Facile Access to an NHC-Coordinated Silicon Ring Compound with a Si=N Group and a Two-Coordinate Silicon Atom.

Reaction of the bicyclo[1.1.0]tetrasilatetraamide Si4 {N(SiMe3 )Dipp}4 1 (Dipp=2,6-diisopropylphenyl) with 5 equiv of the N-heterocyclic carbene NHCMe4 (1,3,4,5-tetramethylimidazol-2-ylidene) affords a bifunctional carbene-coordinated four-membered-ring compound with a Si=N group and a two-coordinate silicon atom Si4 {N(SiMe3 )Dipp}2 (NHCMe4 )2 (NDipp) 2. When 2 reacts with 0.25 equiv sulfur (S8 ), two sulfur atoms add to the divalent silicon atom in plane and perpendicular to the plane of the Si4 ring, which confirms the silylone character of the two-coordinate silicon atom in 2.