Redetermination of a copper(II) complex of violuric acid

In the title compound, diaquabis[2,4,5,6(1H,3H)-pyrimidinetetrone 5-oximato]copper(II) dihydrate, [Cu-(C4H2N3O4)(2)(H3O)(2)].2H(2)O, the corrdination geometry about the Cu atom is distorted octahedral. The Cu atom is bonded to the N atoms of the isonitroso groups and to two carbonyl O atoms of the two violurate ligands in the equatorial plane, and to two water molecules in axial positions. The crystal structure is stabilized by a three-dimensional network of N-H ... O and O-H ... O intermolecular hydrogen bonds. The structure was originally determined based on Weissenberg film data taken using CuK alpha radiation [Hamelin (1972). Acta Cryst. B28, 228-235].