Silicon tetrafluoride

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Silicon tetrafluoride
Silicon tetrafluoride
Silicon tetrafluoride
IUPAC name Silicon tetrafluoride
Other names Tetrafluorosilane
Silicon fluoride
Fluoro acid air
Identifiers
CAS number [7783-61-1]
RTECS number VW2327000
SMILES FSi(F)(F)F
Properties
Molecular formula SiF4
Molar mass 104.08 g/mol
Appearance colourless gas
( fuming in moist air)
Density 1.66 g/cm3, solid (-95 C)
Melting point

-86 °C
Boiling point

sublimes at -95.5 °C at 1 atm
Solubility in water hydrolysis
Viscosity  ? cP at ?°C
Structure
Molecular shape tetrahedral
Dipole moment 0 D
Hazards
Main hazards toxic, corrosive
R-phrases 14-26/27/28-31-34
S-phrases 23-26-36/37/39-45
Related compounds
Related compounds SiCl4
SiH4
Dihydrogen hexafluorosilicate
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references

Silicon tetrafluoride is the chemical compound with the formula SiF4. This tetrahedral molecule is striking because it has 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

[edit] Preparation

SiF4 is a by-product of the production of phosphate fertilizers, resulting from the attack of HF (derived from fluoroapatite 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 fluorosilicic acid with barium chloride.[2] The corresponding GeF4 is prepared analogously, except that the thermal "cracking" requires 700 °C.[3]

[edit] Uses

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

[edit] Occurrence

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

[edit] 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. 
  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. 
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