Organic chemistry of subvalent transition metal complexes part 16 - Novel synthesis of ansa-metallocenes via the reductive dimerization of fulvenes with group 4 metal divalent halides

Substituted ethylene-bridged ansa-metallocenes of group 4 dihalides can be prepared in high yields by the interaction of the titanium zirconium, or ha fnium dihalide with 2 equiv of the appropriate fulvene. The requisite metal dihalides are readily produced by the alkylative reduction of the metal te trahalide with 2 equiv of an alkyllithium reagent in THF or in toluene.