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.