Aqueous biphasic hydrogenations catalyzed by rhodium and iridium complexes modified with human serum albumin

Water soluble complexes derived from the interaction between Rh(CO)2(acac) and [Ir(COD)Cl]2, respectively, with human serum albumin (HSA), were employed in the aqueous biphasic hydrogenation of a,b-unsaturated compounds as 2-cyclohexen-1-one (I), 2-butenal (V), 3-phenyl-2-propenal (IX) and 3-aryl-2-methyl-2-propenals (XIII and XVII). Both catalytic systems Rh/HSA and Ir/HSA showed to be very active in the hydrogenation of ketone I even at low temperature and hydrogen pressure; in particular, the rhodium based catalyst showed to be very selective affording exclusively cyclohexanone (II). The a,b-unsaturated aldehydes investigated required higher temperature (up to 60 8C) and pressure (5 MPa) to obtain good conversions. In this case Rh/HSA resulted to bemore active than Ir based catalyst. In all cases both Rh/HSA and Ir/HSA were easily recycled without significant loss of activity.