Process for preparing dialkyl oxide metallocenes or diaryl oxide metallocenes

Process for preparing bridged, stereorigid, diastereomerically pure dialkoxide metallocenes, diaryl oxide metallocenes and preferably diphenoxide metallocenes of the general formula Q(Cp)(Cp′)M(OR3)2 in which Cp=a cyclopentadienyl, an indenyl or a fluorenyl radical Cp′=one of the Cp groups Q=a single- or multimembered bridge (R1—Z—R2)b between Cp and Cp′, in which R1 and R2 may be the same or different and are each a hydrogen atom, a CrCio-alkyl group, a Cβ-Cio-aryl group, and Z is carbon, silicon or germanium where b=1, 2 or 3 M=a transition metal of group 4, especially Zr and Hf and Ti O=oxygen R3=a Ci-Cio-alkyl group, a Cβ-Cio-aryl group, where the alkyl group may be branched or unbranched and may be substituted by aryl groups, and the aryl group may contain further substituents, characterized in that, in the first stage, a bridged, stereorigid metallocene dihalide in the form of a diastereomeric rac/meso mixture, said metallocene dihalide having the general formula Q(Cp)(CpOM(X)2 in which Cp=a cyclopentadienyl, an indenyl, a fluorenyl radical Cp′=one of the Cp groups, which may be different or the same Q=a single- or multimembered bridge (Rx—Z—R2)b between Cp and Cp′, in which R1 and R2 may be the same or different and are each a hydrogen atom, a CrCio-alkyl group, a Cβ-Cio-aryl group, and Z is carbon, silicon or germanium where b=1, 2 or 3M=a transition metal of group 4, especially Zr and Hf X=a halogen, especially Cl is reacted with an alkylating reagent of the general formula R4-M-(X)n in which R4=a CrCio-alkyl group, a Ci-Cio-aryl group M=an alkali metal or alkaline earth metal, preferably Mg, Na or LiX=halogen, especially Cl and Br n=the oxidation number of M reduced by 1, and then the resulting reaction mixture or the intermediately isolated dialkylmetallocene is reacted with an alcohol, an aryl alcohol or a phenol of the general formula HO—R3 in which HO=a hydroxyl group R3=a Ci-Cio-alkyl group, a Cβ-Cio-aryl group, where the alkyl group may be branched or unbranched and may be substituted by aryl groups, and the aryl group may contain further substituents.