT3 (signal transducer and activator of transcription 3). Herein, rhodium(II)-catalyzed, proximity-driven modification identifies the STAT3 coiled-coil domain (CCD) as a novel ligand-binding site, and we describe a new naphthalene sulfonamide inhibitor that targets the CCD, blocks STAT3 function, and halts its disease-promoting effects in vitro, in tumor growth models, and in a leukemia mouse model, validating this new therapeutic target for resistant AML. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

About the extraction recovery of fission rhodium from radioactive wastes

International Nuclear Information System (INIS)

Khaperskaya, A.V.; Renard, E.V.; Koltunov, V.S.

2000-01-01

The report will cover a radically new approach to the problem of rhodium recovery from HLLW after the transformation of kinetically inert poly-aqua cation of trivalent rhodium (which is not recoverable by the majority known extractants) to Rh (IV) form by chemical methods. Presented are the research results of Rh (IV) extraction from nitric acid solutions by several extractants that are of considerable current use in noble metals and radiochemical industries (tri-n-butyl phosphate, di-octyl-sulphide, tri-n-octylamine, quaternary ammonium bases). High level of rhodium extraction has been found for the above extractants: for several systems, for example, tri-n-octylamine - diethyl-benzene, rhodium distribution coefficient achieves high values (10-plus), as well as the sufficient extraction kinetics. Rhodium extraction increases with a decrease of the acidity, a rise in phase mixing time and in the following series: tri-n-butyl phosphate → di-octyl-sulphide → quaternary ammonium bases → tri-n-octylamine. Rh (IV) can be easily reduced to non-extractable Rh (III) by such reductants as Fe (II), HCOOH, C 6 H 8 O 6 , NH 2 OH, N 2 H 4 et al, that may be applied for the re-extraction process. (authors)

Stepwise dehydrogenation of ammonia on Fcc-Co surfaces: A DFT study

Energy Technology Data Exchange (ETDEWEB)

Ma, F.F.; Ma, S.H., E-mail: mash.phy@htu.edu.cn; Jiao, Z.Y.; Dai, X.Q.

2017-05-31

Highlights: • On Co surfaces, oxygen atom not only strengthens ammonia-substrate interaction but also facilitates ammonia dissociation on the Co surfaces. • Pre-adsorbed O atom significantly promotes the stepwise dehydrogenation of ammonia on Co(110), giving rise to N atom strongly binding with the surface. • The dissociation of NH appears to be the rate-determining step on O-covered Co(111) and Co(100) surfaces. • The species N and NH produced in ammonia dehydrogenation are likely responsible for cobalt catalyst deactivation in the excess of oxygen atom. - Abstract: The stepwise dehydrogenation of ammonia on clean and O-covered Co surfaces have been studied by performing density functional theory (DFT) calculations. It is found that the interaction of species NH{sub x} (x = 0–3) with the Co surfaces become stronger with its further dehydrogenation, and oxygen atom not only strengthens ammonia-substrate interaction but also facilitates ammonia dissociation. Specifically, pre-adsorbed O atom significantly promotes the stepwise dehydrogenation of ammonia on Co(110), giving rise to N atom strongly binding with the surface. In contrast, the dissociation of NH appears to be the rate-determining step on O-covered Co(111) and Co(100) surfaces, due to the high energy barriers. And present results demonstrate that the species N and NH produced in ammonia dehydrogenation are likely responsible for cobalt catalyst deactivation in the excess of oxygen atom.

Stepwise dehydrogenation of ammonia on Fcc-Co surfaces: A DFT study

International Nuclear Information System (INIS)

Ma, F.F.; Ma, S.H.; Jiao, Z.Y.; Dai, X.Q.

2017-01-01

Highlights: • On Co surfaces, oxygen atom not only strengthens ammonia-substrate interaction but also facilitates ammonia dissociation on the Co surfaces. • Pre-adsorbed O atom significantly promotes the stepwise dehydrogenation of ammonia on Co(110), giving rise to N atom strongly binding with the surface. • The dissociation of NH appears to be the rate-determining step on O-covered Co(111) and Co(100) surfaces. • The species N and NH produced in ammonia dehydrogenation are likely responsible for cobalt catalyst deactivation in the excess of oxygen atom. - Abstract: The stepwise dehydrogenation of ammonia on clean and O-covered Co surfaces have been studied by performing density functional theory (DFT) calculations. It is found that the interaction of species NH x (x = 0–3) with the Co surfaces become stronger with its further dehydrogenation, and oxygen atom not only strengthens ammonia-substrate interaction but also facilitates ammonia dissociation. Specifically, pre-adsorbed O atom significantly promotes the stepwise dehydrogenation of ammonia on Co(110), giving rise to N atom strongly binding with the surface. In contrast, the dissociation of NH appears to be the rate-determining step on O-covered Co(111) and Co(100) surfaces, due to the high energy barriers. And present results demonstrate that the species N and NH produced in ammonia dehydrogenation are likely responsible for cobalt catalyst deactivation in the excess of oxygen atom.

Reversible Interconversion between 2,5-Dimethylpyrazine and 2,5-Dimethylpiperazine by Iridium-Catalyzed Hydrogenation/Dehydrogenation for Efficient Hydrogen Storage.

Science.gov (United States)

Fujita, Ken-Ichi; Wada, Tomokatsu; Shiraishi, Takumi

2017-08-28

A new hydrogen storage system based on the hydrogenation and dehydrogenation of nitrogen heterocyclic compounds, employing a single iridium catalyst, has been developed. Efficient hydrogen storage using relatively small amounts of solvent compared with previous systems was achieved by this new system. Reversible transformations between 2,5-dimethylpyrazine and 2,5-dimethylpiperazine, accompanied by the uptake and release of three equivalents of hydrogen, could be repeated almost quantitatively at least four times without any loss of efficiency. Furthermore, hydrogen storage under solvent-free conditions was also accomplished. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ni-Catalyzed Dehydrogenative Cross-Coupling: Direct Transformation of Aldehydes to Esters and Amides

Science.gov (United States)

Whittaker, Aaron M.; Dong, Vy M.

2015-01-01

By exploring a new mode of Ni-catalyzed cross-coupling, we have developed a protocol to transform both aromatic and aliphatic aldehydes into either esters or amides directly. The success of this oxidative coupling depends on the appropriate choice of catalyst and organic oxidant, including the use of either α,α,α-trifluoroacetophenone or excess aldehyde. We present mechanistic data that supports a catalytic cycle involving oxidative addition into the aldehyde C–H bond. PMID:25424967

Transition metal-catalyzed carbocyclization of nitrogen and oxygen-tethered 1,n-enynes and diynes: synthesis of five or six-membered heterocyclic compounds.

Science.gov (United States)

Zhang, Di-Han; Zhang, Zhen; Shi, Min

2012-10-25

Cycloisomerization of 1,n-enynes and diynes is a powerful method in organic synthesis to access heterocyclic compounds and has drawn increasing attention from organic chemists. In this paper, we attempted to summarize our recent results on the transition metal-catalyzed cycloisomerization to synthesize five or six-membered heterocyclic compounds using 1,n-enynes and diynes having a propargylic ester moiety. First, we will describe the synthesis of 2,3-disubstituted 3-pyrrolines via gold catalyzed cycloisomerization of 1,6-diynes. In addition, we will also disclose a novel silver catalyzed tandem 1,3-acyloxy migration/Mannich-type addition/elimination of the sulfonyl group of N-sulfonylhydrazone-propargylic esters to 5,6-dihydropyridazin-4-one derivatives. Furthermore, we will introduce three interesting examples of the synthesis of bicyclic compounds via titanium or rhodium catalyzed carbocyclization of enynes. In this context, we have presented that 1,n-enynes and diynes containing propargylic esters are highly reactive and useful starting materials for the cycloisomerization catalyzed by a transition metal catalyst.

"On-water" rhodium-catalysed hydroformylation for the production of linear alcohols

NARCIS (Netherlands)

Diebolt, O.H.; Müller, Christian; Vogt, D.

2012-01-01

Optimisation of the reaction conditions for the rhodium-catalysed aldehyde hydrogenation under hydroformylation conditions showed that water used as co-solvent enhances both rate and selectivity towards primary alcohols. One-pot hydroformylation–hydrogenation using rhodium as the only transition

Enhanced hydrogen storage properties of MgH2 co-catalyzed with K2NiF6 and CNTs.

Science.gov (United States)

Sulaiman, N N; Ismail, M

2016-12-06

The composite of MgH 2 /K 2 NiF 6 /carbon nanotubes (CNTs) is prepared by ball milling, and its hydrogenation properties are studied for the first time. MgH 2 co-catalyzed with K 2 NiF 6 and CNTs exhibited an improvement in the onset dehydrogenation temperature and isothermal de/rehydrogenation kinetics compared with the MgH 2 -K 2 NiF 6 composite. The onset dehydrogenation temperature of MgH 2 doped with 10 wt% K 2 NiF 6 and 5 wt% CNTs is 245 °C, which demonstrated a reduction of 25 °C compared with the MgH 2 + 10 wt% K 2 NiF 6 composite. In terms of rehydrogenation kinetics, MgH 2 doped with 10 wt% K 2 NiF 6 and 5 wt% CNTs samples absorbed 3.4 wt% of hydrogen in 1 min at 320 °C, whereas the MgH 2 + 10 wt% K 2 NiF 6 sample absorbed 2.6 wt% of hydrogen under the same conditions. For dehydrogenation kinetics at 320 °C, the MgH 2 + 10 wt% K 2 NiF 6 + 5 wt% CNTs sample released 3.3 wt% hydrogen after 5 min of dehydrogenation. By contrast, MgH 2 doped with 10 wt% K 2 NiF 6 released 3.0 wt% hydrogen in the same time period. The apparent activation energy, E a , for the dehydrogenation of MgH 2 doped with 10 wt% K 2 NiF 6 reduced from 100.0 kJ mol -1 to 70.0 kJ mol -1 after MgH 2 was co-doped with 10 wt% K 2 NiF 6 and 5 wt% CNTs. Based on the experimental results, the hydrogen storage properties of the MgH 2 /K 2 NiF 6 /CNTs composite is enhanced because of the catalytic effects of the active species of KF, KH and Mg 2 Ni that are formed in situ during dehydrogenation, as well as the unique structure of CNTs.

Oxidative dehydrogenation of isobutane over a titanium pyrophosphate catalyst

Directory of Open Access Journals (Sweden)

IOAN-CEZAR MARCU

2005-06-01

Full Text Available The catalytic properties of titanium pyrophosphate in the oxidative dehydrogenation of isobutane to isobutylene were investigated in the 400 – 550 ºC temperature range. Asignificant change of the product distribution and of the apparent activation energy of the reactionwas observed at about 490 ºC. This phenomenon, already observed in the oxidative dehydrogenation of n-butane, has been interpreted by the existence of two reaction mechanisms depending upon the reaction temperature. Comparison with the n-butane reaction allowed different activation pathways for the activation of alkanes to be proposed. The catalytic properties of TiP2O7 in the oxidative dehydrogenation of isobutane was also compared to those obtained previously with several other pyrophosphates and TiP2O7 was found to be less active and selective for this reaction.

Expedient synthesis of fused azepine derivatives using a sequential rhodium(II)-catalyzed cyclopropanation/1-aza-Cope rearrangement of dienyltriazoles.

Science.gov (United States)

Schultz, Erica E; Lindsay, Vincent N G; Sarpong, Richmond

2014-09-08

A general method for the formation of fused dihydroazepine derivatives from 1-sulfonyl-1,2,3-triazoles bearing a tethered diene is reported. The process involves an intramolecular cyclopropanation of an α-imino rhodium(II) carbenoid, leading to a transient 1-imino-2-vinylcyclopropane intermediate which rapidly undergoes a 1-aza-Cope rearrangement to generate fused dihydroazepine derivatives in moderate to excellent yields. The reaction proceeds with similar efficiency on gram scale. The use of catalyst-free conditions leads to the formation of a novel [4.4.0] bicyclic heterocycle. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Antagonizing STAT3 dimerization with a rhodium(III) complex.

Science.gov (United States)

Ma, Dik-Lung; Liu, Li-Juan; Leung, Ka-Ho; Chen, Yen-Ting; Zhong, Hai-Jing; Chan, Daniel Shiu-Hin; Wang, Hui-Min David; Leung, Chung-Hang

2014-08-25

Kinetically inert metal complexes have arisen as promising alternatives to existing platinum and ruthenium chemotherapeutics. Reported herein, to our knowledge, is the first example of a substitutionally inert, Group 9 organometallic compound as a direct inhibitor of signal transducer and activator of transcription 3 (STAT3) dimerization. From a series of cyclometalated rhodium(III) and iridium(III) complexes, a rhodium(III) complex emerged as a potent inhibitor of STAT3 that targeted the SH2 domain and inhibited STAT3 phosphorylation and dimerization. Significantly, the complex exhibited potent anti-tumor activities in an in vivo mouse xenograft model of melanoma. This study demonstrates that rhodium complexes may be developed as effective STAT3 inhibitors with potent anti-tumor activity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Metal–organic layers stabilize earth-abundant metal–terpyridine diradical complexes for catalytic C–H activation

Energy Technology Data Exchange (ETDEWEB)

Lin, Zekai; Thacker, Nathan C.; Sawano, Takahiro; Drake, Tasha; Ji, Pengfei; Lan, Guangxu; Cao, Lingyun; Liu, Shubin; Wang, Cheng; Lin, Wenbin (UNC); (UC); (Xiamen)

2017-10-30

Metal–organic layers stabilize Fe^IIor Co^II-terpyridine diradical complexes to catalyze alkylazide C_sp3–H amination and benzylic C–H borylation, respectively.

Synthesis of borylated porphyrin and bromo- porphyrin as building blocks for light harvesting antenna molecule

Science.gov (United States)

Radzuan, Nuur Haziqah Mohd; Hassan, Nurul Izzaty; Bakar, Muntaz Abu

2018-04-01

The building blocks for synthesis of light harvesting antenna which are 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolane)-10,20-diphenylporphyrin, 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolane)-10,20-dihexylporphyrin and 5,10,15,20-tetra-(bromophenyl)porphyrin were synthesized. Borylated porphyrin was synthesized by Suzuki coupling reaction between A2BC bromo-porphyrin and pinacolborane. Whereas 5,10,15,20-tetra-(bromophenyl) porphyrin was synthesized by Lindsey condensation reaction between pyrrole and 4-bromobenzaldehyde. 1H-NMR, 13C-NMR spectroscopy and UV-visible spectroscopy confirmed the successful formation of all compounds.

Quinone-Catalyzed Selective Oxidation of Organic Molecules

Science.gov (United States)

Wendlandt, Alison E.

2016-01-01

Lead In Quinones are common stoichiometric reagents in organic chemistry. High potential para-quinones, such as DDQ and chloranil, are widely used and typically promote hydride abstraction. In recent years, many catalytic applications of these methods have been achieved by using transition metals, electrochemistry or O2 to regenerate the oxidized quinone in situ. Complementary studies have led to the development of a different class of quinones that resemble the ortho-quinone cofactors in Copper Amine Oxidases and mediate efficient and selective aerobic and/or electrochemical dehydrogenation of amines. The latter reactions typically proceed via electrophilic transamination and/or addition-elimination reaction mechanisms, rather than hydride abstraction pathways. The collective observations show that the quinone structure has a significant influence on the reaction mechanism and have important implications for the development of new quinone reagents and quinone-catalyzed transformations. PMID:26530485

Rhodium and Hafnium Influence on the Microstructure, Phase Composition, and Oxidation Resistance of Aluminide Coatings

OpenAIRE

Maryana Zagula-Yavorska; Małgorzata Wierzbińska; Jan Sieniawski

2017-01-01

A 0.5 μm thick layer of rhodium was deposited on the CMSX 4 superalloy by the electroplating method. The rhodium-coated superalloy was hafnized and aluminized or only aluminized using the Chemical vapour deposition method. A comparison was made of the microstructure, phase composition, and oxidation resistance of three aluminide coatings: nonmodified (a), rhodium-modified (b), and rhodium- and hafnium-modified (c). All three coatings consisted of two layers: the additive layer and the interdi...

Iodine-Catalyzed Isomerization of Dimethyl Muconate

Energy Technology Data Exchange (ETDEWEB)

Settle, Amy E [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Berstis, Laura R [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Zhang, Shuting [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Rorrer, Nicholas [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Hu, Haiming [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Richards, Ryan [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Beckham, Gregg T [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Crowley, Michael F [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Vardon, Derek R [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

2018-04-12

cis,cis-Muconic acid is a platform biobased chemical that can be upgraded to drop-in commodity and novel monomers. Among the possible drop-in products, dimethyl terephthalate can be synthesized via esterification, isomerization, Diels-Alder cycloaddition, and dehydrogenation. The isomerization of cis,cis-dimethyl muconate (ccDMM) to the trans,trans-form (ttDMM) can be catalyzed by iodine; however, studies have yet to address (i) the mechanism and reaction barriers unique to DMM, and (ii) the influence of solvent, potential for catalyst recycle, and recovery of high-purity ttDMM. To address this gap, we apply a joint computational and experimental approach to investigate iodine-catalyzed isomerization of DMM. Density functional theory calculations identified unique regiochemical considerations due to the large number of halogen-diene coordination schemes. Both transition state theory and experiments estimate significant barrier reductions with photodissociated iodine. Solvent selection was critical for rapid kinetics, likely due to solvent complexation with iodine. Under select conditions, ttDMM yields of 95% were achieved in <1 h with methanol, followed by high purity recovery (>98%) with crystallization. Lastly, post-reaction iodine can be recovered and recycled with minimal loss of activity. Overall, these findings provide new insight into the mechanism and conditions necessary for DMM isomerization with iodine to advance the state-of-the-art for biobased chemicals.

Dehydrogenation of aromatic molecules under a scanning tunneling microscope: pathways and inelastic spectroscopy simulations.

Science.gov (United States)

Lesnard, Hervé; Bocquet, Marie-Laure; Lorente, Nicolas

2007-04-11

We have performed a theoretical study on the dehydrogenation of benzene and pyridine molecules on Cu(100) induced by a scanning tunneling microscope (STM). Density functional theory calculations have been used to characterize benzene, pyridine, and different dehydrogenation products. The adiabatic pathways for single and double dehydrogenation have been evaluated with the nudge elastic band method. After identification of the transition states, the analysis of the electronic structure along the reaction pathway yields interesting information on the electronic process that leads to H-scission. The adiabatic barriers show that the formation of double dehydrogenated fragments is difficult and probably beyond reach under the actual experimental conditions. However, nonadiabatic processes cannot be ruled out. Hence, in order to identify the final dehydrogenation products, the inelastic spectra are simulated and compared with the experimental ones. We can then assign phenyl (C6H5) and alpha-pyridil (alpha-C5H4N) as the STM-induced dehydrogenation products of benzene and pyridine, respectively. Our simulations permit us to understand why phenyl, pyridine, and alpha-pyridil present tunneling-active C-H stretch modes in opposition to benzene.

Recent advances in the ruthenium(ii)-catalyzed chelation-assisted C-H olefination of substituted aromatics, alkenes and heteroaromatics with alkenes via the deprotonation pathway.

Science.gov (United States)

Manikandan, Rajendran; Jeganmohan, Masilamani

2017-08-08

The transition-metal-catalyzed chelation-assisted alkenylation at the inert C-H bond of aromatics with alkenes is one of the efficient methods to synthesize substituted vinylarenes in a highly regio- and stereoselective manner. Palladium, rhodium and ruthenium complexes are frequently used as catalysts for this type of transformation. The present review describes the recent advances in the ruthenium-catalyzed chelation-assisted alkenylation at the C-H bond of aromatics, alkenes and heteroaromatics with alkenes via the deprotonation pathway. Several directing groups including 2-pyridyl, carbonyl, amidine, amide, amine, imidate, sulphonic acid, triazole, cyano, oxazolidinone and hydontoin are widely used in the reaction. The scope, limitation and mechanistic investigation of the alkenylation reactions are discussed elaborately. This feature article includes all the reported ruthenium-catalyzed alkenylation reactions via the deprotonation pathway until the end of March 2017.

In vitro permeation of platinum and rhodium through Caucasian skin.

Science.gov (United States)

Franken, A; Eloff, F C; Du Plessis, J; Badenhorst, C J; Jordaan, A; Du Plessis, J L

2014-12-01

During platinum group metals (PGMs) refining the possibility exists for dermal exposure to PGM salts. The dermal route has been questioned as an alternative route of exposure that could contribute to employee sensitisation, even though literature has been focused on respiratory exposure. This study aimed to investigate the in vitro permeation of platinum and rhodium through intact Caucasian skin. A donor solution of 0.3mg/ml of metal, K2PtCl4 and RhCl3 respectively, was applied to the vertical Franz diffusion cells with full thickness abdominal skin. The receptor solution was removed at various intervals during the 24h experiment, and analysed with high resolution ICP-MS. Skin was digested and analysed by ICP-OES. Results indicated cumulative permeation with prolonged exposure, with a significantly higher mass of platinum permeating after 24h when compared to rhodium. The mass of platinum retained inside the skin and the flux of platinum across the skin was significantly higher than that of rhodium. Permeated and skin retained platinum and rhodium may therefore contribute to sensitisation and indicates a health risk associated with dermal exposure in the workplace. Copyright © 2014 Elsevier Ltd. All rights reserved.

Noble metal catalyzed hydrogen generation from formic acid in nitrite-containing simulated nuclear waste media

International Nuclear Information System (INIS)

King, R.B.; Bhattacharyya, N.K.; Wiemers, K.D.

1994-08-01

Simulants for the Hanford Waste Vitrification Plant (HWVP) feed containing the major non-radioactive components Al, Cd, Fe, Mn, Nd, Ni, Si, Zr, Na, CO 3 2- , NO 3 -, and NO 2 - were used as media to evaluate the stability of formic acid towards hydrogen evolution by the reaction HCO 2 H → H 2 + CO 2 catalyzed by the noble metals Ru, Rh, and/or Pd found in significant quantities in uranium fission products. Small scale experiments using 40-50 mL of feed simulant in closed glass reactors (250-550 mL total volume) at 80-100 degree C were used to study the effect of nitrite and nitrate ion on the catalytic activities of the noble metals for formic acid decomposition. Reactions were monitored using gas chromatography to analyze the CO 2 , H 2 , NO, and N 2 O in the gas phase as a function of time. Rhodium, which was introduced as soluble RhCl 3 ·3H 2 O, was found to be the most active catalyst for hydrogen generation from formic acid above ∼80 degree C in the presence of nitrite ion in accord with earlier observations. The inherent homogeneous nature of the nitrite-promoted Rh-catalyzed formic acid decomposition is suggested by the approximate pseudo first-order dependence of the hydrogen production rate on Rh concentration. Titration of the typical feed simulants containing carbonate and nitrite with formic acid in the presence of rhodium at the reaction temperature (∼90 degree C) indicates that the nitrite-promoted Rh-catalyzed decomposition of formic acid occurs only after formic acid has reacted with all of the carbonate and nitrite present to form CO 2 and NO/N 2 O, respectively. The catalytic activities of Ru and Pd towards hydrogen generation from formic acid are quite different than those of Rh in that they are inhibited rather than promoted by the presence of nitrite ion

Selective and Stable Ethylbenzene Dehydrogenation to Styrene over Nanodiamonds under Oxygen-lean Conditions.

Science.gov (United States)

Diao, Jiangyong; Feng, Zhenbao; Huang, Rui; Liu, Hongyang; Hamid, Sharifah Bee Abd; Su, Dang Sheng

2016-04-07

For the first time, significant improvement of the catalytic performance of nanodiamonds was achieved for the dehydrogenation of ethylbenzene to styrene under oxygen-lean conditions. We demonstrated that the combination of direct dehydrogenation and oxidative dehydrogenation indeed occurred on the nanodiamond surface throughout the reaction system. It was found that the active sp(2)-sp(3) hybridized nanostructure was well maintained after the long-term test and the active ketonic carbonyl groups could be generated in situ. A high reactivity with 40% ethylbenzene conversion and 92% styrene selectivity was obtained over the nanodiamond catalyst under oxygen-lean conditions even after a 240 h test, demonstrating the potential of this procedure for application as a promising industrial process for the ethylbenzene dehydrogenation to styrene without steam protection. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Relationship between electronic structure and electric conductivity of double rhodium oxides from X-ray spectral data

International Nuclear Information System (INIS)

Firsov, M.N.; Nefedov, V.I.; Shaplygin, I.S.

1983-01-01

Quantum yield spectra of X-ray photoemission of O K - and Rh M 3 -bands of double rhodium oxides with Be, Mg, Ca, Sr, Ba, Cd, V, Nb, Ta, Mo, W are obtained. Quantum yield spectra are analogous to absorption spectra and reflect vacant states in a crystal, in particular, the quantum yield spectrum of O K-band is associated with oxygen vacant states of p-symmetry while Rh M 3 -band spectrum with rhomium vacant states of d-symmetry. In all rhodium compounds investigated the first vacant band is formed by the rhodium 4d-states. The forbidden zone between the last occupied and first free states of rhodiUm has a small width (eV fractions), which explains the semiconductor character of electric conductivity of the investigated compounds. Electric resistance variation in investigated series of rhodium compounds is in agreement with peculiarities of their electronic structure and entirely depends on variation in the electron density on rhodium atoms

Novel high band gap pendant-borylated carbazole polymers with deep HOMO levels through direct ⁺N=B^- interaction for organic photovoltaics

DEFF Research Database (Denmark)

Brandt, Rasmus G.; Sveegaard, Steffen G.; Xiao, Manjun

2016-01-01

In this communication, we investigate the direct and still conjugated intramolecular +N=B- interactions in novel high band gap borylated carbazole containing polymers, namely, poly(3,6-(N-di(2,4,6-trimethyl)-phenylboryl-carbazole)-alt- 4,8-di(5-(2-ethylhexyl)thiophene-2-yl)benzo[1,2-b: 4,5-b...

Superconductivity in zirconium-rhodium alloys

Science.gov (United States)

Zegler, S. T.

1969-01-01

Metallographic studies and transition temperature measurements were made with isothermally annealed and water-quenched zirconium-rhodium alloys. The results clarify both the solid-state phase relations at the Zr-rich end of the Zr-Rh alloy system and the influence upon the superconducting transition temperature of structure and composition.

Rhodium-Catalyzed Asymmetric N-H Functionalization of Quinazolinones with Allenes and Allylic Carbonates: The First Enantioselective Formal Total Synthesis of (-)-Chaetominine.

Science.gov (United States)

Zhou, Yirong; Breit, Bernhard

2017-12-22

An unprecedented asymmetric N-H functionalization of quinazolinones with allenes and allylic carbonates was successfully achieved by rhodium catalysis with the assistance of chiral bidentate diphosphine ligands. The high efficiency and practicality of this method was demonstrated by a low catalyst loading of 1 mol % as well as excellent chemo-, regio-, and enantioselectivities with broad functional group compatibility. Furthermore, this newly developed strategy was applied as key step in the first enantioselective formal total synthesis of (-)-chaetominine. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ethylbenzene dehydrogenation over FeOx/(Mg,Zn)(Al)O catalysts derived from hydrotalcites: Role of MgO as basic sites

KAUST Repository

Balasamy, Rabindran J.; Tope, Balkrishna B.; Khurshid, Alam; Al-Ali, Ali A S; Atanda, Luqman A.; Sagata, Kunimasa; Asamoto, Makiko; Yahiro, Hidenori; Nomura, Kiyoshi; Sano, Tsuneji; Takehira, Katsuomi; Al-Khattaf, Sulaiman S.

2011-01-01

A series of Mg3-xZnxFe0.5Al0.5 mixed oxide catalysts derived from hydrotalcites were tested in the ethylbenzene dehydrogenation to styrene in He atmosphere at 550 °C. The catalysts were prepared by coprecipitation from the nitrates of metal components followed by calcination to mixed oxides at 550 °C. A part of Mg2+ in Mg 3Fe0.5Al0.5 mixed oxide was replaced with Zn2+ to test the effect of MgO as the support. The mixed oxides were composed of periclase and spinel-type compounds with a high surface area of 100-180m2gcat-1. Mössbauer and XPS measurements indicated the presence of Fe3+ on the catalysts and H2-TPR measurement suggested that the dehydrogenation reaction is catalyzed by the reduction-oxidation between Fe3+/Fe2+. The activity of Mg3-xZnxFe0.5Al0.5 mixed oxide decreased with increasing x, indicating an important role of MgO on the activity. Both CO2-TPD measurements as well as IR measurements of adsorbed CO2 clearly indicated the presence of basic sites of Mg 2+O2- on the catalysts. It seems that the combination of Mg2+O2- and Fe3+ was essential for the catalytic activity. It is concluded that the surface base sites generated on O2- bound Mg2+ near Fe3+ sites are responsible for H+-abstraction; the dehydrogenation of ethylbenzene was initiated by the H+ abstraction on Mg2+O2- basic sites, and accelerated by the reduction-oxidation of Fe3+/Fe2+ active species. © 2011 Elsevier B.V.

Ethylbenzene dehydrogenation over FeOx/(Mg,Zn)(Al)O catalysts derived from hydrotalcites: Role of MgO as basic sites

KAUST Repository

Balasamy, Rabindran J.

2011-05-01

A series of Mg3-xZnxFe0.5Al0.5 mixed oxide catalysts derived from hydrotalcites were tested in the ethylbenzene dehydrogenation to styrene in He atmosphere at 550 °C. The catalysts were prepared by coprecipitation from the nitrates of metal components followed by calcination to mixed oxides at 550 °C. A part of Mg2+ in Mg 3Fe0.5Al0.5 mixed oxide was replaced with Zn2+ to test the effect of MgO as the support. The mixed oxides were composed of periclase and spinel-type compounds with a high surface area of 100-180m2gcat-1. Mössbauer and XPS measurements indicated the presence of Fe3+ on the catalysts and H2-TPR measurement suggested that the dehydrogenation reaction is catalyzed by the reduction-oxidation between Fe3+/Fe2+. The activity of Mg3-xZnxFe0.5Al0.5 mixed oxide decreased with increasing x, indicating an important role of MgO on the activity. Both CO2-TPD measurements as well as IR measurements of adsorbed CO2 clearly indicated the presence of basic sites of Mg 2+O2- on the catalysts. It seems that the combination of Mg2+O2- and Fe3+ was essential for the catalytic activity. It is concluded that the surface base sites generated on O2- bound Mg2+ near Fe3+ sites are responsible for H+-abstraction; the dehydrogenation of ethylbenzene was initiated by the H+ abstraction on Mg2+O2- basic sites, and accelerated by the reduction-oxidation of Fe3+/Fe2+ active species. © 2011 Elsevier B.V.

A study on the sensitivity depletion laws for rhodium self-powered neutron detectors

International Nuclear Information System (INIS)

Kim, Gil Gon

1999-02-01

The rhodium self-powered neutron detectors (SPND) in a reactor core provide the operator with the on-line 3-dimensional nuclear power distribution. The signal produced by rhodium SPND is interpreted into the local neutron flux by using a sensitivity depletion law and the local neutron flux is interpreted into the local power by using a power conversion factor. This work on the sensitivity depletion laws for rhodium self-powered neutron detectors (SPND) is performed to improve the uncertainty of the sensitivity depletion law used in ABB-CE reactors employing a rhodium SPND and to develop a calculational tool for providing the sensitivity depletion laws to interpret the signal of the newly designed rhodium SPND into the local neutron flux. The calculational tools for a time dependent neutron flux distribution in the rhodium emitter during depletion and for a time dependent beta escape probability that a beta generated in the emitter is escaped into the collector were developed. Due to the cost, the exposure to the radiation, and the longer fuel cycle, there is a strong incentive that the loading density of an in-core instrumentation is reduced and the lifetime of the detector is lengthened. These objectives can be achieved by reducing the uncertainty which is amplified as it depletes. The calculational tools above provide the sensitivity depletion law and show the reduction of the uncertainty to about 1 % in interpreting the signal into the local neutron flux compared to the method employed by ABB-CE. The reduction in the uncertainty of 1 % in interpreting the signal into the local neutron flux is equivalent to the reduction in the uncertainty of 1 % or more in interpreting the signal into the local power and to the extension of the lifetime of rhodium SPND to about 10 % as reported by ABB-CE

Highly Stereoselective Synthesis of Cyclopentanes bearing Four Stereocenters by a Rhodium Carbene–Initiated Domino Sequence

Science.gov (United States)

Parr, Brendan T.; Davies, Huw M. L.

2014-01-01

Stereoselective synthesis of a cyclopentane nucleus by convergent annulations constitutes a significant challenge for synthetic chemists. Though a number of biologically relevant cyclopentane natural products are known, more often than not, the cyclopentane core is assembled in a stepwise fashion due to lack of efficient annulation strategies. Herein, we report the rhodium-catalyzed reactions of vinyldiazoacetates with (E)-1,3-disubstituted 2-butenols generate cyclopentanes, containing four new stereogenic centers with very high levels of stereoselectivity (99% ee, >97 : 3 dr). The reaction proceeds by a carbene–initiated domino sequence consisting of five distinct steps: rhodium–bound oxonium ylide formation, [2,3]-sigmatropic rearrangement, oxy-Cope rearrangement, enol–keto tautomerization, and finally an intramolecular carbonyl ene reaction. A systematic study is presented detailing how to control chirality transfer in each of the four stereo-defining steps of the cascade, consummating in the development of a highly stereoselective process. PMID:25082301

Structure of Rhodium in an Ultradispersed Rhodium/Alumina Catalyst as Studied by EXAFS and Other Technique

NARCIS (Netherlands)

Koningsberger, D.C.; Blik, H.F.J. van 't; Zon, J.B.A.D. van; Huizinga, T.; Vis, J.C.; Prins, R.

1985-01-01

The structure of rhodium in an ultradispersed 0.57 wt % Rh/y-Al,O, catalyst before and after CO adsorption was studied with extended X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), temperature programmed reduction (TPR), CO infrared

Amine-free reversible hydrogen storage in formate salts catalyzed by ruthenium pincer complex without pH control or solvent change.

Science.gov (United States)

Kothandaraman, Jotheeswari; Czaun, Miklos; Goeppert, Alain; Haiges, Ralf; Jones, John-Paul; May, Robert B; Prakash, G K Surya; Olah, George A

2015-04-24

Due to the intermittent nature of most renewable energy sources, such as solar and wind, energy storage is increasingly required. Since electricity is difficult to store, hydrogen obtained by electrochemical water splitting has been proposed as an energy carrier. However, the handling and transportation of hydrogen in large quantities is in itself a challenge. We therefore present here a method for hydrogen storage based on a CO2 (HCO3 (-) )/H2 and formate equilibrium. This amine-free and efficient reversible system (>90 % yield in both directions) is catalyzed by well-defined and commercially available Ru pincer complexes. The formate dehydrogenation was triggered by simple pressure swing without requiring external pH control or the change of either the solvent or the catalyst. Up to six hydrogenation-dehydrogenation cycles were performed and the catalyst performance remained steady with high selectivity (CO free H2 /CO2 mixture was produced). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhodium-catalyzed NH insertion of pyridyl carbenes derived from pyridotriazoles: a general and efficient approach to 2-picolylamines and imidazo[1,5-a]pyridines.

Science.gov (United States)

Shi, Yi; Gulevich, Anton V; Gevorgyan, Vladimir

2014-12-15

A general and efficient NH insertion reaction of rhodium pyridyl carbenes derived from pyridotriazoles was developed. Various NH-containing compounds, including amides, anilines, enamines, and aliphatic amines, smoothly underwent the NH insertion reaction to afford 2-picolylamine derivatives. The developed transformation was further utilized in a facile one-pot synthesis of imidazo[1,5-a]pyridines. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cluster size selectivity in the product distribution of ethene dehydrogenation on niobium clusters.

