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Preparation

Antimony pentafluoride is prepared by the reaction of antimony pentachloride with anhydrous hydrogen fluoride:²

It can also be prepared from antimony trifluoride and fluorine.³

Structure and chemical reactions

In the gas phase, SbF5 adopts a trigonal bipyramidal structure of D3h point group symmetry (see picture). The material adopts a more complicated structure in the liquid and solid states. The liquid contains polymers wherein each Sb is octahedral, the structure being described with the formula [SbF4(μ-F)2]n ((μ-F) denotes the fact that fluoride centres bridge two Sb centres). The crystalline material is a tetramer, meaning that 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.⁴ 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.⁵

Antimony pentafluoride is a very strong oxidizing agent. Phosphorus burns on contact with it.

Fluorine oxidizes oxygen in the presence of SbF5:⁶

SbF5 has also been used in the first discovered chemical reaction that produces fluorine gas from fluoride compounds:

The driving force for this reaction is the high affinity of SbF5 for F−, which is the same property that recommends the use of SbF5 to generate superacids.

Hexafluoroantimonate

SbF5 is a strong Lewis acid, exceptionally so toward sources of F− to give the very stable anion [SbF6]−, called hexafluoroantimonate. It is the conjugate base of the superacid fluoroantimonic acid. [SbF6]− is a weakly coordinating anion akin to PF6−. Although it is only weakly basic, [SbF6]− does react with additional SbF5 to give a centrosymmetric adduct:

The [Sb2F11]− anion is one of the ions found in HF/SbF5 Mixture.

Safety

SbF5 is highly corrosive to the skin and the eyes. It is extremely toxic and hazardous to health. It's lethal dose (LD50) is reported to be 270 mg/kg (mouse, subcutaneous) with lowest concentration (LCLo) of 15 mg/m3 or 1.69 ppm (rat, inhalation, 2 hours). Occupational exposure limit set by NIOSH stands at 50 mg/m3 (5 ppm). It is considered to be Immediately dangerous to life and health at this concentration. Other than that, SbF5 reacts violently with water along with many other compounds, often releasing dangerous hydrogen fluoride. It is a very strong oxidizer.⁷⁸

External links

• WebBook page for SbF5
• National Pollutant Inventory - Antimony and compounds fact sheet
• National Pollutant Inventory - Fluoride compounds fact sheet

References

1. 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:10.1002/047084289X. /wiki/Doi_(identifier) ↩

2. Sabina C. Grund, Kunibert Hanusch, Hans J. Breunig, Hans Uwe Wolf "Antimony and Antimony Compounds" in Ullmann's Encyclopedia of Industrial Chemistry 2006, Wiley-VCH, Weinheim doi:10.1002/14356007.a03_055.pub2 /wiki/Doi_(identifier) ↩

3. Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 200. ↩

4. 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 /wiki/Doi_(identifier) ↩

5. Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5. /wiki/ISBN_(identifier) ↩

6. Shamir, J.; Binenboym, J. "Dioxygenyl Salts" Inorganic Syntheses 1973, XIV, 109-122. ISSN 0073-8077 /wiki/ISSN_(identifier) ↩

7. International Programme on Chemical Safety (2005). "Antimony pentafluoride". Commission of the European Communities (CEC). Retrieved 2010-05-10. http://www.inchem.org/documents/icsc/icsc/eics0220.htm ↩

8. Barbalace, Kenneth (2006). "Chemical Database - Antimony Pentafluoride". Environmental Chemistry. Retrieved 2010-05-10. http://environmentalchemistry.com/yogi/chemicals/cn/Antimony%A0Pentafluoride.html ↩