From Silylone to an Isolable Monomeric Silicon Disulfide Complex

The synthesis and characterization of the first bis-N-heterocyclic carbene stabilized monomeric silicon disulfide (bis-NHC) SiS2 2 (bis-NHC= H2C[{NC(H)C(H) N-(Dipp)}C:](2), Dipp=2,6-iPr(2)C(6)H(3)) is reported. Compound 2 is prepared in 89% yield from the reaction of the zero-valent silicon complex ('silylone') 1 [(bis-NHC) Si] with elemental sulfur. Compound 2 can react with GaCl3 in acetonitrile to give the corresponding (bis-NHC) Si(S) S -> GaCl3 Lewis acid-base adduct 3 in 91% yield. Compound 3 is also accessible through the reaction of the unprecedented silylone-GaCl3 adduct [(bis-NHC) Si! GaCl3] 4 with elemental sulfur. Compounds 2, 3, and 4 could be isolated and characterized by elemental analyses, HR-MS, IR, C-13-and Si-29-NMR spectroscopy. The structures of 3 and 4 could be determined by single-crystal Xray diffraction analyses. DFT-derived bonding analyses of 2 and 3 exhibited highly polar Si-S bonds with moderate p(pi)-p(pi) bonding character.