Dehydrocoupling of SiMe2H substituents in permethylated zirconocene complexes

Complex [Zr{η5-C5Me4(SiMe2H)}2Cl2] (1) was prepared by the reaction of lithium salt of 2,3,4,5-tetramethyl-1-(dimethylsilyl)cyclopenta-2,4-diene with [ZrCl4] in boiling THF. The reduction of 1 with excess magnesium in THF in the presence of excess bis(trimethylsilyl)acetylene (btmsa) afforded the bivalent metal ansa-disilylene complex with π-coordinated btmsa [Zr(η2-btmsa){η5-C5Me4(SiMe2)}2] (2). The dehydrocoupling of SiMe2H groups was accompanied by a hydrogen transfer to releasing btmsa to give a mixture of cis- and trans-1,2-bis(trimethylsilyl)ethene. Chlorination of 2 with PbCl2 afforded ansa-[Zr{η5-C5Me4(SiMe2)}2Cl2] (3) and liberated btmsa. The crystal structures of complexes, 1, 2 and 3 have been determined by X-ray crystallography.