Synthesis of pentacoordinate silicon complexes from SiO₂

Abstract

THE potential role of inorganic and organometallic silicon compounds in the development of new chemical reagents, polymers, glasses and ceramics¹ is limited at present by the paucity of simple silicon-containing starting materials. Whereas industrial carbon-based chemistry can draw on the diversity of compounds produced from crude oil, coal or other natural sources, silicon chemistry² relies almost exclusively on the carbothermal reduction of SiO₂ to silicon. This is then transformed into feedstock chemicals by reaction with HCl, or by routes such as the 'direct process' for making methylchlorosilanes², in which silicon is reacted with methyl chloride at 200–350°C over a copper/tin catalyst. Organosilicon compounds are in demand in fields ranging from organic synthesis to ceramics to the electronics industry. New synthetic routes to these materials are therefore highly desirable, especially if they rely on low-cost SiO₂ and on rocessing methods that avoid the energy-intensive and equipment-intensive carbothermal reduction step which currently precedes almost all silicon chemistry. Here we describe a direct process in which SiO₂ is reacted with ethylene glycol and an alkali base to produce highly reactive, pentacoordinate silicates which provide access to a wide variety of new silicon compounds.