Science.gov (United States)

Parnis, J Mark; Escobar-Cabrera, Eric; Thompson, Matthew G K; Jacula, J Paul; Lafleur, Rick D; Guevara-García, Alfredo; Martínez, Ana; Rayner, David M

2005-08-18

Ethene reactions with niobium atoms and clusters containing up to 25 constituent atoms have been studied in a fast-flow metal cluster reactor. The clusters react with ethene at about the gas-kinetic collision rate, indicating a barrierless association process as the cluster removal step. Exceptions are Nb8 and Nb10, for which a significantly diminished rate is observed, reflecting some cluster size selectivity. Analysis of the experimental primary product masses indicates dehydrogenation of ethene for all clusters save Nb10, yielding either Nb(n)C2H2 or Nb(n)C2. Over the range Nb-Nb6, the extent of dehydrogenation increases with cluster size, then decreases for larger clusters. For many clusters, secondary and tertiary product masses are also observed, showing varying degrees of dehydrogenation corresponding to net addition of C2H4, C2H2, or C2. With Nb atoms and several small clusters, formal addition of at least six ethene molecules is observed, suggesting a polymerization process may be active. Kinetic analysis of the Nb atom and several Nb(n) cluster reactions with ethene shows that the process is consistent with sequential addition of ethene units at rates corresponding approximately to the gas-kinetic collision frequency for several consecutive reacting ethene molecules. Some variation in the rate of ethene pick up is found, which likely reflects small energy barriers or steric constraints associated with individual mechanistic steps. Density functional calculations of structures of Nb clusters up to Nb(6), and the reaction products Nb(n)C2H2 and Nb(n)C2 (n = 1...6) are presented. Investigation of the thermochemistry for the dehydrogenation of ethene to form molecular hydrogen, for the Nb atom and clusters up to Nb6, demonstrates that the exergonicity of the formation of Nb(n)C2 species increases with cluster size over this range, which supports the proposal that the extent of dehydrogenation is determined primarily by thermodynamic constraints. Analysis of

Bulk gold catalyzed oxidation reactions of amines and isocyanides and iron porphyrin catalyzed N-H and O-H bond insertion/cyclization reactions of diamines and aminoalcohols

Energy Technology Data Exchange (ETDEWEB)

Klobukowski, Erik [Iowa State Univ., Ames, IA (United States)

2011-01-01

This work involves two projects. The first project entails the study of bulk gold as a catalyst in oxidation reactions of isocyanides and amines. The main goal of this project was to study the activation and reactions of molecules at metal surfaces in order to assess how organometallic principles for homogeneous processes apply to heterogeneous catalysis. Since previous work had used oxygen as an oxidant in bulk gold catalyzed reactions, the generality of gold catalysis with other oxidants was examined. Amine N-oxides were chosen for study, due to their properties and use in the oxidation of carbonyl ligands in organometallic complexes. When amine N-oxides were used as an oxidant in the reaction of isocyanides with amines, the system was able to produce ureas from a variety of isocyanides, amines, and amine N-oxides. In addition, the rate was found to generally increase as the amine N-oxide concentration increased, and decrease with increased concentrations of the amine. Mechanistic studies revealed that the reaction likely involves transfer of an oxygen atom from the amine N-oxide to the adsorbed isocyanide to generate an isocyanate intermediate. Subsequent nucleophilic attack by the amine yields the urea. This is in contrast to the bulk gold-catalyzed reaction mechanism of isocyanides with amines and oxygen. Formation of urea in this case was proposed to proceed through a diaminocarbene intermediate. Moreover, formation of the proposed isocyanate intermediate is consistent with the reactions of metal carbonyl ligands, which are isoelectronic to isocyanides. Nucleophilic attack at coordinated CO by amine N-oxides produces CO{sub 2} and is analogous to the production of an isocyanate in this gold system. When the bulk gold-catalyzed oxidative dehydrogenation of amines was examined with amine N-oxides, the same products were afforded as when O{sub 2} was used as the oxidant. When the two types of oxidants were directly compared using the same reaction system and

Dehydrogenative Coupling of Primary Alcohols To Form Esters Catalyzed by a Ruthenium N-Heterocyclic Carbene Complex

DEFF Research Database (Denmark)

Sølvhøj, Amanda Birgitte; Madsen, Robert

2011-01-01

The ruthenium complex [RuCl2(IiPr)(p-cymene)] catalyzes the direct condensation of primary alcohols into esters and lactones with the release of hydrogen gas. The reaction is most effective with linear aliphatic alcohols and 1,4-diols and is believed to proceed with a ruthenium dihydride...

Rhodium/chiral diene-catalyzed asymmetric 1,4-addition of arylboronic acids to chromones: a highly enantioselective pathway for accessing chiral flavanones.

Science.gov (United States)

He, Qijie; So, Chau Ming; Bian, Zhaoxiang; Hayashi, Tamio; Wang, Jun

2015-03-01

Chromone has been noted to be one of the most challenging substrates in the asymmetric 1,4-addition of α,β-unsaturated carbonyl compounds. By employing the rhodium complex associated with a chiral diene ligand, (R,R)-Ph-bod*, the 1,4-addition of a variety of arylboronic acids was realized to give high yields of the corresponding flavanones with excellent enantioselectivities (≥97% ee, 99% ee for most substrates). Ring-opening side products, which would lead to erosion of product enantioselectivity, were not observed under the stated reaction conditions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Scalar Relativistic Study of the Structure of Rhodium Acetate

Directory of Open Access Journals (Sweden)

Emily E. Edwards

2004-01-01

Full Text Available Abstract: Rhodium acetate, related rhodium carboxylates, and rhodium amide complexes are powerful catalysts for carbene chemistry. They readily promote the decomposition of diazo compounds and transfer the resulting carbene to a variety of substrates. There have been several quantum chemistry studies of these compounds, particularly of the acetate. These have all used non-relativistic methods, and all have shown optimized Rh-Rh bond lengths significantly longer than the experimental value. In this study we have surveyed several scalar relativistic DFT methods using Gaussian, Slater, and numerical basis functions (in DGAUSS, ADF, and DMOL3. Several combinations of exchange-correlation functionals with relativistic and non-relativistic effective core potentials (ECP were investigated, as were non-relativistic and all electron scalar relativistic methods. The combination of the PW91 exchange and PW91 correlation functional with the Christiansen-Ermler ECP gave the best results: 2.3918 Å compared to the experimental value of 2.3855±0.0005 Å.

Radiolytic and photochemical reduction of carbon dioxide in solution catalyzed by transition metal complexes with some selected macrocycles

International Nuclear Information System (INIS)

Grodkowski, J.

2004-01-01

The main goal of the work presented in this report is an explanation of the mechanism of carbon dioxide (CO 2 ) reduction catalyzed by transition metal complexes with some selected macrocycles. The catalytic function of two electron exchange centers in the reduction of CO 2 , an inner metal and a macrocycle ring, was defined. Catalytic effects of rhodium, iron and cobalt porphyrins, cobalt and iron phthalocyanines and corroles as well as cobalt corrins have been investigated. CO 2 reduction by iron ions without presence of macrocycles and also in presence of copper compounds in aqueous solutions have been studied as well

Crystal structures of fac-tri?chlorido?tris?(tri?methyl?phosphane-?P)rhodium(III) monohydrate and fac-tri?chlorido?tris?(tri?methyl?phosphane-?P)rhodium(III) methanol hemisolvate: rhodium structures that are isotypic with their iridium analogs

OpenAIRE

Merola, Joseph S.; Franks, Marion A.

2015-01-01

The crystal structures of two solvates of fac-tri-chlorido-tris-(tri-methyl-phosphane-κP)rhodium(III) are reported, i.e. one with water in the crystal lattice, fac-[RhCl3(Me3P)3]·H2O, and one with methanol in the crystal lattice, fac-[RhCl3(Me3P)3]·0.5CH3OH. These rhodium compounds exhibit distorted octahedral coordination spheres at the metal and are isotypic with the analogous iridium compounds previously reported by us [Merola et al. (2013 ▶). Polyhedron, 54, 67-73]. Comparison is made bet...

Current-induced runaway vibrations in dehydrogenated graphene nanoribbons

Directory of Open Access Journals (Sweden)

Rasmus Bjerregaard Christensen

2016-01-01

Full Text Available We employ a semi-classical Langevin approach to study current-induced atomic dynamics in a partially dehydrogenated armchair graphene nanoribbon. All parameters are obtained from density functional theory. The dehydrogenated carbon dimers behave as effective impurities, whose motion decouples from the rest of carbon atoms. The electrical current can couple the dimer motion in a coherent fashion. The coupling, which is mediated by nonconservative and pseudo-magnetic current-induced forces, change the atomic dynamics, and thereby show their signature in this simple system. We study the atomic dynamics and current-induced vibrational instabilities using a simplified eigen-mode analysis. Our study illustrates how armchair nanoribbons can serve as a possible testbed for probing the current-induced forces.

Effect of alloying on carbon formation during ethane dehydrogenation

DEFF Research Database (Denmark)

Rovik, Anne; Kegnæs, Søren; Dahl, Søren

2009-01-01

The structure sensitivity of different transition metals in the hydrogenolysis, dehydrogenation, and coking reactions during ethane conversion has been investigated. The investigated metals, Ni, Ru, Rh, and Pd, are co-impregnated with Ag onto an inactive MgAl2O4 spinel support and tested in the c......The structure sensitivity of different transition metals in the hydrogenolysis, dehydrogenation, and coking reactions during ethane conversion has been investigated. The investigated metals, Ni, Ru, Rh, and Pd, are co-impregnated with Ag onto an inactive MgAl2O4 spinel support and tested...... in the conversion of ethane. A tendency is clear for all catalysts: In the first period of time 100% ethane is converted and roughly half of the carbon is converted into coke and deposited on the catalyst. The other half of the carbon is converted into methane. The active sites in the hydrogenolysis are blocked...... by coke during the initial period where after dehydrogenation of ethane is observed. It has previously been predicted in surface science studies that Ag covers the steps of certain transition metals. Here it is documented that the hydrogenolysis and coking reactions are significantly suppressed by co...

Integration of catalyst design and reactor engineering in paraffins dehydrogenation

Energy Technology Data Exchange (ETDEWEB)

Sanfilippo, D.; Miracca, I. [Snamprogetti S.p.A., S. Donato Milanese (Italy)

2005-07-01

Unfortunately, olefins are not a natural fossil resource. Their production requires sophisticated and costly technologies, highly demanding in terms of investments and energy. Dehydrogenations are applied industrially to light alkanes (propane to propylene for polymers and isobutane to iso-butylene for gasoline and polymers) as well as long linear ones (C{sub 10}-C{sub 14} to linear-alkyl-benzenes) and for the production of styrene from ethylbenzene. The light paraffins dehydrogenation sustains a network of technologies allowing an integrated approach to create value from Natural Gas. (orig.)

Ni/La2O3 catalyst containing low content platinum-rhodium for the dehydrogenation of N2H4·H2O at room temperature

Science.gov (United States)

O, Song-Il; Yan, Jun-Min; Wang, Hong-Li; Wang, Zhi-Li; Jiang, Qing

2014-09-01

Ni/La2O3 nanocatalyst with Pt and Rh content as low as 5 mol%, respectively, is successfully synthesized by a facile co-reduction method in the presence of hexadecyl trimethyl ammonium chloride aqueous solution under ambient atmosphere. Interestingly, the resulted Ni/La2O3 catalyst with low cost exhibits excellent catalytic activity to dehydrogenation of hydrous hydrazine (N2H4·H2O), producing hydrogen with 100% selectivity at room temperature (298 K), which represents a promising step toward the practical application for N2H4·H2O system on fuel cells.

Olefins hydro-formylation catalysed by rhodium complexes using ionic liquids; Hydroformylation des olefines par les complexes du rhodium dans les liquides ioniques

Energy Technology Data Exchange (ETDEWEB)

Favre, F.

2000-10-26

Biphasic long chain olefins hydro-formylation catalysed by rhodium complexes using ionic liquids allows a selective reaction and an easy separation of the products from the catalyst. This study reports the synthesis of ionic liquids that were used as the catalyst's solvent. Their physical and chemical properties (melting point, solubility of organic substrates) can be varied with the structure of the organic cation (imidazolium, pyridinium, pyrrolydinium) and with its substituents (nature, length, number). It depends also on the nature of the inorganic anion (hexa-fluoro-phosphate, tetrafluoroborate, tri-fluoro-acetate, triflate, bistriflylamidure...). The use of phosphorus ligands bearing ionic functions proved to be efficient to maintain the onerous rhodium catalyst in the ionic liquid phase. Phosphines, phosphites and phosphinites including anionic (sulfonate, carboxylate) or cationic (imidazolium, pyridinium, guanidinium, phosphonium) groups have been synthesised. Finally, the influences of the ligand and of the ionic liquid on the catalytic system performances are described. Selectivities in aldehydes and reaction rates proved to be highly dependent on the nature of the ligand and of the ionic liquid. The different possibilities of recycling the ionic phase containing the rhodium catalyst have been also studied. (author)

Spectrophotometric determination of ruthenium(III) and rhodium(III) after extraction of their cyclohexylthioglycolate complexes into chloroform

International Nuclear Information System (INIS)

Rao, A.L.J.; Gupta, Usha; Puri, B.K.

1986-01-01

Cyclohexylthioglycolate has been used as a reagent for the spectrophotometric determination of ruthenium(III) and rhodium(III) after the extraction of their complexes into chloroform. Various parameters involved in the extraction have been studied and the composition of the extracted complex has been established in each instance. Ruthenium and rhodium complexes are extracted into chloroform in the pH ranges 5.0-9.0 and 9.0-12.5, respectively. The ruthenium complex absorbs strongly at 365 nm, whereas the rhodium complex shows a maximum absorption at 345 nm. Beer's law is obeyed over the concentration range 6-96 μg for ruthenium and 2-41 μg for rhodium in 10 ml of the chloroform solution. The molar absorptivities are 5.02 x 10 3 l mol -1 cm -1 for ruthenium and 1.60 x 10 4 l mol -1 cm -1 for rhodium. Ten replicate determinations on a sample solution containing 60.3 μg of ruthenium or 20.6 μg of rhodium gave mean absorbances of 0.300 and 0.320 with standard deviations of 0.0021 and 0.0025 and relative standard deviations of 0.70% and 0.78%, respectively. The interference of various ions has been studied and the method has been applied to the determination of the metals in various synthetic samples. Conditions have also been developed for the simultaneous determination of ruthenium and rhodium. (author)

Light alkane (mixed feed) selective dehydrogenation using bi ...

African Journals Online (AJOL)

... refinery processes and their catalytic dehydrogenation gives corresponding alkenes. ... was prepared by sequentional impregnation method and characterized by BET, ... Optimum propene selectivity is about 48 %, obtained at 600 oC and ...

Snapshot analysis for rhodium fixed incore detector using BEACON methodology

International Nuclear Information System (INIS)

Cha, Kyoon Ho; Choi, Yu Sun; Lee, Eun Ki; Park, Moon Ghu; Morita, Toshio; Heibel, Michael D.

2004-01-01

The purpose of this report is to process the rhodium detector data of the Yonggwang nuclear unit 4 cycle 5 core for the measured power distribution by using the BEACON methodology. Rhodium snapshots of the YGN 4 cycle 5 have been analyzed by both BEACON/SPINOVA and CECOR to compare the results of both codes. By analyzing a large number of snapshots obtained during normal plant operation. Reviewing the results of this analysis, the BEACON/SPNOVA can be used for the snapshot analysis of Korean Standard Nuclear Power (KSNP) plants

Spectroscopic evidence for origins of size and support effects on selectivity of Cu nanoparticle dehydrogenation catalysts.

Science.gov (United States)

Witzke, M E; Dietrich, P J; Ibrahim, M Y S; Al-Bardan, K; Triezenberg, M D; Flaherty, D W

2017-01-03

Selective dehydrogenation catalysts that produce acetaldehyde from bio-derived ethanol can increase the efficiency of subsequent processes such as C-C coupling over metal oxides to produce 1-butanol or 1,3-butadiene or oxidation to acetic acid. Here, we use in situ X-ray absorption spectroscopy and steady state kinetics experiments to identify Cu δ+ at the perimeter of supported Cu clusters as the active site for esterification and Cu 0 surface sites as sites for dehydrogenation. Correlation of dehydrogenation and esterification selectivities to in situ measures of Cu oxidation states show that this relationship holds for Cu clusters over a wide-range of diameters (2-35 nm) and catalyst supports and reveals that dehydrogenation selectivities may be controlled by manipulating either.

Spectrophotometric determination of ruthenium (III) and rhodium (III) with 9,10-phenanthrenequinone monoxime after extraction into molten naphthalene

International Nuclear Information System (INIS)

Wasey, A.; Bansal, R.K.; Puri, B.K.; Satake, Masatada.

1983-01-01

9,10-Phenanthrenequinone monoxime has been used as a reagent for the spectrophotometric determination of ruthenium(III) and rhodium(III) after extraction into molten naphthalene. The extracted mixture of the metal complex and naphthalene was dissolved in chloroform and ruthenium and rhodium were determined spectrophotometrically. Beer's law holds in the concentration range of 0.2-4.1 μg/cm 3 for ruthenium and 0.3-5.3 μg/cm 3 for rhodium in 10 cm 3 of the final solution. The molar absorptivities and Sandell sensitivities are calculated to be 9.70 x 10 3 l mol -1 cm -1 and 0.01 μg/cmsup(2 ) (660 nm) for ruthenium and 1.13 x 10 4 l mol -1 cm -1 and 0.009 μg/cm 2 (410 nm) for rhodium respectively. Aliquots containing 2.0 μg of ruthenium and 4.1 μg of rhodium give mean absorbances of 0.192 and 0.451 with standard deviations of 0.0017 and 0.0039, respectively. Interference of various ions has been studied and the method has been applied to the determination of ruthenium and rhodium in various synthetic mixtures. This procedure is also applied to the simultaneous determination of ruthenium and rhodium present together in a solution. (author)

CHARACTERIZING THE INFRARED SPECTRA OF SMALL, NEUTRAL, FULLY DEHYDROGENATED POLYCYCLIC AROMATIC HYDROCARBONS

Energy Technology Data Exchange (ETDEWEB)

Mackie, C. J.; Peeters, E.; Cami, J. [Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7 (Canada); Bauschlicher, C. W. Jr., E-mail: mackie@strw.leidenuniv.nl [NASA Ames Research Center, MS 245-6, Moffett Field, CA 94035 (United States)

2015-02-01

We present the results of a computational study to investigate the infrared spectroscopic properties of a large number of polycyclic aromatic hydrocarbon (PAH) molecules and their fully dehydrogenated counterparts. We constructed a database of fully optimized geometries for PAHs that is complete for eight or fewer fused benzene rings, thus containing 1550 PAHs and 805 fully dehydrogenated aromatics. A large fraction of the species in our database have clearly non-planar or curved geometries. For each species, we determined the frequencies and intensities of their normal modes using density functional theory calculations. Whereas most PAH spectra are fairly similar, the spectra of fully dehydrogenated aromatics are much more diverse. Nevertheless, these fully dehydrogenated species show characteristic emission features at 5.2 μm, 5.5 μm, and 10.6 μm; at longer wavelengths, there is a forest of emission features in the 16-30 μm range that appears as a structured continuum, but with a clear peak centered around 19 μm. We searched for these features in Spitzer-IRS spectra of various positions in the reflection nebula NGC 7023. We find a weak emission feature at 10.68 μm in all positions except that closest to the central star. We also find evidence for a weak 19 μm feature at all positions that is not likely due to C{sub 60}. We interpret these features as tentative evidence for the presence of a small population of fully dehydrogenated PAHs, and discuss our results in the framework of PAH photolysis and the formation of fullerenes.

Interaction between water-soluble rhodium complex RhCl(CO)(TPPTS)₂ and surfactants probed by spectroscopic methods.

Science.gov (United States)

Zhou, Li-Mei; Guo, Cai-Hong; Fu, Hai-Yan; Jiang, Xiao-Hui; Chen, Hua; Li, Rui-Xiang; Li, Xian-Jun

2012-07-01

The interactions of rhodium complex RhCl(CO)(TPPTS)(2) [TPPTS=P(m-C(6)H(4)SO(3)Na)(3)] with cationic, nonionic, and anionic surfactants have been investigated by UV-vis, fluorescence and (1)H NMR measurements. The presence of four different species of RhCl(CO)(TPPTS)(2) in cationic cetyltrimethylammonium (CTAB) solution has been demonstrated: free rhodium complex, rhodium complex bound to CTAB monomer, rhodium complex bound to CTAB premicelles, rhodium complex bound to CTAB micelles. The spectroscopy data show that RhCl(CO)(TPPTS)(2) can adsorb on the interface of cationic CTAB micelles by strong electrostatic attraction, weakly bind to the nonionic polyoxyethylene (20) sorbitan monolaurate (Tween 20) micelles by hydrophobic interaction, and does not interact with anion sodium dodecyl sulfate (SDS) micelles due to the strong electrostatic repulsion. Copyright © 2012 Elsevier B.V. All rights reserved.

The influence of pH on the in vitro permeation of rhodium through human skin.

Science.gov (United States)

Jansen Van Rensburg, Sané; Franken, Anja; Du Plessis, Jeanetta; Du Plessis, Johannes Lodewykus

2017-06-01

Workers in precious metals refineries are at risk of exposure to salt compounds of the platinum group metals through inhalation, as well as through the skin. Rhodium salt permeation through the skin has previously been proven using rhodium trichloride (RhCl 3 ) dissolved in synthetic sweat at a pH of 6.5. However, the skin surface pH of refinery workers may be lower than 6.5. The aim of this study was to investigate the influence of pH 6.5 and 4.5 on the in vitro permeation of rhodium through intact Caucasian skin using Franz diffusion cells. A concentration of 0.3 mg mL -1 rhodium was used and analyses were performed using inductively coupled plasma mass spectrometry and inductively coupled plasma optical emission spectrometry. Results indicated a cumulative increase in permeation over 24 h. Rhodium permeation after 12 h was significantly greater at pH 4.5 (1.56 ± 0.24 ng cm -2 ) than at 6.5 (0.85 ± 0.13 ng cm -2 ; p = 0.02). At both pH levels, there was a highly significant difference ( p rhodium remaining in the skin (1428.68 ± 224.67 ng cm -2 at pH 4.5 and 1029.90 ± 115.96 ng cm -2 at pH 6.5) and the mass that diffused through (0.88 ± 0.17 ng cm -2 at pH 4.5 and 0.62 ± 0.10 ng cm -2 at pH 6.5). From these findings, it is evident that an acidic working environment or low skin surface pH may enhance permeation of rhodium salts, contributing to sensitization and adverse health effects.

Modifiers in rhodium catalysts for carbon monoxide hydrogenation: Structure-activity relationships

Energy Technology Data Exchange (ETDEWEB)

Bhore, N. A.

1989-05-01

This report is aimed at identifying interesting modified rhodium systems and elucidating structure-activity relationships in these systems with the overall goal of understanding the scientific issues in the catalytic conversion of syngas to oxygenates. Specific additives (sodium and molybdenum) are selected based on the scoping experiments. The effect of the additives on supported rhodium catalysts is then investigated. Throughout the investigation, experiments and analysis were performed on real systems instead of ideal systems. 374 refs., 82 figs., 57 tabs.

Facile Dehydrogenation of Ethane on the IrO2(110) Surface.

Science.gov (United States)

Bian, Yingxue; Kim, Minkyu; Li, Tao; Asthagiri, Aravind; Weaver, Jason F

2018-02-21

Realizing the efficient and selective conversion of ethane to ethylene is important for improving the utilization of hydrocarbon resources, yet remains a major challenge in catalysis. Herein, ethane dehydrogenation on the IrO 2 (110) surface is investigated using temperature-programmed reaction spectroscopy (TPRS) and density functional theory (DFT) calculations. The results show that ethane forms strongly bound σ-complexes on IrO 2 (110) and that a large fraction of the complexes undergo C-H bond cleavage during TPRS at temperatures below 200 K. Continued heating causes as much as 40% of the dissociated ethane to dehydrogenate and desorb as ethylene near 350 K, with the remainder oxidizing to CO x species. Both TPRS and DFT show that ethylene desorption is the rate-controlling step in the conversion of ethane to ethylene on IrO 2 (110) during TPRS. Partial hydrogenation of the IrO 2 (110) surface is found to enhance ethylene production from ethane while suppressing oxidation to CO x species. DFT predicts that hydrogenation of reactive oxygen atoms of the IrO 2 (110) surface effectively deactivates these sites as H atom acceptors, and causes ethylene desorption to become favored over further dehydrogenation and oxidation of ethane-derived species. The study reveals that IrO 2 (110) exhibits an exceptional ability to promote ethane dehydrogenation to ethylene near room temperature, and provides molecular-level insights for understanding how surface properties influence selectivity toward ethylene production.

Inhibiting prolyl isomerase activity by hybrid organic-inorganic molecules containing rhodium(II) fragments.

Science.gov (United States)

Coughlin, Jane M; Kundu, Rituparna; Cooper, Julian C; Ball, Zachary T

2014-11-15

A small molecule containing a rhodium(II) tetracarboxylate fragment is shown to be a potent inhibitor of the prolyl isomerase FKBP12. The use of small molecules conjugates of rhodium(II) is presented as a general strategy for developing new protein inhibitors based on distinct structural and sequence features of the enzyme active site. Copyright © 2014 Elsevier Ltd. All rights reserved.

Energetic driving force of H spillover between rhodium and titania surfaces : a DFT view

NARCIS (Netherlands)

Conradie, J.; Gracia, J.; Niemantsverdriet, J.W.

2012-01-01

Hydrogen spillover from a rhodium particle, over the most stable (111) surface, to a TiO2 rutile support occurs at low hydrogen coverage because the adsorption energy of H atoms at low hydrogen coverage on rutile is larger than that on rhodium. H diffuses over the support with an activation barrier

DNA Mismatch Binding and Antiproliferative Activity of Rhodium Metalloinsertors

Science.gov (United States)

Ernst, Russell J.; Song, Hang; Barton, Jacqueline K.

2009-01-01

Deficiencies in mismatch repair (MMR) are associated with carcinogenesis. Rhodium metalloinsertors bind to DNA base mismatches with high specificity and inhibit cellular proliferation preferentially in MMR-deficient cells versus MMR-proficient cells. A family of chrysenequinone diimine complexes of rhodium with varying ancillary ligands that serve as DNA metalloinsertors has been synthesized, and both DNA mismatch binding affinities and antiproliferative activities against the human colorectal carcinoma cell lines HCT116N and HCT116O, an isogenic model system for MMR deficiency, have been determined. DNA photocleavage experiments reveal that all complexes bind to the mismatch sites with high specificities; DNA binding affinities to oligonucleotides containing single base CA and CC mismatches, obtained through photocleavage titration or competition, vary from 104 to 108 M−1 for the series of complexes. Significantly, binding affinities are found to be inversely related to ancillary ligand size and directly related to differential inhibition of the HCT116 cell lines. The observed trend in binding affinity is consistent with the metalloinsertion mode where the complex binds from the minor groove with ejection of mismatched base pairs. The correlation between binding affinity and targeting of the MMR-deficient cell line suggests that rhodium metalloinsertors exert their selective biological effects on MMR-deficient cells through mismatch binding in vivo. PMID:19175313

Improvement of the dehydrogenating kinetics of the Mg(NH{sub 2}){sub 2}/LiH materials by inducing LiBH{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Wang, Jingchuan, E-mail: wangjingchuan@caep.cn; Song, Jiangfeng; Chen, Changan; Luo, Deli

2016-12-15

Highlights: • This work indicates that inducing 10 wt.% LiBH{sub 4} into the Mg(NH{sub 2}){sub 2}/LiH mixture significantly improves the dehydrogenating kinetics. It has a near 40 times as large as the effect of the Ti{sub 3}Cr{sub 3}V{sub 4} nanoparticles catalyst under the 200 °C and 0.1 MPa dehydrogenating environment. • Based on diffusion model, the dehydrogenating kinetic curve was fitted for illuminating the mechanism of dehydrogenation improvement. • The mechanism is proposed that the eutectic reaction takes a big role in the catalysis process as the arising of nanorods inside of the matrix after several re-/dehydrogenation cycles. - Abstract: The lightweight high-capacity Li-Mg-N-H system is a promising candidate for the hydrogen energy storage materials. Nevertheless, the slow dehydrogenating process limits its application. This work is focusing on the effect of LiBH{sub 4} on the dehydrogenating kinetics of the Mg(NH{sub 2}){sub 2}/LiH mixture. It indicates that inducing 10 wt.% LiBH{sub 4} into the Mg(NH{sub 2}){sub 2}/LiH mixture significantly improves the dehydrogenating kinetics. As a result, it has a near 40 times as large as the effect of the Ti alloy nanoparticles catalyst, under the 200 °C and 0.1 MPa dehydrogenating environment. Based on our previous dehydrogenating kinetics model, the mechanism of this improving effect of LiBH{sub 4} is discussed as well, which shows that the eutectic reaction takes a big role in the catalysis process as the arising of nanorods inside of the matrix after several re-/dehydrogenation cycles.

Kinetic modeling of ethylbenzene dehydrogenation over hydrotalcite catalysts

KAUST Repository

Atanda, Luqman

2011-07-01

Kinetics of ethylbenzene dehydrogenation to styrene was investigated over a series of quaternary mixed oxides of Mg3Fe0.25Me0.25Al0.5 (Me=Co, Mn and Ni) catalysts prepared by calcination of hydrotalcite-like compounds and compared with commercial catalyst. The study was carried out in the absence of steam using a riser simulator at 400, 450, 500 and 550°C for reaction times of 5, 10, 15 and 20s. Mg3Fe0.25Mn0.25Al0.5 afforded the highest ethylbenzene conversion of 19.7% at 550°C. Kinetic parameters for the dehydrogenation process were determined using the catalyst deactivation function based on reactant conversion model. The apparent activation energies for styrene production were found to decrease as follows: E1-Ni>E1-Co>E1-Mn. © 2011 Elsevier B.V.

Light alkane (mixed feed selective dehydrogenation using bi-metallic zeolite supported catalyst

Directory of Open Access Journals (Sweden)

Zeeshan Nawaz

2009-12-01

Full Text Available Light alkanes are the important intermediates of many refinery processes and their catalytic dehydrogenation gives corresponding alkenes. The aim behind this experimentation is to investigate reaction behavior of mixed alkanes during direct catalytic dehydrogenation and emphasis has been given to enhance propene. Bi-metallic zeolite supported catalyst Pt-Sn/ZSM-5 was prepared by sequentional impregnation method and characterized by BET, EDS and XRD. Direct dehydrogenation reaction is highly endothermic and its conversion is thermodynamically limited. Results showed that the increase in temperature increases the conversion to some extent but there is no overall effect on selectivity of propene. Increase in time-on-stream (TOS remarkably improves propene selectivity at the expense of lower conversion. The performances of bi-metallic zeolite based catalyst largely affected by coke deposition. The presence of butane and ethane adversely affected propane conversion. Optimum propene selectivity is about 48 %, obtained at 600 oC and time-on-stream 10 h.

Separation of carrier-free rhodium isotopes from ruthenium cyclotron targets by the extraction of nitrosylruthenium from hydrochloric acid solution

International Nuclear Information System (INIS)

Haasbroek, F.J.; Strelow, F.W.E.; Van der Walt, T.N.

1981-01-01

A method is presented for the separation of rhodium isotopes from ruthenium cyclotron targets. After bombardment with deuterons and dissolution of the target material, the ruthenium is converted into a nitrosyl complex by treatment with hydroxylammonium chloride. Aluminium and other elements which have been introduced in the dissolution step, are separated by cation exchange. Ruthenium is then separated by extraction with a mixture of tri-n-butyl phosphate and hexane (4:1), leaving the rhodium in the aqueous phase. No ruthenium is found in the rhodium fraction and the recovery of rhodium is better than 90 per cent [af

A New Homogeneous Catalyst for the Dehydrogenation of Dimethylamine Borane Starting with Ruthenium(III Acetylacetonate

Directory of Open Access Journals (Sweden)

Ebru Ünel Barın

2015-06-01

Full Text Available The catalytic activity of ruthenium(III acetylacetonate was investigated for the first time in the dehydrogenation of dimethylamine borane. During catalytic reaction, a new ruthenium(II species is formed in situ from the reduction of ruthenium(III and characterized using UV-Visible, Fourier transform infrared (FTIR, 1H NMR, and mass spectroscopy. The most likely structure suggested for the ruthenium(II species is mer-[Ru(N2Me43(acacH]. Mercury poisoning experiment indicates that the catalytic dehydrogenation of dimethylamine-borane is homogeneous catalysis. The kinetics of the catalytic dehydrogenation of dimethylamine borane starting with Ru(acac3 were studied depending on the catalyst concentration, substrate concentration and temperature. The hydrogen generation was found to be first-order with respect to catalyst concentration and zero-order regarding the substrate concentration. Evaluation of the kinetic data provides the activation parameters for the dehydrogenation reaction: the activation energy Ea = 85 ± 2 kJ·mol−1, the enthalpy of activation ∆H# = 82 ± 2 kJ·mol−1 and the entropy of activation; ∆S# = −85 ± 5 J·mol−1·K−1. The ruthenium(II catalyst formed from the reduction of ruthenium(III acetylacetonate provides 1700 turnovers over 100 hours in hydrogen generation from the dehydrogenation of dimethylamine borane before deactivation at 60 °C.

Activation of heterogenised rhodium carbonylation catalyst infrared spectroscopic study

Energy Technology Data Exchange (ETDEWEB)

Scurrell, M S

1977-01-01

In a study related to heterogeneous versions of homogeneous catalysts active in carbonylation of methanol to acetic acid, the catalyst consisted of 1Vertical Bar3< rhodium as rhodium trichloride supported on 13X zeolite and evacuated at 437/sup 0/K. Contacting the catalyst with carbon monoxide caused two bands, at 2025 and 2095 cm/sup -1/, to appear. Contact with a mixture of carbon monoxide and methyl iodide (the usual promoter) caused bands at 2085, 1710, 1440, and 1370 cm/sup -1/ to appear; the first two correspond to the bands at 2062 and 1711 cm/sup -1/ in homogeneous catalysts attributed to the formation of Rh(CH/sup 3/CO)(CO)X/sup 2/I/sup -/. Spectra.

Dehydrogenation and concurrent isomerization of n-butenes on mixed tin and antimony oxide catalysts

Energy Technology Data Exchange (ETDEWEB)

Irvine, E.A.; Taylor, D.

1978-01-01

The dehydrogenation and concurrent isomerization of n-butenes on mixed tin and antimony oxide catalysts which had been outgassed at 698/sup 0/K were carried out in the presence of oxygen at 474/sup 0/K, and the initial approximately zero-order rates of 1,3-butadiene formation and rates of isomerization were used as a measure of catalytic activity to construct activity patterns as a function of catalyst composition. A comparison of the patterns with those for the isomerization of 3,3-dimethyl-1-butene and for the selective oxidation of propane on the same catalysts indicated that the dehydrogenation of 1-butene involves a m-allyl intermediate, but isomerization occurs through carbonium ion formation. For the cis- and trans-isomers, both reactions apparently occurred via a common allyl (but not m-allyl) intermediate. Dehydrogenation to butadiene decreased in the order 1-butene > cis-2-butene trans-2-butene and was maximum at 10% antimony for 1-butene and 21% antimony for 2-butene. Isomerization was always slower than dehydrogenation and showed two maEima, at 21 (or 27%) and at 75% antimony.

The extraction of rhodium from aqueous nitric acid by dinonylnaphthalene sulphonic acid

International Nuclear Information System (INIS)

Patel, N.M.; Miles, J.H.; Thornback, J.R.

1987-01-01

The extraction of rhodium from aqueous nitric acid using dinonylnaphthalene sulphonic acid has been investigated. The extraction occurs readily from 0.1 M to 1.0 M nitric acid and, since the rhodium is extracted as {Rh(H 2 O) 6 } 3+ into the inverted micelles of the organic solution, equilibration times are less than 5 minutes. Extraction is enhanced by addition of nitrite ion to form {Rh(H 2 O) 5 NO 2 } 2+ as the extracted species. (author)

Development of Non-Noble Metal Ni-Based Catalysts for Dehydrogenation of Methylcyclohexane

KAUST Repository

Al-ShaikhAli, Anaam H.

2016-11-30

Liquid organic chemical hydride is a promising candidate for hydrogen storage and transport. Methylcyclohexane (MCH) to toluene (TOL) cycle has been considered as one of the feasible hydrogen carrier systems, but selective dehydrogenation of MCH to TOL has only been achieved using the noble Pt-based catalysts. The aim of this study is to develop non-noble, cost-effective metal catalysts that can show excellent catalytic performance, mainly maintaining high TOL selectivity achievable by Pt based catalysts. Mono-metallic Ni based catalyst is a well-known dehydrogenation catalyst, but the major drawback with Ni is its hydrogenolysis activity to cleave C-C bonds, which leads to inferior selectivity towards dehydrogenation of MCH to TOL. This study elucidate addition of the second metal to Ni based catalyst to improve the TOL selectivity. Herein, ubiquitous bi-metallic nanoparticles catalysts were investigated including (Ni–M, M: Ag, Zn, Sn or In) based catalysts. Among the catalysts investigated, the high TOL selectivity (> 99%) at low conversions was achieved effectively using the supported NiZn catalyst under flow of excess H2. In this work, a combined study of experimental and computational approaches was conducted to determine the main role of Zn over Ni based catalyst in promoting the TOL selectivity. A kinetic study using mono- and bimetallic Ni based catalysts was conducted to elucidate reaction mechanism and site requirement for MCH dehydrogenation reaction. The impact of different reaction conditions (feed compositions, temperature, space velocity and stability) and catalyst properties were evaluated. This study elucidates a distinctive mechanism of MCH dehydrogenation to TOL reaction over the Ni-based catalysts. Distinctive from Pt catalyst, a nearly positive half order with respect to H2 pressure was obtained for mono- and bi-metallic Ni based catalysts. This kinetic data was consistent with rate determining step as (somewhat paradoxically) hydrogenation

Improved Dehydrogenation Properties of 2LiNH2-MgH2 by Doping with Li3AlH6

Directory of Open Access Journals (Sweden)

Shujun Qiu

2017-01-01

Full Text Available Doping with additives in a Li-Mg-N-H system has been regarded as one of the most effective methods of improving hydrogen storage properties. In this paper, we prepared Li3AlH6 and evaluated its effect on the dehydrogenation properties of 2LiNH2-MgH2. Our studies show that doping with Li3AlH6 could effectively lower the dehydrogenation temperatures and increase the hydrogen content of 2LiNH2-MgH2. For example, 2LiNH2-MgH2-0.1Li3AlH6 can desorb 6.43 wt % of hydrogen upon heating to 300 °C, with the onset dehydrogenation temperature at 78 °C. Isothermal dehydrogenation testing indicated that 2LiNH2-MgH2-0.1Li3AlH6 had superior dehydrogenation kinetics at low temperature. Moreover, the release of byproduct NH3 was successfully suppressed. Measurement of the thermal diffusivity suggests that the enhanced dehydrogenation properties may be ascribed to the fact that doping with Li3AlH6 could improve the heat transfer for solid–solid reaction.

