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.