Abstract: | The first isolable molecular silicon dicarbonate complex (bis‐NHC)Si(CO3)2 2 (bis‐NHC=H2C[{NC(H)=C(H)N(Dipp)}C:]2, Dipp=2,6‐iPr2C6H3) 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)SiO2 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 CO2 under liberation of CO; its subsequent Lewis acid–base reaction with CO2 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. |