Antimony pentafluoride

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Antimony pentafluoride
Antimony pentafluoride Antimony pentafluoride
Identifiers
CAS number 7783-70-2 YesY
ChemSpider 10617727 YesY
UN number 1732
RTECS number CC5800000
Jmol-3D images Image 1
Image 2
Properties
Molecular formula 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)
Solubility in water Reacts
Solubility soluble in KF, liquid SO2
Hazards
MSDS ICSC 0220
EU Index 051-003-00-9
EU classification Harmful (Xn)
Dangerous for the environment (N)
R-phrases R20/22, R51/53
S-phrases (S2), S61
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 4: Very short exposure could cause death or major residual injury. E.g., VX gas Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazard W: Reacts with water in an unusual or dangerous manner. E.g., cesium, sodiumNFPA 704 four-colored diamond
Related compounds
Other anions Antimony pentachloride
Other cations Phosphorus pentafluoride
Arsenic pentafluoride
Bismuth pentafluoride
Related compounds Antimony trifluoride
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

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. It is notable for its Lewis acidity and its ability to react with almost all known compounds.[2]

Preparation[edit]

Antimony pentafluoride is prepared by the reaction of antimony pentachloride with anhydrous hydrogen fluoride:[3]

SbCl5 + 5 HF → SbF5 + 5 HCl

It can also be prepared from antimony trifluoride and fluorine.[4]

Structure and chemical reactions[edit]

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.[5] 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.[6]

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:[7]

2 SbF5 + F2 + 2 O2 → 2 [O
2
]+
[SbF
6
]

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

4 SbF
5
+ 2 K
2
MnF
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[edit]

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[edit]

SbF5 reacts violently with many compounds, often releasing dangerous hydrogen fluoride. It is corrosive to the skin and eyes.[8][9]

References[edit]

  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. ^ 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.
  3. ^ 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
  4. ^ Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 200.
  5. ^ 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
  6. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  7. ^ Shamir, J.; Binenboym, J. "Dioxygenyl Salts" Inorganic Syntheses, 1973, XIV, 109-122. ISSN 0073-8077
  8. ^ International Programme on Chemical Safety (2005). "Antimony pentafluoride". Commission of the European Communities (CEC). Retrieved 2010-05-10. 
  9. ^ Barbalace, Kenneth (2006). "Chemical Database - Antimony Pentafluoride". Environmental Chemistry. Retrieved 2010-05-10. 

External links[edit]