Silicon tetrafluoride


Silicon tetrafluoride or tetrafluorosilane is the chemical compound with the formula SiF4. This colorless compound is notable for having a narrow liquid range: its boiling point is only 4 °C above its melting point. It was first synthesized by John Davy in 1812. It is a tetrahedral molecule.

Preparation

is a by-product of the production of phosphate fertilizers, resulting from the attack of HF on silicates, which are present as impurities in the phosphate rock. In the laboratory, the compound is prepared by heating above 300 °C, whereupon the solid releases volatile, leaving a residue of. The required is prepared by treating aqueous hexafluorosilicic acid with barium chloride. The corresponding Germanium tetrafluoride| is prepared analogously, except that the thermal "cracking" requires 700 °C.
can in principle also be generated by the reaction of silicon dioxide and hydrofluoric acid, but this process tends to give hexafluorosilicic acid:

Uses

This volatile compound finds limited use in microelectronics and organic synthesis.

Comparison with other SiX4 compounds

Occurrence

Volcanic plumes contain significant amounts of silicon tetrafluoride. Production can reach several tonnes per day. Some amounts are also emitted from spontaneous coal fires. The silicon tetrafluoride is partly hydrolysed and forms hexafluorosilicic acid.