Arsenic pentafluoride is a
chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
of
arsenic
Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, b ...
and
fluorine
Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative reactive element, it is extremely reactiv ...
. It is a toxic, colorless gas. The
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...
of arsenic is +5.
Synthesis
Arsenic pentafluoride can be prepared by direct combination of arsenic and
fluorine
Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative reactive element, it is extremely reactiv ...
:
:2As + 5F
2 → 2AsF
5
It can also be prepared by the reaction of
arsenic trifluoride
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.
Preparation and properties
It can be prepared by reacting hydrogen fluoride, HF, with ars ...
and fluorine:
:AsF
3 + F
2 → AsF
5
or the addition of fluorine to
arsenic pentoxide or
arsenic trioxide
Arsenic trioxide, sold under the brand name Trisenox among others, is an inorganic compound and medication. As an industrial chemical, whose major uses include in the manufacture of wood preservatives, pesticides, and glass. As a medication, it ...
.
:2As
2O
5 + 10F
2 → 4AsF
5 + 5O
2
:2As
2O
3 + 10F
2 → 4AsF
5 + 3O
2
Properties
Arsenic pentafluoride is a colourless gas and has a
trigonal bipyramidal
In chemistry, a trigonal bipyramid formation is a molecular geometry with one atom at the center and 5 more atoms at the corners of a triangular bipyramid. This is one geometry for which the bond angles surrounding the central atom are not iden ...
structure.
In the solid state the axial As−F bond lengths are 171.9 pm and the equatorial 166.8 pm.
Its point group is D3h.
Reactions
Arsenic pentafluoride forms halide complexes and is a powerful fluoride acceptor. An example is the reaction with
sulfur tetrafluoride, forming an ionic
hexafluoroarsenate
The hexafluoroarsenate (sometimes shortened to fluoroarsenate) anion is a chemical species with formula . Hexafluoroarsenate is relatively inert, being the conjugate base of the notional superacid hexafluoroarsenic acid ().
Synthesis
The fir ...
complex.
[An investigation of the structures of the adducts of SF4 with BF3, PF5, AsF5, and SbF5 in the solid state and in solution in HF, M. Azeem, M. Brownstein, and R. J. Gillespie Can. J. Chem. 47(22): 4159–4167 (1969), ]
:AsF
5 + SF
4 → SF
3+ + AsF
6−
Safety
Arsenic pentafluoride is an extremely dangerous toxin, mainly poisoning liver cells. It has a smell that is similar to
vinyl chloride
Vinyl chloride is an organochloride with the formula H2C=CHCl. It is also called vinyl chloride monomer (VCM) or chloroethene. This colorless compound is an important industrial chemical chiefly used to produce the polymer polyvinyl chloride (PVC ...
gas.
See also
*
List of highly toxic gases
Many gases have toxic properties, which are often assessed using the LC50 (median lethal dose) measure. In the United States, many of these gases have been assigned an NFPA 704 health rating of 4 (may be fatal) or 3 (may cause serious or perman ...
References
{{fluorine compounds
Arsenic(V) compounds
Fluorides
Arsenic halides