Abstract: Compounds of the formula (I) in the form of racemates, mixtures of diastereomers or pure diastereomers, where RO and Roo are each, independently of one another, hydrogen, C1-C20-alkyl, C3-C8-cycloalkyl, C6-C14-aryl or C3-C12-heteroaryl having heteroatoms selected from the group consisting of O, S and N, which are unsubstituted or substituted by C1-C6-alkyl, C1-C6-alkoxy, C5-C8-cycloalkyl, C5-C8-cycloalkoxy, phenyl, C1-C6-alkylphenyl, C1-C6-alkoxyphenyl, C3-C8-heteroaryl, F or trifluoromethyl; the radicals R1 are each, independently of one another, a hydrogen atom, a halogen atom or a substituent bound to the cyclopentadienyl rings via a C atom, S atom, Si atom, a P(O) or P(S) group; R2 and R02 are each, independently of one another, a hydrogen atom, C1-C20-alkyl, C3-C8-cycloalkyl, C6-C14-aryl or C3-C12-heteroaryl having heteroatoms selected from the group consisting of O, S and N, which are unsubstituted or substituted by C1-C6-alkyl, C1-C6-alkoxy, C5-C8-cycloalkyl, C5-C8-cycloalkoxy, phenyl, C1-C6-alkylpheny