Tungsten pentoxide

Tungsten pentoxide was reported in early literature but proved to have the stoichiometry W₁₈O₄₉. Sometimes called mineral blue, it is a blue solid formed by the reaction of tungsten trioxide and tungsten metal at 700 °C.

Intermediate oxides of tungsten

There are a number of these unusual intermediate oxides formed from reacting metal and trioxide, including W₂₀O₅₈ and W₂₄O₇₀. W₁₈O₄₉ contains both octahedral and pentagonal bipyramidal co-ordination of the metal atoms by oxygen.