A μ3-η(2):η(2):η(2)-silane complex, [(Cp*Ru)3(μ3-η(2):η(2):η(2)-H3SitBu)(μ-H)3] (2 a; Cp* = η(5)-C5Me5), was synthesized from the reaction of [{Cp*Ru(μ-H)}3(μ3-H)2] (1) with tBuSiH3. Complex 2 a is the first example of a silane ligand adopting a μ3-η(2):η(2):η(2) coordination mode. This unprecedented coordination mode was established by NMR and IR spectroscopy as well as X-ray diffraction analysis and supported by a density functional study. Variable-temperature NMR analysis implied that 2 a equilibrates with a tautomeric μ3-silyl complex (3 a). Although 3 a was not isolated, the corresponding μ3-silyl complex, [(Cp*Ru)3(μ3-η(2):η(2)-H2SiPh)(H)(μ-H)3] (3 b), was obtained from the reaction of 1 with PhSiH3. Treatment of 2 a with PhSiH3 resulted in a silane exchange reaction, leading to the formation of 3 b accompanied by the elimination of tBuSiH3. This result indicates that the μ3-silane complex can be regarded as an "arrested" intermediate for the oxidative addition/reductive elimination of a primary silane to a trinuclear site.

The reaction of the μ3-silane complex {Cp*Ru­(μ-H)}3(μ3-η2:η2:η2-H3Si t Bu) (2) with t BuSiH3 caused η2-Si–H bond scissions and yielded the bis­(μ3-silyl) complex (Cp*Ru)3(μ3-η2:η2-H2Si t Bu)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-Si t Bu)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 t Bu 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 n BuSiH3, whereas its propensity toward oxidative addition is similar to that of t BuSiH3. 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.

A μ3‐η2:η2:η2‐silane complex, [(Cp*Ru)3(μ3‐η2:η2:η2‐H3SitBu)(μ‐H)3] (2 a; Cp*=η5‐C5Me5), was synthesized from the reaction of [{Cp*Ru(μ‐H)}3(μ3‐H)2] (1) with tBuSiH3. Complex 2 a is the first example of a silane ligand adopting a μ3‐η2:η2:η2 coordination mode. This unprecedented coordination mode was established by NMR and IR spectroscopy as well as X‐ray diffraction analysis and supported by a density functional study. Variable‐temperature NMR analysis implied that 2 a equilibrates with a tautomeric μ3‐silyl complex (3 a). Although 3 a was not isolated, the corresponding μ3‐silyl complex, [(Cp*Ru)3(μ3‐η2:η2‐H2SiPh)(H)(μ‐H)3] (3 b), was obtained from the reaction of 1 with PhSiH3. Treatment of 2 a with PhSiH3 resulted in a silane exchange reaction, leading to the formation of 3 b accompanied by the elimination of tBuSiH3. This result indicates that the μ3‐silane complex can be regarded as an “arrested” intermediate for the oxidative addition/reductive elimination of a primary silane to a trinuclear site.

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