The invention is concerned with new phosphine ligands of formula I ##STR1##

wherein

R¹ and R² are independently of each other unsubstituted alkyl, aryl, cycloalkyl or heteroaryl, or alkyl, aryl, cycloalkyl or heteroaryl each of which independently is substituted by alkyl, alkoxy, halogen, hydroxy, amino, mono- or dialkylamino, aryl, —SO₂—R⁷, —SO₃^-, —CO—NR⁸R⁸, carboxy, alkoxycarbonyl, trialkylsilyl, diarylalkylsilyl, dialkylarylsilyl or triarylsilyl; R³ is alkyl, cycloalkyl, aryl or heteroaryl; R⁴ and R⁴ are independently of each other hydrogen, alkyl or optionally substituted aryl; or R⁴ and R⁴ together with the C-atom they are attached, form a 3-8-membered carbocyclic ring; dotted line is optionally a double bond; R⁵ and R⁶ are independently of each other hydrogen, alkyl or aryl, R⁷ is alkyl or aryl; and R⁸ and R⁸ are independently of each other hydrogen, alkyl or aryl; the substituents attached by the bold bonds are in cis relation to each other; metal complexes with such ligands in asymmetric reactions.