μ3-η2:η2:η2-Coordination of Primary Silane on a Triruthenium Plane

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. Silane on a plane: The reaction of [{Cp*Ru(μ‐H)}3(μ3‐H)2] with tBuSiH3 afforded a μ3‐silane complex in which primary silane coordinates to the triruthenium plane while maintaining three SiH interactions. The unique μ3‐η2:η2:η2‐coordination can be regarded as an arrested intermediate of oxidative addition of a primary silane to the trinuclear site as well as a model for the chemisorption of saturated compounds on a metal surface.