Tungsten(IV) oxide is the
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 ...
with the
formula W O2. The bronze-colored solid crystallizes in a
monoclinic
In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic s ...
cell.
The
rutile
Rutile is an oxide mineral composed of titanium dioxide (TiO2), the most common natural form of TiO2. Rarer polymorphs of TiO2 are known, including anatase, akaogiite, and brookite.
Rutile has one of the highest refractive indices at visib ...
-like structure features distorted octahedral WO
6 centers with alternate short W–W bonds (248 pm).
Each tungsten center has the d
2 configuration, which gives the material a high
electrical conductivity.
WO
2 is prepared by reduction of
WO3 with tungsten powder over the course of 40 hours at 900 °C. An intermediate in this reaction is the partially reduced, mixed valence species
W18O49.
:2 WO
3 + W → 3 WO
2
The
molybdenum analogue
MoO2 is prepared similarly. Single crystals are obtained by
chemical transport technique using
iodine. Iodine transports the WO
2 in the form of the volatile species WO
2I
2.
References
Tungsten compounds
Transition metal oxides
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