Abstract: Compounds of the formulae (I) and (Ia) where X1 is secondary phosphino; R3 is a hydrocarbon radical having from 1 to 20 C atoms, a heterohydrocarbon radical which has from 2 to 20 atoms and at least one heteroatorn selected from the group consisting of O, S, NH and NR, or an —SO2—R radical; R is C1-C18-alkyl, phenyl or benzyl; the radicals R4 are each, or the two radicals R4 together a hydrocarbon radical having from 1 to 20 C atoms; R01 is a hydrocarbon radical having from 1 to 20 C atoms; and R02 and R?o2 are each, independently of one another, a hydrogen atom or independently have the meaning of R01, or R01 and R02 together with the C atom to which they are bound form a three- to eight-membered hydrocarbon or hetero hydrocarbon ring. The compounds are chiral ligands for complexes of metals of transition groups I and VIII which act as catalysts for asymmetric additions, for example of hydrogen, onto prochiral unsaturated organic compounds.