| Sumario: | OsH5(SiHPh2)(PiPr3)2 (1) catalyzes the monoalcoholysis of diphenylsilane with a variety of alcohols. Density functional theory (DFT) calculations suggest that the reactions occur via a highly ordered transition state resulting from the nucleophilic attack of the alcohol to the silane coordinated to the osmium center in an η1-H–SiHPh2 fashion. The alcoholysis or aminolysis of the Si–H bond of 1 with 2-hydroxypyridine or 2-aminopyridine affords OsH3{κ2-Si,N-(SiPh2-E-py)}(PiPr3)2 (E = O (4), NH (5)). Analogously, OsH4(SiH2Ph)2(PiPr3)2 (2) reacts with 2-hydroxypyridine and 2-aminopyridine to give OsH3{κ2-Si,N-(SiPh(Epy)-E-py)}(PiPr3)2 (E = O (6), NH (7)), as a result of the alcoholysis or aminolysis, respectively, of both Si–H bonds of one of the phenylsilyl ligands. Additionally, 1 catalyzes the tandem hydrosilylation/dehydrogenative silylation of salicylaldehydes with diphenylsilane to afford silacycles. DFT calculations suggest that this process happens via an outer-sphere hydrogenation of the aldehyde moiety to give a diol and tetrahydride-silylene OsH4(=SiPh2)(PiPr3)2. Next, the silylative dehydrogenation of the Ph–OH function affords a silyl-O-functionalized pentahydride, which, upon the nucleophilic intramolecular attack of the benzylic OH group, gives the silacycle and intermediate OsH4(η2-H2)(PiPr3)2, which reacts with diphenylsilane, giving H2 and regenerating OsH5(SiHPh2)(PiPr3)2.
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