Catalysts suitable for asymmetric hydrogenation reactions is described comprising the reaction product of a group (8) transition metal compound a chiral phosphine and a chiral diamine of formula (1) in which R , R R or R are independently hydrogen, a saturated or unsaturated alkyl, or cycloalkyl group, an aryl group, a urethane or sulphonyl group and R , R , R or R are independently hydrogen, a saturated or unsaturated alkyl or cycloalkyl group, or an aryl group, at least one of R , R , R or R is hydrogen and A is a linking group comprising one or two substituted or unsubstituted carbon atoms.