149733-58-4Relevant articles and documents
New Zwitterionic λ5-Spirosilicates: Syntheses, Single-Crystal X-Ray Structure Analyses, and Solid-State NMR Studies
Tacke, Reinhold,Lopez-Mras, Angel,Sperlich, Joerg,Strohmnann, Carsten,Kuhs, Werner F.,et al.
, p. 851 - 862 (2007/10/02)
The zwitterionic spirocyclic λ5-silicates bissilicate (5; and its monohydrate 5*H2O) and bissilicate (6) were synthesized by various methods including Si-C bond cleavage reactions.The crystal structures of 5, 5*H2O, and 6 were investigated by X-ray diffraction.Furthermore, 5, 5*H2O, 6, and the related zwitterionic λ5-spirosilicates 1*1/4 CH3CN, 2*CH3CN, 3*CH3CN, and 4 were characterized by solid-state NMR spectroscopy (29Si and 15N CP/MAS).The pentacoordinate silicon atoms of 5, 5*H2O (two crystallographically independent zwitterions and two crystallographically independent water molecules), and 6 (two crystallographically independent zwitterions) are surrounded by four oxygen atoms and one carbon atom.The coordination polyhedrons around the silicon atoms of 5 and 6 can be described as distorted (5) or nearly ideal (6) trigonal bipyramids, the carbon atoms being in equatorial positions. 5 forms intramolecular and 6 intermolecular (-> formation of dimeric units) N-H...O hydrogen bonds.The coordination polyhedrons around the two crystallographically independent silicon atoms of 5*H2O can be described as a nearly ideal and slightly distorted square pyramid, respectively, the carbon atoms being in the apical positions.In the crystal lattice of 5*H2O, intermolecular N-H...O and O-H...O hydrogen bonds between the zwitterions and water molecules are observed.The results obtained by X-ray diffraction and solid-state NMR spectroscopy are consistent for each compound studied. Key Words: Spirosilicates, zwitterionic / Silicon, pentacoordinate / Bond cleavage, Si-C / Solid-state NMR, 29Si and 15N
