Synthesis and Characterization of Dianionic Hexacoordinate Silicon(IV) Complexes of Substituted Catechols, Flavones, and Fluorone: X-Ray Crystal Structures of [(n-C3H7)2NH2]2[(Cl4C6O2)3Si] · 3 CH3CN and [(n-C3H7)2NH2]2[(Br4C6O2)3Si] · 2 (CH3)2SO

Abstract

Reaction of tetraethoxysilane (TEOS) with substituted catechols (I-X), 7,8-dihydroxyflavone (XI), 3,3′,4′-trihydroxyflavone (XII), 3′,4′,5,7-tetrahydroxyflavone (XIII), and 9-phenyl-2,3,7-trihydroxy-6-fluorone (XIV) in the presence of an amine (molar ratio 1:3:2) in acetonitrile affords the corresponding dianionic hexacoordinate silicon(IV) complexes 1-15 having a “SiO6” structural fragment. The dianionic silicates were isolated as di-n-propylammonium/triethylammonium/di-n-butylammonium salts and were characterized by elemental analysis and various spectroscopic data (IR, 1H, 13C, and 29Si NMR). The solid state structures of compounds [(n-C3H7)2NH2]2[{Cl4C6O2}3Si] (1) and [(n-C3H7)2NH2]2[{Br4C6O2}3Si] (2) were determined by single crystal X-ray diffraction. Both 1 and 2 crystallize in the monoclinic space group C2/c and reveal (i) bidentate mode of ligation, (ii) octahedral coordination around silicon, and (iii) hydrogen bonding features. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.