Synthesis, structure and properties of the Cp 2Zr{CH(SiMe 3) 2} + cation

Abstract

The generation and properties of the Cp 2Zr{CH(SiMe 3) 2} + cation are described. An X-ray crystallographic analysis shows that the carborane salt [Cp 2Zr{CH(SiMe 3) 2}][HCB 11Me 5Br 6] contains an agostic Zr–μ-Me–Si interaction in the solid state. Low temperature NMR spectra of the borate salt [Cp 2Zr{CH(SiMe 3) 2}][B(C 6F 5) 4] show that this interaction is retained in solution. Variable temperature NMR spectra establish that the SiMe 2(μ-Me) and unbound SiMe 3 units of Cp 2Zr{CH(SiMe 3) 2} + exchange by a “pivot” process involving partial rotation around the Zr–CH(SiMe 3) 2 bond, with a barrier of Δ G ‡ = 9.2(1) kcal/mol at −89 °C. Cp 2Zr{CH(SiMe 3) 2} + does not coordinate alkenes or alkynes.