Antimony pentafluoride
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| UN number | 1732 |
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| Template:Longitem | SbF5 |
| Molar mass | 216.74 g/mol |
| Appearance | colorless oily, viscous liquid hygroscopic |
| Odor | pungent, sharp |
| Density | 2.99 g/cm3 [1] |
| Melting point | Template:Chembox CalcTemperatures |
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| Solubility | soluble in KF, liquid SO2 |
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| Template:Longitem | Antimony pentachloride |
| Template:Longitem | Phosphorus pentafluoride Arsenic pentafluoride Bismuth pentafluoride |
| Template:Longitem | Antimony trifluoride |
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Antimony pentafluoride is the inorganic compound with the formula SbF5. This colorless, viscous liquid is a strong Lewis acid and a component of the superacid fluoroantimonic acid, formed upon mixing liquid HF with liquid SbF5 in 1:1 ratio. It is notable for its strong Lewis acidity and the ability to react with almost all known compounds.[3]
Preparation
Antimony pentafluoride is prepared by the reaction of antimony pentachloride with anhydrous hydrogen fluoride:[4]
- SbCl5 + 5 HF → SbF5 + 5 HCl
It can also be prepared from antimony trifluoride and fluorine.[5]
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 centers). 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.[6] 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.[7]
Antimony pentafluoride is a very strong oxidizing agent. Phosphorus burns on contact with it.
SbF5 increases the oxidizing power of Fluorine, making it able to oxidize oxygen:
- 2 SbF5 + F2 + 2 O2 → 2 [O2]+[SbF6]−
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 Template:Chem2, 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:
- SbF5 + [SbF6]− → [Sb2F11]−
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. Its 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.[8][9]
References
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- ↑ Script error: No such module "citation/CS1".
- ↑ a b Script error: No such module "citation/CS1".
- ↑ 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. Script error: No such module "CS1 identifiers"..
- ↑ 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 Script error: No such module "CS1 identifiers".
- ↑ Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 200.
- ↑ Edwards, A. J.; Taylor, P. "Crystal structure of Antimony Pentafluoride" Journal of the Chemical Society, Chemical Communications 1971, pp. 1376-7.Script error: No such module "CS1 identifiers".
- ↑ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. Template:ISBN.
- ↑ Script error: No such module "citation/CS1".
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External links
- WebBook page for SbF5
- National Pollutant Inventory - Antimony and compounds fact sheet
- National Pollutant Inventory - Fluoride compounds fact sheet
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