Co-deposition of rhodium and tungsten films for the first-mirror on ITER

International Nuclear Information System (INIS)

Marot, Laurent; Steiner, Roland; Gantenbein, Markus; Mathys, Daniel; Meyer, Ernst

2011-01-01

The detailed characterizations of rhodium/tungsten films prepared by co-deposition using a dual magnetron sputtering have been carried out on silicon substrates at room temperature. Effects of the tungsten incorporated in the film on the chemical bonding state, optical reflectivity and crystallinity were investigated using X-ray photoelectron spectroscopy (XPS), reflectivity measurements, X-rays diffraction (XRD) and scanning electron microscopy (SEM). The incorporation of tungsten changes the films crystalline structure i.e. leading to Rh 3 W formation. The reflectivity of the films decreases linearly with the decrease of rhodium concentration. XPS and ultraviolet photoemission spectroscopy (UPS) measurements show a positive shift of the core level binding energy of rhodium which is coupled to a shift of the Rh d-band ΔE d away from the Fermi level. Opposite shifts are observed for tungsten.

Structural properties of small rhodium clusters

Energy Technology Data Exchange (ETDEWEB)

Soon, Yee Yeen; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technology, Multimedia University, Melaka Campus, 75450 Melaka (Malaysia)

2015-04-24

We report a systematic study of the structural properties of rhodium clusters at the atomistic level. A novel global-minimum search algorithm, known as parallel tempering multicanonical basin hopping plus genetic algorithm (PTMBHGA), is used to obtain the geometrical structures with lowest minima at the semi-empirical level where Gupta potential is used to describe the atomic interaction among the rhodium atoms. These structures are then re-optimized at the density functional theory (DFT) level with exchange-correlation energy approximated by Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA). The structures are optimized for different spin multiplicities. The ones with lowest energies will be taken as ground-state structures. In most cases, we observe only minor changes in the geometry and bond length of the clusters as a result of DFT-level re-optimization. Only in some limited cases, the initial geometries obtained from the PTMBHGA are modified by the re-optimization. The variation of structural properties, such as ground-state geometry, symmetry and binding energy, with respect to the cluster size is studied and agreed well with other results available in the literature.

Light-induced reduction of rhodium(III) and palladium(II) on titanium dioxide dispersions and the selective photochemical separation and recovery of gold(III), platinum(IV), and rhodium(III) in chloride media

Energy Technology Data Exchange (ETDEWEB)

Borgarello, E.; Serpone, N.; Emo, G.; Harris, R.; Pelizzetti, E.; Minero, C.

1986-12-03

Irradiation of aqueous TiO/sub 2/ dispersions containing palladium(II) or rhodium(III) chloride salts with AM1 simulated sunlight leads to the photoreduction of these metals, which are deposited on the semiconductor particle surface. Oxygen is detrimental to the photoreduction of rhodium(III) but not the photoreduction of palladium(II). However, in both cases the reduction process is most efficient if the solution contains CH/sub 3/OH, which acts to scavenge valence band holes of the illuminated TiO/sub 2/ semiconductor. The selective photoreduction and recovery of precious metals from a dilute solution (as might be found in industrial wastes) have been investigated for a mixture of gold(III), platinum(IV), and rhodium(III) chloride salts as a function of various parameters (pH, presence or absence of O/sub 2/, presence or absence of a hole scavenger, and the concentration of the semiconductor). At pH 0, gold is easily separated from platinum and rhodium. The rate of photoreduction of gold(III) on TiO/sub 2/ is nearly independent of the concentration of the semiconductor, under the experimental conditions employed; the limiting rate is 2.7 x 10/sup -7/ M s/sup -1/. The potential utility of this selective photochemical technique is discussed.

Rhodium SPND's Error Reduction using Extended Kalman Filter combined with Time Dependent Neutron Diffusion Equation

International Nuclear Information System (INIS)

Lee, Jeong Hun; Park, Tong Kyu; Jeon, Seong Su

2014-01-01

The Rhodium SPND is accurate in steady-state conditions but responds slowly to changes in neutron flux. The slow response time of Rhodium SPND precludes its direct use for control and protection purposes specially when nuclear power plant is used for load following. To shorten the response time of Rhodium SPND, there were some acceleration methods but they could not reflect neutron flux distribution in reactor core. On the other hands, some methods for core power distribution monitoring could not consider the slow response time of Rhodium SPND and noise effect. In this paper, time dependent neutron diffusion equation is directly used to estimate reactor power distribution and extended Kalman filter method is used to correct neutron flux with Rhodium SPND's and to shorten the response time of them. Extended Kalman filter is effective tool to reduce measurement error of Rhodium SPND's and even simple FDM to solve time dependent neutron diffusion equation can be an effective measure. This method reduces random errors of detectors and can follow reactor power level without cross-section change. It means monitoring system may not calculate cross-section at every time steps and computing time will be shorten. To minimize delay of Rhodium SPND's conversion function h should be evaluated in next study. Neutron and Rh-103 reaction has several decay chains and half-lives over 40 seconds causing delay of detection. Time dependent neutron diffusion equation will be combined with decay chains. Power level and distribution change corresponding movement of control rod will be tested with more complicated reference code as well as xenon effect. With these efforts, final result is expected to be used as a powerful monitoring tool of nuclear reactor core

Rhodium SPND's Error Reduction using Extended Kalman Filter combined with Time Dependent Neutron Diffusion Equation

Energy Technology Data Exchange (ETDEWEB)

Lee, Jeong Hun; Park, Tong Kyu; Jeon, Seong Su [FNC Technology Co., Ltd., Yongin (Korea, Republic of)

2014-05-15

The Rhodium SPND is accurate in steady-state conditions but responds slowly to changes in neutron flux. The slow response time of Rhodium SPND precludes its direct use for control and protection purposes specially when nuclear power plant is used for load following. To shorten the response time of Rhodium SPND, there were some acceleration methods but they could not reflect neutron flux distribution in reactor core. On the other hands, some methods for core power distribution monitoring could not consider the slow response time of Rhodium SPND and noise effect. In this paper, time dependent neutron diffusion equation is directly used to estimate reactor power distribution and extended Kalman filter method is used to correct neutron flux with Rhodium SPND's and to shorten the response time of them. Extended Kalman filter is effective tool to reduce measurement error of Rhodium SPND's and even simple FDM to solve time dependent neutron diffusion equation can be an effective measure. This method reduces random errors of detectors and can follow reactor power level without cross-section change. It means monitoring system may not calculate cross-section at every time steps and computing time will be shorten. To minimize delay of Rhodium SPND's conversion function h should be evaluated in next study. Neutron and Rh-103 reaction has several decay chains and half-lives over 40 seconds causing delay of detection. Time dependent neutron diffusion equation will be combined with decay chains. Power level and distribution change corresponding movement of control rod will be tested with more complicated reference code as well as xenon effect. With these efforts, final result is expected to be used as a powerful monitoring tool of nuclear reactor core.

Study on excimer laser irradiation for controlled dehydrogenation and crystallization of boron doped hydrogenated amorphous/nanocrystalline silicon multilayers

International Nuclear Information System (INIS)

Gontad, F.; Conde, J.C.; Filonovich, S.; Cerqueira, M.F.; Alpuim, P.; Chiussi, S.

2013-01-01

We report on the excimer laser annealing (ELA) induced temperature gradients, allowing controlled crystallization and dehydrogenation of boron-doped a-Si:H/nc-Si:H multilayers. Depth of the dehydrogenation and crystallization process has been studied numerically and experimentally, showing that temperatures below the monohydride decomposition can be used and that significant changes of the doping profile can be avoided. Calculation of temperature profiles has been achieved through numerical modeling of the heat conduction differential equation. Increase in the amount of nano-crystals, but not in their size, has been demonstrated by Raman spectroscopy. Effective dehydrogenation and shape of the boron profile have been studied by time of flight secondary ion mass spectroscopy. The relatively low temperature threshold for dehydrogenation, below the monohydride decomposition temperature, has been attributed to both, the large hydrogen content of the original films and the partial crystallization during the ELA process. The results of this study show that UV-laser irradiation is an effective tool to improve crystallinity and dopant activation in p + -nc-Si:H films without damaging the substrate. - Highlights: • An efficient dehydrogenation is possible through excimer laser annealing. • 140 mJ/cm 2 is enough for dehydrogenation without significant changes in doping profile. • Fluences up to 300 mJ/cm 2 promote partial crystallization of the amorphous structures

Study on excimer laser irradiation for controlled dehydrogenation and crystallization of boron doped hydrogenated amorphous/nanocrystalline silicon multilayers

Energy Technology Data Exchange (ETDEWEB)

Gontad, F., E-mail: fran_gontad@yahoo.es [Applied Physics Department, University of Vigo, E.I. Industrial, Campus de As Lagoas, Marcosende, E-36310, Vigo (Spain); Conde, J.C. [Applied Physics Department, University of Vigo, E.I. Industrial, Campus de As Lagoas, Marcosende, E-36310, Vigo (Spain); Filonovich, S.; Cerqueira, M.F.; Alpuim, P. [Department of Physics, University of Minho, Campus de Azurém, 4800-058 Guimarães (Portugal); Chiussi, S. [Applied Physics Department, University of Vigo, E.I. Industrial, Campus de As Lagoas, Marcosende, E-36310, Vigo (Spain)

2013-06-01

We report on the excimer laser annealing (ELA) induced temperature gradients, allowing controlled crystallization and dehydrogenation of boron-doped a-Si:H/nc-Si:H multilayers. Depth of the dehydrogenation and crystallization process has been studied numerically and experimentally, showing that temperatures below the monohydride decomposition can be used and that significant changes of the doping profile can be avoided. Calculation of temperature profiles has been achieved through numerical modeling of the heat conduction differential equation. Increase in the amount of nano-crystals, but not in their size, has been demonstrated by Raman spectroscopy. Effective dehydrogenation and shape of the boron profile have been studied by time of flight secondary ion mass spectroscopy. The relatively low temperature threshold for dehydrogenation, below the monohydride decomposition temperature, has been attributed to both, the large hydrogen content of the original films and the partial crystallization during the ELA process. The results of this study show that UV-laser irradiation is an effective tool to improve crystallinity and dopant activation in p{sup +}-nc-Si:H films without damaging the substrate. - Highlights: • An efficient dehydrogenation is possible through excimer laser annealing. • 140 mJ/cm{sup 2} is enough for dehydrogenation without significant changes in doping profile. • Fluences up to 300 mJ/cm{sup 2} promote partial crystallization of the amorphous structures.

Transient-response study of CO insertion into CHx surface intermediates on a vanadium-promoted rhodium catalyst

NARCIS (Netherlands)

Koerts, T.; Santen, van R.A.

1992-01-01

The rate of CO insertion into surface CHx species was investigated on silica-supported rhodium and rhodium-vanadium catalysts. Isotopically labelled 13CO was used in a transient kinetic experiment under steady-state conditions. A main conclusion is that vanadium promotion does not affect the rate of

Tailored ceria nanoparticles for CO2 mediated ethylbenzene dehydrogenation

NARCIS (Netherlands)

Kovacevic, M.

2016-01-01

Styrene production via ethylbenzene dehydrogenation (EBDH) is one of the ten most important petrochemical processes. Possessing highly reactive double bond which facilitates self-polymerization and polymerization with other monomers, styrene is the fourth utmost essential bulk monomer at present.

An efficient strategy for designing ambipolar organic semiconductor material: Introducing dehydrogenated phosphorus atoms into pentacene core

Science.gov (United States)

Tang, Xiao-Dan

2017-09-01

The charge transport properties of phosphapentacene (P-PEN) derivatives were systematically explored by theoretical calculation. The dehydrogenated P-PENs have reasonable frontier molecular orbital energy levels to facilitate both electron and hole injection. The reduced reorganization energies of dehydrogenated P-PENs could be intimately connected to the bonding nature of phosphorus atoms. From the idea of homology modeling, the crystal structure of TIPSE-4P-2p is constructed and fully optimized. Fascinatingly, TIPSE-4P-2p shows the intrinsic property of ambipolar transport in both hopping and band models. Thus, introducing dehydrogenated phosphorus atoms into pentacene core could be an efficient strategy for designing ambipolar material.

Rhodium coated mirrors deposited by magnetron sputtering for fusion applications

International Nuclear Information System (INIS)

Marot, L.; De Temmerman, G.; Oelhafen, P.; Covarel, G.; Litnovsky, A.

2007-01-01

Metallic mirrors will be essential components of all optical spectroscopy and imaging systems for ITER plasma diagnostics. Any change in the mirror performance, in particular, its reflectivity, due to erosion of the surface by charge exchange neutrals or deposition of impurities will influence the quality and reliability of the detected signals. Due to its high reflectivity in the visible wavelength range and its low sputtering yield, rhodium appears as an attractive material for first mirrors in ITER. However, the very high price of the raw material calls for using it in the form of a film deposited onto metallic substrates. The development of a reliable technique for the preparation of high reflectivity rhodium films is therefore of the highest importance. Rhodium layers with thicknesses of up to 2 μm were produced on different substrates of interest (Mo, stainless steel, Cu) by magnetron sputtering. Produced films exhibit a low roughness and crystallite size of about 10 nm with a dense columnar structure. No impurities were detected on the surface after deposition. Scratch tests demonstrate that adhesion properties increase with substrate hardness. Detailed optical characterizations of Rh-coated mirrors as well as results of erosion tests performed both under laboratory conditions and in the TEXTOR tokamak are presented in this paper

Rhodium-coated mirrors deposited by magnetron sputtering for fusion applications

International Nuclear Information System (INIS)

Marot, L.; Temmermann, G. de; Oelhafen, P.; Mathys, D.; Covarel, G.; Litnovsky, A.

2007-01-01

Metallic mirrors will be essential components of all optical spectroscopy and imaging systems for plasma diagnostics that will be used in ITER. Any change in the mirror performance, in particular its reflectivity, will influence the quality and reliability of detected signals. Due to its high reflectivity in the visible wavelength range and its low sputtering yield, rhodium may be a good candidate material for first mirrors in ITER. However, the very high price of the raw material calls for using it in the form of a film deposited onto metallic substrates. The development of a reliable technique for the preparation of high reflectivity rhodium films is therefore of the highest importance. Rhodium layers with thicknesses of up to 2 μm were produced on different relevant substrates (Mo, Stainless Steel, Cu) by magnetron sputtering. Produced films exhibit a low roughness, crystallite size of about 10 nm with a dense columnar structure. No impurities were detected on the surface after deposition. Scratch test results demonstrate that adhesion properties increase with the substrate hardness. The detailed optical characterizations of Rh coated mirrors as well as the results of erosion tests performed both under laboratory conditions and in TEXTOR will be presented in this paper. (orig.)

Communication: Visualization and spectroscopy of defects induced by dehydrogenation in individual silicon nanocrystals

Science.gov (United States)

Kislitsyn, Dmitry A.; Mills, Jon M.; Kocevski, Vancho; Chiu, Sheng-Kuei; DeBenedetti, William J. I.; Gervasi, Christian F.; Taber, Benjamen N.; Rosenfield, Ariel E.; Eriksson, Olle; Rusz, Ján; Goforth, Andrea M.; Nazin, George V.

2016-06-01

We present results of a scanning tunneling spectroscopy (STS) study of the impact of dehydrogenation on the electronic structures of hydrogen-passivated silicon nanocrystals (SiNCs) supported on the Au(111) surface. Gradual dehydrogenation is achieved by injecting high-energy electrons into individual SiNCs, which results, initially, in reduction of the electronic bandgap, and eventually produces midgap electronic states. We use theoretical calculations to show that the STS spectra of midgap states are consistent with the presence of silicon dangling bonds, which are found in different charge states. Our calculations also suggest that the observed initial reduction of the electronic bandgap is attributable to the SiNC surface reconstruction induced by conversion of surface dihydrides to monohydrides due to hydrogen desorption. Our results thus provide the first visualization of the SiNC electronic structure evolution induced by dehydrogenation and provide direct evidence for the existence of diverse dangling bond states on the SiNC surfaces.

Diphosphinoazine Rhodium(I) and Iridium(I) Complexes

Czech Academy of Sciences Publication Activity Database

Pošta, Martin; Čermák, Jan; Vojtíšek, P.; Císařová, I.

2006-01-01

Roč. 71, č. 2 (2006), s. 197-206 ISSN 0010-0765 R&D Projects: GA ČR(CZ) GA203/01/0554; GA ČR(CZ) GA203/99/M037 Institutional research plan: CEZ:AV0Z40720504 Keywords : diphosphinoazines * rhodium complexes * iridium complexes Subject RIV: CC - Organic Chemistry Impact factor: 0.881, year: 2006

Substitution of Tyr254 with Phe at the active site of flavocytochrome b2: consequences on catalysis of lactate dehydrogenation

International Nuclear Information System (INIS)

Dubois, J.; Chapman, S.K.; Mathews, F.S.; Reid, G.A.; Lederer, F.

1990-01-01

A role for Tyr254 in L-lactate dehydrogenation catalyzed by flavocytochrome b2 has recently been proposed on the basis of the known active-site structure and of studies that had suggested a mechanism involving the initial formation of a lactate carbanion. This role is now examined after replacement of Tyr254 with phenylalanine. The kcat is decreased about 40-fold, Km for lactate appears unchanged, and the mainly rate-limiting step is still alpha-hydrogen abstraction, as judged from the steady-state deuterium isotope effect. Modeling studies with lactate introduced into the active site indicate two possible substrate conformations with different hydrogen-bonding partners for the substrate hydroxyl. If the hydrogen bond is formed with Tyr254, as was initially postulated, the mechanism must involve removal by His373 of the C2 hydrogen, with carbanion formation. If, in the absence of the Tyr254 phenol group, the hydrogen bond is formed with His373 N3, the substrate is positioned in such a way that the reaction must proceed by hydride transfer. Therefore the mechanism of the Y254F enzyme was investigated so as to distinguish between the two mechanistic possibilities. 2-Hydroxy-3-butynoate behaves with the mutant as a suicide reagent, as with the wild-type enzyme. Similarly, the mutant protein also catalyzes the reduction and the dehydrohalogenation of bromopyruvate under transhydrogenation conditions

Determination of rhodium in metallic alloy and water samples using cloud point extraction coupled with spectrophotometric technique

Science.gov (United States)

Kassem, Mohammed A.; Amin, Alaa S.

2015-02-01

A new method to estimate rhodium in different samples at trace levels had been developed. Rhodium was complexed with 5-(4‧-nitro-2‧,6‧-dichlorophenylazo)-6-hydroxypyrimidine-2,4-dione (NDPHPD) as a complexing agent in an aqueous medium and concentrated by using Triton X-114 as a surfactant. The investigated rhodium complex was preconcentrated with cloud point extraction process using the nonionic surfactant Triton X-114 to extract rhodium complex from aqueous solutions at pH 4.75. After the phase separation at 50 °C, the surfactant-rich phase was heated again at 100 °C to remove water after decantation and the remaining phase was dissolved using 0.5 mL of acetonitrile. Under optimum conditions, the calibration curve was linear for the concentration range of 0.5-75 ng mL-1 and the detection limit was 0.15 ng mL-1 of the original solution. The enhancement factor of 500 was achieved for 250 mL samples containing the analyte and relative standard deviations were ⩽1.50%. The method was found to be highly selective, fairly sensitive, simple, rapid and economical and safely applied for rhodium determination in different complex materials such as synthetic mixture of alloys and environmental water samples.

Combustion kinetics of the coke on deactivated dehydrogenation catalysts

NARCIS (Netherlands)

Luo, Sha; He, Songbo; Li, XianRu; Li, Jingqiu; Bi, Wenjun; Sun, Chenglin

2015-01-01

The coke combustion kinetics on the deactivated catalysts for long chain paraffin dehydrogenation was studied by the thermogravimetry and differential thermogravimetry (TG–DTG) technique. The amount and H/C mole ratio of the coke were determined by the TG and elemental analysis. And the

Rh(iii)-catalyzed C–H olefination of N-pentafluoroaryl benzamides using air as the sole oxidant† †Electronic supplementary information (ESI) available: Data for new compounds and experimental procedures. CCDC 1042327. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4sc03350g

Science.gov (United States)

Wang, Huai-Wei; Spangler, Jillian E.; Chen, Kai; Cui, Pei-Pei; Zhao, Yue

2015-01-01

The oxidative olefination of a broad array of arenes and heteroarenes with a variety of activated and unactivated olefins has be achieved via a rhodium(iii)-catalyzed C–H activation reaction. The use of an N-pentafluorophenyl benzamide directing group is crucial for achieving catalytic turnovers in the presence of air as the sole oxidant without using a co-oxidant. PMID:29449919

Short-chain dehydrogenase/reductase catalyzing the final step of noscapine biosynthesis is localized to laticifers in opium poppy.

Science.gov (United States)

Chen, Xue; Facchini, Peter J

2014-01-01

The final step in the biosynthesis of the phthalideisoquinoline alkaloid noscapine involves a purported dehydrogenation of the narcotinehemiacetal keto moiety. A short-chain dehydrogenase/reductase (SDR), designated noscapine synthase (NOS), that catalyzes dehydrogenation of narcotinehemiacetal to noscapine was identified in opium poppy and functionally characterized. The NOS gene was isolated using an integrated transcript and metabolite profiling strategy and subsequently expressed in Escherichia coli. Noscapine synthase is highly divergent from other characterized members of the NADPH-dependent SDR superfamily involved in benzylisoquinoline alkaloid metabolism, and it exhibits exclusive substrate specificity for narcotinehemiacetal. Kinetic analyses showed that NOS exhibits higher catalytic efficiency with NAD+ as the cofactor compared with NADP+. Suppression of NOS transcript levels in opium poppy plants subjected to virus-induced gene silencing resulted in a corresponding reduction in the accumulation of noscapine and an increase in narcotinehemiacetal levels in the latex. Noscapine and NOS transcripts were detected in all opium poppy organs, but both were most abundant in stems. Unlike other putative biosynthetic genes clustered in the opium poppy genome, and their corresponding proteins, NOS transcripts and the cognate enzyme were abundant in latex, indicating that noscapine metabolism is completed in a distinct cell type compared with the rest of the pathway.

Sorption properties study of nitron fibre S-3 relative to rhodium (III)

International Nuclear Information System (INIS)

Rustamov, S.; Khusainov, A.D.; Shadieva, S.F.

2001-01-01

The purpose of present work is studying of sorption properties of nitron fibre S-3 relative to rhodium (III) from chloride solutions. Nitron sorbent S-3 was synthesised by reprocessing of wastes of production of nitron fibre by sulfited compound Na 2 Sn:NH 4 SCN=50:50 during 3 hours at temperature 90 d ig C . The sulfur containing in the sorbent was about 9%. During investigation by authors was determined that fibre nitron-S has good kinetic characteristics relative to rhodium (III), limitative stage of sorption process is diffusion and kinetics of sorption has mixed-diffusion character

The Mechanism of Rh-Catalyzed Transformation of Fatty Acids to Linear Alpha olefins

Directory of Open Access Journals (Sweden)

Sondre H. Hopen Eliasson

2017-12-01

Full Text Available Linear alpha olefins (LAOs are key commodity chemicals and petrochemical intermediates that are currently produced from fossil resources. Fatty acids are the obvious renewable starting material for LAOs, which can be obtained via transition-metal-catalyzed decarbonylative dehydration. However, even the best catalysts that have been obtained to date, which are based on palladium, are not active and stable enough for industrial use. To provide insight for design of better catalysts, we here present the first computationally derived mechanism for another attractive transition-metal for this reaction, rhodium. By comparing the calculated mechanisms and free energy profiles for the two metals, Pd and Rh, we single out important factors for a facile, low-barrier reaction and for a stable catalyst. While the olefin formation is rate limiting for both of the metals, the rate-determining intermediate for Rh is, in contrast to Pd, the starting complex, (PPh32Rh(COCl. This complex largely draws its stability from the strength of the Rh(I–CO bond. CO is a much less suitable ligand for the high-oxidation state Rh(III. However, for steric reasons, rhodium dissociates a bulkier triphenylphosphine and keeps the carbonyl during the oxidative addition, which is less favorable than for Pd. When compared to Pd, which dissociates two phosphine ligands at the start of the reaction, the catalytic activity of Rh also appears to be hampered by its preference for high coordination numbers. The remaining ancillary ligands leave less space for the metal to mediate the reaction.

Hydrogen bonding-mediated dehydrogenation in the ammonia borane combined graphene oxide systems

Science.gov (United States)

Kuang, Anlong; Liu, Taijuan; Kuang, Minquan; Yang, Ruifeng; Huang, Rui; Wang, Guangzhao; Yuan, Hongkuan; Chen, Hong; Yang, Xiaolan

2018-03-01

The dehydrogenation of ammonia borane (AB) adsorbed on three different graphene oxide (GO) sheets is investigated within the ab initio density functional theory. The energy barriers to direct combination the hydrogens of hydroxyl groups and the hydridic hydrogens of AB to release H2 are relatively high, indicating that the process is energetically unfavorable. Our theoretical study demonstrates that the dehydrogenation mechanism of the AB-GO systems has undergone two critical steps, first, there is the formation of the hydrogen bond (O-H-O) between two hydroxyl groups, and then, the hydrogen bond further react with the hydridic hydrogens of AB to release H2 with low reaction barriers.

Preparation of Pt/USY catalysers and application in the reformation of n-octane; Preparacao de catalisadores Pt/USY e aplicacao na reforma do n-octano

Energy Technology Data Exchange (ETDEWEB)

Araujo, Alfredina dos S.; Sousa, Bianca V.; Grau, Javier M.; Rodrigues, Meiry Glaucia F. [Universidade Federal de Campina Grande (UFCG), PB (Brazil)

2008-07-01

During the catalytic reform, the hydrocarbons of long chain are reconstructed, through reactions of isomerization, hydrogenation, desidrocyclization and dehydrogenation, among others. These reactions occur in acid or metallic small farms, on a bifunctional catalyzer of type Pt/Al{sub 2}O{sub 3}-Cl. The metallic component is active in the hydrogenation and dehydrogenation, while the support (chlorinated alumine) possess acidity enough to promote isomerization reactions. The joint action of the two small farms promotes other reactions, as the desidrocyclization, through a bifunctional mechanism. Reactions also occur undesirable (hydrocracking and hydrogenation) that they diminish the selectivity and they deactivate the catalyzer for coke formation. The catalyzers most promising for this reaction are the acid zeolites of great pores, had to its textural characteristics that facilitate the access of the reagents to active small farms. In this work, the catalytic performance of the metallic function in the dehydrogenation reaction, the conversion and income in the reaction of reform of n-octane will be studied, of the catalyzers of the Pt/USY type. (author)

A meta-selective C-H borylation directed by a secondary interaction between ligand and substrate

Science.gov (United States)

Kuninobu, Yoichiro; Ida, Haruka; Nishi, Mitsumi; Kanai, Motomu

2015-09-01

Regioselective C-H bond transformations are potentially the most efficient method for the synthesis of organic molecules. However, the presence of many C-H bonds in organic molecules and the high activation barrier for these reactions make these transformations difficult. Directing groups in the reaction substrate are often used to control regioselectivity, which has been especially successful for the ortho-selective functionalization of aromatic substrates. Here, we describe an iridium-catalysed meta-selective C-H borylation of aromatic compounds using a newly designed catalytic system. The bipyridine-derived ligand that binds iridium contains a pendant urea moiety. A secondary interaction between this urea and a hydrogen-bond acceptor in the substrate places the iridium in close proximity to the meta-C-H bond and thus controls the regioselectivity. 1H NMR studies and control experiments support the participation of hydrogen bonds in inducing regioselectivity. Reversible direction of the catalyst through hydrogen bonds is a versatile concept for regioselective C-H transformations.

Dehydrogenation of Surface-Oxidized Mixtures of 2LiBH4 + Al/Additives (TiF3 or CeO2

Directory of Open Access Journals (Sweden)

Juan Luis Carrillo-Bucio

2017-11-01

Full Text Available Research for suitable hydrogen storage materials is an important ongoing subject. LiBH4–Al mixtures could be attractive; however, several issues must be solved. Here, the dehydrogenation reactions of surface-oxidized 2LiBH4 + Al mixtures plus an additive (TiF3 or CeO2 at two different pressures are presented. The mixtures were produced by mechanical milling and handled under welding-grade argon. The dehydrogenation reactions were studied by means of temperature programmed desorption (TPD at 400 °C and at 3 or 5 bar initial hydrogen pressure. The milled and dehydrogenated materials were characterized by scanning electron microscopy (SEM, X-ray diffraction (XRD, and Fourier transformed infrared spectroscopy (FT-IR The additives and the surface oxidation, promoted by the impurities in the welding-grade argon, induced a reduction in the dehydrogenation temperature and an increase in the reaction kinetics, as compared to pure (reported LiBH4. The dehydrogenation reactions were observed to take place in two main steps, with onsets at 100 °C and 200–300 °C. The maximum released hydrogen was 9.3 wt % in the 2LiBH4 + Al/TiF3 material, and 7.9 wt % in the 2LiBH4 + Al/CeO2 material. Formation of CeB6 after dehydrogenation of 2LiBH4 + Al/CeO2 was confirmed.

Cell-Selective Biological Activity of Rhodium Metalloinsertors Correlates with Subcellular Localization

Science.gov (United States)

Komor, Alexis C.; Schneider, Curtis J.; Weidmann, Alyson G.; Barton, Jacqueline K.

2013-01-01

Deficiencies in the mismatch repair (MMR) pathway are associated with several types of cancers, as well as resistance to commonly used chemotherapeutics. Rhodium metalloinsertors have been found to bind DNA mismatches with high affinity and specificity in vitro, and also exhibit cell-selective cytotoxicity, targeting MMR-deficient cells over MMR-proficient cells. Ten distinct metalloinsertors with varying lipophilicities have been synthesized and their mismatch binding affinities and biological activities determined. Although DNA photocleavage experiments demonstrate that their binding affinities are quite similar, their cell-selective antiproliferative and cytotoxic activities vary significantly. Inductively coupled plasma mass spectrometry (ICP-MS) experiments have uncovered a relationship between the subcellular distribution of these metalloinsertors and their biological activities. Specifically, we find that all of our metalloinsertors localize in the nucleus at sufficient concentrations for binding to DNA mismatches. However, the metalloinsertors with high rhodium localization in the mitochondria show toxicity that is not selective for MMR-deficient cells, whereas metalloinsertors with less mitochondrial rhodium show activity that is highly selective for MMR-deficient versus proficient cells. This work supports the notion that specific targeting of the metalloinsertors to nuclear DNA gives rise to their cell-selective cytotoxic and antiproliferative activities. The selectivity in cellular targeting depends upon binding to mismatches in genomic DNA. PMID:23137296

Catalytic mechanisms of direct pyrrole synthesis via dehydrogenative coupling mediated by PNP-Ir or PNN-Ru pincer complexes: Crucial role of proton-transfer shuttles in the PNP-Ir system

KAUST Repository

Qu, Shuanglin

2014-04-02

Kempe et al. and Milstein et al. have recently advanced the dehydrogenative coupling methodology to synthesize pyrroles from secondary alcohols (e.g., 3) and β-amino alcohols (e.g., 4), using PNP-Ir (1) and PNN-Ru (2) pincer complexes, respectively. We herein present a DFT study to characterize the catalytic mechanism of these reactions. After precatalyst activation to give active 1A/2A, the transformation proceeds via four stages: 1A/2A-catalyzed alcohol (3) dehydrogenation to give ketone (11), base-facilitated C-N coupling of 11 and 4 to form an imine-alcohol intermediate (18), base-promoted cyclization of 18, and catalyst regeneration via H2 release from 1R/2R. For alcohol dehydrogenations, the bifunctional double hydrogen-transfer pathway is more favorable than that via β-hydride elimination. Generally, proton-transfer (H-transfer) shuttles facilitate various H-transfer processes in both systems. Notwithstanding, H-transfer shuttles play a much more crucial role in the PNP-Ir system than in the PNN-Ru system. Without H-transfer shuttles, the key barriers up to 45.9 kcal/mol in PNP-Ir system are too high to be accessible, while the corresponding barriers (<32.0 kcal/mol) in PNN-Ru system are not unreachable. Another significant difference between the two systems is that the addition of alcohol to 1A giving an alkoxo complex is endergonic by 8.1 kcal/mol, whereas the addition to 2A is exergonic by 8.9 kcal/mol. The thermodynamic difference could be the main reason for PNP-Ir system requiring lower catalyst loading than the PNN-Ru system. We discuss how the differences are resulted in terms of electronic and geometric structures of the catalysts and how to use the features in catalyst development. © 2014 American Chemical Society.

Selectivity of a heterogeneous rhodium catalyst for the carbonylation of monohydric alcohols

Energy Technology Data Exchange (ETDEWEB)

Christensen, B; Scurrell, M S

1977-01-01

Selectivity of a heterogeneous rhodium catalyst for the carbonylation of monohydric alcohols with carbon monoxide in the presence of the corresponding alkyl iodides as promotors was studied in a glass reactor at approx. 0.05:1 alcohol/carbon monoxide ratio. The 1% by wt rhodium-zeolite catalyst was prepared by immersing a Linde molecular sieve zeolite Type 13X in rhodium trichloride at 80/sup 0/C for 15 hr. Methanol was converted to methyl acetate at 433/sup 0/-513/sup 0/K with selectivites > 90% even at the highest temperatures, and dimethyl ether was by-produced. In the absence of methyl iodide, the carbonylation rate decreased drastically but the dehydration was virtually unaffected. The selectivity for ethanol carbonylation decreased from 99% at 383/sup 0/K to 6% at 523/sup 0/K due to the formation of ethylene (predominant at > 470/sup 0/K) and diethyl ether. The only product of the reaction with propan-2-ol studied at 433/sup 0/ or 473/sup 0/K was propene with 100% conversion at 473/sup 0/K. These results are consistent with the relative ease of reactant dehydration on polar catalysts. Table and 13 references.

Kinetics on NiZn Bimetallic Catalysts for Hydrogen Evolution via Selective Dehydrogenation of Methylcyclohexane to Toluene

KAUST Repository

Shaikh Ali, Anaam

2017-01-18

Liquid organic chemical hydrides are effective hydrogen storage media for easy and safe transport. The chemical couple of methylcyclohexane (MCH) and toluene (TOL) has been considered one of the feasible cycles for a hydrogen carrier, but the selective dehydrogenation of MCH to TOL has been reported using only Pt-based noble metal catalysts. This study reports MCH dehydrogenation to TOL using supported NiZn as a selective, non-noble-metal catalyst. A combined experimental and computational study was conducted to provide insight into the site requirements and reaction mechanism for MCH dehydrogenation to TOL, which were compared with those for cyclohexane (CH) dehydrogenation to benzene (BZ). The kinetic measurements carried out at 300-360°C showed an almost zero order with respect to MCH pressure in the high-pressure region (≥10 kPa) and nearly a positive half order with respective to H pressure (≤40 kPa). These kinetic data for the dehydrogenation reaction paradoxically indicate that hydrogenation of a strongly chemisorbed intermediate originating from TOL is the rate-determining step. Density functional theory (DFT) calculation confirms that the dehydrogenated TOL species at the aliphatic (methyl) position group (CHCH) were strongly adsorbed on the surface, which must be hydrogenated to desorb as TOL. This hydrogen-assisted desorption mechanism explains the essential role of excess H present in the feed in maintaining the activity of the metallic surface for hydrogenation. The rate of the CH to BZ reaction was less sensitive to H pressure than that of MCH to TOL, which can be explained by the absence of a methyl group in the structure, which in turn reduces the binding energy of the adsorbed species. DFT suggests that the improved TOL selectivity by adding Zn to Ni was due to Zn atoms preferentially occupying low-coordination sites on the surface (the corner and edge sites), which are likely the unselective sites responsible for the C-C dissociation of the

Kinetics on NiZn Bimetallic Catalysts for Hydrogen Evolution via Selective Dehydrogenation of Methylcyclohexane to Toluene

KAUST Repository

Shaikh Ali, Anaam; Jedidi, Abdesslem; Anjum, Dalaver H.; Cavallo, Luigi; Takanabe, Kazuhiro

2017-01-01

Liquid organic chemical hydrides are effective hydrogen storage media for easy and safe transport. The chemical couple of methylcyclohexane (MCH) and toluene (TOL) has been considered one of the feasible cycles for a hydrogen carrier, but the selective dehydrogenation of MCH to TOL has been reported using only Pt-based noble metal catalysts. This study reports MCH dehydrogenation to TOL using supported NiZn as a selective, non-noble-metal catalyst. A combined experimental and computational study was conducted to provide insight into the site requirements and reaction mechanism for MCH dehydrogenation to TOL, which were compared with those for cyclohexane (CH) dehydrogenation to benzene (BZ). The kinetic measurements carried out at 300-360°C showed an almost zero order with respect to MCH pressure in the high-pressure region (≥10 kPa) and nearly a positive half order with respective to H pressure (≤40 kPa). These kinetic data for the dehydrogenation reaction paradoxically indicate that hydrogenation of a strongly chemisorbed intermediate originating from TOL is the rate-determining step. Density functional theory (DFT) calculation confirms that the dehydrogenated TOL species at the aliphatic (methyl) position group (CHCH) were strongly adsorbed on the surface, which must be hydrogenated to desorb as TOL. This hydrogen-assisted desorption mechanism explains the essential role of excess H present in the feed in maintaining the activity of the metallic surface for hydrogenation. The rate of the CH to BZ reaction was less sensitive to H pressure than that of MCH to TOL, which can be explained by the absence of a methyl group in the structure, which in turn reduces the binding energy of the adsorbed species. DFT suggests that the improved TOL selectivity by adding Zn to Ni was due to Zn atoms preferentially occupying low-coordination sites on the surface (the corner and edge sites), which are likely the unselective sites responsible for the C-C dissociation of the

Enantioselective rhodium/ruthenium photoredox catalysis en route to chiral 1,2-aminoalcohols.

