Method for producing metallocenes

A process for preparing a rac/meso-metallocene of formula I

• having a rac/meso ratio of from 20:1 to 200:1, wherein
• M is a metal of groups IIIb, IVb, Vb or VIb of the Periodic Table of the Elements,
• X1 and X2 are identical or different and are each a hydrogen atom, a group comprising from 1 to 40 carbon atoms, an OH group, a halogen atom or a pseudohalogen,
• R1a, R1b, R2a, and R2b are identical or different and are each a hydrogen atom, a group comprising from 1 to 40 carbon atoms, an OH group, a halogen atom or a pseudohalogen, or a NR52, SR5, OSiR53, SiR53 or RR52 group, and R5 is one of the radicals set forth for X1,
• B is a single- to four membered bridging moiety, comprising the steps:
• a) reacting a cyclopentadiene of formula A
• wherein R1 is one of the radicals R1a or R1b, and R2 is one of the radicals R2a or R2b, with a bridging reagent BY2 wherein Y is a leaving group, to form a bridged biscyclopentadienyl ligand system,
• b) reacting the bridged biscyclopentadienyl ligand system with a metal halide to form a metallocene of formula Ia
• wherein X1 and X2 are halogen,
• c) hydrogenating the metallocene of formula Ia to form a metallocene of formula Ib
• d) and, optionally, reacting the metallocene of formula Ib with an organometallic compound R3M1 wherein R3 is a radical X1 or X2 different from halogen, and M1 is an element of main group I, II or III of the Periodic Table of the Elements, to form a metallocene Ic
• wherein all steps are carried out in the same solvent or solvent mixture.