Electron-Induced Conversion of Silylones to Six-Membered Cyclic Silylenes

A silicon
atom in the zero oxidation state stabilized by two carbene
ligands is known as sila­dicarbene (silyl­one). There are
two pairs of electrons on the silicon atom in silyl­one. This
was recently confirmed by both experimental and theoretical charge
density investigations. The silyl­one is stable up to 195 °C
in an inert atmosphere. However, a substoichiometric amount (33 mol%)
of potassium metal triggers the activation of the unsaturated C:Si:C
backbone, leading to a selective reaction with a tertiary C–H
bond in an atom-economical approach to form a six-membered cyclic
silylene with three-coordinate silicon atom. Cyclic voltammetry shows
that this reaction proceeds via the formation of a silyl­one
radical anion intermediate, which is further confirmed by EPR spectroscopy.