Novel Synthesis of Unbridged, Sterically Substituted Zirconocene Dichlorides from Fulvenes and Dialkylzirconium Dichlorides via Zirconium(IV) Hydride Transfer1

Unbridged, sterically substituted zirconocene dichlorides can be prepared in high yields by the interaction of a dialkylzirconium dichloride with 2 equiv of the appropriate fulvene in hydrocarbon medium with alkene displacement. The requisite dialkylzirconium dichloride can readily be produced by the alkylation of ZrCl 4 in hydrocarbon media with 2 equiv of an alkyllithium reagent. Generating the R 2 ZrCl 2 reagents in hydrocarbon media permits their use as hydrozirconating agents for a variety of polar unsaturated organic substrates.