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

Reaction
of thiolate 1 with carbene-stabilized diiodo-bis-silylene
(2) (in a 2:1 ratio) in THF unexpectedly gives both the
first five-membered, sulfur-containing, zwitterionic silylene ring
(3) via insertion of the “SiI2” unit of 2 into the olefinic CH bond
of the imidazole ring of 1 and four-membered cyclic silylene
(4) via insertion of a silicon­(I) atom of 2 into the CphenylN bond of the carbene ligand.
The parallel reaction in toluene only gives 3 as the
major product. The nature of the bonding in isomeric 3 and 4 was probed by experimental and theoretical methods.