Tungsten(IV) oxide is the chemical compound with the formula WO2. The bronze-colored solid crystallizes in a monoclinic cell. The rutile-like structure features distorted octahedral WO6 centers with alternate short W–W bonds (248 pm). 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.
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- ^ 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