Science.gov (United States)

Ma, Jiajia; Harms, Klaus; Meggers, Eric

2016-08-09

A rhodium-based chiral Lewis acid catalyst combined with [Ru(bpy)3](PF6)2 as a photoredox sensitizer allows for the visible-light-activated redox coupling of α-silylamines with 2-acyl imidazoles to afford, after desilylation, 1,2-amino-alcohols in yields of 69-88% and with high enantioselectivity (54-99% ee). The reaction is proposed to proceed via an electron exchange between the α-silylamine (electron donor) and the rhodium-chelated 2-acyl imidazole (electron acceptor), followed by a stereocontrolled radical-radical reaction. Substrate scope and control experiments reveal that the trimethylsilyl group plays a crucial role in this reductive umpolung of the carbonyl group.

A multi-target caffeine derived rhodium(i) N-heterocyclic carbene complex: evaluation of the mechanism of action.

Science.gov (United States)

Zhang, Jing-Jing; Muenzner, Julienne K; Abu El Maaty, Mohamed A; Karge, Bianka; Schobert, Rainer; Wölfl, Stefan; Ott, Ingo

2016-08-16

A rhodium(i) and a ruthenium(ii) complex with a caffeine derived N-heterocyclic carbene (NHC) ligand were biologically investigated as organometallic conjugates consisting of a metal center and a naturally occurring moiety. While the ruthenium(ii) complex was largely inactive, the rhodium(i) NHC complex displayed selective cytotoxicity and significant anti-metastatic and in vivo anti-vascular activities and acted as both a mammalian and an E. coli thioredoxin reductase inhibitor. In HCT-116 cells it increased the reactive oxygen species level, leading to DNA damage, and it induced cell cycle arrest, decreased the mitochondrial membrane potential, and triggered apoptosis. This rhodium(i) NHC derivative thus represents a multi-target compound with promising anti-cancer potential.

Copper oxide as efficient catalyst for oxidative dehydrogenation of alcohols with air

DEFF Research Database (Denmark)

Poreddy, Raju; Engelbrekt, Christian; Riisager, Anders

2015-01-01

The oxidative dehydrogenation of alcohols to carbonyl compounds was studied using CuO nanoparticle catalysts prepared by solution synthesis in buffered media. CuO nanoparticles synthesized in N-cyclohexyl- 3-aminopropanesulfonic acid buffer showed high catalytic activity for the oxidation...... of benzylic, alicyclic and unsaturated alcohols to their corresponding carbonyl compounds with excellent selectivities. The observed trend in activity for conversion of substituted alcohols suggested a β-H elimination step to be involved, thus enabling a possible reaction mechanism for oxidative...... dehydrogenation of benzyl alcohols to be proposed. The use of CuO as an inexpensive and efficient heterogeneous catalyst under aerobic conditions provides a new noble metal-free and green reaction protocol for carbonyl compound synthesis....

Nitrile-assisted oxidation over oxidative-annulation: Pd-catalyzed α,β-dehydrogenation of α-cinnamyl β-keto nitriles.

Science.gov (United States)

Nallagonda, Rajender; Reddy, Reddy Rajasekhar; Ghorai, Prasanta

2017-09-13

A palladium-catalyzed oxidation reaction is disclosed where the nitrile functionality on the substrate simply changes the course of the reaction. Our previous finding showed that using the Pd(ii)-catalyst in the presence of benzoquinone as an oxidant, 2-cinnamyl-1,3-dicarbonyls provides functionalized furans via oxidative cyclization. When a nitrile group is replaced with one of the carbonyl functionalities of the same substrate, the oxidative cyclization was completely suppressed; instead, the oxidation at the α,β-position occurred to provide α,β,γ,δ-diene containing β-keto nitriles.

A rhodium(III)-based inhibitor of autotaxin with antiproliferative activity.

Science.gov (United States)

Kang, Tian-Shu; Wang, Wanhe; Zhong, Hai-Jing; Liang, Jia-Xin; Ko, Chung-Nga; Lu, Jin-Jian; Chen, Xiu-Ping; Ma, Dik-Lung; Leung, Chung-Hang

2017-02-01

Cancer of the skin is by far the most common of all cancers. Melanoma accounts for only about 1% of skin cancers but causes a large majority of skin cancer deaths. Autotaxin (ATX), also known as ectonucleotide pyrophosphatase/phosphodiesterase 2 (ENPP2), regulates physiological and pathological functions of lysophosphatidic acid (LPA), and is thus an important therapeutic target. We synthesized ten metal-based complexes and a novel cyclometalated rhodium(III) complex 1 was identified as an ATX enzymatic inhibitor using multiple methods, including ATX enzymatic assay, thermal shift assay, western immunoblotting and so on. Protein thermal shift assays showed that 1 increased the melting temperature (T m ) of ATX by 3.5°C. 1 also reduced ATX-LPA mediated downstream survival signal pathway proteins such as ERK and AKT, and inhibited the activation of the transcription factor nuclear factor κB (NF-κB) and signal transducer and activator of transcription 3 (STAT3). 1 also exhibited strong anti-proliferative activity against A2058 melanoma cells (IC 50 =0.58μM). Structure-activity relationship indicated that both the rhodium(III) center and the auxiliary ligands of complex 1 are important for bioactivity. 1 represents a promising scaffold for the development of small-molecule ATX inhibitors for anti-tumor applications. To our knowledge, complex 1 is the first metal-based ATX inhibitor reported to date. Rhodium complexes will have the increased attention in therapeutic and bioanalytical applications. Copyright © 2016 Elsevier B.V. All rights reserved.

A Concise Synthesis of the Erythrina Alkaloid 3–Demethoxyerythratidinone via Combined Rhodium Catalysis

Science.gov (United States)

Joo, Jung Min; David, Ramoncito A.; Yuan, Yu; Lee, Chulbom

2010-01-01

The total synthesis of the erythrina alkaloid 3–demethoxyerythratidinone has been achieved via a strategy based on combined rhodium catalysis. The catalytic tandem cyclization effected by the interplay of alkynyl and vinylidene rhodium species allows for efficient access to the A and B rings of the tetracyclic erythrinane skeleton in a single step. The synthesis also features rapid preparation of the requisite precursor for the double ring closure and thus has been completed in only 7 total steps in 41% overall yield. PMID:21090648

Adducts of nitrogenous ligands with rhodium(II) tetracarboxylates and tetraformamidinate: NMR spectroscopy and density functional theory calculations.

Science.gov (United States)

Cmoch, Piotr; Głaszczka, Rafał; Jaźwiński, Jarosław; Kamieński, Bohdan; Senkara, Elżbieta

2014-03-01

Complexation of tetrakis(μ2-N,N'-diphenylformamidinato-N,N')-di-rhodium(II) with ligands containing nitrile, isonitrile, amine, hydroxyl, sulfhydryl, isocyanate, and isothiocyanate functional groups has been studied in liquid and solid phases using (1)H, (13)C and (15)N NMR, (13)C and (15)N cross polarisation-magic angle spinning NMR, and absorption spectroscopy in the visible range. The complexation was monitored using various NMR physicochemical parameters, such as chemical shifts, longitudinal relaxation times T1 , and NOE enhancements. Rhodium(II) tetraformamidinate selectively bonded only unbranched amine (propan-1-amine), pentanenitrile, and (1-isocyanoethyl)benzene. No complexation occurred in the case of ligands having hydroxyl, sulfhydryl, isocyanate, and isothiocyanate functional groups, and more expanded amine molecules such as butan-2-amine and 1-azabicyclo[2.2.2]octane. Such features were opposite to those observed in rhodium(II) tetracarboxylates, forming adducts with all kind of ligands. Special attention was focused on the analysis of Δδ parameters, defined as a chemical shift difference between signal in adduct and corresponding signal in free ligand. In the case of (1)H NMR, Δδ values were either negative in adducts of rhodium(II) tetraformamidinate or positive in adducts of rhodium(II) tetracarboxylates. Experimental findings were supported by density functional theory molecular modelling and gauge independent atomic orbitals chemical shift calculations. The calculation of chemical shifts combined with scaling procedure allowed to reproduce qualitatively Δδ parameters. Copyright © 2013 John Wiley & Sons, Ltd.

Functionalized cyclopentadienyl rhodium(III) bipyridine complexes: synthesis, characterization, and catalytic application in hydrogenation of ketones.

Science.gov (United States)

Wang, Wan-Hui; Suna, Yuki; Himeda, Yuichiro; Muckerman, James T; Fujita, Etsuko

2013-07-14

A series of highly functionalized cyclopentadienyl rhodium(III) complexes, [Cp'Rh(bpy)Br](ClO4) (Cp' = substituted cyclopentadienyl), was synthesized from various multi-substituted cyclopentadienes (Cp'H). [Rh(cod)Cl]2 and Cp'H were firstly converted to [Cp'Rh(cod)] complexes, which were then treated with Br2 to give the rhodium(III) dibromides [Cp'RhBr2]2. The novel complexes [Cp'Rh(bpy)Br](ClO4) were obtained readily by the reaction of 2,2'-bipyridine with [Cp'RhBr2]2. These rhodium complexes [Cp'Rh(bpy)Br](ClO4) were fully characterized and utilized in the hydrogenation of cyclohexanone and acetophenone with generally high yields, but they did not exhibit the same reactivity trends for the two substrate ketones. The different activity of these complexes for the different substrates may be due to the influence of the substituents on the Cp' rings.

Exposure of the German general population to platinum and rhodium - Urinary levels and determining factors.

Science.gov (United States)

Munker, Sven; Kilo, Sonja; Röß, Christoph; Jeitner, Peter; Schierl, Rudolf; Göen, Thomas; Drexler, Hans

2016-11-01

In this study the exposure of the general population in Germany to platinum and rhodium and its determinants was investigated in 259 participants (subdivided in three groups) by urine analyses and assessment of the dental status. Complementary, an interview including questions characterising possible exposure to traffic exhaust was conducted. The median excretion was 2.42ng platinum/g creatinine and 7.27ng rhodium/g creatinine. The detailed analysis of the collected data showed significant higher platinum excretion values with increasing number of surfaces covered with restorations containing precious metals (R=0.389; prhodium excretion values (median=7.27ng/g; 95th percentile=13.5 ng/g). In summary, the study showed that exhaust emissions have an influence on platinum and rhodium excretion, but for platinum this influence is rather low compared to the influence of precious metals containing restorations. Copyright © 2016 Elsevier GmbH. All rights reserved.

Mechanistic insights into the oxidative dehydrogenation of amines to nitriles in continuous flow

DEFF Research Database (Denmark)

Corker, Emily C.; Ruiz-Martínez, Javier; Riisager, Anders

2015-01-01

The oxidative dehydrogenation of various aliphatic amines to their corresponding nitrile compounds using RuO2/Al2O3 catalysts in air was successfully applied to a continuous flow reaction. Conversions of amines (up to >99%) and yields of nitriles (up to 77%) varied depending on reaction conditions...... and the amine utilised. The presence of water was found to be important for the activity and stability of the RuO2/Al2O3 catalyst. The Hammett relationship and in situ infrared spectroscopy were applied to divulge details about the catalytic mechanism of the oxidative dehydrogenation of amines over RuO2/Al2O3...

Dihydropyranone Formation by Ipso C–H Activation in a Glucal 3-Carbamate-Derived Rhodium Acyl Nitrenoid

Science.gov (United States)

Hurlocker, Brisa; Abascal, Nadia C.; Repka, Lindsay M.; Santizo-Deleon, Elsy; Smenton, Abigail L.; Baranov, Victoria; Gupta, Ritu; Bernard, Sarah E.; Chowdhury, Shenjuti; Rojas, Christian M.

2011-01-01

By using (N-tosyloxy)-3-O-carbamoyl-D-glucal 10, which removes the need for a hypervalent iodine(III) oxidant, we provide evidence for rhodium nitrenoid-mediated ipso C–H activation as the origin of a C3-oxidized dihydropyranone product 3. This system may be especially susceptible to such a pathway due to the ease of forming a cation upon hydride transfer to the rhodium-complexed acyl nitrene. PMID:21381715

Regioselective C2 Oxidative Olefination of Indoles and Pyrroles through Cationic Rhodium(III)-Catalyzed C-H Bond Activation.

Science.gov (United States)

Li, Bin; Ma, Jianfeng; Xie, Weijia; Song, Haibin; Xu, Shansheng; Wang, Baiquan

2013-09-02

Be economic with your atoms! An efficient Rh-catalyzed oxidative olefination of indoles and pyrroles with broad substrate scope and tolerance is reported. The catalytic reaction proceeds with excellent regio- and stereoselectivity. The directing group N,N-dimethylcarbamoyl was crucial for the reaction and could be removed easily. Copyright © 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrodeposition of carrier-free 57Co on rhodium as an approach to the preparation of Moessbauer sources

International Nuclear Information System (INIS)

Cieszykowska, Izabela; ZoLtowska, MaLgorzata; Mielcarski, MieczysLaw

2011-01-01

Electrodeposition of carrier-free 57 Co on a rhodium matrix as the first step of preparing Moessbauer sources was studied. To optimize the plating parameters, the influences of current density, volume and pH of the electrolyte solution, shape, thickness, and surface area of the rhodium cathode, mode of cathode pretreatment, concentration of 57 Co and duration of electrolysis were investigated.

Extraction of ruthenium thiocyanate and its separation from rhodium by polyurethane foam

International Nuclear Information System (INIS)

Al-Bazi, S.J.; Chow, A.

1984-01-01

Conditions for the formation and extraction of the thiocyanate complex of ruthenium are reported. Distribution coefficients of more than 10 4 and a capacity of about 0.24 mole per kg of foam were obtained. The effect of the chloride salts of various univalent cations on the extraction of Ru(SCN) 6 3- indicated that the efficiency of ruthenium extraction depends on how well the cation fits into the polyether segment of the polyurethane foam, which agrees with the 'cation-chelation' mechanism. The separation of ruthenium and rhodium indicated that more than 95% of the rhodium remained in the aqueous phase and about 95% of the ruthenium was retained by the polyurethane foam and could be easily recovered. (author)

Antitumor effect of free rhodium (II) citrate and rhodium (II) citrate-loaded maghemite nanoparticles on mice bearing breast cancer: a systemic toxicity assay.

Science.gov (United States)

Peixoto, Raphael Cândido Apolinário; Miranda-Vilela, Ana Luisa; de Souza Filho, José; Carneiro, Marcella Lemos' Brettas; Oliveira, Ricardo G S; da Silva, Matheus Oliveira; de Souza, Aparecido R; Báo, Sônia Nair

2015-05-01

Breast cancer is one of the most prevalent cancer types among women. The use of magnetic fluids for specific delivery of drugs represents an attractive platform for chemotherapy. In our previous studies, it was demonstrated that maghemite nanoparticles coated with rhodium (II) citrate (Magh-Rh2Cit) induced in vitro cytotoxicity and in vivo antitumor activity, followed by intratumoral administration in breast carcinoma cells. In this study, our aim was to follow intravenous treatment to evaluate the systemic antitumor activity and toxicity induced by these formulations in Balb/c mice bearing orthotopic 4T1 breast carcinoma. Female Balb/c mice were evaluated with regard to toxicity of intravenous treatments through analyses of hemogram, serum levels of alanine aminotransferase, iron, and creatinine and liver, kidney, and lung histology. The antitumor activity of rhodium (II) citrate (Rh2Cit), Magh-Rh2Cit, and maghemite nanoparticles coated with citrate (Magh-Cit), used as control, was evaluated by tumor volume reduction, histology, and morphometric analysis. Magh-Rh2Cit and Magh-Cit promoted a significant decrease in tumor area, and no experimental groups presented hematotoxic effects or increased levels of serum ALT and creatinine. This observation was corroborated by the histopathological examination of the liver and kidney of mice. Furthermore, the presence of nanoparticles was verified in lung tissue with no morphological changes, supporting the idea that our nanoformulations did not induce toxicity effects. No studies about the systemic action of rhodium (II) citrate-loaded maghemite nanoparticles have been carried out, making this report a suitable starting point for exploring the therapeutic potential of these compounds in treating breast cancer.

Rapid PMR determination of hydrogen in titanium hydride and dehydrogenated titanium powders

International Nuclear Information System (INIS)

Il'enko, V.S.; Demidenko, L.M.

1987-01-01

Proton magnetic resonance (PMR) enables determining hydrogen quantitatively in titanium hydride and dehydrogenated titanium powders without destroying the specimen and is also more informative than high-temperature extraction methods. PMR provides data on the electron-nuclear interactions and the activation energies for hydrogen diffusion while also providing conclusions on the forms and positives of the hydrogen in the lattice and the binding to the metal atoms. The authors have developed a rapid method for determining hydrogen in titanium hydride and dehydrogenated titanium powders which reduces the analysis time and improves the metrological characteristics. The authors use a YaMR-5535 spectrometer working at 40 MHz upgraded for use with hydrogen in solids. The authors used specimens of mass about 2 g ground to 0.1 mm powder

Improved magnetic properties and fracture strength of NdFeB by dehydrogenation

Energy Technology Data Exchange (ETDEWEB)

Yan, M. [State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China)]. E-mail: mse_yanmi@dial.zju.edu.cn; Yu, L.Q. [State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China); Wu, J.M. [State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China); Cui, X.G. [State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China)

2006-11-15

Effects of the dehydrogenation of the hydrogen decrepitated (HD) powders on the magnetic properties and the fracture strength of sintered NdFeB magnets were studied. It was found that the lattice parameters and the crystal phase of NdFeB changed significantly with the various hydrogen contents of the resultant HD powders due to the different degrees of dehydrogenation. The magnetic properties and fracture strength increased with decreasing hydrogen content, reaching the maximum increases of 200% for both intrinsic coercivity and bending strength, which can be ascribed to the improved microstructure of the sintered NdFeB magnets. The hydrogen remaining in the HD powders diffused out and affected drastically the grain and grain boundaries by the hydrogen out-take channel during the subsequent sintering process.

Improved magnetic properties and fracture strength of NdFeB by dehydrogenation

International Nuclear Information System (INIS)

Yan, M.; Yu, L.Q.; Wu, J.M.; Cui, X.G.

2006-01-01

Effects of the dehydrogenation of the hydrogen decrepitated (HD) powders on the magnetic properties and the fracture strength of sintered NdFeB magnets were studied. It was found that the lattice parameters and the crystal phase of NdFeB changed significantly with the various hydrogen contents of the resultant HD powders due to the different degrees of dehydrogenation. The magnetic properties and fracture strength increased with decreasing hydrogen content, reaching the maximum increases of 200% for both intrinsic coercivity and bending strength, which can be ascribed to the improved microstructure of the sintered NdFeB magnets. The hydrogen remaining in the HD powders diffused out and affected drastically the grain and grain boundaries by the hydrogen out-take channel during the subsequent sintering process

The liquid-liquid extraction of chloro-(trichlorostannato)-rhodium(I/III) and -ruthenium (II) complexes from dilute hydrochloric acid into 4-methylpentan-2-one

International Nuclear Information System (INIS)

Wyrley-Birch, J.M.

1984-10-01

The effect of stannous chloride on the liquid-liquid extraction of rhodium and ruthenium from hydrochloric acid solutions into 4-methyl-pentan-2-one (MIBK)/hexane mixtures was studied in detail. Stannous chloride concentrations were found to considerably increase the efficiency of the extraction of rhodium and ruthenium into the organic phase. Chloro-(trichlorostannato)-rhodium (I/III) complexes were formed at room temperature. The rate of chloro-(trichlorostannato)-ruthenium (II) complex formation was extremely slow at room temperature, but increased on heating of the aqueous solutions. The amount of rhodium and ruthenium extracted into the organic phase depend on the Sn(II):M molar ratio, the HCl, H sup(+) and Cl sup(-) concentrations, as well as the equilibration time. A 119 Sn NMR study of the MIBK extracts, showed that the stoichiometry of the chloro-(trichlorostannato)-rhodium (I/III) complexes extracted into the organic phase was dependent on the Sn(II):Rh(III) molar ratio as well as the HCl, H sup(+) and Cl sup(-) concentrations in the aqueous phase. The predominant species observed in the organic phase from HCl solutions containing Sn(II):Rh(III) ratios >= 5:1, was shown to be an hydrido complex having the form [RhH(SnCl 3 ) 4 Cl] 3 sup(-) or [RhH(SnCl 3 ) 4 ]2 sup(-). An essentially quantitative separation of rhodium and ruthenium was achieved utilising the variation in the rates of rhodium-tin and ruthenium-tin complex formation

Selective Cytotoxicity of Rhodium Metalloinsertors in Mismatch Repair-Deficient Cells†

Science.gov (United States)

Ernst, Russell J.; Komor, Alexis C.; Barton, Jacqueline K.

2011-01-01

Mismatches in DNA occur naturally during replication and as a result of endogenous DNA damaging agents, but the mismatch repair (MMR) pathway acts to correct mismatches before subsequent rounds of replication. Rhodium metalloinsertors bind to DNA mismatches with high affinity and specificity and represent a promising strategy to target mismatches in cells. Here we examine the biological fate of rhodium metalloinsertors bearing dipyridylamine ancillary ligands in cells deficient in MMR versus those that are MMR-proficient. These complexes are shown to exhibit accelerated cellular uptake which permits the observation of various cellular responses, including disruption of the cell cycle, monitored by flow cytometry assays, and induction of necrosis, monitored by dye exclusion and caspase inhibition assays, that occur preferentially in the MMR-deficient cell line. These cellular responses provide insight into the mechanisms underlying the selective activity of this novel class of targeted anti-cancer agents. PMID:22103240

Recent advances in the ruthenium-catalyzed hydroarylation of alkynes with aromatics: synthesis of trisubstituted alkenes.

Science.gov (United States)

Manikandan, Rajendran; Jeganmohan, Masilamani

2015-11-14

The hydroarylation of alkynes with substituted aromatics in the presence of a metal catalyst via chelation-assisted C-H bond activation is a powerful method to synthesize trisubstituted alkenes. Chelation-assisted C-H bond activation can be done by two ways: (a) an oxidative addition pathway and (b) a deprotonation pathway. Generally, a mixture of cis and trans stereoisomeric as well as regioisomeric trisubstituted alkenes was observed in an oxidative addition pathway. In the deprotonation pathway, the hydroarylation reaction can be done in a highly regio- and stereoselective manner, and enables preparation of the expected trisubstituted alkenes in a highly selective manner. Generally, ruthenium, rhodium and cobalt complexes are used as catalysts in the reaction. In this review, a ruthenium-catalyzed hydroarylation of alkynes with substituted aromatics is covered completely. The hydroarylation reaction of alkynes with amide, azole, carbamate, phosphine oxide, amine, acetyl, sulfoxide and sulphur directed aromatics is discussed.

Structure and bonding of transition metal-boryl compounds. Theoretical study of [(PH3)2(CO)ClOs-BR2] and [(PH3)2(CO)2ClOs-BR2] (BR2 = BH2, BF2, B(OH)2, B(OCH=CHO), Bcat).

Science.gov (United States)

Giju, K T; Bickelhaupt, F M; Frenking, G

2000-10-16

Quantum chemical DFT calculations using the B3LYP functionals have been carried out for the electronically unsaturated 16 VE five-coordinate osmium boryl-complexes [(PH3)2(CO)ClOs-BR2] and the 18 VE six-coordinate complexes [(PH3)2(CO)2ClOs-BR2] with BR2 = BH2, BF2, B(OH)2, B(OHC=CHO), and Bcat (cat = catecholate O2C6H4). The bonding situation of the Os-BR2 bond was analyzed with the help of the NBO partitioning scheme. The Os-B bond dissociation energies of the 16 VE complexes are very high, and they do not change very much for the different boryl ligands. The 18 VE complexes have only slightly lower bond energies than the 16 VE species. The Os-B bond in both classes of compounds is provided by a covalent sigma-bond which is polarized toward osmium and by strong charge attraction. Os-->B pi-donation is not important for the Os-B binding interactions, except for the Os-BH2 complexes. The stability of the boryl complexes [Os]-BR2 comes mainly from BB pi-donation. The intraligand charge distribution of the BR2 group changes little when the Os-B bond is formed, except for BH2. The CO ligand in [(PH3)2(CO)2ClOs-BR2] which is trans to BR2 has a relatively weak bond to the osmium atom.

Rhodium. Suppl. Vol. B1

International Nuclear Information System (INIS)

Griffith, W.P.; Jehn, H.; McCleverty, J.A.; Raub, C.J.; Robinson, S.D.

1982-01-01

The present rhodium vol. B1 is concerned largely with linary compounds and coordination complexes of this important metal, which is used either alone or in alloy form for fabrication of other materials or for heterogeneous catalysis. In first two chapters are devoted for hydrides, oxides, ternary and quaternary oxorhodates. Third chapter is on different type of complexes with nitrogen. From chapter four to seven is on halogen complexes with this metal. Next chapters are on sulphides, sulphoxide and sulphito complexes, sulphates and sulphato complexes, selenides and tellurides, borides, borane complexes, carbides, carbonato, cyno, fulminato and thiocyanato complexes. Finally, silicide, phosphides, phosphito and arsenides are treated over here. (AB)

THE MATHEMATICAL MODEL DEVELOPMENT OF THE ETHYLBENZENE DEHYDROGENATION PROCESS KINETICS IN A TWO-STAGE ADIABATIC CONTINUOUS REACTOR

Directory of Open Access Journals (Sweden)

V. K. Bityukov

2015-01-01

Full Text Available The article is devoted to the mathematical modeling of the kinetics of ethyl benzene dehydrogenation in a two-stage adiabatic reactor with a catalytic bed functioning on continuous technology. The analysis of chemical reactions taking place parallel to the main reaction of styrene formation has been carried out on the basis of which a number of assumptions were made proceeding from which a kinetic scheme describing the mechanism of the chemical reactions during the dehydrogenation process was developed. A mathematical model of the dehydrogenation process, describing the dynamics of chemical reactions taking place in each of the two stages of the reactor block at a constant temperature is developed. The estimation of the rate constants of direct and reverse reactions of each component, formation and exhaustion of the reacted mixture was made. The dynamics of the starting material concentration variations (ethyl benzene batch was obtained as well as styrene formation dynamics and all byproducts of dehydrogenation (benzene, toluene, ethylene, carbon, hydrogen, ect.. The calculated the variations of the component composition of the reaction mixture during its passage through the first and second stages of the reactor showed that the proposed mathematical description adequately reproduces the kinetics of the process under investigation. This demonstrates the advantage of the developed model, as well as loyalty to the values found for the rate constants of reactions, which enable the use of models for calculating the kinetics of ethyl benzene dehydrogenation under nonisothermal mode in order to determine the optimal temperature trajectory of the reactor operation. In the future, it will reduce energy and resource consumption, increase the volume of produced styrene and improve the economic indexes of the process.

Microstructures and Dehydrogenation Properties of Ball-milled MgH2-K2Ti6O13-Ni Composite Systems

Directory of Open Access Journals (Sweden)

ZHANG Jian

2016-11-01

Full Text Available The K2Ti6O13 whisker separate-doped and K2Ti6O13 whisker and Ni powder multi-doped MgH2 hydrogen storage composite systems were prepared by mechanical milling method. The microstructures and dehydrogenation properties of the prepared samples were characterized by some testing methods such as X-ray diffraction (XRD, scanning electron microscope (SEM and differential scanning calorimeter (DSC. The results show that the K2Ti6O13 whisker not only plays the roles in refining the MgH2 crystalline grain, but also inhibit the agglomeration of MgH2 particles in K2Ti6O13 whisker separate-doped system, which results in the decreased dehydrogenation temperature of MgH2 matrix. When the mass ratio of K2Ti6O13 to MgH2 is 3:7, the improvement effect on dehydrogenation properties of MgH2 is the most remarkable. As compared with pure ball-milled MgH2, the dehydrogenation temperature of MgH2 in K2Ti6O13 whisker separate-doped system is decreased by nearly 75℃. For K2Ti6O13 whisker and Ni powder multi-dopedsystem, the dehydrogenation temperature of MgH2 matrix is further decreased compared to K2Ti6O13 whisker separate-doped one due to the dual effects of refined MgH2 crystalline grain by K2Ti6O13 whisker and destabilized MgH2 lattice by Ni solution. As compared with pure ball-milled MgH2, the dehydrogenation temperature of MgH2 in K2Ti6O13 whisker and Ni powder multi-doped system is decreased by nearly 87℃.

Dehydrogenation of Light Alkanes over Supported Pt Catalysts

OpenAIRE

Wu, Jason

2015-01-01

The production of light alkenes comprises a 250 million ton per year industry due to their extensive use in the production of plastics, rubbers, fuel blending agents, and chemical intermediates. While steam cracking and fluid catalytic cracking of petroleum crude oils are the most common methods for obtaining light alkenes, rising oil prices and low selectivities toward specific alkenes have driven the search for a more economical and efficient process. Catalytic dehydrogenation of light alka...

A comparative DFT study on the dehydrogenation of methanol on Rh(100) and Rh(110)

Science.gov (United States)

Zhang, Minhua; Wu, Xingyu; Yu, Yingzhe

2018-04-01

Numerous density functional theory calculations have been performed to investigate the complete mechanisms of methanol dehydrogenation on Rh(100) and Rh(110) surfaces. The adsorption properties of relevant species were discussed in details. In addition, a comprehensive reaction network including four reaction pathways was built and analyzed. It is found that the initial Osbnd H bond scission of CH3OH seems to be more favorable than Csbnd H bond cleavage on both Rh(100) and Rh(110) surfaces from the perspective of activation barriers. It is also concluded that path1 (CH3OH → CH3O → CH2O → CHO → CO) is the predominant pathway on both Rh(100) and Rh (110) surfaces. On the whole, in most of the dehydrogenation reactions investigated, the energy barriers on Rh(100) are lower than those on Rh (110). Remarkable differences in the activity and predominant reaction pathway on Rh(100), Rh(110) and Rh(111) indicate that the dehydrogenation of methanol might be structure-sensitive.

Production of high-octane, unleaded motor fuel by alkylation of isobutane with isoamylenes obtained by dehydrogenation of isopentane

Energy Technology Data Exchange (ETDEWEB)

Hutson, T. Jr.; Hann, P.D.

1981-01-31

A process combination, with inter-cooperation, for producing high-octane alkylates comprising (a) dehydrogenating isopentane to isopentenes (amylenes), (b) introducing the mixture of said amylenes and unconverted isopentane into an HF alkylation unit for reaction with fresh or recycled isobutane, (c) separating the alkylation products into high octane alkylates, isopentane (for recycling to the dehydrogenation reactor) and isobutane (for recycling to the alkylation reactor).

Rhodium target preparation from homemade chloride plating baths used for the industrial cyclotron production of palladium-L03

International Nuclear Information System (INIS)

Sadeghi, M.; Van den Winkel, P.; Afarideh, H.; Haji-Saeid, M.; Syrafi Nafis, H.

2004-01-01

Purpose: To avoid acquisition problems of commercially available western rhodium plating solutions in developing countries, a new plating/recovery cycle for Rh-103 electroplated target material (1 g Rh per target) used for the industrial cyclotron production of Pd-103 was developed. Rhodium chloride plating solutions can be prepared by dissolution of the analytical grade compound or from rhodium recovery solutions obtained after electrosolubilisation of irradiated targets and extraction of palladium. Methods: The technology involves the selective removal of the copper target backing of an irradiated target in concentrated nitric acid using a homemade flow-through stripper. The resulting rhodium fragments are dissolved in a constant-volume (40 ml), homemade graphite centrifugal ac-electrodissolution mini-reactor operating at 90 degree C, 2 A.cm-2 and 1000-rpm rotation speed. The system allows time-controlled 99 % solubilisation of up to 3g rhodium (as fragments, powder or small pieces of wire) in less than 3 hours when 12 N hydrochloric acid is applied. Upon solvent-solvent extraction of the non-carrier added Pd-103 from the resulting HCI solution; the following procedure can be used for the simultaneous preparation of 4 targets showing a surface area of 11.69 cm 2 and a physical thickness of 48 Um. Dissolve an amount of hydrated RhC13 containing 2.8 g of rhodium in 400 ml of water. Alternatively, the filtered (0.45 μm filter) combined recovery solutions containing the same weight of rhodium can be evaporated to near dryness (350 degree C at the start, 150 degree C near the end) and residue taken up (gentle stirring, 50 degree C) in 400 ml of distilled water, After filtration, a stress reducing agent (sulfamic acid) is added and the pH sodium hydroxide. Upon make up to volume (450 ml) adjusted to the optimum value (pH = 2) with and preheating to 40 degree C, the resulting solution is introduced in a cylindrical home-made constant-volume, 4- target plating vessel

Liquid-liquid extraction/separation of platinum(IV) and rhodium(III) from acidic chloride solutions using tri-iso-octylamine

Energy Technology Data Exchange (ETDEWEB)

Lee, Jin-Young, E-mail: jinlee@kigam.re.kr [Metals Recovery Department, Minerals Resources Research Division, Korea Institute of Geoscience and Mineral Resources (KIGAM), 92 Gahangno, Yuesong-gu, Daejeon 305-350 (Korea, Republic of); Rajesh Kumar, J., E-mail: rajeshkumarphd@rediffmail.com [Metals Recovery Department, Minerals Resources Research Division, Korea Institute of Geoscience and Mineral Resources (KIGAM), 92 Gahangno, Yuesong-gu, Daejeon 305-350 (Korea, Republic of); Kim, Joon-Soo; Park, Hyung-Kyu; Yoon, Ho-Sung [Metals Recovery Department, Minerals Resources Research Division, Korea Institute of Geoscience and Mineral Resources (KIGAM), 92 Gahangno, Yuesong-gu, Daejeon 305-350 (Korea, Republic of)

2009-08-30

Liquid-liquid extraction/separation of platinum(IV) and rhodium(III) from acidic chloride solutions was carried out using tri-iso-octylamine (Alamine 308) as an extractant diluted in kerosene. The percentage extraction of platinum(IV) and rhodium(III) increased with increase in acid concentration up to 8 mol L{sup -1}. However, at 10 mol L{sup -1} HCl concentration, the extraction behavior was reversed, indicating the solvation type mechanism during extraction. The quantitative extraction of {approx}98% platinum(IV) and 36% rhodium(III) was achieved with 0.01 mol L{sup -1} Alamine 308. The highest separation factor (S.F. = 184.7) of platinum(IV) and rhodium(III) was achieved with 0.01 mol L{sup -1} Alamine 308 at 1.0 mol L{sup -1} of hydrochloric acid concentration. Alkaline metal salts like sodium chloride, sodium nitrate, sodium thiocyanate, lithium chloride, lithium nitrate, potassium chloride and potassium thiocyanate used for the salting-out effect. LiCl proved as best salt for the extraction of platinum(IV). Temperature effect demonstrates that the extraction process is exothermic. Hydrochloric acid and thiourea mixture proved to be better stripping reagents when compared with other mineral acids and bases.

Spatial and temporal distribution of platinum, palladium and rhodium in Zagreb air.

Science.gov (United States)

Rinkovec, Jasmina; Pehnec, Gordana; Godec, Ranka; Davila, Silvije; Bešlić, Ivan

2018-09-15

Platinum (Pt), palladium (Pd) and rhodium (Rh) are most widely used in the production of automotive catalytic converters that serve to reduce toxic emissions from motor vehicles. The aim of this study was to quantitatively determine the levels of platinum, palladium and rhodium in the PM 10 and PM 2.5 fraction of airborne particle matter and find their spatial and temporal distribution at different polluted areas of the city of Zagreb, Croatia. The method used in this paper included weekly sampling of airborne particle matter on quartz filters, microwave digestion in acid under high pressure and temperature, and analysis by inductively coupled plasma mass spectrometry (ICP MS). The results have shown that the highest mean values at all three sampling stations (North, Center, South) were obtained for palladium (3.856 pg m -3 , 5.396 pg m -3 , 5.600 pg m -3 ) and the lowest for rhodium (0.444 pg m -3 , 0.643 pg m -3 , 0.750 pg m -3 ). The average mass concentrations of platinum group elements (PGE) in PM 10 increased for all three elements in the direction North Zagreb are the first results of their kind for this area and will provide insights into the contribution of catalytic converters to the presence of these elements in the environment. Copyright © 2018 Elsevier B.V. All rights reserved.

The influence of ball-milling time on the dehydrogenation properties of the NaAlH4-MgH2 composite

NARCIS (Netherlands)

Bendyna, J.K.; Dyjak, S.M.; Notten, P.H.L.

