Homogeneous Hydrogenation of Unsaturated Carboxylic Acids Using Chlororhodate(I) Complexes and Rhodium(I) Diethylsulfide Complexes

Abstract

BRIAN R. JAMES and FLORA T. T. NG. Can. J. Chem. 53,797(1975). N,N-Dimethylacetamide solutions of the cyclooctene complex [Rh(C8H,,)2CI]2, in the presence of excess chloride or diethylsulfide, are effective for the homogeneous hydrogenation of unsaturated carboxylic acids at c a . 80 ' C and 1 atm H,. Kinetic studies on the hydrogenation of maleic acid are consistent with a rate determining step involving oxidative addition of H2 to square planar rhodium([) olefin species. Rate constants and activation parameters agree with those determined previously from similar studies using corresponding rhodium(II1) complexes and give confirmation that rhodium(1) catalysts are involved in the rhodium(II1) systems. Discussion of the systems is limited by the somewhat uncertain nature of the catalysts; however, chlororhodate(1) species are involved in the chloride solutions, and bis(diethylsu1fide) complexes appear likely in the sulfide systems.

Hydrogenation of olefinic substrates in aqueous and aqueous-organic biphase systems using rhodium complex of sulphonated triphenyl phosphine

“…The observation of higher rate of reaction for fumaric acid (trans isomer) than for meleic acid (cis isomer) is somewhat unusual when compared to the studies with Wilkinson's catalyst, in the case of maleate and fumarate esters (James 1973). However a higher rate of reaction has been observed for trans isomer using [RH(cyclooctene)2Cl]2 + Cl-or Et2S as the catalyst in dimethylacetamide solution (James and Ng 1975). Similar observations were made for hydrogenation of maleic and fumaric acid .…”

Studies on the Activation and Hydrosilylation Catalysis of RhCl3(Bu2S)3

“…Beyond hydrosilylation, the catalytic activity of RhCl 3 (SR 2 ) 3 has not been extensively explored. The most notable exception is the hydrogenation of carboxylic acid-containing olefins (such as maleic, fumaric, and cinnamic acid) by James et al, for which RhCl 3 (SEt 2 ) 3 is used as a precatalyst. − The catalytic reaction occurs under somewhat mild conditions (1 atm H 2 , 70 °C) and requires dimethylacetamide as a solvent; activity is not observed with benzene as a solvent . They also report that the reaction requires dissociation of SBu 2 and that the catalytic reaction is preceded by reduction of Rh III to Rh I .…”