A series of diphosphines including those that are configurationally flexible were examined in the Ru(II) catalysed enantioselective hydrogenation of 1-acetonaphthone in the presence of a chiral diamine. These ligands were found to exert significant effects on both the activity and enantioselectivity of Ru(II)-diamine catalysts, with the ligand with the smallest bite angle yielding the lowest conversion and the one with largest bite angle yielding the lowest enantioselection. (C) 2002 Elsevier Science B.V. All rights reserved.