Reaction of alkylzirconocene cation complexes with (R-C C-)(2)SiR(2) reagents: Preparation of heterodimetallic compounds containing A mu-alkynyl ligand bridge between zirconium and silicon

The methylzirconocene cation, employed as the [Cp(2)ZrCH(3)(THF)](+)BPh(4)(-) reagent 1a reacts with (R'C=C)(2)SiR(2) substrates (6a-d) by means of carbometallation of an alkynyl group to yield the mixed metal ring systems 8a-d, containing both a 1,1-disubstituted mu-alkenyl and an alkynyl bridge between zirconium and silicon (e.g. shown by X-ray crystal structure analyses of complexes 8a and 8c). A similar addition reaction takes place upon treatment of the (butadiene)zirconocene/tris(pentafluorophenyl)- borane 1:1 addition product 9 with (CH3-C=C)(2)Si(CH3)(2) (6c) to give 10. Here the incipient alkyl zirconocene cation character of the metanocene/borate betaine complex 9 shows up in the alkynyl silane carbometallation reaction.