2015-01-01

The recently developed NaAlH4eMgH2 composite shows improved hydrogen-storage properties compared to MgH2 and NaAlH4. However, the dehydrogenation reaction rates are still too limited, hampering practical applications. Mechanical ball milling is broadly used to improve the dehydrogenation reaction

Oxidative dehydrogenation of ethane on rare-earth oxide-based catalysts

Energy Technology Data Exchange (ETDEWEB)

Buyevskaya, O.; Baerns, M. [Institut fuer Angewandte Chemie Berlin-Adlershof e.V., Berlin (Germany)

1998-12-31

Results on the oxidative dehydrogenation of ethane on rare-earth oxide (REO) based catalysts (Na-P-Sm-O, Sm-Sr(Ca)-O, La-Sr-O and Nd-Sr-O) are described. Oxygen adsorption was found to be a key factor which determines the activity of this type of catalysts. Continuous flow experiments in the presence of catalysts which reveal strong oxygen adsorption showed that the reaction mixture is ignited resulting in an enhanced heat generation at the reactor inlet. The heat produced by the oxidative reactions was sufficient under the conditions chosen for the endothermic thermal pyrolysis which takes place preferentially in the gas phase. Ignition of the reaction mixture is an important catalyst function. Contrary to non-catalytic oxidative dehydrogenation, reaction temperatures above 700 C could be achieved without significant external heat input. Ethylene yields of up to 34-45% (S=66-73%) were obtained on REO-based catalysts under non-isothermal conditions (T{sub max}=810-865 C) at contact times in the order of 30 to 40 ms. (orig.)

Estudo da oxidação parcial do etanol em catalisadores de Rh por DRIFTS

Directory of Open Access Journals (Sweden)

Raquel Lima Oliveira

2013-01-01

Full Text Available The partial oxidation of ethanol on γ-Al2O3, CeO2, ZrO2 and Ce xZr1-xO2 supported rhodium catalysts was investigated by Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS. The catalysts were characterized by temperature-programmed reduction (TPR and cyclohexane dehydrogenation. DRIFTS studies on the partial oxidation of ethanol showed that ethanol is adsorbed dissociatively, through O-H bond breaking, with the formation of ethoxy species, followed by successive dehydrogenation to acetaldehyde and acetyl species. Further oxidation to acetate and carbonate species lead to the formation of CO, CH4 and H2 by decomposition. The presence of CeO2 in the catalysts favored the oxidation steps due to its oxygen storage capacity.

Adsorption and dehydrogenation of ammonia at the V{sub 2}O{sub 5}(010) surface: DFT cluster studies

Energy Technology Data Exchange (ETDEWEB)

Gruber, Mathis; Hermann, Klaus [Fritz-Haber-Institut der MPG, Berlin (Germany)

2008-07-01

Transition metal oxide catalysts are widely used for selective oxidation reactions. However, in many cases details of the catalytic reaction mechanisms are still under discussion. One prominent example is the ammoxidation of propylene to acrylonitrile at transition metal oxide surfaces (SOHIO process). This catalytic reaction includes, amongst other steps, the adsorption and dehydrogenation of NH{sub x}, x<4, at the catalyst surface. We have performed theoretical studies on these reaction steps where the catalyst is simulated by a finite section of the V{sub 2}O{sub 5}(010) surface. The calculations use density-functional theory combined with clusters modeling the surface and adsorbate system. Calculations for the clean V{sub 2}O{sub 5}(010) surface show that binding energies of the H atom are always significantly larger than of the NH{sub x} species. Further, the substrate is found to lower corresponding dehydrogenation energies compared with values for the gas phase reaction. However, the lowering is too small to make dehydrogenation likely to happen under ammoxidation reaction conditions. This suggests that surface defects such as oxygen vacancies become important for the reaction. Therefore, the role of oxygen vacancies for the dehydrogenation of NH{sub x} is discussed in detail.

Selective catalytic reduction system and process for treating NOx emissions using a palladium and rhodium or ruthenium catalyst

Science.gov (United States)

Sobolevskiy, Anatoly [Orlando, FL; Rossin, Joseph A [Columbus, OH; Knapke, Michael J [Columbus, OH

2011-07-12

A process for the catalytic reduction of nitrogen oxides (NOx) in a gas stream (29) in the presence of H.sub.2 is provided. The process comprises contacting the gas stream with a catalyst system (38) comprising zirconia-silica washcoat particles (41), a pre-sulfated zirconia binder (44), and a catalyst combination (40) comprising palladium and at least one of rhodium, ruthenium, or a mixture of ruthenium and rhodium.

Theoretical Study of Palladium Membrane Reactor Performance During Propane Dehydrogenation Using CFD Method

Directory of Open Access Journals (Sweden)

Kamran Ghasemzadeh

2017-04-01

Full Text Available This study presents a 2D-axisymmetric computational fluid dynamic (CFD model to investigate the performance Pd membrane reactor (MR during propane dehydrogenation process for hydrogen production. The proposed CFD model provided the local information of temperature and component concentration for the driving force analysis. After investigation of mesh independency of CFD model, the validation of CFD model results was carried out by other modeling data and a good agreement between CFD model results and theoretical data was achieved. Indeed, in the present model, a tubular reactor with length of 150 mm was considered, in which the Pt-Sn-K/Al2O3 as catalyst were filled in reaction zone. Hence, the effects of the important operating parameter (reaction temperature on the performances of membrane reactor (MR were studied in terms of propane conversion and hydrogen yield. The CFD results showed that the suggested MR system during propane dehydrogenation reaction presents higher performance with respect to once obtained in the conventional reactor (CR. In particular, by applying Pd membrane, was found that propane conversion can be increased from 41% to 49%. Moreover, the highest value of propane conversion (X = 91% was reached in case of Pd-Ag MR. It was also established that the feed flow rate of the MR is to be the one of the most important factors defining efficiency of the propane dehydrogenation process.

Thermodynamic assessment of the rhodium-ruthenium-oxygen (Rh-Ru-O) system

Science.gov (United States)

Gossé, S.; Bordier, S.; Guéneau, C.; Brackx, E.; Domenger, R.; Rogez, J.

2018-03-01

Ruthenium (Ru) and rhodium (Rh) are abundant platinum-group metals formed during burn-up of nuclear fuels. Under normal operating conditions, Rh and Ru accumulate and predominantly form metallic precipitates with other fission products like Mo, Pd and Tc. In the framework of vitrification of high-level nuclear waste, these fission products are poorly soluble in molten glasses. They precipitate as metallic particles and oxide phases. Moreover, these Ru and Rh rich phases strongly depend on temperature and the oxygen fugacity of the glass melt. In case of severe accidental conditions with air ingress, oxidation of the Ru and Rh is possible. At low temperatures (T 1422 K for rhodium sesquioxide and T > 1815 K for ruthenium dioxide), they may decompose into (Rh)-FCC or (Ru)-HCP metallic phases and radiotoxic volatile gaseous species. A thermodynamic assessment of the Rh-Ru-O system will enable the prediction of: (1) the metallic and oxide phases that form during the vitrification of high-level nuclear wastes and (2) the release of volatile gaseous species during a severe accident. The Calphad method developed herein employs a thermodynamic approach in the investigation of the thermochemistry of rhodium and ruthenium at high temperatures. Current literature on the thermodynamic properties and phase diagram data enables preliminary thermodynamic assessments of the Rh-O and Ru-O systems. Additionally, select compositions in the ternary Rh-Ru-O system underwent experimental tests to complement data found in literature and to establish the phase equilibria in the ternary system.

Heterogeneous catalytic oxidative dehydrogenation of ethylbenzene to styrene with carbon dioxide

Energy Technology Data Exchange (ETDEWEB)

Badstube, T.; Papp, H. [Leipzig Univ. (Germany). Inst. fuer Technische Chemie; Kustrowski, P.; Dziembaj, R. [Jagiellonian Univ., Crakow (Poland). Faculty of Chemistry

1998-12-31

Alkaline promoted active carbon supported iron catalysts are very active in the oxidative dehydrogenation of ethylbenzene to styrene in the presence of carbon dioxide. The best results were obtained at 550 C for a Li-promoted catalyst with a conversion of ethylbenzene of 75% and a selectivity towards styrene of nearly 95%. These results are better than those obtained with industrial catalysts which perform the dehydrogenation process with an excess of water. The main product of the dehydrogenation reaction with CO{sub 2} was styrene, but the following by-products were detected - benzene and toluene. The selectivity towards toluene was always higher than towards benzene. We observed also the formation of carbon monoxide and water, which were produced with a constant molar ratio of about 0.8. The weight of the catalysts increased up to 20% during the reaction due to deposition of carbon. Using a too large excess of CO{sub 2} (CO{sub 2}/EB>10) was harmful for the styrene yield. The most favorable molar ratio of CO{sub 2} to EB was 10:1. No correlation between the molar ratios of reactants and the amount of deposited coke on the surface of catalysts was observed. The highest catalytic activity showed iron loaded D-90 catalysts which were promoted with alkali metals in a molar ratio of 1:10. Iron, nickel and cobalt loaded carbonized PPAN, PC, inorganic supports like Al{sub 2}O{sub 3}, SiO{sub 2}/ZrO{sub 2} or TiO{sub 2} respectively and commercial iron catalysts applied for styrene production did not show comparable catalytic activity in similar conditions. (orig.)

STABLE SILICA-GRAFTED POLYMER-BOUND BULKY-PHOSPHITE MODIFIED RHODIUM HYDROFORMYLATION CATALYSTS

NARCIS (Netherlands)

JONGSMA, T; VANAERT, H; FOSSEN, M; CHALLA, G; VANLEEUWEN, PWNM

1993-01-01

The present study demonstrates that silica-grafted polymer-bound phosphite modified rhodium complexes can be used in continuous flow reactors. The hydroformylation of styrene was carried out at moderate pressure (p(CO/H-2) = 30 bar) and temperature (T = 100-degrees-C), yielding constant conversions

ENHANCEMENT OF EQUILIBRIUMSHIFT IN DEHYDROGENATION REACTIONS USING A NOVEL MEMBRANE REACTOR; FINAL

International Nuclear Information System (INIS)

Shamsuddin Ilias, Ph.d., P.E.; Franklin G. King, D.Sc.

2001-01-01

With the advances in new inorganic materials and processing techniques, there has been renewed interest in exploiting the benefits of membranes in many industrial applications. Inorganic and composite membranes are being considered as potential candidates for use in membrane-reactor configuration for effectively increasing reaction rate, selectivity and yield of equilibrium limited reactions. To investigate the usefulness of a palladium-ceramic composite membrane in a membrane reactor-separator configuration, we investigated the dehydrogenation of cyclohexane by equilibrium shift. A two-dimensional pseudo-homogeneous reactor model was developed to study the dehydrogenation of cyclohexane by equilibrium shift in a tubular membrane reactor. Radial diffusion was considered to account for the concentration gradient in the radial direction due to permeation through the membrane. For a dehydrogenation reaction, the feed stream to the reaction side contained cyclohexane and argon, while the separation side used argon as the sweep gas. Equilibrium conversion for dehydrogenation of cyclohexane is 18.7%. The present study showed that 100% conversion could be achieved by equilibrium shift using Pd-ceramic membrane reactor. For a feed containing cyclohexane and argon of 1.64 x 10(sup -6) and 1.0 x 10(sup -3) mol/s, over 98% conversion could be readily achieved. The dehydrogenation of cyclohexane was also experimentally investigated in a palladium-ceramic membrane reactor. The Pd-ceramic membrane was fabricated by electroless deposition of palladium on ceramic substrate. The performance of Pd-ceramic membrane was compared with a commercially available hydrogen-selective ceramic membrane. From limited experimental data it was observed that by appropriate choice of feed flow rate and sweep gas rate, the conversion of cyclohexane to benzene and hydrogen can increased to 56% at atmospheric pressure and 200 C in a Pd-ceramic membrane reactor. In the commercial ceramic membrane

Decarbonylative Cross-Couplings: Nickel Catalyzed Functional Group Interconversion Strategies for the Construction of Complex Organic Molecules

KAUST Repository

Guo, Lin; Rueping, Magnus

2018-01-01

The utilization of carboxylic acid esters as electrophiles in metal-catalyzed cross-coupling reactions is increasingly popular, as environmentally friendly and readily available ester derivatives can be powerful alternatives to the commonly used organohalides. However, key challenges associated with the use of these chemicals remain to be addressed, including the stability of ester substrates and the high energy barrier associated with their oxidative addition to low-valent metal species. Due to recent developments in nickel catalysis that make it easier to perform oxidative additions, chemists have become interested in applying less reactive electrophiles as coupling counterparts in nickel-catalyzed transformations. Hence, our group and others have independently investigated various ester group substitutions and functionalizations enabled by nickel catalysis. Such methods are of great interest as they enable the exchange of ester groups, which can be used as directing groups in metal-catalyzed C-H functionalizations prior to their replacement. Here, we summarize our recent efforts toward the development of nickel-catalyzed decarbonylative cross-coupling reactions of carboxylic esters. Achievements accomplished by other groups in this area are also included. To this day, a number of new transformations have been successfully developed, including decarbonylative arylations, alkylations, cyanations, silylations, borylations, aminations, thioetherifications, stannylations, and hydrogenolysis reactions. These transformations proceed via a nickel-catalyzed decarbonylative pathway and have shown a high degree of reactivity and chemoselectivity, as well as several other unique advantages in terms of substrate availability, due to the use of esters as coupling partners. Although the mechanisms of these reactions have not yet been fully understood, chemists have already provided some important insights. For example, Yamamoto explored the stoichiometric nickel

Decarbonylative Cross-Couplings: Nickel Catalyzed Functional Group Interconversion Strategies for the Construction of Complex Organic Molecules.

Science.gov (United States)

Guo, Lin; Rueping, Magnus

2018-05-15

The utilization of carboxylic acid esters as electrophiles in metal-catalyzed cross-coupling reactions is increasingly popular, as environmentally friendly and readily available ester derivatives can be powerful alternatives to the commonly used organohalides. However, key challenges associated with the use of these chemicals remain to be addressed, including the stability of ester substrates and the high energy barrier associated with their oxidative addition to low-valent metal species. Due to recent developments in nickel catalysis that make it easier to perform oxidative additions, chemists have become interested in applying less reactive electrophiles as coupling counterparts in nickel-catalyzed transformations. Hence, our group and others have independently investigated various ester group substitutions and functionalizations enabled by nickel catalysis. Such methods are of great interest as they enable the exchange of ester groups, which can be used as directing groups in metal-catalyzed C-H functionalizations prior to their replacement. Here, we summarize our recent efforts toward the development of nickel-catalyzed decarbonylative cross-coupling reactions of carboxylic esters. Achievements accomplished by other groups in this area are also included. To this day, a number of new transformations have been successfully developed, including decarbonylative arylations, alkylations, cyanations, silylations, borylations, aminations, thioetherifications, stannylations, and hydrogenolysis reactions. These transformations proceed via a nickel-catalyzed decarbonylative pathway and have shown a high degree of reactivity and chemoselectivity, as well as several other unique advantages in terms of substrate availability, due to the use of esters as coupling partners. Although the mechanisms of these reactions have not yet been fully understood, chemists have already provided some important insights. For example, Yamamoto explored the stoichiometric nickel

Decarbonylative Cross-Couplings: Nickel Catalyzed Functional Group Interconversion Strategies for the Construction of Complex Organic Molecules

KAUST Repository

Guo, Lin

2018-04-13

The utilization of carboxylic acid esters as electrophiles in metal-catalyzed cross-coupling reactions is increasingly popular, as environmentally friendly and readily available ester derivatives can be powerful alternatives to the commonly used organohalides. However, key challenges associated with the use of these chemicals remain to be addressed, including the stability of ester substrates and the high energy barrier associated with their oxidative addition to low-valent metal species. Due to recent developments in nickel catalysis that make it easier to perform oxidative additions, chemists have become interested in applying less reactive electrophiles as coupling counterparts in nickel-catalyzed transformations. Hence, our group and others have independently investigated various ester group substitutions and functionalizations enabled by nickel catalysis. Such methods are of great interest as they enable the exchange of ester groups, which can be used as directing groups in metal-catalyzed C-H functionalizations prior to their replacement. Here, we summarize our recent efforts toward the development of nickel-catalyzed decarbonylative cross-coupling reactions of carboxylic esters. Achievements accomplished by other groups in this area are also included. To this day, a number of new transformations have been successfully developed, including decarbonylative arylations, alkylations, cyanations, silylations, borylations, aminations, thioetherifications, stannylations, and hydrogenolysis reactions. These transformations proceed via a nickel-catalyzed decarbonylative pathway and have shown a high degree of reactivity and chemoselectivity, as well as several other unique advantages in terms of substrate availability, due to the use of esters as coupling partners. Although the mechanisms of these reactions have not yet been fully understood, chemists have already provided some important insights. For example, Yamamoto explored the stoichiometric nickel

Rhodium-103m generator

International Nuclear Information System (INIS)

Mamadaliev, N.; Levin, V.I.; Malinin, A.B.

1978-01-01

103 Pd separated from metal rhodium irradiated with deuterons has been used without a carrier for sup( 03m)Rh generator The generator of sup(103m)Rh is a column 6mm in diameter filled with an anionite in Cl - form (Dowex-2,8,200-400 mesh) with an adsorbed parent isotope of 103 Pd. As a result of its decay, a 103 Rh daughter isotope is accumulated, which can be washed out from the generator from time to time with a corresponding solution. To prepare the generator, 0.5g of the resin with an adsorbed 103 Pd is charged into the column containing 1g of the same resin. Washing out with 2N HCl yields more than 90% of sup(103m)Rh with a radionuclide purity of more than 99.99%

Imaging sequential dehydrogenation of methanol on Cu(110) with a scanning tunneling microscope.

Science.gov (United States)

Kitaguchi, Y; Shiotari, A; Okuyama, H; Hatta, S; Aruga, T

2011-05-07

Adsorption of methanol and its dehydrogenation on Cu(110) were studied by using a scanning tunneling microscope (STM). Upon adsorption at 12 K, methanol preferentially forms clusters on the surface. The STM could induce dehydrogenation of methanol sequentially to methoxy and formaldehyde. This enabled us to study the binding structures of these products in a single-molecule limit. Methoxy was imaged as a pair of protrusion and depression along the [001] direction. This feature is fully consistent with the previous result that it adsorbs on the short-bridge site with the C-O axis tilted along the [001] direction. The axis was induced to flip back and forth by vibrational excitations with the STM. Two configurations were observed for formaldehyde, whose structures were proposed based on their characteristic images and motions.

Oxidative dehydrogenation of aqueous ethanol on a carbon supported platinum catalyst

NARCIS (Netherlands)

Tillaart, van den J.A.A.; Kuster, B.F.M.; Marin, G.B.M.M.

1994-01-01

The kinetics of the selective oxidative dehydrogenation of ethanol to ethanal over a platinum on graphite catalyst with oxygen in water was investigated in a three-phase continuous stirred tank reactor by variation of temp., pH and reactant concns. No effect of the pH on the disappearance rate of

Oxidative dehydrogenation of ethylbenzene using nitrous oxide over vanadia-magnesia catalysts

NARCIS (Netherlands)

Shiju, N.R.; Anilkumar, M.; Gokhale, S.P.; Rao, B.S.; Satyanarayana, C.V.V.

2011-01-01

A series of V-Mg-O catalysts with different loadings of vanadia were prepared by the wet impregnation method and the effect of the local structure of these catalysts on the oxidative dehydrogenation of ethylbenzene with N2O was investigated. High styrene selectivity (97%) was obtained at 773 K. The

Controlled Oxygen Chemisorption on an Alumina Supported Rhodium Catalyst. The Formation of a New Metal-Metal Oxide Interface Determined with EXAFS.

NARCIS (Netherlands)

Koningsberger, D.C.; Martens, J.H.A.; Prins, R.

1989-01-01

An alumina-supported rhodium catalyst has been studied with EXAFS. After reduction and evacuation, oxygen was admitted at 100 and 300 K. EXAFS spectra of the catalyst after oxygen admission at 100 K indicated the beginning of oxidation. At 300 K only a small part of the rhodium particles remained

Dehydrogenation of Ethylbenzene with Carbon Dioxide as Soft Oxidant over Supported Vanadium-Antimony Oxide Catalyst

Energy Technology Data Exchange (ETDEWEB)

Hong, Do Young; Vislovskiy, Vladislav P.; Yoo, Jin S.; Chang, Jong San [Korea Research Institute of Chemical Technology, Daejeon (Korea, Republic of); Park, Sang Eon [Inha University, Incheon (Korea, Republic of); Park, Min Seok [Mongolia International University, Ulaanbaatar (Mongolia)

2005-11-15

This work presents that carbon dioxide, which is a main contributor to the global warming effect, could be utilized as a selective oxidant in the oxidative dehydrogenation of ethylbenzene. The dehydrogenation of ethylbenzene over alumina-supported vanadium-antimony oxide catalyst has been studied under different atmospheres such as inert nitrogen, steam, oxygen or carbon dioxide as diluent or oxidant. Among them, the addition of carbon dioxide gave the highest styrene yield (up to 82%) and styrene selectivity (up to 97%) along with stable activity. Carbon dioxide could play a beneficial role of a selective oxidant in the improvement of the catalytic behavior through the oxidative pathway.

Correlation between the Stereochemistry and Bioactivity in Octahedral Rhodium Prolinato Complexes.

Science.gov (United States)

Rajaratnam, Rajathees; Martin, Elisabeth K; Dörr, Markus; Harms, Klaus; Casini, Angela; Meggers, Eric

2015-08-17

Controlling the relative and absolute configuration of octahedral metal complexes constitutes a key challenge that needs to be overcome in order to fully exploit the structural properties of octahedral metal complexes for applications in the fields of catalysis, materials sciences, and life sciences. Herein, we describe the application of a proline-based chiral tridentate ligand to decisively control the coordination mode of an octahedral rhodium(III) complex. We demonstrate the mirror-like relationship of synthesized enantiomers and differences between diastereomers. Further, we demonstrate, using the established pyridocarbazole pharmacophore ligand as part of the organometallic complexes, the importance of the relative and absolute stereochemistry at the metal toward chiral environments like protein kinases. Protein kinase profiling and inhibition data confirm that the proline-based enantiopure rhodium(III) complexes, despite having all of the same constitution, differ strongly in their selectivity properties despite their unmistakably mutual origin. Moreover, two exemplary compounds have been shown to induce different toxic effects in an ex vivo rat liver model.

Adhesion of rhodium films on metallic substrates

International Nuclear Information System (INIS)

Marot, L.; Covarel, G.; Tuilier, M.-H.; Steiner, R.; Oelhafen, P.

2008-01-01

Rhodium coated metallic films were prepared by magnetron sputtering on metallic substrates. All films were elaborated in same conditions on copper, molybdenum and stainless steel. Adhesion strength tests were carried out by scratch test. The results reveal that the adhesion strength between the film and the substrate is influenced by the hardness of the substrate. Increase of deposition temperature improves the adhesion of the coating. In addition, pre-treatment of substrates by a filtered cathodic vacuum arc and the layer thickness have has some effects on the final adhesion strength

Adhesion of rhodium films on metallic substrates

Energy Technology Data Exchange (ETDEWEB)

Marot, L. [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)], E-mail: laurent.marot@unibas.ch; Covarel, G.; Tuilier, M.-H. [Laboratoire Mecanique, Materiaux et Procedes de Fabrication, Pole STIC-SPI-Math 61 rue Albert Camus, Universite de Haute-Alsace, F-68093 - Mulhouse Cedex (France); Steiner, R.; Oelhafen, P. [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)

2008-09-01

Rhodium coated metallic films were prepared by magnetron sputtering on metallic substrates. All films were elaborated in same conditions on copper, molybdenum and stainless steel. Adhesion strength tests were carried out by scratch test. The results reveal that the adhesion strength between the film and the substrate is influenced by the hardness of the substrate. Increase of deposition temperature improves the adhesion of the coating. In addition, pre-treatment of substrates by a filtered cathodic vacuum arc and the layer thickness have has some effects on the final adhesion strength.

Relaxation of polarized nuclei in superconducting rhodium

DEFF Research Database (Denmark)

Knuuttila, T.A.; Tuoriniemi, J.T.; Lefmann, K.

2000-01-01

Nuclear spin lattice relaxation rates were measured in normal and superconducting (sc) rhodium with nuclear polarizations up to p = 0.55. This was sufficient to influence the sc state of Rh, whose T, and B-c, are exceptionally low. Because B-c ... is unchanged, the nuclear spin entropy was fully sustained across the sc transition. The relaxation in the sc state was slower at all temperatures without the coherence enhancement close to T-c. Nonzero nuclear polarization strongly reduced the difference between the relaxation rates in the sc and normal...

Non-Precious Bimetallic Catalysts for Selective Dehydrogenation of an Organic Chemical Hydride System

KAUST Repository

Shaikh Ali, Anaam; Jedidi, Abdesslem; Cavallo, Luigi; Takanabe, Kazuhiro

2015-01-01

Methylcyclohexane (MCH)-Toluene (TOL) chemical hydride cycles as a hydrogen carrier system is successful with the selective dehydrogenation reaction of MCH to TOL, which has been achieved only using precious Pt-based catalysts. Herein, we report

Treatment of ammonia by catalytic wet oxidation process over platinum-rhodium bimetallic catalyst in a trickle-bed reactor: effect of pH.

Science.gov (United States)

Hung, Chang-Mao; Lin, Wei-Bang; Ho, Ching-Lin; Shen, Yun-Hwei; Hsia, Shao-Yi

2010-08-01

This work adopted aqueous solutions of ammonia for use in catalytic liquid-phase reduction in a trickle-bed reactor with a platinum-rhodium bimetallic catalyst, prepared by the co-precipitation of chloroplatinic acid (H2PtCl6) and rhodium nitrate [Rh(NO3)3]. The experimental results demonstrated that a minimal amount of ammonia was removed from the solution by wet oxidation in the absence of any catalyst, while approximately 97.0% of the ammonia was removed by wet oxidation over the platinum-rhodium bimetallic catalyst at 230 degrees C with an oxygen partial pressure of 2.0 MPa. The oxidation of ammonia has been studied as a function of pH, and the main reaction products were determined. A synergistic effect is manifest in the platinum-rhodium bimetallic structure, in which the material has the greatest capacity to reduce ammonia. The reaction pathway linked the oxidizing ammonia to nitric oxide, nitrogen, and water.

Catalytic wet oxidation of ammonia solution: Activity of the nanoscale platinum-palladium-rhodium composite oxide catalyst

International Nuclear Information System (INIS)

Hung, C.-M.

2009-01-01

Aqueous solutions of 400-1000 mg/L of ammonia were oxidized in a trickle-bed reactor (TBR) in this study of nanoscale platinum-palladium-rhodium composite oxide catalysts, which were prepared by the co-precipitation of H 2 PtCl 6 , Pd(NO 3 ) 3 and Rh(NO 3 ) 3 . Hardly any of the dissolved ammonia was removed by wet oxidation in the absence of any catalyst, whereas about 99% of the ammonia was reduced during wet oxidation over nanoscale platinum-palladium-rhodium composite oxide catalysts at 503 K in an oxygen partial pressure of 2.0 MPa. A synergistic effect exists in the nanoscale platinum-palladium-rhodium composite structure, which is the material with the highest ammonia reduction activity. The nanometer-sized particles were characterized by TEM, XRD and FTIR. The effect of the initial concentration and reaction temperature on the removal of ammonia from the effluent streams was also studied at a liquid hourly space velocity of under 9 h -1 in the wet catalytic processes

Catalytic wet oxidation of ammonia solution: Activity of the nanoscale platinum-palladium-rhodium composite oxide catalyst

Energy Technology Data Exchange (ETDEWEB)

Hung, C.-M. [Department of Industry Engineering and Management, Yung-Ta Institute of Technology and Commerce, 316 Chung-shan Road, Linlo, Pingtung 909, Taiwan (China)], E-mail: hungcm1031@gmail.com

2009-04-15

Aqueous solutions of 400-1000 mg/L of ammonia were oxidized in a trickle-bed reactor (TBR) in this study of nanoscale platinum-palladium-rhodium composite oxide catalysts, which were prepared by the co-precipitation of H{sub 2}PtCl{sub 6}, Pd(NO{sub 3}){sub 3} and Rh(NO{sub 3}){sub 3}. Hardly any of the dissolved ammonia was removed by wet oxidation in the absence of any catalyst, whereas about 99% of the ammonia was reduced during wet oxidation over nanoscale platinum-palladium-rhodium composite oxide catalysts at 503 K in an oxygen partial pressure of 2.0 MPa. A synergistic effect exists in the nanoscale platinum-palladium-rhodium composite structure, which is the material with the highest ammonia reduction activity. The nanometer-sized particles were characterized by TEM, XRD and FTIR. The effect of the initial concentration and reaction temperature on the removal of ammonia from the effluent streams was also studied at a liquid hourly space velocity of under 9 h{sup -1} in the wet catalytic processes.

Catalytic wet oxidation of ammonia solution: activity of the nanoscale platinum-palladium-rhodium composite oxide catalyst.

Science.gov (United States)

Hung, Chang-Mao

2009-04-15

Aqueous solutions of 400-1000 mg/L of ammonia were oxidized in a trickle-bed reactor (TBR) in this study of nanoscale platinum-palladium-rhodium composite oxide catalysts, which were prepared by the co-precipitation of H(2)PtCl(6), Pd(NO(3))(3) and Rh(NO(3))(3). Hardly any of the dissolved ammonia was removed by wet oxidation in the absence of any catalyst, whereas about 99% of the ammonia was reduced during wet oxidation over nanoscale platinum-palladium-rhodium composite oxide catalysts at 503 K in an oxygen partial pressure of 2.0 MPa. A synergistic effect exists in the nanoscale platinum-palladium-rhodium composite structure, which is the material with the highest ammonia reduction activity. The nanometer-sized particles were characterized by TEM, XRD and FTIR. The effect of the initial concentration and reaction temperature on the removal of ammonia from the effluent streams was also studied at a liquid hourly space velocity of under 9 h(-1) in the wet catalytic processes.

Column preconcentration and electrothermal atomic absorption spectrometric determination of rhodium in some food and standard samples.

Science.gov (United States)

Taher, Mohammad Ali; Pourmohammad, Fatemeh; Fazelirad, Hamid

2015-12-01

In the present work, an electrothermal atomic absorption spectrometric method has been developed for the determination of ultra-trace amounts of rhodium after adsorption of its 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol/tetraphenylborate ion associated complex at the surface of alumina. Several factors affecting the extraction efficiency such as the pH, type of eluent, sample and eluent flow rates, sorption capacity of alumina and sample volume were investigated and optimized. The relative standard deviation for eight measurements of 0.1 ng/mL of rhodium was ±6.3%. In this method, the detection limit was 0.003 ng/mL in the original solution. The sorption capacity of alumina and the linear range for Rh(III) were evaluated as 0.8 mg/g and 0.015-0.45 ng/mL in the original solution, respectively. The proposed method was successfully applied for the extraction and determination of rhodium content in some food and standard samples with high recovery values. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Extraction of fission product rhodium from nitric acid solutions. 1

International Nuclear Information System (INIS)

Gorski, B.; Beer, M.; Russ, L.

1988-01-01

The extraction of noble metals from nitric acid solutions represents one problem of separating valueable substances from nuclear wastes in nuclear fuel reprocessing. Results of distribution experiments demonstrate the possibility of solvent extraction of rhodium using tertiary amines in presence of nitrite. Even short mixing times realize high distribution coefficients allowing quantitative separation from aqueous solutions. (author)

Komplexe zouten van trans-1-2-diaminocyclohexaan met driewaardig rhodium en kobalt

NARCIS (Netherlands)

Bijkerk, Lucas

1937-01-01

Some complex salts of trans-I-2-díominocyclohexane with trivalent cobaltum and rhodium were prepared and their properties described in detail. Diaminocyclohexanwe as obtained by the following series of reactions: cyclohexanone --> cyclohexanone-I-oxalylicester --> cyclohexonone-I-carboxylicester-2

A NEW TYPE OF HIGHLY-ACTIVE POLYMER-BOUND RHODIUM HYDROFORMYLATION CATALYST

NARCIS (Netherlands)

JONGSMA, T; KIMKES, P; CHALLA, G; VANLEEUWEN, PWNM

1992-01-01

A new route of attaching phosphites to a (co)polymer chain is described. These copolymers are used for the preparation of a rhodium phosphite hydroformylation catalyst. The catalytic activity of this polymer-bound system is identical to that of the low molecular weight analogue. The catalysts show a

Synergistic effect of Ti and F co-doping on dehydrogenation properties of MgH2 from first-principles calculations

International Nuclear Information System (INIS)

Zhang, J.; Huang, Y.N.; Mao, C.; Peng, P.

2012-01-01

Highlights: ► The co-incorporation of Ti and F into MgH 2 lattice is energetically favorable. ► The incorporated Ti and F in MgH 2 preferably generate TiH 2 and MgF 2 , respectively. ► The synergistic effect of Ti and F is superior to that of pure Ti. ► The weakened interactions of Mg–H explain enhanced dehydrogenation properties. - Abstract: The energetic and electronic properties of MgH 2 co-doped with Ti and F are investigated using first-principles calculations based on density functional theory. The calculation results show that incorporation of Ti combined with F atoms into MgH 2 lattice is energetically favorable relative to single incorporation of Ti atom. After dehydrogenation, the co-doped Ti and F in MgH 2 preferably generate TiH 2 and MgF 2 , respectively. Comparatively, the combined effect of Ti and F in improving the dehydrogenation properties of MgH 2 is superior to that of pure Ti. These results provide a reasonable explanation for experimental observations. Analysis of electronic structures suggests the enhanced dehydrogenation properties of doped MgH 2 can be attributed to the weakened bonding interactions between Mg and H due to foreign species doping.

Effects of human serun albumin in some biological properties of rhodium(II complexes

Directory of Open Access Journals (Sweden)

Espósito Breno P.

2000-01-01

Full Text Available The affinities for human albumin (HSA of five rhodium(II complexes of general formula [Rh2(bridge4] (bridge = acetate, propionate, butyrate, trifluoroacetate and trifluoroacetamidate were determined by spectrophotometry. In the case of the alkylcarboxylates, an inverse correlation of affinity with their liposolubilities was observed. Diffusion of the free or protein-bound complexes into Ehrlich cells in vitro seems to be primarily governed by the hydrophobic character of the complex. The complex [Rh2(tfc4] exhibited affinity towards the protein (K = 214.1 as well as cell partition both in the absence (32.1% and presence (48.6% of HSA. The compound HSA: [Rh2(tfc4] has had its antitumoral action in tumor-bearing Balb-c mice investigated, showing that HSA can be a drug reservoir for the rhodium complex.

Rh-Catalyzed (5+2) Cycloadditions of 3-Acyloxy-1,4-enynes and Alkynes: Computational Study of Mechanism, Reactivity, and Regioselectivity

Science.gov (United States)

Xu, Xiufang; Liu, Peng; Shu, Xing-zhong; Tang, Weiping; Houk, K. N.

2013-01-01

The mechanism of Rh-catalyzed (5+2) cycloadditions of 3-acyloxy-1,4-enyne (ACE) and alkynes is investigated using density functional theory calculations. The catalytic cycle involves 1,2-acyloxy migration, alkyne insertion, and reductive elimination to form the cycloheptatriene product. In contrast to the (5+2) cycloadditions with vinylcyclopropanes (VCP), in which alkyne inserts into a rhodium-allyl bond, alkyne insertion into a Rh–C(sp2) bond is preferred. The 1,2-acyloxy migration is found to be the rate-determining step of the catalytic cycle. The electron-rich p-dimethylaminobenzoate substrate promotes 1,2-acyloxy migration and significantly increases the reactivity. In the regioselectivity-determining alkyne insertion step, the alkyne substituent prefers to be distal to the forming C–C bond and thus distal to the OAc group in the product. PMID:23725341

Dehydrogenation of Isobutane with Carbon Dioxide over SBA-15-Supported Vanadium Oxide Catalysts

Directory of Open Access Journals (Sweden)

Chunling Wei

2016-10-01

Full Text Available A series of vanadia catalysts supported on SBA-15 (V/SBA with a vanadia (V content ranging from 1% to 11% were prepared by an incipient wetness method. Their catalytic behavior in the dehydrogenation of isobutane to isobutene with CO2 was examined. The catalysts were characterized by N2 adsorption, X-ray diffraction (XRD, scanning electron microscopy (SEM, Raman spectroscopy, and temperature-programmed reduction (TPR. It was found that these catalysts were effective for the dehydrogenation reaction, and the catalytic activity is correlated with the amount of dispersed vanadium species on the SBA-15 support. The 7% V/SBA catalyst shows the highest activity, which gives 40.8% isobutane conversion and 84.8% isobutene selectivity. The SBA-15-supported vanadia exhibits higher isobutane conversion and isobutene selectivity than the MCM-41-supported one.

Development of packed bed membrane reactor for the oxidative dehydrogenation of propane

NARCIS (Netherlands)

Kotanjac, Zeljko

2009-01-01

In this research, a reactor concept for the oxidative dehydrogenation of propane was studied. First a literature survey was performed, to investigate which are the best catalyst systems and best operating conditions that result in the largest propylene yield. In the kinetic study of ODHP over a

Lactic acid and hydrogen from glycerol via acceptorless dehydrogenation using homogeneous catalysts

NARCIS (Netherlands)

Bottari, Giovanni; Barta, Katalin

2015-01-01

Acceptorless dehydrogenation of alcohols has emerged as a powerful methodology for the valorization of biomass derived platform chemicals and building blocks. In this review we provide a short overview of the advantages and possible product outcomes of this method. The main focus will be devoted to

Arylation of Rhodium(II) Azavinyl Carbenes with Boronic Acids

Science.gov (United States)

Selander, Nicklas; Worrell, Brady T.; Chuprakov, Stepan; Velaparthi, Subash; Fokin, Valery V.

