Enantioselective hydrogenation over immobilized rhodium diphosphine complexes on mesostructured materials

New heterogeneous chiral catalysts were prepared from rhodium diphosphine complexes [Rh(P-P)COD]CI ((P-P) = diphosphine ligand and COD = cyclooctadiene), and Al-MCM-41, Al-MCM-48, and Al-SBA-15, respectively. Impregnation of the mesoporous Al-MCM-41, Al-MCM-48, and Al-SBA-15 with the organometallic complexes in dichloromethane led to strongly bonded hydrogenation catalysts. The catalysts were characterised with XRD, FT-IR and MAS-NMR, as well as thermoprogrammed desorption of ammonia, thermogravimetric analysis, and nitrogen sorption experiments. The hydrogenation of dimethyl itaconate, methyl a-acetamidoacrylate, and methyl alpha-acetamidocinnamate were studied as test reactions. The immobilized catalysts showed high activities and excellent chemo- and enantioselectivities. Up to 98% e.e., > 99% conversion and 99% selectivity were observed in the case of studied prochiral olefins. The catalysts could be reused without a loss of catalytic activity. Leaching of the homogeneous complex out of the mesoporous framework was not observed. (c) 2006 Published by Elsevier B.V.