Tungsten(IV) oxide

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Tungsten(IV) oxide
Image:Tungsten(IV) oxide.jpg
Other names	Tungsten dioxide
Identifiers
CAS number	[12036-22-5]
Properties
Molecular formula	O2W
Molar mass	215.84 g/mol
Appearance	bronze solid
Density	10.8 g/cm³, solid
Melting point	1700 °C (decomposes)
Solubility in water	Insoluble
Structure
Crystal structure	monoclinic
Hazards
EU classification	not listed
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Tungsten dioxide is the chemical compound with the formula WO₂. The bronze-colored solid crystallizes in a monoclinic cell. The rutile-like structure features octahedral WO₆ centers. Each W center has the d² configuration, which makes the material 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.^[1]

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