Synthesis, structure and properties of the Cp2Zr{CH(SiMe3)2}+ cation

The generation and properties of the Cp2Zr{CH(SiMe3)2}+ cation are described. An X-ray crystallographic analysis shows that the carborane salt [Cp2Zr{CH(SiMe3)2}][HCB11Me5Br6] contains an agostic Zr–μ-Me–Si interaction in the solid state. Low temperature NMR spectra of the borate salt [Cp2Zr{CH(SiMe3)2}][B(C6F5)4] show that this interaction is retained in solution. Variable temperature NMR spectra establish that the SiMe2(μ-Me) and unbound SiMe3 units of Cp2Zr{CH(SiMe3)2}+ exchange by a “pivot” process involving partial rotation around the Zr–CH(SiMe3)2 bond, with a barrier of ΔG‡ = 9.2(1) kcal/mol at −89 °C. Cp2Zr{CH(SiMe3)2}+ does not coordinate alkenes or alkynes.