SiCl4

SiCl4, or silicon tetrachloride (tetrachlorosilane), is a colorless, volatile liquid that boils at 57.6°C. It features a tetrahedral silicon center bonded to four chlorine ligands and is a highly reactive, moisture-sensitive compound. In air, it fumes due to hydrolysis.

Production and handling

Industrial production of SiCl4 typically involves direct chlorination of metallurgical silicon with chlorine gas at elevated temperatures. It can also be formed from silica under appropriate conditions using carbon and chlorine. Because SiCl4 reacts vigorously with moisture, it is handled under strictly anhydrous conditions and stored in moisture-free containers.

Chemical behavior

SiCl4 hydrolyzes readily in water to form silicic acid and hydrogen chloride: SiCl4 + 4 H2O → Si(OH)4 + 4 HCl. The silicic acid can polymerize and ultimately yield silica. SiCl4 also reacts with alcohols to give alkoxysilanes via SiCl4 + 4 ROH → Si(OR)4 + 4 HCl. In addition, as a Lewis acid, it engages with nucleophiles and other reagents in various silicon-chemistry Transformations.

Uses

SiCl4 is a key silicon source in organosilicon synthesis. It is used to prepare silicon alkoxides (Si(OR)4), which serve as building blocks for siloxanes, silsesquioxanes, and related coatings. It also functions as a precursor for silicon-containing materials in chemical vapor deposition and semiconductor processing, and can be converted to silicon-containing compounds through reactions with Grignard reagents or by reduction.

Safety

SiCl4 is highly reactive and corrosive. It reacts with water to release hydrogen chloride, producing noxious fumes. Handling requires dry conditions, appropriate protective equipment, and storage away from moisture. Spills demand immediate containment and proper ventilation.