Metal-Silicon Triple Bonds: Access to [Si(η⁵-C₅Me₅)]⁺ from SiX₂(NHC) and its Conversion to the Silylidyne Complex [Tp^Me(CO)₂MoSi(η³-C₅Me₅)] (Tp^Me = κ³- N, N ′, N ″-hydridotris(3,5-dimethyl-1-pyrazolyl)borate)

A novel method to prepare SiCp∗₂ (1) (Cp∗ = C₅Me₅) is presented involving the reaction of N-heterocyclic carbene (NHC)-stabilized Si^II halides SiX₂(NHC) (X = Cl, Br) with 2 equiv of KCp∗. This route is a superior alternative to the laborious, multistep synthesis of 1 presently known and provides via the selective protonolysis of 1 with [H(Et₂O)₂][B(C₆F₅)₄] facile access to [Si(η⁵-Cp∗)][B(C₆F₅)₄] (2) in multigram scale and high yield. Reaction of 2 with the tailored metallate Na[Tp^MeMo(CO)₂(PMe₃)] afforded the unprecedented silylidyne complex [Tp^Me(CO)₂MoSi(η³-Cp∗)] (3; Tp^Me = κ³-N,N′,N″-hydridotris(3,5-dimethyl-1-pyrazolyl)borate). Single crystal X-ray diffraction and spectroscopic studies in combination with quantum chemical calculations shed light on the unique bonding situation of 3 featuring a delocalized Mo-Si bond with partial triple bond character and a Cp∗ substituent, which is η³-coordinated to silicon.