Synthesis of SiCl4 from Gaseous HCl and Si(OMe)4. Reaction Development and Kinetic Studies

This report describes a method to synthesize SiCl4 from alkyl orthosilicates and gaseous HCl. Reacting tetramethyl orthosilicate with HCl gas at 0 °C in the presence of a catalytic amount of hexamethyl phosphoramide (10 mol %) and four equivalents of acetonitrile afforded an 86% yield of SiCl4 after 6 h. Exchange between HCl and alkoxy groups on silicon during the reaction generates methanol. The methanol then reacts with acetonitrile (in the presence of HCl) to form an imidate, thus removing it from the reaction mixture. Other Lewis acid and base catalysts were also observed to accelerate the reaction. A kinetics experiment using 29Si NMR to monitor reaction intermediates in situ was conducted to determine the rates of chloride/alkoxide exchange on silicon.