Taming Silicon Congeners of CO and CO2: Synthesis of Monomeric SiII and SiIV Chalcogenide Complexes.

The synthesis of the unprecedented monomeric Si^II selenide complex (bis-NHC)Si=Se→GaCl₃ 2 (bis-NHC=bis-N heterocyclic carbene, H₂C[{NC(H)=C(H)N(Dipp)}C:]₂, Dipp=2,6-iPr₂C₆H₃), bearing the elusive SiSe ligand as a heavy CO homologue by the reaction of the silylone-GaCl₃ adduct (bis-NHC)Si→GaCl₃ 1 with elemental selenium in acetonitrile, is reported. The similar conversion of 1 with excess selenium conducted in THF afforded the SiSe₂ complex (bis-NHC)Si(=Se)Se→GaCl₃ 3. Remarkably, the reaction of 1 with Te=P( nBu)₃ as a gentle Te transfer reagent led to the isolation of the monomeric SiTe₂ complex (bis-NHC)SiTe₂ 4, the first structurally characterized Lewis acid free heavy CO₂ homologue complex. The isolated compounds 2, 3, and 4 have been fully characterized, including single-crystal X-ray diffraction analyses. Their electronic structures and spectroscopic data have also been studied by quantum-chemical calculations. [ABSTRACT FROM AUTHOR]