2013-01-01

A highly efficient and stereoselective arylation of in situ generated azavinyl carbenes affording 2,2-diaryl enamines at ambient temperatures has been developed. These transition metal carbenes are directly produced from readily available and stable 1-sulfonyl-1,2,3-triazoles in the presence of a rhodium carboxylate catalyst. In several cases, the enamines generated in this reaction can be cyclized into substituted indoles employing copper catalysts. PMID:22913576

Inter-diffusion study of rhodium and tantalum by RBS

International Nuclear Information System (INIS)

Nuttens, V.E.; Hubert, R.L.; Bodart, F.; Lucas, S.

2005-01-01

The inter-diffusion of rhodium and tantalum has been studied with the goal of synthesizing an alloy acting as a diffusion barrier for high temperature applications. Rh/Ta sandwiched samples were annealed in vacuum at temperature ranging from 800 to 900 deg. C and from 1000 to 1075 deg. C. The diffusion profiles were obtained by RBS. They suggest the formation of two clearly different phases in each temperature range considered

Bimetallic poly- and oligo-nuclear complexes based on a rhodium(III) metalloligand

Science.gov (United States)

Vasilchenko, Danila B.; Venediktov, Anatoliy B.; Korenev, Sergey V.; Filatov, Evgeniy Yu.; Baidina, Iraida A.; Nadolinnyi, Vladimir A.

2012-10-01

Interaction of trans-[Rh(i-Nic)4Cl2]3- anions (i-Nic- - isonicotinate anion) with Cuaq2+ and Coaq2+ cations in water has afforded complex salts Co3[Rh(i-Nic)4Cl2]2·17H2O (1) and Cu3[Rh(i-Nic)4Cl2]2·14H2O (2). Oligonuclear character of 1 and 2 has been established. A coordination polymer Cu5[Rh(i-Nic)4Cl2]2(i-Nic)2(OH)2·2H2O (3) has been crystallized by hydrothermal treatment of 2 at 160 °C, and its structure was determined by X-ray structural analysis. EPR data for the complexes has been collected and interpreted. Thermal decomposition of the salts was studied by c-DTA. Bimetallic alloys rhodium-copper and rhodium-cobalt have been obtained as final products of thermal decomposition.

A DRIFTS study of the partial oxidation of ethanol on Rh catalysts; Estudo da oxidacao parcial do etanol em catalisadores de Rh por DRIFTS

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Raquel Lima; Passos, Fabio Barboza, E-mail: fbpassos@vm.uff.br [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Departamento de Engenharia Quimica e de Petroleo

2013-09-01

The partial oxidation of ethanol on {gamma}-Al{sub 2}O{sub 3}, CeO{sub 2}, ZrO{sub 2} and Ce{sub x}Zr{sub 1-x}O{sub 2} supported rhodium catalysts was investigated by Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). The catalysts were characterized by temperature-programmed reduction (TPR) and cyclohexane dehydrogenation. DRIFTS studies on the partial oxidation of ethanol showed that ethanol is adsorbed dissociatively, through O-H bond breaking, with the formation of ethoxy species, followed by successive dehydrogenation to acetaldehyde and acetyl species. Further oxidation to acetate and carbonate species lead to the formation of CO, CH{sub 4} and H{sub 2} by decomposition. The presence of CeO{sub 2} in the catalysts favored the oxidation steps due to its oxygen storage capacity. (author)

Incorporation of catalytic dehydrogenation into fischer-tropsch synthesis to significantly reduce carbon dioxide emissions

Science.gov (United States)

Huffman, Gerald P.

2012-11-13

A new method of producing liquid transportation fuels from coal and other hydrocarbons that significantly reduces carbon dioxide emissions by combining Fischer-Tropsch synthesis with catalytic dehydrogenation is claimed. Catalytic dehydrogenation (CDH) of the gaseous products (C1-C4) of Fischer-Tropsch synthesis (FTS) can produce large quantities of hydrogen while converting the carbon to multi-walled carbon nanotubes (MWCNT). Incorporation of CDH into a FTS-CDH plant converting coal to liquid fuels can eliminate all or most of the CO.sub.2 emissions from the water-gas shift (WGS) reaction that is currently used to elevate the H.sub.2 level of coal-derived syngas for FTS. Additionally, the FTS-CDH process saves large amounts of water used by the WGS reaction and produces a valuable by-product, MWCNT.

Synthesis and Evaluation of Nanostructured Gold-Iron Oxide Catalysts for the Oxidative Dehydrogenation of Cyclohexane

Science.gov (United States)

Wu, Peng

Shape-controlled iron oxide and gold-iron oxide catalysts with a cubic inverse spinel structure were studied in this thesis for the oxidative dehydrogenation of cyclohexane. The structure of iron oxide and gold-iron oxide catalysts has no major impact on their oxidative dehydrogenation activity. However, the product selectivity is influenced. Both cyclohexene and benzene are formed on bare iron oxide nanoshapes, while benzene is the only dehydrogenation product in the presence of gold. The selectivity of benzene over CO2 depends strongly on the stability of the iron oxide support and the gold-support interaction. The highest benzene yield has been observed on gold-iron oxide octahedra. {111}-bound nanooctahedra are highly stable in reaction conditions at 300 °C, while {100}-bound nanocubes start to sinter above 250 °C. The highest benzene yield has been observed on gold-iron oxide nanooctahedra, which are likely to have gold atoms, and few-atom gold clusters strongly-bound on their surface. Cationic gold appears to be the active site for benzene formation. An all-organic method to prepare Au-FeOx nano-catalysts is needed due to the inconvenience of the half-organic, half-inorganic synthesis process discussed above. Several methods from the literature to prepare gold-iron oxide nanocomposites completely in organic solvents were reviewed and followed. FeOx Au synthesis procedures in literatures are initially designed for a Au content of over 70%. This approach was tried here to prepare composites with a much lower Au content (2-5 atom. %). Heat treatment is required to bond Au and FeOx NPs in the organic-phase syntheses. Au-FeOx-4 was obtained as a selective catalyst for the ODH of cyclohexane. A Audelta+ peak is observed in the UV-Vis spectrum of sample Au-FeOx-4. This different Au delta+ form may be cationic Au nano-clusters interacting with the FeOx support. It has been demonstrated that cationic gold is responsible for dehydrogenation behavior. Furthermore, the

Hydrogen adsorption on skeletal rhodium-tantalum electrodes-catalysts

International Nuclear Information System (INIS)

Tsinstevich, V.M.; Krejnina, N.M.

1975-01-01

Skeleton rhodium-tantalic catalyst electrodes with a tantalum mass percentage of 0 to 100 have been obtained by the methodology of Crupp and others. The hydrogen adsorption is studied through the method of removing the galvano-static and potentiodynamic curves of charging in sulfuric acid and potassium hydroxide. It has been discovered that the maximum adsorption ability relatively to the hydrogen can be observed in an alloy with a 5% tantalum contents. The energetic characteristics of the alloys are higher in alkali than in acid

Molecular recognition in protein modification with rhodium metallopeptides

Science.gov (United States)

Ball, Zachary T.

2015-01-01

Chemical manipulation of natural, unengineered proteins is a daunting challenge which tests the limits of reaction design. By combining transition-metal or other catalysts with molecular recognition ideas, it is possible to achieve site-selective protein reactivity without the need for engineered recognition sequences or reactive sites. Some recent examples in this area have used ruthenium photocatalysis, pyridine organocatalysis, and rhodium(II) metallocarbene catalysis, indicating that the fundamental ideas provide opportunities for using diverse reactivity on complex protein substrates and in complex cell-like environments. PMID:25588960

Examining Rhodium Catalyst complexes for Use with Conducting Polymers Designed for Fuel Cells in Preparing Biosensors

Energy Technology Data Exchange (ETDEWEB)

Carpio, M.M.; Kerr, J.B.

2005-01-01

Biosensing devices are important because they can detect, record, and transmit information regarding the presence of, or physiological changes in, different chemical or biological materials in the environment. The goal of this research is to prepare a biosensing device that is effective, quick, and low cost. This is done by examining which chemicals will work best when placed in a biosensor. The first study involved experimenting on a rhodium catalyst complexed with ligands such as bipyridine and imidazole. The rhodium catalyst is important because it is reduced from RhIII to RhI, forms a hydride by reaction with water and releases the hydride to react with nicotinamide adenine dinucleotide (NAD+) to selectively produce 1,4-NADH, the reduced form of NAD+. The second study looked at different types of ketones and enzymes for the enzyme-substrate reaction converting a ketone into an alcohol. Preliminary results showed that the rhodium complexed with bipyridine was able to carry out all the reactions, while the rhodium complexed with imidazole was not able to produce and release hydrides. In addition, the most effective ketone to use is benzylacetone with the enzyme alcohol dehydrogenase from baker’s yeast. Future work includes experimenting with bis-imidazole, which mimics the structure of bipyridine to see if it has the capability to reduce and if the reduction rate is comparable to the bipyridine complex. Once all testing is completed, the fastest catalysts will be combined with polymer membranes designed for fuel cells to prepare biosensing devices that can be used in a variety of applications including ones in the medical and environmental fields.

The reaction mechanism of the partial oxidation of methane to synthesis gas: a transient kinetic study over rhodium and a comparison with platinum

NARCIS (Netherlands)

Mallens, E.P.J.; Hoebink, J.H.B.J.; Marin, G.B.M.M.

1997-01-01

The partial oxidation of methane to synthesis gas over rhodium sponge has been investigated by admitting pulses of pure methane and pure oxygen as well as mixtures of methane and oxygen to rhodium sponge at temperatures from 873 to 1023 K. Moreover, pulses of oxygen followed by methane and vice

Catalytic mechanism of the dehydrogenation of ethylbenzene over Fe–Co/Mg(Al)O derived from hydrotalcites

KAUST Repository

Tope, Balkrishna B.

2011-11-01

Catalytic mechanism of ethylbenzene dehydrogenation over Fe-Co/Mg(Al)O derived from hydrotalcites has been studied based on the XAFS and XPS catalyst characterization and the FTIR measurements of adsorbed species. Fe-Co/Mg(Al)O showed synergy, whereas Fe-Ni/Mg(Al)O showed no synergy, in the dehydrogenation of ethylbenzene. Ni species were stably incorporated as Ni2+ in the regular sites in periclase and spinel structure in the Fe-Ni/Mg(Al)O. Contrarily, Co species exists as a mixture of Co3+/Co2+ in the Fe-Co/Mg(Al)O and was partially isolated from the regular sites in the structures with increasing the Co content. Co addition enhanced Lewis acidity of Fe3+ active sites by forming Fe3+-O-Co 3+/2+(1/1) bond, resulting in an increase in the activity. FTIR of ethylbenzene adsorbed on the Fe-Co/Mg(Al)O clearly showed formations of C-O bond and π-adsorbed aromatic ring. This suggests that ethylbenzene was strongly adsorbed on the Fe3+ acid sites via π-bonding and the dehydrogenation was initiated by α-H+ abstraction from ethyl group on Mg2+-O2- basic sites, followed by C-O-Mg bond formation. The α-H+ abstraction by O2-(-Mg 2+) was likely followed by β-H abstraction, leading to the formations of styrene and H2. Such catalytic mechanism by the Fe 3+ acid-O2-(-Mg2+) base couple and the Fe 3+/Fe2+ reduction-oxidation cycle was further assisted by Co3+/Co2+, leading to a good catalytic activity for the dehydrogenation of ethylbenzene. © 2011 Elsevier B.V. All rights reserved.

Permeation of platinum and rhodium nanoparticles through intact and damaged human skin

International Nuclear Information System (INIS)

Mauro, Marcella; Crosera, Matteo; Bianco, Carlotta; Adami, Gianpiero; Montini, Tiziano; Fornasiero, Paolo; Jaganjac, Morana; Bovenzi, Massimo; Filon, Francesca Larese

2015-01-01

The aim of the study was to evaluate percutaneous penetration of platinum and rhodium nanoparticles (PtNPs: 5.8 ± 0.9 nm, RhNPs: 5.3 ± 1.9 nm) through human skin. Salts compounds of these metals are sensitizers and some also carcinogenic agents. In vitro permeation experiments were performed using Franz diffusion cells with intact and damaged skin. PtNPs and RhNPs, stabilized with polyvinylpyrrolidone, were synthesized by reduction of Na 2 PtC l6 and RhCl 3 ·3H 2 O respectively. Suspensions with a concentration of 2.0 g/L of PtNPs and RhNPs were dispersed separately in synthetic sweat at pH 4.5 and applied as donor phases to the outer surface of the skin for 24 h. Measurements of the content of the metals in the receiving solution and in the skin were performed subsequently. Rhodium skin permeation was demonstrated through damaged skin, with a permeation flux of 0.04 ± 0.04 μg cm −2  h −1 and a lag time of 7.9 ± 1.1 h, while no traces of platinum were found in receiving solutions. Platinum and rhodium skin-analysis showed significantly higher concentrations of the metals in damaged skin. Rh and Pt applied as NPs can penetrate the skin barrier and Rh can be found in receiving solutions. These experiments pointed out the need for skin contamination prevention, since even a minor injury to the skin barrier can significantly increase penetration

Permeation of platinum and rhodium nanoparticles through intact and damaged human skin

Energy Technology Data Exchange (ETDEWEB)

Mauro, Marcella [University of Trieste, Clinical Unit of Occupational Medicine, Department of Medical Sciences (Italy); Crosera, Matteo; Bianco, Carlotta; Adami, Gianpiero; Montini, Tiziano; Fornasiero, Paolo [University of Trieste, Department of Chemical and Pharmaceutical Sciences (Italy); Jaganjac, Morana [Rudjer Boskovic Institute, Laboratory for Oxidative Stress, Department of Molecular Medicine (Croatia); Bovenzi, Massimo; Filon, Francesca Larese, E-mail: larese@units.it [University of Trieste, Clinical Unit of Occupational Medicine, Department of Medical Sciences (Italy)

2015-06-15

The aim of the study was to evaluate percutaneous penetration of platinum and rhodium nanoparticles (PtNPs: 5.8 ± 0.9 nm, RhNPs: 5.3 ± 1.9 nm) through human skin. Salts compounds of these metals are sensitizers and some also carcinogenic agents. In vitro permeation experiments were performed using Franz diffusion cells with intact and damaged skin. PtNPs and RhNPs, stabilized with polyvinylpyrrolidone, were synthesized by reduction of Na{sub 2}PtC{sub l6} and RhCl{sub 3}·3H{sub 2}O respectively. Suspensions with a concentration of 2.0 g/L of PtNPs and RhNPs were dispersed separately in synthetic sweat at pH 4.5 and applied as donor phases to the outer surface of the skin for 24 h. Measurements of the content of the metals in the receiving solution and in the skin were performed subsequently. Rhodium skin permeation was demonstrated through damaged skin, with a permeation flux of 0.04 ± 0.04 μg cm{sup −2} h{sup −1} and a lag time of 7.9 ± 1.1 h, while no traces of platinum were found in receiving solutions. Platinum and rhodium skin-analysis showed significantly higher concentrations of the metals in damaged skin. Rh and Pt applied as NPs can penetrate the skin barrier and Rh can be found in receiving solutions. These experiments pointed out the need for skin contamination prevention, since even a minor injury to the skin barrier can significantly increase penetration.

Study of the niobium dehydrogenation process by transmission electron microscopy

International Nuclear Information System (INIS)

Bulhoes, I.A.M.; Akune, K.

1983-01-01

The evolution of the micro-structure of Nb-H, during the dehydrogenation process through thermal treatment, has been studied by Transmission Electron Microscopy. The results are used in order to interpret the variation of the line resolution of Electron Channeling Pattern (ECP) of Nb-H as a function of isochronous annealing temperature. It is concluded that the improvement of the ECP line resolution is enhanced of β hydrate in Nb. (Author) [pt

Bioenvironmental aspects of europium and rhodium: a selected bibliography

International Nuclear Information System (INIS)

Fore, C.S.; Carrier, R.F.; Talmage, S.S.; Fielden, J.M.; Daniel, E.W.

1983-09-01

This bibliography of 428 abstracted references represents a summary of the domestic and foreign literature relevant to the biological and environmental aspects of europium and rhodium. The collected data are organized by current NAEG interests - research highlighting inventory and distribution of the radionulcides, ecological studies covering terrestrial and aquatic systems, and biological studies in both man and animals. Studies that focus directly on research conducted at specific sites (e.g., the Nevada Test Site) are emphasized throughout the bibliography

Double-spin-flip resonance of rhodium nuclei at positive and negative spin temperatures

DEFF Research Database (Denmark)

Tuoriniemi, J.T.; Knuuttila, T.A.; Lefmann, K.

2000-01-01

Sensitive SQUID-NMR measurements were used to study the mutual interactions in the highly polarized nuclear-spin system of rhodium metal. The dipolar coupling gives rise to a weak double-spin-flip resonance. The observed frequency shifts allow deducing separately the dipolarlike contribution...

Dehydrogenation of light alkanes over rhenium catalysts on conventional and mesoporous MFI supports

DEFF Research Database (Denmark)

Rovik, Anne Krogh; Hagen, Anke; Schmidt, I.

2006-01-01

Recently, Re/HZSM-5 (Si/Al = 15) was shown to be an efficient catalyst for ethane dehydrogenation and aromatization at 823 K and atmospheric pressure. In this reaction, the major initial products were benzene, toluene and xylene (BTX), but increasing amounts of ethene were produced with time...

Controlling reaction pathways for alcohol dehydration and dehydrogenation over FeSBA-15 catalysts

NARCIS (Netherlands)

Guan, Y.; Li, Y.; Santen, van R.A.; Hensen, E.J.M.; Li, Can

2007-01-01

The iron location in FeSBA-15 strongly influences the selectivity to dehydrogenation and dehydration in ethanol conversion. At low iron loading, Fe is present as isolated species in the amorphous silica phase. At higher loading additional aggregated forms of iron oxide exist. Isolated species in the

Effects of Al{sub 2}O{sub 3} phase and Cl component on dehydrogenation of propane

Energy Technology Data Exchange (ETDEWEB)

Liu, Jie; Liu, Changcheng; Ma, Aizeng; Rong, Junfeng; Da, Zhijian, E-mail: dazhijianripp@163.com; Zheng, Aiguo; Qin, Ling

2016-04-15

Graphical abstract: - Highlights: • Comparative study of Al{sub 2}O{sub 3} phase on dehydrogenation of propane was implemented. • Pore structures and acid properties of Pt-Al{sub 2}O{sub 3} are correlated to the activities. • Pt-θ-Al{sub 2}O{sub 3} with abundant Cl content shows the highest activity and stability. - Abstract: The effects of two Al{sub 2}O{sub 3} phases, γ- and θ-Al{sub 2}O{sub 3}, and Cl component on the performances of Pt-Al{sub 2}O{sub 3} catalysts in the dehydrogenation of propane were investigated in this work. The catalysts were systematically characterized by various techniques, such as scanning transmission electron microscopy (STEM), temperature-programmed desorption with ammonia as probe molecules (NH{sub 3}-TPD) and temperature-programmed oxidation (TPO). The characterizations and catalytic results show that: (i) the pore structures and acid properties of the two Al{sub 2}O{sub 3} phases can change the quantity, location and property of the carbon deposition, (ii) the existence of Cl plays a significant role on the agglomeration of Pt particles and carbon deposition, which further influence the catalytic performances of Pt-Al{sub 2}O{sub 3} catalysts with different support phases for propane dehydrogenation.

Divergent Reactivity of Rhodium(I) Carbenes Derived from Indole Annulations.

Science.gov (United States)

Li, Xiaoxun; Li, Hui; Song, Wangze; Tseng, Po-Sen; Liu, Lingyan; Guzei, Ilia A; Tang, Weiping

2015-10-26

Rhodium(I) carbenes were generated from propargylic alcohol derivatives as the result of a dehydrative indole annulation. Depending on the choice of the electron-withdrawing group on the aniline nitrogen nucleophile, either a cyclopropanation product or dimerization product was obtained chemoselectively. Intramolecular hydroamidation occurred for the same type of propargylic alcohol derivatives when other transition-metal catalysts were employed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interfacial bonding stabilizes rhodium and rhodium oxide nanoparticles on layered Nb oxide and Ta oxide supports.

Science.gov (United States)

Strayer, Megan E; Binz, Jason M; Tanase, Mihaela; Shahri, Seyed Mehdi Kamali; Sharma, Renu; Rioux, Robert M; Mallouk, Thomas E

2014-04-16

Metal nanoparticles are commonly supported on metal oxides, but their utility as catalysts is limited by coarsening at high temperatures. Rhodium oxide and rhodium metal nanoparticles on niobate and tantalate supports are anomalously stable. To understand this, the nanoparticle-support interaction was studied by isothermal titration calorimetry (ITC), environmental transmission electron microscopy (ETEM), and synchrotron X-ray absorption and scattering techniques. Nanosheets derived from the layered oxides KCa2Nb3O10, K4Nb6O17, and RbTaO3 were compared as supports to nanosheets of Na-TSM, a synthetic fluoromica (Na0.66Mg2.68(Si3.98Al0.02)O10.02F1.96), and α-Zr(HPO4)2·H2O. High surface area SiO2 and γ-Al2O3 supports were also used for comparison in the ITC experiments. A Born-Haber cycle analysis of ITC data revealed an exothermic interaction between Rh(OH)3 nanoparticles and the layered niobate and tantalate supports, with ΔH values in the range -32 kJ·mol(-1) Rh to -37 kJ·mol(-1) Rh. In contrast, the interaction enthalpy was positive with SiO2 and γ-Al2O3 supports. The strong interfacial bonding in the former case led to "reverse" ripening of micrometer-size Rh(OH)3, which dispersed as 0.5 to 2 nm particles on the niobate and tantalate supports. In contrast, particles grown on Na-TSM and α-Zr(HPO4)2·H2O nanosheets were larger and had a broad size distribution. ETEM, X-ray absorption spectroscopy, and pair distribution function analyses were used to study the growth of supported nanoparticles under oxidizing and reducing conditions, as well as the transformation from Rh(OH)3 to Rh nanoparticles. Interfacial covalent bonding, possibly strengthened by d-electron acid/base interactions, appear to stabilize Rh(OH)3, Rh2O3, and Rh nanoparticles on niobate and tantalate supports.

A Recyclable Nanoparticle-Supported Rhodium Catalyst for Hydrogenation Reactions

Directory of Open Access Journals (Sweden)

Maria Michela Dell’Anna

2010-05-01

Full Text Available Catalytic hydrogenation under mild conditions of olefins, unsaturated aldeydes and ketones, nitriles and nitroarenes was investigated, using a supported rhodium complex obtained by copolymerization of Rh(cod(aaema [cod: 1,5-cyclooctadiene, aaema–: deprotonated form of 2-(acetoacetoxyethyl methacrylate] with acrylamides. In particular, the hydrogenation reaction of halonitroarenes was carried out under 20 bar hydrogen pressure with ethanol as solvent at room temperature, in order to minimize hydro-dehalogenation. The yields in haloanilines ranged from 85% (bromoaniline to 98% (chloroaniline.

The determination, by atomic-absorption spectrophotometry using electrothermal atomization, of platinum, palladium, rhodium, ruthenium, and iridium

International Nuclear Information System (INIS)

Haines, J.; Robert, R.V.D.

1982-01-01

A method that involves measurement by atomic-absorption spectrophotometry using electrothermal atomization has been developed for the determination of trace quantities of platinum, palladium, rhodium, ruthenium, and iridium in mineralogical samples. The elements are separated and concentrated by fusion, nickel sulphide being used as the collector, and the analyte elements are measured in the resulting acid solution. An organic extraction procedure was found to offer no advantages over the proposed method. Mutual interferences between the five platinum-group metals examined, as well as interferences from gold, silver, and nickel were determined. The accuracy of the measurement was established by the analysis of a platinum-ore reference material. The lower limits of determination of each of the analyte elements in a sample material are as follows: platinum 1,6μg/l, palladium 0,2μg/1, rhodium 0,5μg/l, ruthenium 3μg/l, and iridium 2,5μg/l. The relative standard deviations range from 0,05 for rhodium to 0.08 for iridium. The method, which is described in detail in the Appendix, is applicable to the determination of these elements in ores, tailings, and geological materials in which the total concentration of the noble metals is less than 1g/t

Complexation of rhodium(II) tetracarboxylates with aliphatic diamines in solution: 1H and 13C NMR and DFT investigations.

Science.gov (United States)

Jaźwiński, Jarosław; Sadlej, Agnieszka

2013-10-01

The complexation of rhodium(II) tetraacetate, tetrakistrifluoroaceate and tetrakisoctanoate with a set of diamines (ethane-1,diamine, propane-1,3-diamine and nonane-1,9-diamine) and their N,N'-dimethyl and N,N,N',N'-tetramethyl derivatives in chloroform solution has been investigated by (1) H and (13) C NMR spectroscopy and density functional theory (DFT) modelling. A combination of two bifunctional reagents, diamines and rhodium(II) tetracarboxylates, yielded insoluble coordination polymers as main products of complexation and various adducts in the solution, being in equilibrium with insoluble material. All diamines initially formed the 2 : 1 (blue), (1 : 1)n oligomeric (red) and 1 : 2 (red) axial adducts in solution, depending on the reagents' molar ratio. Adducts of primary and secondary diamines decomposed in the presence of ligand excess, the former via unstable equatorial complexes. The complexation of secondary diamines slowed down the inversion at nitrogen atoms in NH(CH3 ) functional groups and resulted in the formation of nitrogenous stereogenic centres, detectable by NMR. Axial adducts of tertiary diamines appeared to be relatively stable. The presence of long aliphatic chains in molecules (adducts of nonane-1,9-diamines or rhodium(II) tetrakisoctanoate) increased adduct solubility. Hypothetical structures of the equatorial adduct of rhodium(II) tetraacetate with ethane-1,2-diamine and their NMR parameters were explored by means of DFT calculations. Copyright © 2013 John Wiley & Sons, Ltd.

Study of the performance of vanadium based catalysts prepared by grafting in the oxidative dehydrogenation of propane

Energy Technology Data Exchange (ETDEWEB)

Santacesaria, E.; Carotenuto, G.; Tesser, R.; Di Serio, M. [Naples Univ. (Italy). Dept. of Chemistry

2011-07-01

The oxidative dehydrogenation (ODH) of propane has been investigated by using many different vanadia based catalysts, prepared by grafting technique and containing variable amounts of active phase supported on SiO{sub 2} previously coated, by grafting in three different steps, with multilayer of TiO{sub 2}. A depth catalytic screening, conducted in a temperature range of 400-600 C, at atmospheric pressure and in a range of residence time W/F=0.08-0.33 ghmol{sub -1}, has shown that the vanadium oxide catalysts on TiO{sub 2}-SiO{sub 2} support, prepared by grafting have good performances in the ODH of propane. In particular, a preliminary study has demonstrated that higher selectivities can be obtained employing catalysts having a well dispersed active phase that can be achieved with a V{sub 2}O{sub 5} content lower than 10%{sub w}t. It is well known that, in the case of redox catalysts, an increase of the selectivity can be achieved not only by using an adequate catalytic system but also via engineering routes like decoupling catalytic steps of reduction and re-oxidation. In fact it has been observed that by operating in dehydrogenating mode, on the same catalysts, a higher selectivity is obtained although the catalyst is poisoned by the formation of coke on the surface. As consequence of the results obtained in dehydrogenation, in this work has been explored the possibility to feed low amounts of oxygen, below the stoichiometric level with the aim to keep clean the surface from coke but maintaining high the selectivity, because, dehydrogenation reaction prevails. In this work, the behavior of catalysts containing different amounts of V2O5 has been studied in the propane-propene reaction by using different ratios C{sub 3}H{sub 8}/O{sub 2} included in the range 0-2. (orig.)

Bifunctional Rhodium Intercalator Conjugates as Mismatch-Directing DNA Alkylating Agents

OpenAIRE

Schatzschneider, Ulrich; Barton, Jacqueline K.

2004-01-01

A conjugate of a DNA mismatch-specific rhodium intercalator, containing the bulky chrysenediimine ligand, and an aniline mustard has been prepared, and targeting of mismatches in DNA by this conjugate has been examined. The preferential alkylation of mismatched over fully matched DNA is found by a mobility shift assay at concentrations where untethered organic mustards show little reaction. The binding site of the Rh intercalator was determined by DNA photocleavage, and the position of covale...

A new and selective cycle for dehydrogenation of linear and cyclic alkanes under mild conditions using a base metal

Science.gov (United States)

Solowey, Douglas P.; Mane, Manoj V.; Kurogi, Takashi; Carroll, Patrick J.; Manor, Brian C.; Baik, Mu-Hyun; Mindiola, Daniel J.

2017-11-01

Selectively converting linear alkanes to α-olefins under mild conditions is a highly desirable transformation given the abundance of alkanes as well as the use of olefins as building blocks in the chemical community. Until now, this reaction has been primarily the remit of noble-metal catalysts, despite extensive work showing that base-metal alkylidenes can mediate the reaction in a stoichiometric fashion. Here, we show how the presence of a hydrogen acceptor, such as the phosphorus ylide, when combined with the alkylidene complex (PNP)Ti=CHtBu(CH3) (PNP=N[2-P(CHMe2)2-4-methylphenyl]2-), catalyses the dehydrogenation of cycloalkanes to cyclic alkenes, and linear alkanes with chain lengths of C4 to C8 to terminal olefins under mild conditions. This Article represents the first example of a homogeneous and selective alkane dehydrogenation reaction using a base-metal titanium catalyst. We also propose a unique mechanism for the transfer dehydrogenation of hydrocarbons to olefins and discuss a complete cycle based on a combined experimental and computational study.

Dehydrogenation of propane in the presence of carbon dioxide over chromium and gallium oxides catalysts

Energy Technology Data Exchange (ETDEWEB)

Lapidus, A.L.; Agafonov, Yu.A.; Gaidai, N.A.; Nekrasov, N.V.; Menshova, M.V.; Kunusova, R.M. [Russian Academy of Sciences, Moscow (Russian Federation). N.D. Zelinsky Inst. of Organic Chemistry

2011-07-01

Effective chromium and gallium oxides supported catalysts were prepared and tested in longduration experiments for propane dehydrogenation in the presence of CO{sub 2}. The optimal concentrations of active metals were found. It was shown that the activity, selectivity and stability of chromium oxides catalysts were higher than these parameters for gallium ones. Mechanism of propane oxidative dehydrogenation was studied over both catalysts using unstationary and spectroscopic methods. The employment of these methods allowed to establish the differences in process mechanism. It was shown that surface hydroxides took participation in propene formation over Cr-catalysts and hydrides - over Ga-ones. Propane and carbon dioxide participated in the reaction from the adsorbed state over both catalysts but they were differed by the adsorption capacity of the reaction components: CO2 was tied more firmly than C{sub 3}H{sub 6} over both catalysts, CO{sub 2} and C{sub 3}H{sub 6} were tied more strongly with Cr-catalysts than with Ga-ones. It was shown that CO{sub 2} took active participation in reverse watergas shift reaction and in oxidation of catalyst surface over chromium oxides catalysts. The main role of CO{sub 2} in propane dehydrogenation over gallium catalysts consisted in a decrease of coke formation. Step-schemes of propene and cracking products formation were proposed on the basis of literature and obtained data: via the redox mechanism over Cr-catalysts and through a heterolytic dissociation reaction pathway over Ga-ones. (orig.)

Oxidative dehydrogenation of the 2-aminomethylpyridine (EDTA) ruthenium (III) complex

International Nuclear Information System (INIS)

Toma, H.E.; Tsurumaki, M.

1990-01-01

The oxidative dehydrogenation of the 2-aminomethylpyridine (ampy) ligand coordinated to the (EDTA)RU(III) complex was investigated based on cyclic voltammetry, spectoelectrochemistry and stopped-flow kinetic measurements in aqueous solution. The reaction mechanism is consistent with the deprotonation of the ampy ligand (pk a =7.48), followed by a reversible one-electron transfer step. The intermediate species generated at this step undergoes a metal-induced electron transfer process, with k=227 s -1 , converting into the corresponding 2-iminomethylpyridine complex. (author) [pt

In-situ TEM on (de)hydrogenation of Pd at 0.5–4.5 bar hydrogen pressure and 20–400°C

International Nuclear Information System (INIS)

Yokosawa, Tadahiro; Alan, Tuncay; Pandraud, Gregory; Dam, Bernard; Zandbergen, Henny

2012-01-01

We have developed a nanoreactor, sample holder and gas system for in-situ transmission electron microscopy (TEM) of hydrogen storage materials up to at least 4.5 bar. The MEMS-based nanoreactor has a microheater, two electron-transparent windows and a gas inlet and outlet. The holder contains various O-rings to have leak-tight connections with the nanoreactor. The system was tested with the (de)hydrogenation of Pd at pressures up to 4.5 bar. The Pd film consisted of islands being 15 nm thick and 50–500 nm wide. In electron diffraction mode we observed reproducibly a crystal lattice expansion and shrinkage owing to hydrogenation and dehydrogenation, respectively. In selected-area electron diffraction and bright/dark-field modes the (de)hydrogenation of individual Pd particles was followed. Some Pd islands are consistently hydrogenated faster than others. When thermally cycled, thermal hysteresis of about 10–16 °C between hydrogen absorption and desorption was observed for hydrogen pressures of 0.5–4.5 bar. Experiments at 0.8 bar and 3.2 bar showed that the (de)hydrogenation temperature is not affected by the electron beam. This result shows that this is a fast method to investigate hydrogen storage materials with information at the nanometer scale. -- Highlights: ► In-situ TEM experiments up to 4.5 bar. ► In-situ TEM on a hydrogen storage material at pressures used in practice. ► No electron beam effect on (de)hydrogenation. ► In-situ TEM allows for fast screening of hydrogen storage materials.

Environmentally benign synthesis of amides and ureas via catalytic dehydrogenation coupling of volatile alcohols and amines in a Pd-Ag membrane reactor

KAUST Repository

Chen, Tao

2016-05-31

In this study, we report the direct synthesis of amides and ureas via the catalytic dehydrogenation of volatile alcohols and amines using the Milstein catalyst in a Pd-Ag/ceramic membrane reactor. A series of amides and ureas, which could not be synthesized in an open system by catalytic dehydrogenation coupling, were obtained in moderate to high yields via catalytic dehydrogenation of volatile alcohols and amines. This process could be monitored by the hydrogen produced. Compared to the traditional method of condensation, this catalytic system avoids the stoichiometric pre-activation or in situ activation of reagents, and is a much cleaner process with high atom economy. This methodology, only possible by employing the Pd-Ag/ceramic membrane reactor, not only provides a new environmentally benign synthetic approach of amides and ureas, but is also a potential method for hydrogen storage.

Environmentally benign synthesis of amides and ureas via catalytic dehydrogenation coupling of volatile alcohols and amines in a Pd-Ag membrane reactor

KAUST Repository

Chen, Tao; Zeng, Gaofeng; Lai, Zhiping; Huang, Kuo-Wei

2016-01-01

In this study, we report the direct synthesis of amides and ureas via the catalytic dehydrogenation of volatile alcohols and amines using the Milstein catalyst in a Pd-Ag/ceramic membrane reactor. A series of amides and ureas, which could not be synthesized in an open system by catalytic dehydrogenation coupling, were obtained in moderate to high yields via catalytic dehydrogenation of volatile alcohols and amines. This process could be monitored by the hydrogen produced. Compared to the traditional method of condensation, this catalytic system avoids the stoichiometric pre-activation or in situ activation of reagents, and is a much cleaner process with high atom economy. This methodology, only possible by employing the Pd-Ag/ceramic membrane reactor, not only provides a new environmentally benign synthetic approach of amides and ureas, but is also a potential method for hydrogen storage.

Synthesis and structural study of the transition metal doped rhodium perovskites

International Nuclear Information System (INIS)

Ting, J.; Kennedy, B.; Zhang, Z.

2009-01-01

Full text: One of the most common structures encountered in solid state chemistry is the perovskite structure. With a general formula of AB0 3, the A-type cations are 12-coordinate within a cubo-octahedral environment, while the B-type cations are 6-coordinate, forming an interconnecting three-dimensional octahedral network with neighbouring oxygen anions. While the ideal perovskite structure is cubic in Pm 3 m, many perovskites exhibit symmetry lowering tilting of the corner-sharing B0 6o ctahedral units as a result of A- and B-type cation size disparity. This is also evident in substituted perovskites, where two cations occupy the smaller octahedral site, AB 1- xB' x0 3' Electronic effects can also lower the symmetry. The two most commonly observed effects are the polarisation of the B-cation with a d 0 electronic configuration and Jahn-Teller distortion where the B-cation has a d 4 or d 9 electronic configuration, such as Mn 3+ or Cu 2+ respectively. Manganese containing perovskites have been shown in some compounds to exhibit long-range orbital ordering, giving rise to interesting properties. Heavier transition metals such as ruthenium and iridium have been previously incorporated into these perovskites as an avenue to regulate the properties of these materials. Two orthorhombic rhodium perovskite structures are presented, LaMn 0 . 5 Rh 0 . 5 O 3 and LaCu 05 Rh 0 . 5 O 3 ' A combination of synchrotron x-ray and neutron powder diffraction has been used to elucidate their structures, and have shown both B- and B'-type cations to be disordered across the same crystallographic site for both compounds. x-ray absorption spectroscopy measurements have been used to provide an insight into the valence states of the cations, which show a valency of +3.5 for rhodium due to an extensive charge delocalisation between copper and rhodium.

