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

Masked silylene complexes Cp*­(IXy-H)­(H)­RuSiH2R (R =
Mes (3) and Trip (4); IXy = 1,3-bis­(2,6-dimethylphenyl)­imidazol-2-ylidene;
“IXy-H” is the deprotonated form of IXy) exhibit metallosilylene-like
(LnM–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
(6) 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.