An Isolable Silicon Dicarbonate Complex from Carbon Dioxide Activation with a Silylone.

The first isolable molecular silicon dicarbonate complex (bis-NHC)Si(CO ) 2 (bis-NHC=H C[{NC(H)=C(H)N(Dipp)}C:] , Dipp=2,6-iPr C H ) was synthesized by facile reaction of the bis-N-heterocyclic carbene stabilized silylone (bis-NHC)Si 1, bearing a zero-valent silicon atom, with carbon dioxide. The monomeric silicon dioxide complex (bis-NHC)SiO 3 supported by the bis-NHC ligand was proposed as a key intermediate resulting from double oxygenation of the zero-valent silicon atom in 1 by two molar equivalents of CO under liberation of CO; its subsequent Lewis acid-base reaction with CO leads to 2 which has been fully characterized including an single-crystal X-ray diffraction analysis. Its electronic structure, spectroscopic data and the thermochemistry of the formation have been studied quantum-chemically.