Tungsten(IV) oxide

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Tungsten(IV) oxide
Tungsten(IV) oxide
CAS number 12036-22-5 YesY
PubChem 82850
EC number 234-832-7
Jmol-3D images Image 1
Molecular formula WO2
Molar mass 215.839 g/mol
Appearance bronze solid
Density 10.8 g/cm3
Melting point 1,700 °C (3,090 °F; 1,970 K) decomposes
Solubility in water negligible
Magnetic susceptibility 5.7×10−5 cm3/mol
Crystal structure Distorted rutile, (monoclinic), mP12, Space group P21/c, No 14
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
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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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]


  1. ^ a b Wells, A. F. (1984), Structural Inorganic Chemistry (5th ed.), Oxford: Clarendon Press, ISBN 0-19-855370-6 
  2. ^ Conroy, L. E.; Ben-Dor, L. (1995), "Molybdenum(IV) Oxide and Tungsten(IV) Oxides Single-Crystals", Inorg. Synth., Inorganic Syntheses 30: 105–07, doi:10.1002/9780470132616.ch21, ISBN 0-471-30508-1