Rhodium catalysts containing cationic

Other protein-rhodium conjugates containing cationic rhodium catalysts have also been prepared using bis(diphenylphosphino-ethyl)amino derivatives 5-7 and solutions of these bis(phosphine) ligands in the presence of carbonic anhydrase, a-chymotrypsin and bovine serum albumin (47). However, the exact nature of the complexes formed has not been discerned in any of these cases, and these latter enzyme-transition metal complexes evidently do not exhibit enantioselectivity in hydrogenation of a-acetamidoacrylic acid. 

Chauvin et al. reported the asymmetric hydrogenation of acetamidocinnamic acid to (S)-phenylalanine with a cationic chiral rhodium catalyst in [C4-mim][SbF6] ionic liquid, more recently the 2-arylacryhc acid has been produced with a reasonable 64% yield using a chiral ruthenium catalysts in [C4-mim][BF4] ionic hquids. Palladium catalysts immobilized in an ionic liquid-polymer gel membrane containing either [C2-mim][CF3S03] or [C2-mim][BF4] have also been reported as catalysts for heterogeneous hydrogenation reactions. 

Because decarbonylation of the acyl intermediate competes with olefin insertion into the same species, and the carbonyl complexes are inactive as catalysts, the catalyst is poisoned by the competing decarbonylation. The use of a cationic rhodium complex containing a chelating ligand suppresses poisoning of the catalyst by decarbonylation, and reactions of aIk-4-en-l-als catalyzed by rhodium complexes of bisphosphines formed the desired cyclo-pentanones faster than reactions catalyzed by neutral rhodium complexes. "... 

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