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‑<i>N</i>,<i>N</i>′,<i>N</i>″‑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 SiII 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[TpMeMo­(CO)2(PMe3)] afforded the unprecedented silylidyne complex [TpMe(CO)2MoSi­(η3-Cp*)] (3; TpMe = 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.