In-situ TEM on (de)hydrogenation of Pd at 0.5-4.5 bar hydrogen pressure and 20-400°C.

Science.gov (United States)

Yokosawa, Tadahiro; Alan, Tuncay; Pandraud, Gregory; Dam, Bernard; Zandbergen, Henny

2012-01-01

We have developed a nanoreactor, sample holder and gas system for in-situ transmission electron microscopy (TEM) of hydrogen storage materials up to at least 4.5 bar. The MEMS-based nanoreactor has a microheater, two electron-transparent windows and a gas inlet and outlet. The holder contains various O-rings to have leak-tight connections with the nanoreactor. The system was tested with the (de)hydrogenation of Pd at pressures up to 4.5 bar. The Pd film consisted of islands being 15 nm thick and 50-500 nm wide. In electron diffraction mode we observed reproducibly a crystal lattice expansion and shrinkage owing to hydrogenation and dehydrogenation, respectively. In selected-area electron diffraction and bright/dark-field modes the (de)hydrogenation of individual Pd particles was followed. Some Pd islands are consistently hydrogenated faster than others. When thermally cycled, thermal hysteresis of about 10-16°C between hydrogen absorption and desorption was observed for hydrogen pressures of 0.5-4.5 bar. Experiments at 0.8 bar and 3.2 bar showed that the (de)hydrogenation temperature is not affected by the electron beam. This result shows that this is a fast method to investigate hydrogen storage materials with information at the nanometer scale. Copyright © 2011 Elsevier B.V. All rights reserved.

Immobilization of rhodium complexes at thiolate monolayers on gold surfaces : Catalytic and structural studies

NARCIS (Netherlands)

Belser, T; Stöhr, Meike; Pfaltz, A

2005-01-01

Chiral rhodium-diphosphine complexes have been incorporated into self-assembled thiolate monolayers (SAMS) on gold colloids. Catalysts of this type are of interest because they combine properties of homogeneous and heterogeneous systems. In addition, it should be possible to influence the catalytic

A MECHANISTIC STUDY OF RHODIUM TRI(ORTHO-TERT-BUTYLPHENYL)PHOSPHITE COMPLEXES AS HYDROFORMYLATION CATALYSTS

NARCIS (Netherlands)

JONGSMA, T; CHALLA, G; VANLEEUWEN, PWNM

1991-01-01

A mechanistic study of the hydroformylation cycle with a rhodium tri(o-t-butylphenyl)phosphite complex as catalyst is presented. Spectroscopic experiments prove that under hydroformylation conditions this complex is coordinated by only one phosphite. The complex has a high activity in the

The influence of surface oxygen and hydroxyl groups on the dehydrogenation of ethylene, acetic acid and hydrogenated vinyl acetate on pure Pd(1 0 0): A DFT study

Energy Technology Data Exchange (ETDEWEB)

Huang, Yanping [Key Laboratory for Green Chemical Technology of Ministry of Education, R& D Center for Petrochemical Technology, Tianjin University, Tianjin (China); Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072 (China); Dong, Xiuqin [Key Laboratory for Green Chemical Technology of Ministry of Education, R& D Center for Petrochemical Technology, Tianjin University, Tianjin (China); Yu, Yingzhe, E-mail: yzhyu@tju.edu.cn [Key Laboratory for Green Chemical Technology of Ministry of Education, R& D Center for Petrochemical Technology, Tianjin University, Tianjin (China); Zhang, Minhua, E-mail: mhzhangtj@163.com [Key Laboratory for Green Chemical Technology of Ministry of Education, R& D Center for Petrochemical Technology, Tianjin University, Tianjin (China)

2016-12-01

Highlights: • All dehydrogenation reactions in vinyl acetate synthesis on Pd(1 0 0) were studied. • The energy barriers of the transition state of the three reactions were calculated. • The influence of surface Os and OHs on all dehydrogenation actions was discussed. - Abstract: On the basis of a Langmuir–Hinshelwood-type mechanism, the dehydrogenation of ethylene, acetic acid and hydrogenated vinyl acetate (VAH) on pure Pd(1 0 0) with surface oxygen atoms (Os) and hydroxyl groups (OHs) was studied with density functional theory (DFT) method. Our calculation results show that both Os and OHs can consistently reduce the activation energies of dehydrogenation of ethylene, acetic acid and VAH to some degree with only one exception that OHs somehow increase the activation energy of VAH. Based on Langmuir–Hinshelwood mechanism, the three dehydrogenation reactions in presence of surface Os and OHs are almost consistently favored, compared with the corresponding processes on clean Pd(1 0 0) surfaces, and thus a Langmuir–Hinshelwood-type mechanism may not be excluded beforehand when investigating the microscopic performance of the oxygen-assisted vinyl acetate synthesis on Pd(1 0 0) catalysts.

Application of Heterogeneous Copper Catalyst in a Continuous Flow Process: Dehydrogenation of Cyclohexanol

Science.gov (United States)

Glin´ski, Marek; Ulkowska, Urszula; Iwanek, Ewa

2016-01-01

In this laboratory experiment, the synthesis of a supported solid catalyst (Cu/SiO2) and its application in the dehydrogenation of cyclohexanol performed under flow conditions was studied. The experiment was planned for a group of two or three students for two 6 h long sessions. The copper catalyst was synthesized using incipient wetness…

Non-Precious Bimetallic Catalysts for Selective Dehydrogenation of an Organic Chemical Hydride System

KAUST Repository

Shaikh Ali, Anaam

2015-07-06

Methylcyclohexane (MCH)-Toluene (TOL) chemical hydride cycles as a hydrogen carrier system is successful with the selective dehydrogenation reaction of MCH to TOL, which has been achieved only using precious Pt-based catalysts. Herein, we report improved selectivity using non-precious metal nickel-based bimetallic catalysts, where the second metal occupies the unselective step sites.

Synthesis of carbon-supported copper catalyst and its catalytic performance in methanol dehydrogenation

Energy Technology Data Exchange (ETDEWEB)

Shelepova, Ekaterina V. [Boreskov Institute of Catalysis SB RAS, pr. Ac. Lavrentieva, 5, Novosibirsk, 630090 (Russian Federation); National Research Tomsk Polytechnic University, Lenin av., 30, Tomsk, 634050 (Russian Federation); Vedyagin, Aleksey A., E-mail: vedyagin@catalysis.ru [Boreskov Institute of Catalysis SB RAS, pr. Ac. Lavrentieva, 5, Novosibirsk, 630090 (Russian Federation); National Research Tomsk Polytechnic University, Lenin av., 30, Tomsk, 634050 (Russian Federation); Ilina, Ludmila Yu.; Nizovskii, Alexander I. [Boreskov Institute of Catalysis SB RAS, pr. Ac. Lavrentieva, 5, Novosibirsk, 630090 (Russian Federation); Tsyrulnikov, Pavel G. [Institute of Hydrocarbon Processing SB RAS, Neftezavodskaya st., 54, Omsk, 644040 (Russian Federation)

2017-07-01

Highlights: • Carbon-supported copper catalyst was studied in dehydrogenation of methanol. • Reduction temperature affected size of Cu particles and Cu{sup 0}/Cu{sup 2+} ratio. • Reduction at 400 °C was required to obtain high methyl formate yield. - Abstract: Carbon-supported copper catalyst was prepared by incipient wetness impregnation of Sibunit with an aqueous solution of copper nitrate. Copper loading was 5 wt.%. Temperature of reductive pretreatment was varied within a range of 200–400 °C. The samples were characterized by transmission electron microscopy, X-ray diffraction analysis, X-ray photoelectron and X-ray absorption spectroscopies. Catalytic activity of the samples was studied in a reaction of methanol dehydrogenation. Silica-based catalyst with similar copper loading was used as a reference. It was found that copper is distributed over the surface of support in the form of metallic and partially oxidized particles of about 12–17 nm in size. Diminished interaction of copper with support was supposed to be responsible for high catalytic activity.

In Situ Structure-Function Studies of Oxide Supported Rhodium Catalysts by Combined Energy Dispersive XAFS and DRIFTS Spectroscopies

International Nuclear Information System (INIS)

Evans, John; Dent, Andrew J.; Diaz-Moreno, Sofia; Fiddy, Steven G.; Jyoti, Bhrat; Tromp, Moniek; Newton, Mark A.

2007-01-01

The techniques of energy dispersive EXAFS (EDE), diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) and mass spectrometry (MS) have been combined to study the structure and function of an oxide supported metal catalyst, namely 5 wt% Rh/Al2O3. Using a FreLoN camera as the EDE detector and a rapid-scanning IR spectrometer, experiments could be performed with a repetition rate of 50 ms. The results show that the nature of the rhodium centers is a function of the partial pressures of the reacting gases (CO and NO) and also temperature. This combination of gases oxidizes metallic rhodium particles to Rh(CO)2 at room temperature. The proportion of the rhodium adopting this site increases as the temperature is raised (up to 450 K). Above that temperature the dicarbonyl decomposes and the metal reclusters. Once this condition is met, catalysis ensues. Gas switching techniques show that at 573 K with NO in excess, the clusters can be oxidized rapidly to afford a linear nitrosyl complex; re-exposure to CO also promotes reclustering and the CO adopts terminal (atop) and bridging (2-fold) sites

Ruthenium-catalyzed self-coupling of primary and secondary alcohols with the liberation of dihydrogen

DEFF Research Database (Denmark)

Makarov, Ilya; Madsen, Robert

2013-01-01

The dehydrogenative self-condensation of primary and secondary alcohols has been studied in the presence of RuCl2(IiPr)(p-cymene). The conversion of primary alcohols into esters has been further optimized by using magnesium nitride as an additive, which allows the reaction to take place...... at a temperature and catalyst loading lower than those described previously. Secondary alcohols were dimerized into racemic ketones by a dehydrogenative Guerbet reaction with potassium hydroxide as the additive. The transformation gave good yields of the ketone dimers with a range of alkan-2-ols, whereas more...... substituted secondary alcohols were unreactive. The reaction proceeds by dehydrogenation to the ketone, followed by an aldol reaction and hydrogenation of the resulting enone. © 2013 American Chemical Society....

Rhodium self-powered detector for monitoring neutron fluence, energy production, and isotopic composition of fuel

International Nuclear Information System (INIS)

Sokolov, A.P.; Pochivalin, G.P.; Shipovskikh, Yu.M.; Garusov, Yu.V.; Chernikov, O.G.; Shevchenko, V.G.

1993-01-01

The use of self-powered detectors (SPDs) with a rhodium emitter customarily involves monitoring of neutron fields in the core of a nuclear reactor. Since current in an SPD is generated primarily because of the neutron flux, which is responsible for the dynamics of particular nuclear transformations, including fission reactions of heavy isotopes, the detector signal can be attributed unambiguously to energy release at the location of the detector. Computation modeling performed with the KOMDPS package of programs of the current formation in a rhodium SPD along with the neutron-physical processes that occur in the reactor core makes it possible to take account of the effect of the principal factors characterizing the operating conditions and the design features of the fuel channel and the detector, reveal quantitative relations between the generated signal and individual physical parameters, and determine the metrological parameters of the detector. The formation and transport of changed particles in the sensitive part of the SPC is calculated by the Monte Carlo method. The emitter activation, neutron transport, and dynamics of the isotopic composition in the fuel channel containing the SPD are determined by solving the kinetic equation in the multigroup representation of the neutron spectrum, using the discrete ordinate method. In this work the authors consider the operation of a rhodium SPD in a bundle of 49 fuel channels of the RBMK-1000 reactor with a fuel enrichment of 2.4% from the time it is inserted into a fresh channel

Hydrogen storage via polyhydride complexes

Energy Technology Data Exchange (ETDEWEB)

Jensen, C.M.; Zidan, R.A. [Univ. of Hawaii, Honolulu, HI (United States)

1998-08-01

The reversible dehydrogenation of NaAlH{sub 4} is catalyzed in toluene slurries of the NaAlH{sub 4} containing the pincer complex, IrH{sub 4} {l_brace}C{sub 6}H{sub 3}-2,6-(CH{sub 2}PBu{sup t}{sub 2}){sub 2}{r_brace}. The rates of the pincer complex catalyzed dehydrogenation are about five times greater those previously found for NaAlH{sub 4} that was doped with titanium through a wet chemistry method. Homogenization of NaAlH{sub 4} with 2 mole % Ti(OBu{sup n}){sub 4} under an atmosphere of argon produces a novel titanium containing material. TPD measurements show that the dehydrogenation of this material occurs about 30 C lower than that previously found for wet titanium doped NaAlH{sub 4}. In further contrast to wet doped NaAlH{sub 4}, the dehydrogenation kinetics and hydrogen capacity of the novel material are undiminished over several dehydriding/hydriding cycles. Rehydrogenation of the titanium doped material occurs readily at 170 C under 150 atm of hydrogen. TPD measurements show that about 80% of the original hydrogen content (4.2 wt%) can be restored under these conditions.

Study of vanadium based mesoporous silicas for oxidative dehydrogenation of propane and n-butane

Czech Academy of Sciences Publication Activity Database

Bulánek, R.; Kalužová, A.; Setnička, M.; Zukal, Arnošt; Čičmanec, P.; Mayerová, Jana

2012-01-01

Roč. 179, č. 1 (2012), s. 149-158 ISSN 0920-5861 R&D Projects: GA ČR GAP106/10/0196 Institutional research plan: CEZ:AV0Z40400503 Keywords : vanadium * oxidative dehydrogenation * mesoporous silicas Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.980, year: 2012

Moessbauer spectroscopic characterisation of catalysts obtained by interaction between tetra-n-butyl-tin and silica or silica supported rhodium

International Nuclear Information System (INIS)

Millet, J.M.M.; Toyir, J.; Didillon, B.; Candy, J.P.; Nedez, C.; Basset, J.M.

1997-01-01

Moessbauer spectroscopy at 78 K was used to study the interaction between tetra-n-butyl-tin and the surfaces of silica or silica supported rhodium. At room temperature, the tetra-n-butyl-tin was physically adsorbed on the surfaces. After reaction under hydrogen at 373 K, the formation of grafted organometallic fragments on the Rh surface was confirmed whereas with pure silica, ≡SiO-Sn(n-C 4 H 9 ) 3 moieties were observed. After treatment at 523 K, the rhodium grafted organometallic species was completely decomposed and there was formation of a defined bimetallic RhSn compound

Complexes of technetium, rhenium, and rhodium with sexidentate Schiff-base ligands

International Nuclear Information System (INIS)

Hunter, G.; Kilcullen, N.

1989-01-01

The monocationic technetium (IV) and rhenium (IV) complexes with the sexidentate Schiff-base ligands tris[2-(2'-hydroxybenzylideneethyl)]amine and its substituted derivatives have been prepared and their electrochemical properties studied. The variable-temperature 90.6 MHz 13 C-{ 1 H} n.m.r. spectrum of the rhodium (III) complex of tris[2-(2-hydroxy-5'-isopropylbenzylideneethyl)-amine] has been observed, indicating fluxionality at temperatures above 218 K. (author)

Rhodium, iridium and nickel complexes with a 1,3,5-triphenylbenzene tris-MIC ligand. Study of the electronic properties and catalytic activities

Directory of Open Access Journals (Sweden)

Carmen Mejuto

2015-12-01

Full Text Available The coordination versatility of a 1,3,5-triphenylbenzene-tris-mesoionic carbene ligand is illustrated by the preparation of complexes with three different metals: rhodium, iridium and nickel. The rhodium and iridium complexes contained the [MCl(COD] fragments, while the nickel compound contained [NiCpCl]. The preparation of the tris-MIC (MIC = mesoionic carbene complex with three [IrCl(CO2] fragments, allowed the estimation of the Tolman electronic parameter (TEP for the ligand, which was compared with the TEP value for a related 1,3,5-triphenylbenzene-tris-NHC ligand. The electronic properties of the tris-MIC ligand were studied by cyclic voltammetry measurements. In all cases, the tris-MIC ligand showed a stronger electron-donating character than the corresponding NHC-based ligands. The catalytic activity of the tri-rhodium complex was tested in the addition reaction of arylboronic acids to α,β-unsaturated ketones.

Simultaneous determination of palladium, platinum and rhodium by on-line column enrichment and HPLC with 2,4-dihydroxybenzylidenethiorhodanine as pre-column derivatization reagent

Directory of Open Access Journals (Sweden)

Dong Xuechang

2006-01-01

Full Text Available A new method for the simultaneous determination of palladium, platinum and rhodium ions as metal-DHBTR chelates was developed. The palladium, platinum and rhodium ions were pre-column derivatized with 2,4-dihydroxybenzylidenethiorhodanine (DHBTR to form colored chelates. The Pd-DHBTR, Pt-DHBTR and Rh-DHBTR chelates can be absorbed onto the front of the enrichment column when they were injected into the injector and sent to the enrichment column with a 0.05 mol L-1 sodium acetate-acetic acid buffer solution (pH 3.5 as mobile phase. After the enrichment had finished, by switching the six ports switching valve, the retained chelates were back-flushed by mobile phase and traveling towards the analytical column. These chelates separation on the analytical column was satisfactory with 62% (v/v acetonitrile (containing 0.05 mol L-1 of pH 3.5 sodium acetate-acetic acid buffer salt and 0.1% (m/v of tritonX-100 as mobile phase. The Limits of detection of palladium, platinum and rhodium are 3.6 ng L-1, 3.2 ng L-1 and 4.5 ng L-1, respectively. This method was applied to the determination of palladium, platinum and rhodium in water, urine and soil samples with good results.

Ion flotation of rhodium(III) and palladium(II) with anionic surfactants.

Science.gov (United States)

He, X C

1991-03-01

The ion flotation of rhodium(III) and palladium(II) with some anionic surfactants has been investigated. Two flotation procedures are proposed for the separation of some platinum metals, based on differences in the kinetic properties of the chloro-complexes of rhodium(III), palladium(II) and platinum(IV). The first involves the selective flotation of Rh(H(2)O)(3+)(6) from PdCl(2-)(4) and PtCl(2-)(6) in dilute hydrochloric acid with sodium dodecylbenzenesulfonate (SDBS). After precipitation of the hydroxide and redissolution in dilute acid, the Rh(III) is converted into Rh(H(2)O)(3+)(6), Pd(II) and Pt(IV) remaining as PdCl(2-)(4) and PtCl(2-)(6) respectively, and separation is achieved by floating the Rh(H(2)O)(3+)(6) with SDBS. The second is for separation of Pd(II). Prior to flotation, the solution of PdCl(2-)(4) and PtCl(2-)(6) is heated with ammonium acetate to convert PdCl(2-)(4) into Pd(NH(3))(2+)(4). The chloro-complex of Pt(IV) is unaffected. The complex cation, Pd(NH(3))(2+)(4), is then selectively floated with SDBS. The procedures are fast, simple and do not require expensive reagents and apparatus.

Rhodium-catalysed syn-carboamination of alkenes via a transient directing group.

Science.gov (United States)

Piou, Tiffany; Rovis, Tomislav

2015-11-05

Alkenes are the most ubiquitous prochiral functional groups--those that can be converted from achiral to chiral in a single step--that are accessible to synthetic chemists. For this reason, difunctionalization reactions of alkenes (whereby two functional groups are added to the same double bond) are particularly important, as they can be used to produce highly complex molecular architectures. Stereoselective oxidation reactions, including dihydroxylation, aminohydroxylation and halogenation, are well established methods for functionalizing alkenes. However, the intermolecular incorporation of both carbon- and nitrogen-based functionalities stereoselectively across an alkene has not been reported. Here we describe the rhodium-catalysed carboamination of alkenes at the same (syn) face of a double bond, initiated by a carbon-hydrogen activation event that uses enoxyphthalimides as the source of both the carbon and the nitrogen functionalities. The reaction methodology allows for the intermolecular, stereospecific formation of one carbon-carbon and one carbon-nitrogen bond across an alkene, which is, to our knowledge, unprecedented. The reaction design involves the in situ generation of a bidentate directing group and the use of a new cyclopentadienyl ligand to control the reactivity of rhodium. The results provide a new way of synthesizing functionalized alkenes, and should lead to the convergent and stereoselective assembly of amine-containing acyclic molecules.

Mechanistic aspects of hydrosilylation catalyzed by (ArN=)Mo(H)(Cl)(PMe3)3.

Science.gov (United States)

Khalimon, Andrey Y; Shirobokov, Oleg G; Peterson, Erik; Simionescu, Razvan; Kuzmina, Lyudmila G; Howard, Judith A K; Nikonov, Georgii I

2012-04-02

The reaction of (ArN=)MoCl(2)(PMe(3))(3) (Ar = 2,6-diisopropylphenyl) with L-Selectride gives the hydrido-chloride complex (ArN=)Mo(H)(Cl)(PMe(3))(3) (2). Complex 2 was found to catalyze the hydrosilylation of carbonyls and nitriles as well as the dehydrogenative silylation of alcohols and water. Compound 2 does not show any productive reaction with PhSiH(3); however, a slow H/D exchange and formation of (ArN=)Mo(D)(Cl)(PMe(3))(3) (2(D)) was observed upon addition of PhSiD(3). Reactivity of 2 toward organic substrates was studied. Stoichiometric reactions of 2 with benzaldehyde and cyclohexanone start with dissociation of the trans-to-hydride PMe(3) ligand followed by coordination and insertion of carbonyls into the Mo-H bond to form alkoxy derivatives (ArN=)Mo(Cl)(OR)(PMe(2))L(2) (3: R = OCH(2)Ph, L(2) = 2 PMe(3); 5: R = OCH(2)Ph, L(2) = η(2)-PhC(O)H; 6: R = OCy, L(2) = 2 PMe(3)). The latter species reacts with PhSiH(3) to furnish the corresponding silyl ethers and to recover the hydride 2. An analogous mechanism was suggested for the dehydrogenative ethanolysis with PhSiH(3), with the key intermediate being the ethoxy complex (ArN=)Mo(Cl)(OEt)(PMe(3))(3) (7). In the case of hydrosilylation of acetophenone, a D-labeling experiment, i.e., a reaction of 2 with acetophenone and PhSiD(3) in the 1:1:1 ratio, suggests an alternative mechanism that does not involve the intermediacy of an alkoxy complex. In this particular case, the reaction presumably proceeds via Lewis acid catalysis. Similar to the case of benzaldehyde, treatment of 2 with styrene gives trans-(ArN=)Mo(H)(η(2)-CH(2)═CHPh)(PMe(3))(2) (8). Complex 8 slowly decomposes via the release of ethylbenzene, indicating only a slow insertion of styrene ligand into the Mo-H bond of 8.

Ni–Ta–O mixed oxide catalysts for the low temperature oxidative dehydrogenation of ethane to ethylene

KAUST Repository

Zhu, Haibo; Rosenfeld, Devon C.; Anjum, Dalaver H.; Sangaru, Shiv; Saih, Youssef; Ould-Chikh, Samy; Basset, Jean-Marie

2015-01-01

The "wet" sol-gel and "dry" solid-state methods were used to prepare Ni-Ta-O mixed oxide catalysts. The resulting Ni-Ta oxides exhibit high activity and selectivity for the low temperature oxidative dehydrogenation of ethane to ethylene. The Ta

DNA-based prenatal diagnosis for severe and variant forms of multiple acyl-CoA dehydrogenation deficiency

DEFF Research Database (Denmark)

Olsen, Rikke K J; Andresen, Brage S; Christensen, Ernst

2005-01-01

OBJECTIVES: Multiple acyl-CoA dehydrogenation deficiency (MADD) is a clinically heterogeneous disorder of mitochondrial fatty acid, amino acid, and choline oxidation due to mutations in the genes encoding electron transfer flavoprotein (ETF) or ETF ubiquinone oxidoreductase (ETFQO). So far...

Activity of iridium-ruthenium and iridium-rhodium adsorption catalysts in decomposition of hydrogen peroxide

Energy Technology Data Exchange (ETDEWEB)

Zubovich, I A; Mikhaylov, V A; Migulina, N N [Yaroslavskij Politekhnicheskij Inst. (USSR)

1976-06-01

Experimental data for the activities of iridium-ruthenium and iridium-rhodium adsorption catalysts in the decomposition of hydrogen peroxide are considered and the results of magnetic susceptibility measurements are presented. It is concluded that surface structures (complexes) may be formed and that micro-electronic feaures play a role in heterogeneous catalysis.

Sensitivity change of rhodium self -powered detectors with burn-up

International Nuclear Information System (INIS)

Girgis, R.; Akimov, I.S.; Hamouda, I.

1976-01-01

The scope of the present paper is to obtain the calculation formulae to evaluate the rate of sensitivity change of the neutron self-powered detectors with burn-up. A code written in FORTRAN 4 was developed to be operational on the IBM-1130 computer. It has been established in the case of rhodium detectors that neglecting the β-particle absorption in the calculations leads to the underestimation of the detector sensitivity decrease up to 40%. The derived formulae can be used for other self-powered detectors. (author)

Enhancement of ethanol oxidation at Pt and PtRu nanoparticles dispersed over hybrid zirconia-rhodium supports

Science.gov (United States)

Rutkowska, Iwona A.; Koster, Margaretta D.; Blanchard, Gary J.; Kulesza, Pawel J.

2014-12-01

A catalytic material for electrooxidation of ethanol that utilizes PtRu nanoparticles dispersed over thin films of rhodium-free and rhodium-containing zirconia (ZrO2) supports is described here. The enhancement of electrocatalytic activity (particularly in the potential range as low as 0.25-0.5 V vs. RHE), that has been achieved by dispersing PtRu nanoparticles (loading, 100 μg cm-2) over the hybrid Rh-ZrO2 support composed of nanostructured zirconia and metallic rhodium particles, is clearly evident from comparison of the respective voltammetric and chronoamperometric current densities recorded at room temperature (22 °C) in 0.5 mol dm-3 H2SO4 containing 0.5 mol dm-3 ethanol. Porous ZrO2 nanostructures, that provide a large population of hydroxyl groups in acidic medium in the vicinity of PtRu sites, are expected to facilitate the ruthenium-induced removal of passivating CO adsorbates from platinum, as is apparent from the diagnostic experiments with a small organic molecule such as methanol. Although Rh itself does not show directly any activity toward ethanol oxidation, the metal is expected to facilitate C-C bond splitting in C2H5OH. It has also been found during parallel voltammetric and chronoamperometric measurements that the hybrid Rh-ZrO2 support increases activity of the platinum component itself toward ethanol oxidation in the low potential range.

Rhodium (II) cycle alkanecarboxylate: synthesis, spectroscopic and thermo analytic studies and evaluation of the antitumor potential

International Nuclear Information System (INIS)

Souza, Aparecido Ribeiro de

1995-01-01

Four new rhodium(II) carboxylates (cyclopropane, cyclobutane, cyclopentane, and cyclohexanecarboxylate), and other already known rhodium (II) carboxylates (acetate, propionate, butyrate, metoxyacetate, dichloroacetate, and trifluoroacetate), have been prepared for study in this work. The compounds were characterized by elementary and thermogravimetric analysis, magnetic susceptibility, and electronic, Raman, and infrared spectroscopy. The reaction of Rh CL 3 .aq with the sodium carboxylates was studied aiming to improve the understanding of the redox process involved. Spectroscopy studies (Raman and electronic) were made to examine the transition involved in the Rh-Rh and Rh-O bonds. The results have shown a direct relation between the force of the carboxylic acid and the Rh-O force, but show a inverse relation with the Rh-Rh bond force. Thermal analysis studies were undertaken and the obtained date show a resemblance of the TG/DTG curves with that found in literature. In the other hand, the DSC curves show a different results: in open crucible, the peaks associated with the cage breakdown are exothermic and, in closed crucible this peaks are endothermic. The thermodecomposition products were analyzed. The evolved gases were identified by GC?MS and 1 H and 13 C NMR spectra. The residues were analyzed by X-ray diffraction. Antitumor activity of rhodium cyclopropanecarboxylate was evaluated in vitro (cell cultures K562 and Ehrlich) and in vivo (Balb-c mice with ascite Ehrlich tumor), indicating an increased life span (87.5%) of the treated animals. (author)

Stereoselective 1,3-Insertions of Rhodium(II) Azavinyl Carbenes

Science.gov (United States)

Chuprakov, Stepan; Worrell, Brady T.; Selander, Nicklas; Sit, Rakesh K.; Fokin, Valery V.

2014-01-01

Rhodium(II) azavinyl carbenes, conveniently generated from 1-sulfonyl-1,2,3-triazoles, undergo a facile, mild and convergent formal 1,3-insertion into N–H and O–H bonds of primary and secondary amides, various alcohols, and carboxylic acids to afford a wide range of vicinally bis-functionalized Z-olefins with perfect regio- and stereoselectively. Utilizing the distinctive functionality installed through these reactions, a number of subsequent rearrangements and cyclizations expand the repertoire of valuable organic building blocks constructed by reactions of transition metal carbene complexes, including α-allenyl ketones and amino-substituted heterocycles. PMID:24295389

Burnup Estimation of Rhodium Self-Powered Neutron Detector Emitter in VVER Reactor Core Using Monte Carlo Simulations

OpenAIRE

Khrutchinsky, А. А.; Kuten, S. A.; Babichev, L. F.

2011-01-01

Estimation of burn-up in a rhodium-103 emitter of self-powered neutron detector in VVER-1000 reactor core has been performed using Monte Carlo simulations within approximation of a constant neutron flux.

Activity of ruthenium, rhodium, iridium-ruthenium and iridium-rhodium adsorbed catalysts in dehydrogenation of formic acid

Energy Technology Data Exchange (ETDEWEB)

Mikhailov, V A; Zubovich, I A [Yaroslavskij Politekhnicheskij Inst. (USSR)

1977-04-01

The activity of Ru-, Rh- (Ir+nRu)- and (Ir+nRn) catalysts on sugar carbon and silicon dioxide in decomposition of HCOOH was studied. The catalyst activity increases in the series Ir

Mechanistic Study of the Oxidative Coupling of Styrene with 2-Phenylpyridine Derivatives Catalyzed by Cationic Rhodium( III) via C–H Activation

Science.gov (United States)

Brasse, Mikaël; Cámpora, Juan; Ellman, Jonathan A.; Bergman, Robert G.

2013-01-01

The Rh(III) catalyzed oxidative coupling of alkenes with arenes provides a greener alternative to the classical Heck reaction for the synthesis of arene-functionalized alkenes. The present mechanistic study gives insights for the rational development of this key transformation. The catalyst resting states and the rate law of the reaction have been identified. The reaction rate is solely dependent on catalyst and alkene concentrations and the rate determining step is the migratory insertion of alkene into a Rh–C(aryl) bond. PMID:23590843

Chromium oxide over activated carbons as catalyst for oxidative dehydrogenation of isobutane

International Nuclear Information System (INIS)

Cardenas, Agobardo; Acero Fabio N; Diaz, Jose de J

2007-01-01

The functional groups at the surface of an activated carbon Norit ROX 08 were modified through reaction with nitric acid, 8.8% 0 2 in N 2 and H 2 . the modified carbons were impregnated with a CrO 3 aqueous solution and used in the oxidative dehydrogenation of isobutane to isobutene (ODH). The formation of isobutene was observed at 443 k, with a maximum selectivity of 85% and a yield of 9%

Kinetics of aggregation growth with competition between catalyzed birth and catalyzed death

International Nuclear Information System (INIS)

Wang Haifeng; Gao Yan; Lin Zhenquan

2008-01-01

An aggregation growth model of three species A, B and C with the competition between catalyzed birth and catalyzed death is proposed. Irreversible aggregation occurs between any two aggregates of the like species with the constant rate kernels I n (n = 1,2,3). Meanwhile, a monomer birth of an A species aggregate of size k occurs under the catalysis of a B species aggregate of size j with the catalyzed birth rate kernel K(k,j) = Kkj v and a monomer death of an A species aggregate of size k occurs under the catalysis of a C species aggregate of size j with the catalyzed death rate kernel L(k,j)=Lkj v , where v is a parameter reflecting the dependence of the catalysis reaction rates of birth and death on the size of catalyst aggregate. The kinetic evolution behaviours of the three species are investigated by the rate equation approach based on the mean-field theory. The form of the aggregate size distribution of A species a k (t) is found to be dependent crucially on the competition between the catalyzed birth and death of A species, as well as the irreversible aggregation processes of the three species: (1) In the v k (t) satisfies the conventional scaling form; (2) In the v ≥ 0 case, the competition between the catalyzed birth and death dominates the process. When the catalyzed birth controls the process, a k (t) takes the conventional or generalized scaling form. While the catalyzed death controls the process, the scaling description of the aggregate size distribution breaks down completely

Ammonia synthesis in the presence of rhodium-ruthenium-iridium carbonyl clusters

International Nuclear Information System (INIS)

Fedoseev, I.V.; Solov'ev, N.V.

2007-01-01

Researches in the field of platinum metal coordination compounds, where nitrogen enters as a ligand in coordination sphere of metal, are discussed. Results of experiments on the ammonia synthesis during the CO+N 2 mixture passing through alkali solution containing mixture of carbonyl clusters of rhodium, ruthenium and iridium at atmospheric pressure are given. Technique of the experiment and steps of assumed reactions of nitrogen fixation by Rh, Ir and Ru carbonyl clusters are demonstrated [ru

Hydrogen peroxide modified Mg-Al-O oxides supported Pt-Sn catalysts for paraffin dehydrogenation

NARCIS (Netherlands)

Lai, Y.; He, Songbo; Luo, S.; Bi, W.; Li, XianRu; Sun, Chenglin; Seshan, Kulathuiyer

2015-01-01

In this work, a new method to prepare Mg–Al–O oxide by co-precipitation method with addition of H2O2 was developed. The application of Mg–Al–O as a support of Pt–Sn catalysts for paraffin dehydrogenation was investigated. Characterization results indicated that modification of H2O2 (i) enlarged the

Solvent extraction of no-carrier-added 103Pd from irradiated rhodium target with α-furyldioxime

International Nuclear Information System (INIS)

Mahdi Sadeghi; Behrouz Shirazi; Nami Shadanpour

2006-01-01

Solvent extraction of no-carrier-added 103 Pd was investigated from irradiated rhodium target with a-furyldioxime in chloroform from diluted hydrochloric acid. Extraction yield was 85.3% for a single extraction from 0.37M HCl and 103 Pd purity was better than 99%. (author)

Identification of short-lived neutron-rich ruthenium and rhodium isotopes in fission

International Nuclear Information System (INIS)

Franz, G.; Herrmann, G.

1975-01-01

Short-lived ruthenium and rhodium isotopes ( 107 Ru, 108 Ru, 108 Rh, 109 Ru, 109 Rh, 110 Ru, 110 Rh, 111 Ru, 111 Rh, 112 Ru, 112 Rh, 113 Ru) have been separated from fission products by a rapid chemical procedure and identified by means of γ-ray spectroscopy. Nuclides with half-lives down to 3 sec were accessible. Ruthenium isotopes up to mass number 113 have been identified. (author)

Ni–Ta–O mixed oxide catalysts for the low temperature oxidative dehydrogenation of ethane to ethylene

KAUST Repository

Zhu, Haibo

2015-09-01

The "wet" sol-gel and "dry" solid-state methods were used to prepare Ni-Ta-O mixed oxide catalysts. The resulting Ni-Ta oxides exhibit high activity and selectivity for the low temperature oxidative dehydrogenation of ethane to ethylene. The Ta/(Ni + Ta) atomic ratios (varying from 0 to 0.11 in "wet" sol-gel method, and from 0 to 0.20 in "dry" solid-state method) as well as the preparation methods used in the synthesis, play important roles in controlling catalyst structure, activity, selectivity and stability in the oxidative dehydrogenation of ethane. Electron microscopy characterizations (TEM, EELS mapping, and HAADF-STEM) clearly demonstrate that the Ta atoms are inserted into NiO crystal lattice, resulting in the formation of a new Ni-Ta oxide solid solution. More Ta atoms are found to be located at the lattice sites of crystal surface in sol-gel catalyst. While, a small amount of thin layer of Ta2O5 clusters are detected in solid-state catalyst. Further characterization by XRD, N2 adsorption, SEM, H2-TPR, XPS, and Raman techniques reveal different properties of these two Ni-Ta oxides. Due to the different properties of the Ni-Ta oxide catalysts prepared by two distinct approaches, they exhibit different catalytic behaviors in the ethane oxidative dehydrogenation reaction at low temperature. Thus, the catalytic performance of Ni-Ta-O mixed oxide catalysts can be systematically modified and tuned by selecting a suitable synthesis method, and then varying the Ta content. ©2015 Elsevier Inc. All rights reserved.

1,3-dialkyl- and 1,3-diaryl-3,4,5,6-tetrahydropyrimidin-2-ylidene rhodium(i) and palladium(II) complexes: synthesis, structure, and reactivity.

