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.