Arsenic trifluoride

Chembox new
ImageFileL1 =Arsenic(III)fluoride.svg
ImageSizeL1 = 100px
ImageFileR1 = Arsenic-trifluoride-3D-balls.png IUPACName = Arsenic(III) fluoride
OtherNames = Arsenic trifluoride
Section1 = Chembox Identifiers
CASNo = 7784-35-2
PubChem =
SMILES =
Section2 = Chembox Properties
Formula = AsF₃
MolarMass = 131.91g mol^-1
Appearance = colorless liquid
Density = 2.7 g cm^-3 [http://www.webelements.com/webelements/compounds/text/As/As1F3-7784352.html Arsenic trifluoride at webelements.com] ]
MeltingPt = -6 ˚C
BoilingPt = 58 ˚C
Solubility = N/A
Section3 = Chembox Hazards
MainHazards = Toxic, corrosive
RPhrases = R23/25, R50/53
SPhrases = S1/2, S20/21, S28, S45, S60, S61
FlashPt =
Autoignition =

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

Preparation and properties

It can be prepared by reacting hydrogen fluoride,HF, with arsenic trioxide::6HF + As₂O₃ → 2AsF₃ + 3H₂O

It has a pyramidal molecular structure in the gas phase which is also present in the solid. In the gas phase the As-F bond length is 170.6 pm and the F-As-F bond angle 96.2°. [ Wells A.F. (1984) "Structural Inorganic Chemistry" 5th edition Oxford Science Publications ISBN 0-19-855370-6 ] Its enthalpy of formation is -305.0kJ/mol.
Arsenic trifluoride is used as fluorinating non-metal chlorides to fluorides, in this respect it is less reactive than SbF₃.
Salts containing AsF₄⁻ anion can be prepared for example Cs₂AsF₄ [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] . 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. [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]
With SbF₅ the ionic adduct AsF₂⁺ SbF₆⁻ is produced [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]

References