Silicon tetrafluoride

Silicon tetrafluoride

Silicon tetrafluoride
Names
IUPAC names Tetrafluorosilane Silicon tetrafluoride
Other names Silicon fluoride Fluoro acid air
Identifiers
CAS Number	7783-61-1 Y
Jmol 3D model	Interactive image
PubChem	24556
RTECS number	VW2327000
UN number	1859
SMILES F[Si](F)(F)F
Properties
Chemical formula	SiF4
Molar mass	104.0791 g/mol
Appearance	colourless gas, fumes in moist air
Density	1.66 g/cm3, solid (−95 °C) 4.69 g/L (gas)
Melting point	−90 °C (−130 °F; 183 K)
Boiling point	−86 °C (−123 °F; 187 K)
Solubility in water	decomposes
Structure
Molecular shape	tetrahedral
Dipole moment	0 D
Vapor pressure	{{{value}}}
Related compounds
Other anions	Silicon tetrachloride Silicon tetrabromide Silicon tetraiodide
Other cations	Carbon tetrafluoride Germanium tetrafluoride Tin tetrafluoride Lead tetrafluoride
Related compounds	Hexafluorosilicic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

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

Preparation

SiF
₄ is a by-product of the production of phosphate fertilizers, resulting from the attack of HF (derived from fluorapatite protonolysis) on silicates. In the laboratory, the compound is prepared by heating BaSiF
₆ above 300 °C, whereupon the solid releases volatile SiF
₄, leaving a residue of BaF
₂. The required BaSiF
₆ is prepared by treating aqueous hexafluorosilicic acid with barium chloride. The corresponding GeF
₄ is prepared analogously, except that the thermal "cracking" requires 700 °C. SiF
₄ can also be created by placing silicon dioxide in hydrofluoric acid using the following equation:

4HF + SiO₂ → SiF₄ + 2H₂O

Uses

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

Occurrence

Volcanic plumes contain significant amounts of silicon tetrafluoride. Production can reach several tonnes per day. The silicon tetrafluoride is partly hydrolysed and forms hexafluorosilicic acid.