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

The title compound, (NH)[W(CHNO)O]·4HO, was obtained from a mixture of tungstic acid, ammonia and ethyl-enedi-amine-tetra-acetic acid (Hedta) in a 2:4:1 ratio. The anion of the complex contains two WO units and one bridging edta ligand. Each central metal atom is tridentately coordinated by nitro-gen and two carboxyl-ate groups of the edta 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 hydrogen bonds of the N-H⋯O and O-H⋯O type.