Preparation of Bis(μ3‑silylyne) Complexes via Consecutive Si–H Bond Cleavage at a Triruthenium Site

The reaction of the μ3-silane complex {Cp*Ru­(μ-H)}3(μ3-η2:η2:η2-H3SitBu) (2) with tBuSiH3 caused η2-Si–H bond scissions and yielded the bis­(μ3-silyl) complex (Cp*Ru)3(μ3-η2:η2-H2SitBu)2(μ-H) (4). The structure of 4, which adopts an open Ru3 framework, is characteristic of trinuclear complexes adopting a 50-electron configuration and was determined by X-ray diffractometry (XRD). Thermolysis of 4 resulted in further dehydrogenation and afforded a bis­(μ3-silylyne) complex, {Cp*Ru­(μ-H)}3(μ3-SitBu)2 (5a), whose highly symmetrical structure was unambiguously determined by XRD. A phenylsilylyne analogue, 5b, was also obtained by the reaction of {Cp*Ru­(μ-H)}3(μ3-η2:η2-H2SiPh)­(H) (3b) with PhSiH3 but via a different intermediate, the μ3-silylene−μ-silylene complex {Cp*Ru­(μ-H)}3(μ3-η2-HSiPh)­(μ-SiHPh) (6). The difference in intermediate was rationalized as arising from the steric repulsion between the substituent at the silicon atom and the surrounding Cp* groups. That is, the bulky tBu group retards the formation of a Ru–Si σ bond. In fact, μ3-silyl complex 3c was exclusively obtained by the reaction of {Cp*Ru­(μ-H)}3(μ3-H)2 (1) with nBuSiH3, whereas its propensity toward oxidative addition is similar to that of tBuSiH3. The series of μ3-silane, μ3-silyl, μ3-silylene, and μ3-silylyne complexes could be a model for successive σ-bond cleavage at a trinuclear site.