Tungsten(IV) oxide

Tungsten(IV) oxide
Other names Tungsten dioxide
Identifiers
CAS number	12036-22-5 Y
PubChem	82850
	EC number	234-832-7
Jmol-3D images	{{#if:O=[W]=O|Image 1
SMILES O=[W]=O
InChI InChI=1S/2O.W
Properties
Molecular formula	WO2
Molar mass	215.839 g/mol
Appearance	bronze solid
Density	10.8 g/cm3
Melting point	1700 °C decomp.
Solubility in water	negligible
Magnetic susceptibility	5.7×10−5 cm3/mol
Structure
Crystal structure	Distorted rutile, (monoclinic), mP12, Space group P21/c, No 14
Hazards
EU Index	Not listed
Flash point	Non-flammable
Related compounds
Other anions	Tungsten disulfide
Other cations	Chromium(IV) oxide Molybdenum(IV) oxide
Related tungsten oxides	Tungsten(III) oxide Tungsten(VI) oxide
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Tungsten dioxide is the chemical compound with the formula WO₂. The bronze-colored solid crystallizes in a monoclinic cell.^[1] The rutile-like structure features distorted octahedral WO₆ centers with alternate short W–W bonds (248 pm).^[1] Each tungsten center has the d² configuration, which gives the material a high electrical conductivity.

WO₂ 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 WO₃ + W → 3 WO₂

The molybdenum analogue MoO₂ is prepared similarly. Single crystals are obtained by chemical transport technique using iodine. Iodine transports the WO₂ in the form of the volatile species WO₂I₂.^[2]

References