N‑Heterocyclic Silylene Coordinated Dialkyl Borenium Equivalent

In an attempt to
prepare the heavier analogue of NHC-stabilized
borenium cation, we have prepared a silylene-coordinated borenium
equivalent (1a), which can be viewed as a contact ion
pair of borenium and triflate. The triflate anion coordinates to the
oxophilic silicon center, leaving the boron center existing in a trigonal-planar
geometry in the solid state and in solution. Nucleophilic substitution
reactions of 1a all result in the release of free silylene
ligand, demonstrating the borenium-ion-like reactivity of 1a. Chemical reduction of 1a leads to a neutral radical
possessing a partial Si–B double bond.