Compounds of the formula (I) in the form of a mixture of predominantly one diastereomer or in the form of pure diastereomers, Z1-Q-P*R0R1  (I), wherein: Z1 is a C-bonded, secondary phosphine group of the formula —P(R)2, wherein R is a hydrocarbon radical or O-atom(s)-containing heterohydrocarbon radical having 1 to 18 carbon atoms and optionally substituted by C1-C6-alkyl, trifluoromethyl, C1-C6-alkoxy, trifluoromethoxy, (C1-C4-alkyl)2amino, (C6H5)3Si, (C1-C12-alkyl)3Si or halogen; Q is selected from the group consisting of: (i) an optionally substituted achiral aromatic group, wherein the achiral aromatic group is bonded directly to Z1 through a carbon atom of the achiral aromatic group and bonded directly to P*R0R1 through a carbon atom of the achiral aromatic group, and (ii) an optionally substituted C1-C4-alkylene group; P* is a chiral phosphorus atom; R0 is methyl; and R1 is a C-bonded optically enriched or optically pure chiral, mono- or polycyclic, nonaromatic hydrocarbon ring; and preparation and use.