Donor-Promoted 1,2-Hydrogen Migration from Silicon to a Saturated Ruthenium Center and Access to Silaoxiranyl and Silaiminyl Complexes

Abstract

Masked silylene complexes Cp*­(IXy-H)­(H)­RuSiH₂R (R = Mes (<b>3</b>) and Trip (<b>4</b>); IXy = 1,3-bis­(2,6-dimethylphenyl)­imidazol-2-ylidene; “IXy-H” is the deprotonated form of IXy) exhibit metallosilylene-like (L_<i>n</i>M–Si–R) reactivity, as observed in reactions of nonenolizable ketones, enones, and tosyl azides, to give unprecedented silaoxiranyl, oxasilacyclopentenyl, and silaiminyl complexes, respectively. Notably, these silicon-containing complexes are derived from the primary silanes MesSiH₃ and TripSiH₃ via activation of all three Si–H bonds. DFT calculations suggest that the mechanism of formation for the silaoxiranyl complex Cp*­(IXy)­(H)₂Ru–Si­(OCPh₂)­Trip (<b>6</b>) involves coordination of benzophenone to a silylene silicon atom, followed by a single-electron transfer in which Si-bonded, non-innocent benzophenone accepts an electron from the reactive, electron-rich ruthenium center. Importantly, this electron transfer promotes an unusual 1,2-hydrogen migration to the resulting, more electron-deficient ruthenium center via a diradicaloid transition state