Pentacoordination of Silicon by Four Covalent Si−S Bonds and One Covalent Si−C Bond

The zwitterionic compounds 1 and 2 are the first pentacoordinate silicates with covalent SiS4C skeletons. They were characterized by crystal‐structure analyses and NMR spectroscopic studies. Although pentacoordination of silicon is usually favored by ligand atoms of high electronegativity, the structural data of both 1 and 2 are consistent with the presence of five covalent bonds to the silicon atom.