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 Si-4{N(SiMe3)Dipp}(4) 1 (Dipp=2,6-diisopropylphenyl) with 5equiv 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 Si-4{N(SiMe3)Dipp}(2)(NHCMe4)(2)(NDipp) 2. When 2 reacts with 0.25 equiv sulfur (S-8), two sulfur atoms add to the divalent silicon atom in plane and perpendicular to the plane of the Si-4 ring, which confirms the silylone character of the two-coordinate silicon atom in 2.