Chromium pentafluoride is the
inorganic compound
In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistr ...
with the chemical formula CrF
5. It is a red volatile solid that melts at 34 °C.
It is the highest known chromium fluoride, since the hypothetical
chromium hexafluoride has not yet been synthesized.
Chromium pentafluoride is one of the products of the action of fluorine on a mixture of potassium and chromic chlorides.
In terms of its structure, the compound is a one-dimensional
coordination polymer
A coordination polymer is an inorganic or organometallic polymer structure containing metal cation centers linked by ligands. More formally a coordination polymer is a coordination compound with repeating coordination entities extending in 1, 2, o ...
. Each Cr(V) center has
octahedral molecular geometry
In chemistry, octahedral molecular geometry, also called square bipyramidal, describes the shape of compounds with six atoms or groups of atoms or ligands symmetrically arranged around a central atom, defining the vertices of an octahedron. The oc ...
.
It has the same
crystal structure as
vanadium pentafluoride
Vanadium(V) fluoride is the inorganic compound with the chemical formula VF5. It is a colorless volatile liquid. It is a highly reactive compound, as indicated by its ability to fluorinate organic substances.
Properties and structure
The com ...
.
Chromium pentafluoride is strongly oxidizing, able to fluorinate the noble gas
xenon
Xenon is a chemical element with the symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...
and oxidize
dioxygen
There are several known allotropes of oxygen. The most familiar is molecular oxygen (O2), present at significant levels in Earth's atmosphere and also known as dioxygen or triplet oxygen. Another is the highly reactive ozone (O3). Others are:
* ...
to
dioxygenyl
The dioxygenyl ion, , is a rarely-encountered oxycation in which both oxygen atoms have a formal oxidation state of . It is formally derived from oxygen by the removal of an electron:
:O2 → + e−
The energy change for this process is calle ...
.
Due to this property, it decomposes readily in the presence of reducing agents, and easily
hydrolyses
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.
Biological hydrolysi ...
to
chromium(III) and
chromium(VI)
Hexavalent chromium (chromium(VI), Cr(VI), chromium 6) is chromium in any chemical compound that contains the element in the +6 oxidation state (thus hexavalent). Virtually all chromium ore is processed via hexavalent chromium, specifically the ...
.
Reactions
Chromium pentafluoride can react with
Lewis bases such as
caesium fluoride
Caesium fluoride or cesium fluoride is an inorganic compound with the formula CsF and it is a hygroscopic white salt. Caesium fluoride can be used in organic synthesis as a source of the fluoride anion. Caesium also has the highest electropositiv ...
and
nitryl fluoride
Nitryl fluoride, NO2F, is a colourless gas and strong oxidizing agent, which is used as a fluorinating agent and has been proposed as an oxidiser in rocket propellants (though never flown).
It is a molecular species, not ionic, consistent with it ...
to give the respective hexafluorochromate(V) salt.
:CrF
5 + CsF → CsCrF
6
Chromium pentafluoride can also react with the Lewis acid
antimony pentafluoride
Antimony pentafluoride is the inorganic compound with the formula Sb F5. This colourless, viscous liquid is a valuable Lewis acid and a component of the superacid fluoroantimonic acid, formed when mixing liquid HF with liquid SbF5 in a 2:1 ratio. ...
to give the CrF
5·2SbF
5 adduct
An adduct (from the Latin ''adductus'', "drawn toward" alternatively, a contraction of "addition product") is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all co ...
. The adduct was found to be a strong oxidizing agent, liquid at room temperature with a melting point of −23 °C.
See also
*
Chromium difluoride
*
Chromium trifluoride
*
Chromium tetrafluoride
References
Chromium–halogen compounds
Fluorides
Metal halides
Chromium(V) compounds
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