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V. Dhayal, R. Bohra, M. Nagar, A. Kaushik, S. Mathur, S. Barth:
"Low Temperature Sol-Gel Transformation of Methyl Silicon Precursors to Silica-based Hybrid Materials";
Applied Organometallic Chemistry, 22 (2008), 11; 629 - 636.

Six new methyl silicon (IV) precursors of the type [MeSi{ON=C(R)Ar}₃] [when R = Me, Ar = 2-C₅H₄N (1), 2-C₄H₃O (2) or 2-C₄H₃S (3); and when R = H, Ar = 2-C₅H₄N (4), 2-C₄H₃O (5) or 2-C₄H₃S (6)] were prepared and structurally characterized by various spectroscopic techniques. Molecular weight measurements and FAB (Fast Atomic Bombardment) mass spectral studies indicated their monomeric nature. ¹H and ¹³C{¹H} NMR spectral studies suggested the oximate ligands to be monodentate in solution, which was confirmed by ²⁹Si{¹H} NMR signals in the region expected for tetra-coordinated methylsilicon (IV) derivatives. Thermogravimetric analysis of 1 revealed the complex to be thermally labile, decomposing to a hybrid material of definite composition. Two representative compounds (2 and 4) were studied as single source molecular precursor for low-temperature transformation to silica-based hybrid materials using sol-gel technique. Formation of homogenous methyl-bonded silica materials (MeSiO_3/2) at low sintering temperature was observed. The thermogravimetric analysis of the methylsilica material indicated that silicon-methyl bond is thermally stable up to a temperature of 400 degrees C. Reaction of 2 and Al(OPrⁱ)₃ in equimolar ratio in anhydrous toluene yielded a brown-colored viscous liquid of the composition [MeSi{ON=C(CH₃)C₄H₃O}(3).Al(OPrⁱ)₃]. Spectroscopic techniques ¹H, ¹³C{¹H}, ²⁷Al{¹H} and ²⁹Si{¹H} NMR spectra of the viscous product indicated the presence of tetracoordination around both silicon and aluminum atoms. On hydrolysis it yielded methylated aluminosilicate material with high specific surface area (464 m²/g). Scanning electron micrography confirmed a regular porous structure with porosity in the nanometric range.

functionalized oximes; TGA; hybrid material; single-source precursor; methylsilica; aluminosilicate; scanning electron micrograph; nanometric

http://dx.doi.org/10.1002/aoc.1448