Penta­kis(tetra­ethyl­ammonium) diaqua-μ₄-malonato-tetra­malonatodi-μ₃-oxo-di-μ-oxo-tetra­oxo­potassium­tetramolybdenum acetonitrile disolvate

The title compound, (C₈H₂₀N)₅[KMo₄O₈(C₃H₂O₄)₅]·2CH₃CN·2H₂O, was obtained from a ligand substitution reaction of [Et₄N]₃[Mo₃(CO)₉(OMe)₃] with malonic acid and subsequent reaction with oxygen and water. The structure contains two Mo⁵⁺ dimers bridged by a malonate group. Each Mo atom is ligated by an additional chelating malonate group, a terminal oxide and two bridging oxides. A potassium ion occupies the cavity formed by the bridging malonate group.