Tungsten(IV) oxide

Tungsten(IV) oxide 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.

Tungsten(IV) oxide

Tungsten(IV) oxide
Names
Other names Tungsten dioxide
Identifiers
CAS Number	12036-22-5 Y
3D model (JSmol)	Interactive image
ECHA InfoCard	100.031.662
EC Number	234-842-7
PubChem CID	82850
UNII	0Q43JGJ0GV Y
CompTox Dashboard (EPA)	DTXSID0065195
InChI InChI=1S/2O.W
SMILES O=[W]=O
Properties
Chemical formula	WO2
Molar mass	215.839 g/mol
Appearance	Bronze solid
Density	10.8 g/cm3
Melting point	1,474 °C (2,685 °F; 1,747 K) from doi: 10.1007/BF02877593, decomposes at 1700 ◦C
Solubility in water	Negligible
Magnetic susceptibility (χ)	5.7×10−5 cm3/mol
Structure
Crystal 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
Related tungsten oxides	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). N verify (what is YN ?) Infobox references

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][3]

References

1. 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) Oxide Single Crystals". Inorganic Syntheses. Inorganic Syntheses. Vol. 30. pp. 105–07. doi:10.1002/9780470132616.ch21. ISBN 978-0-470-13261-6.
3. Rogers, D. B.; Butler, S. R.; Shannon, R. D. (1972). "Single Crystals of Transition-Metal Dioxides". Inorganic Syntheses. Inorganic Syntheses. Vol. XIII. pp. 135–145. doi:10.1002/9780470132449.ch27. ISBN 978-0-470-13244-9.