Compounds of the formula I, in the form of their racemates, mixtures of stereoisomers or mainly pure stereoisomers CHEM in which Y is C1-C4alkylene or -SiR1R2-; X is a carbon atom and A1 and A2 independently of one another are hydrogen, C1-C12alkyl, C2-C12alkenyl, C3-C8cycloalkyl, C3-C8cycloalkenyl, C3-C8cycloalkyl-C1-C4alkyl, C3-C8cycloalkenyl-C1-C4alkyl, C6-C10aryl or C7-C14aralkyl; or X is a silicon atom and A1 and A2 independently of one another are C1-C12alkyl, C3-C8cycloalkyl, C3-C8cycloalkyl-C1-C4alkyl, C6-C10aryl or C7-C14aralkyl; A3 and A4 independently of one another are hydrogen, C1-C12alkyl, C3-C8cycloalkyl, C3-C8-cycloalkyl-C1-C4alkyl, C6-C10aryl or C7-C14aralkyl; and R1 and R2 independently of one another are C1-C6alkyl, cyclohexyl, phenyl or benzyl, are ligands for metal complexes of the eighth sub-group of the Periodic Table of the Elements, which are suitable as catalysts for asymmetric hydrogenations and transfer hydrogenations of prochiral compounds having carbon/carbon or carbon/heteroatom multiple bonds.
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