A number of unusual intermediate oxides are formed from reacting tungsten metal and tungsten trioxide (), including and . contains both octahedral and pentagonal bipyramidal co-ordination of the metal atoms by oxygen.
Tungsten pentoxide () was reported in early literature but proved to have the stoichiometry .Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications Sometimes called mineral blue, it is a blue solid formed by the reaction of tungsten trioxide and tungsten metal at .
See also Tungsten(III) oxide Tungsten(IV) oxide Tungsten(VI) oxide
References