Tungsten(IV) oxide is the chemical compound with the formula WO<sub>2</sub>. The bronze-colored solid crystallizes in a monoclinic cell. The rutile-like structure features distorted octahedral WO<sub>6</sub> centers with alternate short WâÂÂW bonds (248 pm). Each tungsten center has the d<sup>2</sup> configuration, which gives the material a high electrical conductivity.
WO<sub>2</sub> is prepared by reduction of WO<sub>3</sub> with tungsten powder over the course of 40 hours at 900 ðC. An intermediate in this reaction is the partially reduced, mixed valence species W<sub>18</sub>O<sub>49</sub>.
The molybdenum analogue MoO<sub>2</sub> is prepared similarly. Single crystals are obtained by chemical transport technique using iodine. Iodine transports the WO<sub>2</sub> in the form of the volatile species WO<sub>2</sub>I<sub>2</sub>.