Silicon Complexes from Rice Husk: Synthesis, Crystal Structure, and Properties of 1,2-bis-Silatranyloxyethane

Abstract

The growing demand for non-toxic and relatively inexpensive ways to obtain organosilicon compounds has led to increasing researches on silicon-containing plant raw materials, especially rice husk. The main purpose of this work was to obtain silicon complexes directly from rice husk. A new convenient method to obtain a product containing silatrane fragments from rice husk biomass and triethanolamine in one step was elaborated using ethylene glycol as the solvent. Pure crystalline 1,2-bis(1-silatranyloxy)ethane N(CH2CH2O)3SiOCH2CH2OSi(OCH2CH2)3N, 3 and silatrane-containing products were synthesized from rice husk and triethanolamine in ethylene glycol media, using preliminary alkaline extraction of silica from rice husk followed by acid precipitation. The obtained products were characterized by LDI mass spectroscopy, 1H, 13C, and 29Si nuclear magnetic resonance, FTIR, thermogravimetric, and differential thermal analysis. Whereas complex 3 is stable pure crystalline substance, the next step was to determine its crystal structure, which was done by X-ray diffraction. The X-ray study showed that the crystal structure of 3 is built of centrosymmetric binuclear molecules, and the dioxoethane group is a bridge connecting two silatrane groups.