Enantioselective hydrogenation over immobilized rhodium diphosphine complexes on aluminated SBA-15

A series of heterogeneous chiral catalysts was prepared from rhodium diphosphine complexes [Rh(L-L)COD]Cl ((L-L) = diphosphine ligand and COD = cyclooctadiene) and aluminated SBA-15. Impregnation of mesoporous Al-SBA-15 with organometallic complexes led to strongly bonded hydrogenation catalysts. The complexes were bound to the carrier by the interaction of the cationic rhodium of the organometallic complex with the anionic host framework, and between Al Lewis acid sites and P Lewis basic sites. The hydrogenation of dimethyl itaconate and that of methyl α-acetamidoacrylate were studied as test reactions. The immobilized catalysts showed high activities and excellent chemo- and enantioselectivities. Up to 93% e.e., >99% conversion, and 99% selectivity were observed in the case of studied prochiral olefins. The catalysts could be reused without loss of catalytic activity. These new catalysts were stable toward leaching of the homogeneous complex from the solid framework.