Dianionic complexes with hexacoordinate silicon(IV) or germanium(IV) and three bidentate ligands of the salicylato(2–) type: Syntheses and structural characterization in the solid state and in solution.

Reaction of tetramethoxysilane or tetramethoxygermane with salicylic acid and morpholine (molar ratio 1:3:2) in tetrahydrofuran yielded morpholinium mer-tris[salicylato(2–)-O¹,O³]silicate( mer -5) and morpholinium mer-tris[salicylato(2–)-O¹,O³]germanate ( mer- 8), respectively. Treatment of tetramethoxysilane with 5-chlorosalicylic acid and piperidine (molar ratio 1:3:2) in tetrahydrofuran afforded piperidinium mer-tris[5-chlorosalicylato(2–)-O¹,O³]silicate–ditetrahydrofuran ( mer- 6·2THF). Triethylammonium mer-tris[3-methylsalicylato(2–)-O¹,O³]silicate ( mer- 7) was obtained analogously by reaction of tetramethoxysilane with three molar equivalents of 3-methylsalicylic acid and two molar equivalents of triethylamine in dichloromethane/diethyl ether. The racemic compounds mer- 5, mer- 6· 2THF, mer- 7, and mer- 8 were characterized by elemental analyses (C, H, N), single-crystal X-ray diffraction, as well as solid-state (²⁹Si) and solution(¹H, ¹³C, ²⁹Si) NMR studies. The structural characterizationwas complemented by computational studies (HF studies, TZVP level) of the fac- and mer-tris[salicylato(2–)-O¹,O³]silicatedianion. In addition, the behavior of mer- 7 in solution was studied by VT ¹HNMR experiments. [ABSTRACT FROM AUTHOR]