The zwitterionic spirocyclic λ5 Si-silicate (morpholiniomethyl)bis[salicylato(2−)-O 1,O 2]silicate (5) was synthesized by reaction of trimethoxy(morpholinomethyl)silane and dimethoxy(morpholinomethyl)phenylsilane, respectively, with salicylic acid (molar ratio 1:2) in acetonitrile at room temperature. Bis[salicylato(2−)-O 1,O 2][(2,2,6,6-tetramethylpiperidinio)methyl]silicate (6) was obtained analogously, starting from trimethoxy[(2,2,6,6-tetramethylpiperidino)methyl]silane. Compound 5 was isolated as a crystalline product consisting of enantiomorphic crystals, each containing exclusively zwitterions with the same absolute configuration. Crystallization of this product from acetonitrile yielded the crystalline solvate 5·CH3CN (crystals containing a 1:1 mixture of enantiomers with opposite absolute configuration). Compounds 5 (Δ-enantiomer), 5·CH3CN (racemate), and 6 (racemate) were structurally characterized by single-crystal X-ray diffraction. The spirocyclic frameworks of 5 and 6 are built up by two six-membered SiO2C3 ring systems. The zwitterions in the crystal of 5, 5·CH3CN, and 6 contain a pentacoordinate (formally negatively charged) silicon atom (SiO4C skeleton) and a tetracoordinate (formally positively charged) nitrogen atom. The coordination polyhedra around the silicon atoms are distorted trigonal bipyramids, the axial positions being occupied by the carboxylate oxygen atoms. Solid-state MAS NMR studies revealed the following isotropic 29Si chemical shifts:  δ −120.6 (5), −123.1 (5·CH3CN), −120.4 (6). The zwitterion 6 exists also in solution (CDCl3; 1H, 13C, and 29Si NMR studies).

The zwitterionic spirocyclic λ 5 Ge-germanate bis[citrato(2-)-O 3 ,O 4 ](morpholiniomethyl)-germanate (2) and its silicon analogue bis[citrato(2-)-O 3 ,O 4 ](morpholiniomethyl)silicate (3) were synthesized by reaction of citric acid with trimethoxy(morpholinomethyl)germane (4) and trimethoxy(morpholinomethyl)silane (5), respectively. Both reactions were carried out at room temperature in acetonitrile and the products isolated, after crystallization from water, as the hydrates 2‚H 2 O and 3‚H 2 O. In addition to NMR spectroscopic (solution-state 1 H, 13 C, and 29 Si NMR; solid-state 29 Si CP/MAS NMR) and mass spectrometric (FAB MS) characterization of 2, 2‚H 2 O, 3, and 3‚H 2 O, the hydrates were structurally characterized by single-crystal X-ray diffraction. The zwitterions 2 and 3 contain a pentacoordinate (formally negatively charged) germanium and silicon atom, respectively, and a tetracoordinate (formally positively charged) nitrogen atom. The central atom of 2 (Ge) and 3 (Si) is surrounded by four oxygen atoms and one carbon atom. In the crystal of 2‚H 2 O and 3‚H 2 O, the coordination polyhedra around the germanium and silicon atom can be best described as distorted trigonal bipyramids, the carboxylate oxygen atoms occupying the axial sites. In terms of the Berry pseudorotation coordinate, the geometries are displaced by 14.0% (2‚H 2 O) and 13.4% (3‚H 2 O) from the ideal trigonal bipyramid toward the ideal square pyramid. According to NMR spectroscopic studies, the zwitterions 2 and 3 also exist in solution ([D 6 ]DMSO).

The zwitterionic dispirocyclic (molecular) λ5 Ge,λ5 Ge‘-digermanate 5a is the first example of a dinuclear germanium compound containing two pentacoordinate Ge atoms (GeO4C framework). The coordination polyhedra around the germanium atoms are slightly distorted trigonal bipyramids. The synthesis and crystal structure analysis of 5a are reported.

1,1,2,2-Tetraphenyldisilane-1,2-diol (3) was prepared in a two-step synthesis, starting from 1,2-bis(diethylamino)-1,1,2,2-tetraphenyldisilane (1). Treatment of 1 with acetyl chloride yielded 1,2-dichloro-1,1,2,2-tetraphenyldisilane (2), which upon hydrolysis gave 3 (total yield 83%). Compounds 2 and 3 were characterized by elemental analyses (C,H) and solution NMR experiments (1H, 13C, 29Si; CDCl3). In addition, compound 1 and its condensation product, 1,5-dihydroxy-1,1,2,2,4,4,5,5-octaphenyl-3-oxa-1,2,4,5-tetrasilapentane (4; studied as the hemibenzene solvate 4ּ1/2C6H6), were structurally characterized by single-crystal X-ray diffraction.

A simple preparative method for the stereoselective synthesis of ten-and twelve-membered cyclosiloxanes with two exocyclic trans-silanol and two exocyclic trans-amino functions has been developed. Thus, treatment of trimethoxy-(morpholinomethyl)silane (5) with two molar equivalents of HOPh 2 Si−SiPh 2 OH and HOPh 2 Si−O−SiPh 2 OH, respectively, yielded trans-1,6-bis(2-hydroxy-1,1,2,2-tetraphenyldisilan-1-yloxy)-1,6-bis(morpholinomethyl)-3, 3,4,4,8,8,9,9-octaphenyl-2,5,7,10-tetraoxa-1,3,4,6,8,9-hexasilacyclodecane (6, 10-membered ring) and trans-2,8-bis(3-hydroxy-1,1,3,3-tetra-