Facile Conversion of Bis-Silylene to Cyclic Silylene Isomers: Unexpected C–N and C–H Bond Cleavage

Reaction of thiolate <b>1</b> with carbene-stabilized diiodo-bis-silylene (<b>2</b>) (in a 2:1 ratio) in THF unexpectedly gives both the first five-membered, sulfur-containing, zwitterionic silylene ring (<b>3</b>) via insertion of the “Si<sup>I</sup><sub>2</sub>” unit of <b>2</b> into the olefinic CH bond of the imidazole ring of <b>1</b> and four-membered cyclic silylene (<b>4</b>) via insertion of a silicon­(I) atom of <b>2</b> into the C<sub>phenyl</sub>N bond of the carbene ligand. The parallel reaction in toluene only gives <b>3</b> as the major product. The nature of the bonding in isomeric <b>3</b> and <b>4</b> was probed by experimental and theoretical methods.