Twofold Deprotonated Citric Acid as a Bidentate Ligand of Pentacoordinate Silicon: Synthesis and Structural Characterization of the Zwitterionic λ5Si‐Spirosilicate Bis[citrato(2–)‐O3,O4][(dimethylammonio)methyl]silicate Hydrate

Abstract

AbstractThe zwitterionic λ5Si‐spirosilicate bis[citrato(2–)‐O3,O4][(dimethylammonio)methyl]silicate (4) was synthesized by reaction of (MeO)3SiCH2NMe2 (3) with citric acid (molar ratio 1:2) in acetonitrile at room temperature and isolated, after crystallization from water, as the hydrate 4 . H2O (yield 81%). The crystal structure of 4 . H2O was studied by single‐crystal X‐ray diffraction. The alcoxide oxygen atoms and central carboxylate oxygen atoms of two citrato(2–) ligands and one carbon atom coordinate to the silicon atom of 4 . H2O. The coordination polyhedron around the pentacoordinate silicon atom (SiO4C framework) can be described as a distorted trigonal bipyramid, the two carboxylate oxygen atoms occupying the axial sites. The λ5Si‐silicon(IV) complex 4 also exists in solution (DMSO, H2O).