Silicon tetrafluoride

Silicon tetrafluoride
IUPAC name

Tetrafluorosilane
Silicon tetrafluoride
Other names

Silicon fluoride
Fluoro acid air
Identifiers
CAS number 7783-61-1 Y
PubChem 24556
UN number 1859
RTECS number VW2327000
Jmol-3D images Image 1
Properties
Molecular 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
Boiling point

−86 °C
Solubility in water decomposes
Structure
Molecular shape tetrahedral
Dipole moment 0 D
Hazards
MSDS ICSC 0576
EU Index Not listed
Main hazards toxic, corrosive
NFPA 704
0
3
2
W
Related compounds
Other anions Silicon tetrachloride
Silicon tetrabromide
Silicon tetraiodide
Other cations Carbon tetrafluoride
Germanium tetrafluoride
Tin tetrafluoride
Lead tetrafluoride
Related compounds Hexafluorosilicic acid
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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.[1]

Contents

Preparation

SiF4 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 BaSiF6 >300 °C, whereupon the solid releases volatile SiF4, leaving a residue of BaF2. The required BaSiF6 is prepared by treating aqueous hexafluorosilicic acid with barium chloride.[2] The corresponding GeF4 is prepared analogously, except that the thermal "cracking" requires 700 °C.[3]

Uses

This volatile compound finds limited use in microelectronics and organic synthesis.[4]

Occurrence

Volcanic plumes contain significant amounts of silicon tetrafluoride, the daily production can reach several tonnes per day.[5] The silicon tetrafluoride is partly hydrolysed and forms hexafluorosilicic acid.

References

  1. ^ John Davy (1812). "An Account of Some Experiments on Different Combinations of Fluoric Acid". Philosophical Transactions of the Royal Society of London 102: 352–369. doi:10.1098/rstl.1812.0020. ISSN 0261-0523. JSTOR 107324. 
  2. ^ Hoffman, C. J.; Gutowsky, H. S. “Silicon Tetrafluoride” Inorganic Syntheses McGraw-Hill: New York, Volume 4, pages 145-6, 1953.
  3. ^ Hoffman, C. J.; Gutowsky, H. S. "Germanium Tetrafluoride” Inorganic Syntheses McGraw-Hill: New York, Volume 4, pages 147-8, 1953.
  4. ^ Shimizu, M. "Silicon(IV) Fluoride" Encyclopedia of Reagents for Organic Synthesis, 2001 John Wiley & Sons. DOI: 10.1002/047084289X.rs011
  5. ^ T. Mori, M. Sato, Y. Shimoike, K. Notsu (2002). "High SiF4/HF ratio detected in Satsuma-Iwojima volcano's plume by remote FT-IR observation". Earth Planets Space 54: 249–256. http://www.terrapub.co.jp/journals/EPS/pdf/2002/5403/54030249.pdf.