Dimesitylsilyl derivatives of zirconium

Article abstract of DOI:10.1021/om00104a009

The preparation and characterization of (THF)₂LiSiHMes₂ (1, Mes = mesitvl) are reported. Compound 1 reacts with Cp₂Zr(Me)Cl (Cp = η⁵-C₅H₅) to afford thermally unstable Cp₂Zr(SiHMes₂)Me (2), characterized by NMR spectroscopy. Similarly, the reaction of 1 with Cp*₂Zr(Me)Br (Cp* = η⁵-C₅Me₅) provides the mixed alkyl silyl Cp*₂Zr(SiHMes₂)Me (3), which is stable for prolonged periods at room temperature. Compound 3 reacts cleanly with 1 equiv of HCl to give the chloro derivative Cp*₂Zr(SiHMes₂)Cl (4) and methane. Whereas carbon monoxide inserts cleanly into the Zr-C bond of 2, preferential CO insertion into the Zr-Si bond of 3 is observed. These reactions give Cp₂Zr(η²-COMe)SiHMes₂ (5) and Cp*₂Zr-(η²-COSiHMes₂)Me (6), respectively. Compound 6 is not stable in solution and slowly isomerizes to the enolate hydride Cp*₂Zr[OC(=CH₂)SiHMes₂]H (7). The mechanism of the latter conversion is discussed. Hydrogen is shown to cleave the Zr-Si bond of 3 faster than the Zr-C bond. Reaction of 3 with AgOSO₂CF₃ results in oxidative cleavage of the Zr-Si bond giving MeS₂HSiSiHMes₂, Mes₂SiH(OSO₂CF₃), MeS₂SiH(Me), and Cp*₂Zr(Me)OSO₂CF₃ (9), which was independently prepared from Cp*₂ZrMe₂ and AgOSO₂CF₃. Reaction of Cp*₂ZrCl₂ with 2 equiv of 1 does not give a bis(silyl) complex but instead results in dehydrohalogenation to MeS₂SiH₂ and the metallacycle Cp*₂ZrCH₂CCHCMeCHCMeCSiHMes (10).