Antimony pentafluoride

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ImageNameL1 = Antimony pentafluoride
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ImageNameR1 = Antimony pentafluoride
IUPACName = antimony(V) fluoride
OtherNames = antimony pentafluoride
pentafluoroantimony
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CASNo = 7783-70-2
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Formula = SbF₅
MolarMass = 216.74 g mol⁻¹
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Density = 4.07 g cm^-3
MeltingPt = 8.3 °C (281.3 K)
BoilingPt = 141 °C (414 K)
Solubility = Reacts with water
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Solvent = SO₂, SO₂FCl
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Antimony pentafluoride is the chemical compound with the formula SbF₅. This colourless, viscous liquid is a valuable Lewis acid and a component of the superacid fluoroantimonic acid, the strongest known acid. Some features that give the compound scientific interest are its Lewis acidity and that it also reacts with almost all known compounds. [Olah, G. A.; Prakash, G. K. S.; Wang, Q.; Li, X.-y."Antimony(V) Fluoride" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. DOI: 10.1002/047084289.]

tructure and chemical reactions

In the gas phase, SbF₅ adopts a trigonal bipyramidal structure of D_3h point group symmetry (see picture). The structure is more complex in the liquid and solid state. The liquid contains polymers wherein each Sb is octahedral, the structure being described with the formula [SbF₄(μ-F)₂] _n. The crystalline material is tetrameric, i.e. it has the formula [SbF₄(μ-F)] ₄. The Sb-F bonds are 2.02 Å within the eight-membered Sb₄F₄ ring; the remaining fluoride ligands radiating from the four Sb centers are shorter at 1.82 Å. [Edwards, A. J.; Taylor, P. "Crystal structure of Antimony Pentafluoride" Journal of the Chemical Society, Chemical Communications 1971, pp. 1376-7.DOI|10.1039/C29710001376] The related species PF₅ and AsF₅ are monomeric in the solid and liquid states, probably due to the smaller sizes of the central atom, which limits their coordination number. BiF₅ is a polymer. [Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.]

SbF₅ is a strong Lewis acid, exceptionally so toward sources of F⁻ to give the very stable anion [SbF₆] ⁻. The latter reacts with additional SbF₅ to give [Sb₂F₁₁] ⁻.

In the same way that SbF₅ enhances the Brønsted acidity of HF, it enhances the oxidizing power of F₂. This effect is illustrated by the oxidation of oxygen: [Shamir, J.; Binenboym, J. "Dioxygenyl Salts" Inorganic Syntheses, 1973, XIV, 109-122. ISSN|0073-8077] :SbF₅ + ½F₂ + O₂ → [O₂] ⁺ [SbF₆] ^-

Antimony pentafluoride has also been used in the first discovered chemical reaction that produces fluorine gas from fluoride compounds::2 SbF₅ + K₂MnF₆ → 2 KSbF₆ + MnF₃ + 0.5 F₂The driving force for this reactions is the high affinity of SbF₅ for F^-, which is the same property which recommends the use of SbF₅ to generate superacids.

afety

SbF₅ reacts violently with many compounds, often releasing dangerous hydrogen fluoride.

References

*IPCS, CEC 2005. [http://www.inchem.org/documents/icsc/icsc/eics0220.htm "ANTIMONY PENTAFLUORIDE (ICSC)] Retrieved May 13, 2006.
*Barbalace, Kenneth. [http://environmentalchemistry.com/yogi/chemicals/cn/Antimony%A0Pentafluoride.html "Chemical Database - Antimony Pentafluoride"] . 1995 - 2006. Retrieved May 13, 2006.

External links

* [http://webbook.nist.gov/cgi/cbook.cgi?ID=C7783702 WebBook page for SbF5]
* [http://www.npi.gov.au/database/substance-info/profiles/10.html National Pollutant Inventory - Antimony and compounds fact sheet]
* [http://www.npi.gov.au/database/substance-info/profiles/44.html National Pollutant Inventory - Fluoride compounds fact sheet]