Tetra-ammonium μ-ethyl-enedi-amine-tetra-acetato-1κ 3 O , N , O ':2κ 3 O '', N ', O '''-bis-[trioxidotungstate(VI)] tetra-hydrate.

The title compound, (NH 4 ) 4 [W 2 (C 10 H 12 N 2 O 8 )O 6 ]·4H 2 O, was obtained from a mixture of tungstic acid, ammonia and ethyl-enedi-amine-tetra-acetic acid (H 4 edta) in a 2:4:1 ratio. The anion of the complex contains two WO 3 units and one bridging edta 4- ligand. Each central metal atom is tridentately coordinated by nitro-gen and two carboxyl-ate groups of the edta 4- ligand, together with the three oxido ligands, producing a distorted octa-hedral coordination environment around each tungsten atom. The center of the carbon-carbon bond of the ethyl-ene bridge represents a crystallographic inversion center. The crystal structure consists of a three-dimensional supra-molecular framework built up by the dinuclear cations, the ammonium counter-ions and the solvent water mol-ecules via hydrogen bonds of the N-H⋯O and O-H⋯O type.