Syntheses, Stereochemistry, and Dynamic Behavior of Chiral Zwitterionic (Ammoniomethyl)bis[glycolato(2–)-O1,O2]silicates

The syntheses of the zwitterionic (molecular) spirocyclic λ5Si-silicates 5–9 are described. These chiral compounds contain a pentacoordinate (formally negatively charged) silicon atom and a tetracoordinate (formally positively charged) nitrogen atom. The stereochemistry and dynamic behavior of 5–9 were investigated. For this purpose, compounds 5–9 were studied by solution-state NMR spectroscopy (1H, 13C, 29Si; including VT 1H-NMR studies of 9) and solid-state NMR spectroscopy (13C CP/MAS, 29Si CP/MAS). In addition, compounds 5·H2O, 7, 8, 9·H2O, and 9·2CH3CN were structurally characterized by single-crystal X-ray diffraction, and ab initio investigations of the zwitterion 8 and the related anionic model species 10 were carried out.