Novel Molecular Si(II) Precursors for Synthesis of the First Compounds with Metal-Silicon Triple Bonds

Abstract

NHC-adducts of reactive silylenes were isolated as crystalline thermally stable solids. The NHC-adducts of SiBr₂ and SiI₂ were prepared upon reduction of the corresponding NHC adducts of silicon tetrahalides. The first NHC-adducts of arylchlorosilylenes were also prepared upon dehydrochlorination of the corresponding aryldichlorosilanes with two equivalents of N-heterocyclic carbene. Starting from these Si(II) compounds, a unique approach to silylidene complexes of Group 6 transition-metals was achieved by metathetical exchange with carbonyl metallates was developed. Thereby, a series of zwitterionic silylidene complexes unprecedented up to date was obtained. NHC abstraction from the complex [Cp(CO)₂Mo=SiAr(NHC)] (Ar = -C₆H₃-2,6-Trip₂) afforded the first silylidyne complex. Furthemore, halide abstraction from halosilylidene complexes afforded unprecedented cationic silylidyne complexes of Cr, Mo and W. Reactivity of the silylidyne complexes towards polar molecules, nucleophiles and alkynes has been investigated.