Antimony pentafluoride

Antimony pentafluoride is the inorganic 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, formed when mixing liquid HF with liquid SbF5 in a 2:1 ratio. It is notable for its Lewis acidity and its ability to react with almost all known compounds.[4]

Antimony pentafluoride
Antimony pentafluoride
Antimony pentafluoride
Names
IUPAC name
antimony(V) fluoride
Other names
antimony pentafluoride
pentafluoridoantimony
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.029.110
EC Number
  • 232-021-8
RTECS number
  • CC5800000
UNII
UN number 1732
Properties
SbF5
Molar mass 216.74 g/mol
Appearance colorless oily liquid
hygroscopic
Odor pungent
Density 2.99 g/cm3 [1]
Melting point 8.3 °C (46.9 °F; 281.4 K)
Boiling point 149.5 °C (301.1 °F; 422.6 K)
Reacts
Solubility soluble in KF, liquid SO2
Hazards
Main hazards Releases hydrofluoric acid upon contact with water or biological tissues
Safety data sheet ICSC 0220
GHS pictograms
GHS Signal word Danger
H302, H314, H332, H411, H412
P260, P261, P264, P270, P271, P273, P280, P301+312, P301+330+331, P303+361+353, P304+312, P304+340, P305+351+338, P310, P312, P321, P330, P363, P391, P405, P501
NFPA 704 (fire diamond)
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 0.5 mg/m3 (as Sb)[3]
REL (Recommended)
 TWA 0.5 mg/m3 (as Sb)[3]
Related compounds
Other anions
 Antimony pentachloride
Other cations
 Phosphorus pentafluoride
Arsenic pentafluoride
Bismuth pentafluoride
Related compounds
 Antimony trifluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

Preparation

Antimony pentafluoride is prepared by the reaction of antimony pentachloride with anhydrous hydrogen fluoride:[5]

SbCl5 + 5 HF → SbF5 + 5 HCl

It can also be prepared from antimony trifluoride and fluorine.[6]

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.[7] 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.[8]

In the same way that SbF5 enhances the Brønsted acidity of HF, it augments the oxidizing power of F2. This effect is illustrated by the oxidation of oxygen:[9]

2 SbF5 + F2 + 2 O2 → 2 [O2]+[SbF6]−

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

4 SbF
5 + 2 K
2MnF
6 → 4 KSbF
6 + 2 MnF
3 + F
2

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. [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:

SbF5 + [SbF6]− → [Sb2F11]−

Safety

SbF5 reacts violently with many compounds, often releasing dangerous hydrogen fluoride. It is corrosive to the skin and eyes.[10][11]

References
  1. Lide, David R., ed. (2006). CRC Handbook of Chemistry and Physics (87th ed.). Boca Raton, FL: CRC Press. ISBN 0-8493-0487-3.
  2. World of Chemicals SDS
  3. NIOSH Pocket Guide to Chemical Hazards. "#0036". National Institute for Occupational Safety and Health (NIOSH).
  4. 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.
  5. 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
  6. Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 200.
  7. 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
  8. Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  9. Shamir, J.; Binenboym, J. "Dioxygenyl Salts" Inorganic Syntheses 1973, XIV, 109-122. ISSN 0073-8077
  10. International Programme on Chemical Safety (2005). "Antimony pentafluoride". Commission of the European Communities (CEC). Retrieved 2010-05-10.
  11. Barbalace, Kenneth (2006). "Chemical Database - Antimony Pentafluoride". Environmental Chemistry. Retrieved 2010-05-10.
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