Compounds of the formula I, in the form of mixtures comprising predominantly one enantiomer or in the form of pure enantiomers, secondary phosphine-Q-P*(═O)HR1 (I) in which secondary phosphine is a C-bonded, secondary phosphine group —P(R)2; in which R is in each case independently hydrocarbon radicals or heterohydrocarbon radicals; Q is a bivalent, achiral, aromatic base skeleton, a bivalent, achiral ferrocene base skeleton, an optionally substituted bivalent cycloalkane or heterocycloalkane skeleton, or a C1-C4-alkylene skeleton, and in which base skeletons a secondary phosphine group is bonded directly to a carbon atom, or, in the case of cyclic base skeletons, directly to a carbon atom or via a C1-C4-alkylene group, and in which base skeletons a P-chiral group —P*(O)HR1 is bonded to a carbon atom such that the phosphorus atoms are linked via 1 to 7 atoms of a carbon chain optionally interrupted by heteroatoms from the group of O, S, N, Fe or Si; P* is a chiral phosphorus atom; and R1 is a hydrocarbon radical, a C-bonded heterohydrocarbon radical or a ferrocenyl radical, with the proviso that R1 is an achiral ferrocenyl radical when Q is an achiral ferrocenyl base skeleton. Metal complexes of these ligands in a molar ratio of ligand to metal of about 1.3:1 to 0.9:1 are homogeneous catalysts for asymmetric addition reactions, particularly hydrogenations.