Tungsten(IV) oxide

Tungsten(IV) oxide
Names
Other names
Tungsten dioxide
Identifiers
3D model (JSmol)
ECHA InfoCard 100.031.662
EC Number 234-842-7
Properties
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
negligible
5.7×10−5 cm3/mol
Structure
Distorted rutile, (monoclinic), mP12, Space group P21/c, No 14
Hazards
Flash point Non-flammable
Related compounds
Other anions
 Tungsten disulfide
Other cations
 Chromium(IV) oxide
Molybdenum(IV) oxide
Tungsten(III) oxide
Tungsten(VI) oxide
Except where otherwise noted, 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]

References

  1. 1 2 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, ISBN 0-471-30508-1, doi:10.1002/9780470132616.ch21


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