The reaction of amidinatosilylene LSi(:)Cl [L = PhC(NtBu)₂] with N-heterocyclic carbene I_Ar [:C{N(Ar)CH}₂, where Ar = 2,6-iPr₂C₆H₃] and NaOTf in tetrahydrofuran (THF) facilely afforded a silicon(II) cation [LSi(:)-_aI_Ar]⁺OTf^- (1⁺OTf^-), where I_Ar isomerizes to abnormal N-heterocyclic carbene _aI_Ar, coordinating to the silicon(II) center. Its Ge homologue, [LGe(:)-_aI_Ar]⁺OTf^- (2⁺OTf^-), was also accessed via the same protocol. For the formation of 1⁺, we propose that an in situ-generated Si(II) cation [LSi(:)]⁺ under the treatment of LSi(:)Cl with NaOTf may isomerize I_Ar in THF. In contrast, the replacement of I_Ar with cyclic alkyl(amino) carbene (cAAC) furnished a cAAC-silanyl radical ion [LSi(H)-cAAC]^•+(LiOTf₂)^- [3^•+(LiOTf₂)^-], which may undergo an abstraction of the H radical from THF. All of the products were characterized by nuclear magnetic resonance spectroscopy, electron paramagnetic resonance, and X-ray crystallography, and their bonding scenarios were investigated by density functional theory calculations. These studies provide new perspective on carbene-silicon chemistry.

Keke Zhu

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