Patent ID: 6900343

Claim:
A process for converting a bridged metallocene of formula (IIa) where M is Ti, Zr or Hf, R 4 , R 6 are identical or different and are each hydrogen or a C 1 -C 20 group, R 5 , R 7 are identical or different and are each a hydrogen atom or a C 1 -C 20 group, R 8 , R 9 are identical or different and are each a hydrogen atom, a halogen atom or a C 1 -C 30 group, and two radicals R 8 and R 9 may form a monocyclic or polycyclic ring system which may in turn be substituted, l, l′ are identical or different and are each an integer from zero to 4, X is a halogen atom, and B is a bridging structural element between the two indenyl radicals, to a bridged metallocene of formula (II), where M, X, l, l′, B, R 4 , R 5 , R 6 , R 7 , R 8 and R 9 have the same meaning as above, Y is an element of main group VI of the Periodic Table of the Elements, m′ is 1 or 2, and R 3 are identical or different and are each halogen or a C 1 -C 30 group; comprising the steps a) reacting a bridged metallocene of the formula (IIa) with a ligand exchange component M 1 YR 3 where Y and R 3 are as defined above, M 1 is a cation, a cationic fragment, or an ammonium cation corresponding to an amine, to form the bridged metallocene of formula (II), b) optionally separating off solid residues of the formula M 1 X, c) optionally separating off the inert solvent or solvent mixture, d) recrystallizing the bridged metallocene of the formula (II) from an aprotic hydrocarbon, and e) separating the compound of the formula (II) from the mother liquor.