Science.gov (United States)

Mayr, Monika; Wurst, Klaus; Ongania, Karl-Hans; Buchmeiser, Michael R

2004-03-05

The synthesis of novel 1,3-diaryl- and 1,3-dialkylpyrimidin-2-ylidene-based N-heterocyclic carbenes (NHCs) and their rhodium(i) and palladium(II) complexes is described. The rhodium compounds bromo(cod)[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene]rhodium (7), bromo(cod)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)rhodium (8) (cod=eta(4)-1,5-cyclooctadiene, mesityl=2,4,6-trimethylphenyl), chloro(cod)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)rhodium (9), and chloro(cod)[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene]rhodium (10) were prepared by reaction of [[Rh(cod)Cl](2)] with lithium tert-butoxide followed by addition of 1,3-dimesityl-3,4,5,6-tetrahydropyrimidinium bromide (3), 1,3-dimesityl-3,4,5,6-tetrahydropyrimidinium tetrafluoroborate (4), 1,3-di-2-propyl-3,4,5,6-tetrahydropyrimidinium bromide (6), and 1,3-di-2-propyl-3,4,5,6-tetrahydropyrimidinium tetrafluoroborate, respectively. Complex 7 crystallizes in the monoclinic space group P2(1)/n, and 8 in the monoclinic space group P2(1). Complexes 9 and 10 were used for the synthesis of the corresponding dicarbonyl complexes dicarbonylchloro(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)rhodium (11), and dicarbonylchloro[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene]rhodium (12). The wavenumbers nu(CO I)/nu(CO II) for 11 and 12 were used as a quantitative measure for the basicity of the NHC ligand. The values of 2062/1976 and 2063/1982 cm(-1), respectively, indicate that the new NHCs are among the most basic cyclic ligands reported so far. Compounds 3 and 6 were additionally converted to the corresponding cationic silver(i) bis-NHC complexes [Ag(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(2)]AgBr(2) (13) and [Ag[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene](2)]AgBr(2) (14), which were subsequently used in transmetalation reactions for the synthesis of the corresponding palladium(II) complexes Pd(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2

A rhodium(III) complex inhibits LPS-induced nitric oxide production and angiogenic activity in cellulo.

Science.gov (United States)

Liu, Li-Juan; Lin, Sheng; Chan, Daniel Shiu-Hin; Vong, Chi Teng; Hoi, Pui Man; Wong, Chun-Yuen; Ma, Dik-Lung; Leung, Chung-Hang

2014-11-01

Metal-containing complexes have arisen as viable alternatives to organic molecules as therapeutic agents. Metal complexes possess a number of advantages compared to conventional carbon-based compounds, such as distinct geometries, interesting electronic properties, variable oxidation states and the ability to arrange different ligands around the metal centre in a precise fashion. Meanwhile, nitric oxide (NO) plays key roles in the regulation of angiogenesis, vascular permeability and inflammation. We herein report a novel cyclometalated rhodium(III) complex as an inhibitor of lipopolysaccharides (LPS)-induced NO production in RAW264.7 macrophages. Experiments suggested that the inhibition of NO production in cells by complex 1 was mediated through the down-regulation of nuclear factor-κB (NF-κB) activity. Furthermore, complex 1 inhibited angiogenesis in human umbilical vein endothelial cells (HUVECs) as revealed by an endothelial tube formation assay. This study demonstrates that kinetically inert rhodium(III) complexes may be potentially developed as effective anti-angiogenic agents. Copyright © 2014 Elsevier Inc. All rights reserved.

N-oxide as a traceless oxidizing directing group: mild rhodium(III)-catalyzed C-H olefination for the synthesis of ortho-alkenylated tertiary anilines.

Science.gov (United States)

Huang, Xiaolei; Huang, Jingsheng; Du, Chenglong; Zhang, Xingyi; Song, Feijie; You, Jingsong

2013-12-02

Double role: A traceless directing group also acts as an internal oxidant in a novel Rh(III) -catalyzed protocol developed for the synthesis of ortho-alkenylated tertiary anilines. A five-membered cyclometalated Rh(III) complex is proposed as a plausible intermediate and confirmed by X-ray crystallographic analysis. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In situ electrochemical XRD study of (de)hydrogenation of MgyTi100-y thin films

NARCIS (Netherlands)

Vermeulen, P.; Wondergem, H.J.; Graat, P.C.J.; Borsa, D.M.; Schreuders, H.; Dam, B.; Griessen, R.; Notten, P.H.L.

2008-01-01

X-ray diffraction and electrochemical (de)hydrogenation were performed in situ to monitor the symmetry of the unit cells of MgyTi100-y thin film alloys (with 70 to 90 at.% Mg) along the pressure composition isotherms at room temperature. The diffraction patterns show that the crystal structures of

Tailored Formation of N-Doped Nanoarchitectures by Diffusion-Controlled on-Surface (Cyclo)-Dehydrogenation of Heteroaromatics

Czech Academy of Sciences Publication Activity Database

Pinardi, A. L.; Otero-Irurueta, G.; Palacio, I.; Martinez, J. I.; Sánchez-Sánchez, C.; Tello, M.; Rogero, C.; Cossaro, A.; Preobrajenski, A.; Gomez-Lor, B.; Jančařík, Andrej; Stará, Irena G.; Starý, Ivo; Lopez, M. F.; Méndez, J.; Martin-Gago, J. A.

2013-01-01

Roč. 7, č. 4 (2013), s. 3676-3684 ISSN 1936-0851 R&D Projects: GA ČR(CZ) GAP207/10/2207 Institutional support: RVO:61388963 Keywords : surface-assisted dehydrogenation * dibenzo[5]helicene * N-doped nanographene * heteroaromatic polymer Subject RIV: CC - Organic Chemistry Impact factor: 12.033, year: 2013

Crystal structure of 1,3-bis(2,3-dimethylquinoxalin-6-ylbenzene

Directory of Open Access Journals (Sweden)

Charles E. Diesendruck

2015-12-01

Full Text Available The title compound, C26H22N4 (I, was synthesized by C—H iridium-catalyzed borylation followed by Suzuki coupling. The molecular structure of (I consists of a central benzene ring with 3-dimethylquinoxalin-6-yl groups at the 1 and 3 positions. These 2,3-dimethylquinoxalin-6-yl groups twist significantly out of the plane of the benzene ring. There are intermolecular π–π interactions which result in a two-dimensional extended structure. The layers extend parallel to the ab plane and stack along the c axis.

Complexation of diphenyl(phenylacetenyl)phosphine to rhodium(III) tetraphenyl porphyrins

DEFF Research Database (Denmark)

Stulz, Eugen; Scott, Sonya M; Bond, Andrew D

2003-01-01

). The methylide on rhodium in 3 is not displaced, leading selectively to the mono-phosphine complex (DPAP)(Me)Rh(TPP) (5). The first and second association constants, as determined by isothermal titration calorimetry and UV-vis titrations, are in the range 10(4)-10(7) M(-1) (in CH(2)Cl(2)). Using LDI-TOF mass....... The largest values of DeltaG degrees are found for 6. The thermodynamic and UV-vis data reveal that the methylide and the phosphine ligand have an almost identical electronic trans-influence on the sixth ligand....

Significance of β-dehydrogenation in ethanol electro-oxidation on platinum doped with Ru, Rh, Pd, Os and Ir.

Science.gov (United States)

Sheng, Tian; Lin, Wen-Feng; Hardacre, Christopher; Hu, P

2014-07-14

In the exploration of highly efficient direct ethanol fuel cells (DEFCs), how to promote the CO2 selectivity is a key issue which remains to be solved. Some advances have been made, for example, using bimetallic electrocatalysts, Rh has been found to be an efficient additive to platinum to obtain high CO2 selectivity experimentally. In this work, the mechanism of ethanol electrooxidation is investigated using the first principles method. It is found that CH3CHOH* is the key intermediate during ethanol electrooxidation and the activity of β-dehydrogenation is the rate determining factor that affects the completeness of ethanol oxidation. In addition, a series of transition metals (Ru, Rh, Pd, Os and Ir) are alloyed on the top layer of Pt(111) in order to analyze their effects. The elementary steps, α-, β-C-H bond and C-C bond dissociations, are calculated on these bimetallic M/Pt(111) surfaces and the formation potential of OH* from water dissociation is also calculated. We find that the active metals increase the activity of β-dehydrogenation but lower the OH* formation potential resulting in the active site being blocked. By considering both β-dehydrogenation and OH* formation, Ru, Os and Ir are identified to be unsuitable for the promotion of CO2 selectivity and only Rh is able to increase the selectivity of CO2 in DEFCs.

The influence of water on the oxygen-silver interaction and on the oxidative dehydrogenation of methanol

NARCIS (Netherlands)

Lefferts, Leon; Van Ommen, Jan G.; Ross, Julian R H

1988-01-01

Experiments carried out using temperature-programmed desorption and reduction could detect no interaction between water and silver at 200 °C. However, separate experiments on the effect of water on the oxidative dehydrogenation of methanol over a silver catalyst showed that water affected the

Surface characterizations of TiH{sub 2} powders before and after dehydrogenation

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yeguang [School of Aeronautics & Astronautics, Sichuan University, Chengdu, 610065 (China); Wang, Chunming; Liu, Yang; Liu, Shaopeng; Xiao, Sufen [College of Materials Science and Engineering, Sichuan University, Chengdu, 610065 (China); Chen, Yungui, E-mail: ygchen60@aliyun.com [School of Aeronautics & Astronautics, Sichuan University, Chengdu, 610065 (China); College of Materials Science and Engineering, Sichuan University, Chengdu, 610065 (China)

2017-07-15

Highlights: • Oxides characteristics of TiH{sub 2} and HDH-Ti are investigated by XPS depth profiles. • The relative contents of TiO{sub 2}, Ti{sub 2}O{sub 3} and TiO are lower after dehydrogenation. • The decrease of Ti{sub 2}O{sub 3} is more remarkable followed by TiO{sub 2}, TiO after dehydrogenation. • The H atoms of TiH{sub 2} react preferentially with Ti{sub 2}O{sub 3} followed by TiO{sub 2}, TiO. - Abstract: The oxide film of TiH{sub 2} and HDH-Ti powder are investigated using X-ray photoelectron spectroscopy (XPS). The XPS depth profiles indicate that there exists mainly Ti{sup 2+}, Ti{sup 3+}, Ti{sup 4+} and Ti{sup 0} on TiH{sub 2} and HDH-Ti surface. The intensities of Ti 2p decrease for Ti{sup 4+}, first increase and then decrease for Ti{sup 3+} and Ti{sup 2+}, and increase all the time for Ti{sup 0} in the surface layer of TiH{sub 2} and HDH-Ti with the sputtering depth increasing. The relative fractions of TiO{sub 2}, Ti{sub 2}O{sub 3} and TiO for the Ti 2p of TiH{sub 2} and HDH-Ti first decrease and then slow down with the sputtering depth increasing. Meanwhile, the relative fractions of TiO{sub 2} and TiO of HDH-Ti are lower than that of TiH{sub 2} after the sputtering depth of about 5 nm, and the fraction of Ti{sub 2}O{sub 3} of HDH-Ti is always lower that of TiH{sub 2}. In addition, the decrease of Ti{sub 2}O{sub 3} is much pronounced, followed by TiO{sub 2} and TiO before and after dehydrogenation when the sputtering depth is more than 5 nm. The XPS depth profiles and calculation results suggest that the release of H atoms removes the part of oxygen on TiH{sub 2} surface, which results in the thinner oxide layer and low oxygen content of HDH-Ti powder.

Oxidative Dehydrogenation of n-Butenes to 1,3-Butadiene over Bismuth Molybdate and Ferrite Catalysts: A Review

KAUST Repository

Hong, Eunpyo; Park, Jung-Hyun; Shin, Chae-Ho

2015-01-01

1,3-Butadiene, an important raw material for a variety of chemical products, can be produced via the oxidative dehydrogenation (ODH) of n-butenes over multicomponent oxide catalysts based on bismuth molybdates and ferrites. In this review, the basic

Direct conversion of bio-ethanol to isobutene on nanosized Zn(x)Zr(y)O(z) mixed oxides with balanced acid-base sites.

Science.gov (United States)

Sun, Junming; Zhu, Kake; Gao, Feng; Wang, Chongmin; Liu, Jun; Peden, Charles H F; Wang, Yong

2011-07-27

We report the design and synthesis of nanosized Zn(x)Zr(y)O(z) mixed oxides for direct and high-yield conversion of bio-ethanol to isobutene (~83%). ZnO is addded to ZrO(2) to selectively passivate zirconia's strong Lewis acidic sites and weaken Brönsted acidic sites, while simultaneously introducing basicity. As a result, the undesired reactions of bio-ethanol dehydration and acetone polymerization/coking are suppressed. Instead, a surface basic site-catalyzed ethanol dehydrogenation to acetaldehyde, acetaldehyde to acetone conversion via a complex pathway including aldol-condensation/dehydrogenation, and a Brönsted acidic site-catalyzed acetone-to-isobutene reaction pathway dominates on the nanosized Zn(x)Zr(y)O(z) mixed oxide catalyst, leading to a highly selective process for direct conversion of bio-ethanol to isobutene.

Oxidative dehydrogenation of ethane over vanadium supported on mesoporous materials of M41S family

Czech Academy of Sciences Publication Activity Database

Čapek, J.; Adam, J.; Grygar, Tomáš; Bulánek, R.; Vradman, L.; Košová-Kučerová, G.; Čičmanec, P.; Knotek, P.

2008-01-01

Roč. 342, 1-2 (2008), s. 99-106 ISSN 0926-860X Grant - others:GA ČR(CZ) GP104/07/P038 Program:GP Institutional research plan: CEZ:AV0Z40320502 Keywords : oxidative dehydrogenation * ethane * vanadium * mesoporous materials Subject RIV: CA - Inorganic Chemistry Impact factor: 3.190, year: 2008

Promoting effect of active carbons on methanol dehydrogenation on sodium carbonate - hydrogen spillover

OpenAIRE

Su, S.; Prairie, M.; Renken, A.

1993-01-01

Methanol dehydrogenation to formaldehyde was conducted in a fixed-bed flow reactor with sodium carbonate catalyst mixed with active carbons or transition metals. The additives promoted the reaction rate at 880-970 K without modifying formaldehyde selectivity. This effect increases with increasing carbon content in the carbon-carbonate mixture. Activation energy of methanol conversion is the same for the mixture and the carbonate alone. Temperature-programmed desorption experiments showed that...

Adsorption and diffusion of H and NH{sub x} as key steps of the NH{sub x} dehydrogenation reaction at the V{sub 2}O{sub 5} (010) surface

Energy Technology Data Exchange (ETDEWEB)

Gruber, Mathis; Hermann, Klaus [Fritz-Haber-Institut der MPG, und Sfb 546, Berlin (Germany)

2009-07-01

Various selective oxidation reactions as the selective catalytic reduction (SCR) of NO{sub x} or the ammoxidation of propane/propene to acrylonitrile are processed on vanadium based metal-oxide catalysts in the presence of ammonia. In the reactions the intermediates NH{sub 2}, NH{sub 3}, and NH{sub 4} are involved indicating that the adsorption and dehydrogenation of NH{sub x}, x < 4, are important steps. We have performed theoretical studies of corresponding reaction steps where the catalyst is simulated by a finite section of the V{sub 2}O{sub 5} (010) surface. The calculations apply density-functional theory combined with clusters modeling the adsorbate system. The substrate lowers corresponding dehydrogenation energies considerably compared with values for the gas phase reaction. However, the lowering is too small to make dehydrogenation of NH{sub 3} likely to happen. Our results on the role of oxygen vacancies for the dehydrogenation indicate that such surface defects become important for the reaction. Besides the energetics also the diffusion at the surface influences the reaction. A nudged elastic band (NEB) routine has been implemented to evaluate diffusion paths and barriers. Hydrogen diffusion on the surface will be discussed and additional examples for NH{sub x} diffusion will be shown. Based on these results possible reaction scenarios for the dehydrogenation reaction will be presented.

Substrate-induced antiferromagnetism of ultrathin iron overlayers on the iridium and rhodium (001) surfaces

Czech Academy of Sciences Publication Activity Database

Máca, František; Kudrnovský, Josef; Drchal, Václav; Turek, Ilja; Bengone, O.; Redinger, J.

2009-01-01

Roč. 11, - (2009), s. 38-40 ISSN 1642-6037 R&D Projects: GA ČR GA202/07/0456; GA MŠk OC09028 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z20410507 Keywords : iridium * rhodium * iron * magnetismus in thin layers * density functional calculations Subject RIV: BM - Solid Matter Physics ; Magnetism

Electrochemical Sensor Based on Rh(III) Ion-Imprinted Polymer as a New Modifying Agent for Rhodium Determination.

Science.gov (United States)

Bai, Huiping; Xiong, Caiyun; Wang, Chunqiong; Liu, Peng; Dong, Su; Cao, Qiue

2018-05-01

A rhodium (III) ion carbon paste electrode (CPE) based on an ion imprinted polymer (IIP) as a new modifying agent has been prepared and studied. Rh(III) ion imprinted polymer was synthesized by copolymerization of acrylamide-Rh(III) complex and ethylene glycol dimethacrylate according to the precipitation polymerization. Acrylamide acted as both functional monomer and complexing agent to create selective coordination sites in a cross-linked polymer. The ion imprinted carbon paste electrode (IIP-CPE) was prepared by mixing rhodium IIP-nanoparticles and graphite powder in n-eicosane as an adhesive and then embedding them in a Teflon tube. Amperometric i-t curve method was applied as the determination technique. Several parameters, including the functional monomer, molar ratio of template, monomer and cross-linking agent, the amounts of IIP, the applied potential, the buffer solution and pH have been studied. According to the results, IIP-CPE showed a considerably higher response in comparison with the electrode embedded with non-imprinted polymer (NIP), indicating the formation of suitable recognition sites in the IIP structure during the polymerization stage. The introduced electrode showed a linear range of 1.00×10-8~3.0×10-5 mol·L-1 and detection limit of 6.0 nmol L-1 (S/N = 3). The IIP-CPE was successfully applied for the trace rhodium determination in catalyst and plant samples with RSD of less than 3.3% (n = 5) and recoveries in the range of 95.5~102.5%.

Dynamical model of computation of the rhodium self-powered neutron detector current

International Nuclear Information System (INIS)

Erben, O.; Slovacek, M.; Zerola, L.

1992-01-01

A model is presented for the calculation of the rhodium self-powered neutron detector current in dependence on the neutron flux density during reactor core transients. The total signal consists of a beta emission, prompt, and gamma component and a background signal. The model has been verified by means of experimental data obtained during measurements on the LVR-15 research reactor and at the Dukovany nuclear power plant. (author) 9 figs., 21 refs

Methane Steam Reforming Kinetics for a Rhodium-Based Catalyst

DEFF Research Database (Denmark)

Jakobsen, Jon Geest; Jakobsen, M.; Chorkendorff, Ib

2010-01-01

Methane steam reforming is the key reaction to produce synthesis gas and hydrogen at the industrial scale. Here the kinetics of methane steam reforming over a rhodium-based catalyst is investigated in the temperature range 500-800 A degrees C and as a function of CH4, H2O and H-2 partial pressures....... The methane steam reforming reaction cannot be modeled without taking CO and H coverages into account. This is especially important at low temperatures and higher partial pressures of CO and H-2. For methane CO2 reforming experiments, it is also necessary to consider the repulsive interaction of CO...

Dienone-phenol Rearrangement of C-9 Oxygenated Decalinic Dienone and Analogs through B-Ring Cleavage

Institute of Scientific and Technical Information of China (English)

无

2003-01-01

Dehydrogenation of 9-hydroxy decalinic enones and analogs with DDQ resulted in a formal dienone-phenol type rearrangement via B-ring cleavage, while the corresponding dienone acetates underwent base-catalyzed formal dienone-phenol type rearrangement analogously.

Modification by SiO2 of Alumina Support for Light Alkane Dehydrogenation Catalysts

Directory of Open Access Journals (Sweden)

Giyjaz E. Bekmukhamedov

2016-10-01

Full Text Available Due to the continuously rising demand for C3–C5 olefins it is important to improve the performance of catalysts for dehydrogenation of light alkanes. In this work the effect of modification by SiO2 on the properties of the alumina support and the chromia-alumina catalyst was studied. SiO2 was introduced by impregnation of the support with a silica sol. To characterize the supports and the catalysts the following techniques were used: low-temperature nitrogen adsorption; IR-spectroscopy; magic angle spinning 29Si nuclear magnetic resonance; temperature programmed desorption and reduction; UV-Vis-, Raman- and electron paramagnetic resonance (EPR-spectroscopy. It was shown that the modifier in amounts of 2.5–7.5 wt % distributed on the support surface in the form of SiOx-islands diminishes the interaction between the alumina support and the chromate ions (precursor of the active component. As a result, polychromates are the compounds predominantly stabilized on the surface of the modified support; under thermal activation of the catalyst and are reduced to the amorphous Cr2O3. This in turn leads to an increase in the activity of the catalyst in the dehydrogenation of isobutane.

Unsaturated aldehydes as alkene equivalents in the Diels-Alder reaction

DEFF Research Database (Denmark)

Taarning, Esben; Madsen, Robert

2008-01-01

A one-pot procedure is described for using alpha,beta-unsaturated aldehydes as olefin equivalents in the Diels-Alder reaction. The method combines the normal electron demand cycloaddition with aldehyde dienophiles and the rhodium-catalyzed decarbonylation of aldehydes to afford cyclohexenes...

Rhodium(III)-catalyzed vinylic sp2 C-H bond functionalization: efficient synthesis of pyrido[1,2-α]benzimidazoles and imidazo[1,2-α]pyridines.

Science.gov (United States)

Dong, Lin; Huang, Ji-Rong; Qu, Chuan-Hua; Zhang, Qian-Ru; Zhang, Wei; Han, Bo; Peng, Cheng

2013-09-28

A simple approach for synthesis of novel aza-fused scaffolds such as pyrido[1,2-α]benzimidazoles and imidazo[1,2-α]pyridines was developed by Rh(III)-catalyzed direct oxidative coupling between alkenes and unactivated alkynes without an extra directing group. The method would allow a broad substrate scope, providing fused heterocycles with potential biological properties.

Trans-Selective Rhodium Catalysed Conjugate Addition of Organoboron Reagents to Dihydropyranones

Directory of Open Access Journals (Sweden)

Hannah J. Edwards

2015-04-01

Full Text Available The selective synthesis of 2,6-trans-tetrahydropyran derivatives employing the rhodium catalysed addition of organoboron reagents to dihydropyranone templates, derived from a zinc-catalysed hetero-Diels-Alder reaction, is reported. The addition of both arylboronic acids and potassium alkenyltrifluoroborates have been accomplished in high yields using commercially-available [Rh(cod(OH]2 catalyst. The selective formation of the 2,6-trans-tetrahydropyran stereoisomer is consistent with a mechanism involving alkene association and carbometalation on the less hindered face of the dihydropyranone.

Oxidative Dehydrogenation of n-​Butane: Activity and Kinetics Over VOx​/Al2O3 Catalysts

NARCIS (Netherlands)

Madaan, N.; Haufe, R.; Shiju, N.R.; Rothenberg, G.

2014-01-01

The catalytic activity of a VOx/Al2O3 catalyst for the oxidative dehydrogenation of n-​butane is investigated. The effects of reaction temp., oxygen to n-​butane ratio and GHSV on the catalytic performance are examd. and optimized. Interestingly, this simple catalyst gives good conversion and

The oxidative dehydrogenation of methanol to formaldehyde over silver catalysts in relation to the oxygen-silver interaction

NARCIS (Netherlands)

Lefferts, Leonardus; van Ommen, J.G.; Ross, J.R.H.

1986-01-01

The properties of silver in the oxidative dehydrogenation of methanol were studied in a flow reactor under near industrial conditions. The influences of temperature, concentration of both reactants, gas velocity, space velocity, the form of the silver catalyst and surface composition of the catalyst

Oxidative Dehydrogenation on Nanocarbon: Insights into the Reaction Mechanism and Kinetics via in Situ Experimental Methods.

Science.gov (United States)

Qi, Wei; Yan, Pengqiang; Su, Dang Sheng

2018-03-20

Sustainable and environmentally benign catalytic processes are vital for the future to supply the world population with clean energy and industrial products. The replacement of conventional metal or metal oxide catalysts with earth abundant and renewable nonmetallic materials has attracted considerable research interests in the field of catalysis and material science. The stable and efficient catalytic performance of nanocarbon materials was discovered at the end of last century, and these materials are considered as potential alternatives for conventional metal-based catalysts. With its rapid development in the past 20 years, the research field of carbon catalysis has been experiencing a smooth transition from the discovery of novel nanocarbon materials or related new reaction systems to the atomistic-level mechanistic understanding on the catalytic process and the subsequent rational design of the practical catalytic reaction systems. In this Account, we summarize the recent progress in the kinetic and mechanistic studies on nanocarbon catalyzed alkane oxidative dehydrogenation (ODH) reactions. The paper attempts to extract general concepts and basic regularities for carbon catalytic process directing us on the way for rational design of novel efficient metal-free catalysts. The nature of the active sites for ODH reactions has been revealed through microcalorimetric analysis, ambient pressure X-ray photoelectron spectroscopy (XPS) measurement, and in situ chemical titration strategies. The detailed kinetic analysis and in situ catalyst structure characterization suggests that carbon catalyzed ODH reactions involve the redox cycles of the ketonic carbonyl-hydroxyl pairs, and the key physicochemical parameters (activation energy, reaction order, and rate/equilibrium constants, etc.) of the carbon catalytic systems are proposed and compared with conventional transition metal oxide catalysts. The proposal of the intrinsic catalytic activity (TOF) provides the

Spectroscopic characterization of the on-surface induced (cyclo) dehydrogenation of a N-heteroaromatic compound on noble metal surfaces

Czech Academy of Sciences Publication Activity Database

Palacio, I.; Pinardi, A. L.; Martínez, J. I.; Preobrajenski, A.; Cossaro, A.; Jančařík, Andrej; Stará, Irena G.; Starý, Ivo; Méndez, J.; Martín-Gago, J.A.; López, M.F.

2017-01-01

Roč. 19, č. 33 (2017), s. 22454-22461 ISSN 1463-9076 Institutional support: RVO:61388963 Keywords : dibenzohelicene * on-surface (cyclo)dehydrogenation * spectroscopic characterization Subject RIV: CC - Organic Chemistry OBOR OECD: Organic chemistry Impact factor: 4.123, year: 2016

16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

Science.gov (United States)

2010-01-01

... 16 Commercial Practices 1 2010-01-01 2010-01-01 false Misuse of the words âplatinum,â âiridium,â... § 23.7 Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.” (a) It is unfair or deceptive to use the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium...

CH{sub 4} dehydrogenation on Cu(1 1 1), Cu@Cu(1 1 1), Rh@Cu(1 1 1) and RhCu(1 1 1) surfaces: A comparison studies of catalytic activity

Energy Technology Data Exchange (ETDEWEB)

Zhang, Riguang; Duan, Tian [Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Ling, Lixia [Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Research Institute of Special Chemicals, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Wang, Baojun, E-mail: wangbaojun@tyut.edu.cn [Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China)

2015-06-30

Highlights: • Adsorbed Rh atom on Cu catalyst exhibits better catalytic activity for CH{sub 4} dehydrogenation. • The adsorbed Rh atom is the reaction active center for CH{sub 4} dehydrogenation. • The morphology of Cu substrate has negligible effect on CH{sub 4} dehydrogenation. - Abstract: In the CVD growth of graphene, the reaction barriers of the dehydrogenation for hydrocarbon molecules directly decide the graphene CVD growth temperature. In this study, density functional theory method has been employed to comparatively probe into CH{sub 4} dehydrogenation on four types of Cu(1 1 1) surface, including the flat Cu(1 1 1) surface (labeled as Cu(1 1 1)) and the Cu(1 1 1) surface with one surface Cu atom substituted by one Rh atom (labeled as RhCu(1 1 1)), as well as the Cu(1 1 1) surface with one Cu or Rh adatom (labeled as Cu@Cu(1 1 1) and Rh@Cu(1 1 1), respectively). Our results show that the highest barrier of the whole CH{sub 4} dehydrogenation process is remarkably reduced from 448.7 and 418.4 kJ mol{sup −1} on the flat Cu(1 1 1) and Cu@Cu(1 1 1) surfaces to 258.9 kJ mol{sup −1} on RhCu(1 1 1) surface, and to 180.0 kJ mol{sup −1} on Rh@Cu(1 1 1) surface, indicating that the adsorbed or substituted Rh atom on Cu catalyst can exhibit better catalytic activity for CH{sub 4} complete dehydrogenation; meanwhile, since the differences for the highest barrier between Cu@Cu(1 1 1) and Cu(1 1 1) surfaces are smaller, the catalytic behaviors of Cu@Cu(1 1 1) surface are very close to the flat Cu(1 1 1) surface, suggesting that the morphology of Cu substrate does not obviously affect the dehydrogenation of CH{sub 4}, which accords with the reported experimental observations. As a result, the adsorbed or substituted Rh atom on Cu catalyst exhibit a better catalytic activity for CH{sub 4} dehydrogenation compared to the pure Cu catalyst, especially on Rh-adsorbed Cu catalyst, we can conclude that the potential of synthesizing high-quality graphene with the

A chemical-biological evaluation of rhodium(I) N-heterocyclic carbene complexes as prospective anticancer drugs.

Science.gov (United States)

Oehninger, Luciano; Küster, Laura Nadine; Schmidt, Claudia; Muñoz-Castro, Alvaro; Prokop, Aram; Ott, Ingo

2013-12-23

Rhodium(I) complexes bearing N-heterocyclic carbene (NHC) ligands have been widely used in catalytic chemistry, but there are very few reports of biological properties of these organometallics. A series of Rh(I)-NHC derivatives with 1,5-cyclooctadiene and CO as secondary ligands were synthesized, characterized, and biologically investigated as prospective antitumor drug candidates. Pronounced antiproliferative effects were noted for all complexes, along with moderate inhibitory activity of thioredoxin reductase (TrxR) and efficient binding to biomolecules (DNA, albumin). Biodistribution studies showed that the presence of albumin lowered the cellular uptake and confirmed the transport of rhodium into the nuclei. Changes in the mitochondrial membrane potential (MMP) were observed as well as DNA fragmentation in wild-type and daunorubicin- or vincristine-resistant Nalm-6 leukemia cells. Overall, these studies indicated that Rh(I)-NHC fragments could be used as partial structures of new antitumor agents, in particular in those drugs designed to address resistant malignant tissues. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Method for Preparation of Amides from Alcohols and Amines by Extrusion of Hydrogen

DEFF Research Database (Denmark)

2010-01-01

The present invention relates to a method for preparation of carboxamides using alcohols and amines as starting materials in a dehydrogenative coupling reaction catalyzed by a ruthenium N-heterocyciic carbene (NHC) complex, which may be prepared in situ....

One-pot synthesis of multisubstituted 2-aminoquinolines from annulation of 1-aryl tetrazoles with internal alkynes via double C-H activation and denitrogenation.

Science.gov (United States)

Zhang, Lei; Zheng, Liyao; Guo, Biao; Hua, Ruimao

2014-12-05

An efficient, one-pot synthesis of multisubstituted 2-aminoquinolines from 1-aryl tetrazoles and internal alkynes has been developed. The reaction involves cyclization of 1-aryl tetrazoles with internal alkynes via rhodium(III)-catalyzed double C-H activation and copper(II)-mediated denitrogenation.

A new technique for accurately defined deposition of catalyst thin films in deep flow channels of high-temperature gas microreactors

NARCIS (Netherlands)

Tiggelaar, Roald M.; Berenschot, Johan W.; Oosterbroek, R.E.; van Male, P.; de Croon, M.H.J.M.; Schouten, J.C.; van den Berg, Albert

2003-01-01

By using microreactors fabricated with silicon microtechnology, heterogeneous catalyzed gas-phase reactions can be studied which are difficult to control because of their exothermic nature, are explosive or use toxic/hazardous gases. In this type of microreactors, catalytic materials like rhodium or

Dehydrogenation of ethane to ethylene via radical pathways enhanced by alkali metal based catalyst in oxysteam condition

KAUST Repository

Takanabe, Kazuhiro; Shahid, Salman

2016-01-01

The dehydrogenation of ethane to ethylene in the presence of oxygen and water was conducted using Na2WO4/SiO2 catalyst at high temperatures. At 923 K, the conversion rate without water was proportional to ethane pressure and a half order of oxygen

Kinetics and Mechanism of the Reaction of Coherently Synchronized Oxidation and Dehydrogenation of Cyclohexane by Hydrogen Peroxide

Directory of Open Access Journals (Sweden)

Aghamammadova S.

2016-01-01

Based on this experimental researches, the complex reaction, consisting of parallel-sequential oxidation and dehydrogenation reactions, which are coherently synchronized, proceeds during the process of cyclohexane oxidation with biomimetic catalyst. Depending on the reaction parameters it is possible to deliberately adjust the direction of oxidation reaction and reaction rate.

Process economics and safety considerations for the oxidative dehydrogenation of ethane using the M1 catalyst

Energy Technology Data Exchange (ETDEWEB)

Baroi, Chinmoy; Gaffney, Anne M.; Fushimi, Rebecca

2017-12-01

Olefins or unsaturated hydrocarbons play a vital role as feedstock for many industrially significant processes. Ethylene is the simplest olefin and a key raw material for consumer products. Oxidative Dehydrogenation (ODH) is one of the most promising new routes for ethylene production that can offer a significant advantage in energy efficiency over the conventional steam pyrolysis process. This study is focused on the ODH chemistry using the mixed metal oxide MoVTeNbOx catalysts, generally referred to as M1 for the key phase known to be active for dehydrogenation. Using performance results from the patent literature a series of process simulations were conducted to evaluate the effect of feed composition on operating costs, profitability and process safety. The key results of this study indicate that the ODH reaction can be made safer and more profitable without use of an inert diluent and furthermore by replacing O2 with CO2 as an oxidant. Modifications of the M1 catalyst composition in order to adopt these changes are discussed.

Selectivity in the oxidative dehydrogenation of butene on zinc-iron oxide catalyst

Energy Technology Data Exchange (ETDEWEB)

Kung, H.H.; Kundalkar, B.; Kung, M.C.; Cheng, W.H.

1980-02-21

Adsorption, temperature-programed desorption, and pulse reaction studies of cis-2-butene and butadiene on spinel zinc ferrite by previously described methods provided evidence that the selectivity for oxidative dehydrogenation of butenes increases when zinc is added to the iron oxide catalyst because selective oxidation and complete oxidation proceed on separate sites, as they do on pure iron; because the density of sites for selective oxidation is higher and the density of sites for complete combustion is lower than on pure iron oxide; and because the activity of the combustion sites is lower.

Synthesis and characterization of conventional and mesoporous Ga-MFI for ethane dehydrogenation

DEFF Research Database (Denmark)

Leth, Karen Thrane; Rovik, Anne Krogh; Holm, Martin Spangsberg

2008-01-01

difference being the morphology of the crystals. The catalytic properties of the samples were tested in ethane dehydrogenation at 823 K and at atmospheric pressure. The two Ga-MFI samples differ greatly in conversion of ethane, as a result of their difference in porosity, and it is found that the conversion...... is reported for tetrahedral Ga incorporated in the MFI structure and it is shown that absorbed water molecules have an important impact on the Ga-71 electric field gradients and thereby on the quantitative evaluation of the Ga-71 MAS NMR intensities....

Reversible switching of the sol- gel transition with ultrasound in rhodium(I) and iridium(I) coordination networks

NARCIS (Netherlands)

Paulusse, J.M.J.; Beek, van D.J.M.; Sijbesma, R.P.

2007-01-01

Reversible coordination networks were prepared by combining diphenylphosphinite telechelic polytetrahydrofuran (2) with [RhCl(COD)]2 or [IrCl(COD)]2 in chloroform. Both systems resulted in stable gels at concentrations above 50 and 30 g/L for the rhodium(I) and iridium(I) networks, respectively. The

Supported ionic liquid-phase (SILP) catalysis

DEFF Research Database (Denmark)

Riisager, Anders; Fehrmann, Rasmus; Wasserscheid, P.

2005-01-01

The concept of supported ionic liquid-phase (SILP) catalysis has been demonstrated for gas- and liquid-phase continuous fixed-bed reactions using rhodium phosphine catalyzed hydroformylation of propene and 1-octene as examples. The nature of the support had important influence on both the catalytic...

Synthesis and antiplasmodial evaluation of novel (4-aminobutyloxy)quinolines

NARCIS (Netherlands)

Vandekerckhove, S.; Mueller, C.; Vogt, D.; Lategan, C.; Smith, P.J.; Chibale, K.; Kimpe, de N.; D'hooghe, M.W.A.

2013-01-01

A variety of 5-, 6- and 8-(4-aminobutyloxy)quinolines as novel oxygen analogues of known 4- and 8-(4-aminobutylamino)quinoline antimalarial drugs was generated from hydroxyquinolines through a three-step approach with a rhodium-catalyzed hydroformylation as the key step. Antiplasmodial assays of

Synthesis and Suzuki Cross-Coupling Reactions of 2,6-Bis(trifluoromethyl)pyridine-4-boronic Acid Pinacol Ester

KAUST Repository

Batool, Farhat

2016-11-18

Iridium-catalyzed aromatic borylation provides quick one-step access to 2,6-bis(trifluoromethyl)pyridine-4-boronic acid pinacol ester. Suzuki couplings of this highly electron-deficient pyridine-4-boronic ester with various (hetero)aryl bromides was successfully carried out and the coupled products were obtained in 46–95% isolated yields. Double and triple Suzuki couplings, with dibromo- and tribromoarenes, respectively, were also achieved. Thus demonstrating that this pyridine-4-boronic ester can be a useful source for the installation of one of the strongest electron-withdrawing aromatic group in organic compounds. Copyright © 2016, Georg Thieme Verlag. All rights reserved.