Arsenic trifluoride

Arsenic trifluoride
Names
IUPAC name
Arsenic(III) fluoride
Other names
Arsenic trifluoride, trifluoroarsane
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.029.145
RTECS number CG5775000
Properties
AsF3
Molar mass 131.9168 g/mol
Appearance colorless liquid
Density 2.666 g/cm3[1]
Melting point −8.5 °C (16.7 °F; 264.6 K)
Boiling point 60.4 °C (140.7 °F; 333.5 K)
decomposes
Solubility soluble in alcohol, ether, benzene and ammonia solution
Hazards
Main hazards Toxic, corrosive
R-phrases (outdated) R23/25, R50/53
S-phrases (outdated) (S1/2), S20/21, S28, S45, S60, S61
US health exposure limits (NIOSH):
PEL (Permissible)
 [1910.1018] TWA 0.010 mg/m3[2]
REL (Recommended)
 Ca C 0.002 mg/m3 [15-minute][2]
IDLH (Immediate danger)
 Ca [5 mg/m3 (as As)][2]
Thermochemistry
-821.3 kJ/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Arsenic trifluoride is a chemical compound of arsenic and fluorine with the chemical formula AsF3. It is a colorless liquid which reacts readily with water.[3]

Preparation and properties

It can be prepared by reacting hydrogen fluoride, HF, with arsenic trioxide:[3]

6HF + As2O3 → 2AsF3 + 3H2O

It has a pyramidal molecular structure in the gas phase which is also present in the solid.[3] In the gas phase the As-F bond length is 170.6 pm and the F-As-F bond angle 96.2°.[4]

Arsenic trifluoride is used as fluorinating non-metal chlorides to fluorides, in this respect it is less reactive than SbF3.[3]

Salts containing AsF4− anion can be prepared for example CsAsF4.[5] the potassium salt KAs2F7 prepared from KF and AsF3 contains AsF4− and AsF3 molecules with evidence of interaction between the AsF3 molecule and the anion.[6]

AsF3 reacts with SbF5. The product obtained could be described as an ionic adduct of AsF2+ SbF6−. However, the authors conclude the formed product cannot be viewed only as an ionic compound nor entirely as a neutral adduct of AsF3SbF5. The crystal structure of formed compound displays characteristics of both an ionic pair and neutral adduct strucual motives, taking the middle ground in between both models of molecule description. [7]

References

  1. ↑ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
  2. 1 2 3 "NIOSH Pocket Guide to Chemical Hazards #0038". National Institute for Occupational Safety and Health (NIOSH).
  3. 1 2 3 4 Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9.
  4. ↑ Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6
  5. ↑ New alkali metal and tetramethylammonium tetrafluoroarsenates(III), their vibrational spectra and crystal structure of cesium tetrafluoroarsenate(III)Klampfer P, Benkič P, Lesar A, Volavšek B, Ponikvar M, Jesih A., Collect. Czech. Chem. Commun. 2004, 69, 339-350 doi:10.1135/cccc20040339
  6. ↑ Alkali-metal heptafluorodiarsenates(III): their preparation and the crystal structure of the potassium salt, Edwards A.J., Patel S.N., J. Chem. Soc., Dalton Trans., 1980, 1630-1632, doi:10.1039/DT9800001630
  7. ↑ Fluoride crystal structures. Part XV. Arsenic trifluoride–antimony pentafluoride, Edwards A. J., Sills R. J. C. J. Chem. Soc. A, 1971, 942 - 945, doi:10.1039/J19710000942
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