μ3-η(2):η(2):η(2)-Coordination of Primary Silane on a Triruthenium Plane.

A μ3-η(2):η(2):η(2)-silane complex, [(CpRu)3(μ3-η(2):η(2):η(2)-H3SitBu)(μ-H)3] (2 a; Cp = η(5)-C5Me5), was synthesized from the reaction of [{CpRu(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, [(CpRu)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.