Tin(IV) fluoride

Tin(IV) fluoride
IUPAC name

tin(IV) fluoride
Other names

stannic fluoride, tin tetrafluoride
Identifiers
CAS number 7783-62-2 Y
Properties
Molecular formula SnF4
Molar mass 194.704 g/mol
Appearance white solid
Melting point

above 700 °C (sublimes)
Structure
Crystal structure Tetragonal, tI10
Space group I4/mmm, No. 139
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Tin(IV) fluoride is a chemical compound of tin and fluorine with the chemical formula SnF4 and is a white solid with a melting point above 700 °C.[1]

SnF4 can be prepared by the reaction of tin metal with fluorine gas:[2]

Sn + 2F2 → SnF4

However, a passivating metal fluoride layer will be created and the surface will eventually become unreactive. An alternative synthesis is the reaction of SnCl4 with anhydrous hydrogen fluoride:[1]

SnCl4 + 4HF → SnF4 + 4HCl

With alkali metal fluorides (e.g. KF) hexafluorostannates are produced (e.g.K2SnF6), which contain the octahedral SnF62− anion. SnF4 behaves as a Lewis acid and adducts L2.SnF4 and L.SnF4 have been produced.[2]

Structure

Unlike the other tin tetrahalides, tin(IV) chloride, tin(IV) bromide, tin(IV) iodide which contain tetrahedrally coordinated tin, tin(IV) fluoride has a planar structure consisting of octahedra sharing four corners with the terminal, unshared, fluorine atoms trans to one another.[1] The melting point of SnF4 is much higher (700 °C) than the other tin(IV) halides which are relatively low melting, (SnCl4, −33.3 °C; SnBr4, 31 °C; SnI4, 144 °C).[1] The structure can also be contrasted with the tetrafluorides of the lighter members of group 14, (CF4, SiF4 and GeF4) which in the solid state form molecular crystals.[2]

Commercial applications of the compound include using SnF4 in toothpaste to prevent dental decay.[3]

See also

Stannous fluoride, SnF2, the compound added to toothpastes

References

  1. ^ a b c d Greenwood, N. N.; Earnshaw, A. (1997). Chemistry of the Elements (2nd Edition ed.). Oxford:Butterworth-Heinemann. pp. 381. ISBN 0-7506-3365-4. 
  2. ^ a b c Holleman, A. F.; Wiberg, E.; Wiberg, N. (2001). Inorganic Chemistry, 1st Edition. Academic Press. pp. 908. ISBN 0123526515. 
  3. ^ Alan Heaton and Rob Janes. Case study: Industrial inorganic chemistry. Elements of the P Block. (Charlie Harding, David Johnson and Rob Janes, editors), Royal Society of Chemistry, 2002. ISBN 9780854046904; p. 289