(μ-Methylenediphosphonato-κ⁴ O,O':O'',O''')bis[(ethyl-ene-diamine-κ² N,N')palladium(II)] tetra-hydrate

The title compound, [Pd₂(C₂H₈N₂)₂(CH₂O₆P₂)]·4H₂O, comprises of a binuclear mol-ecule (point group symmetry 2), with a twofold rotation axis running through the central C atom of the methyl-enedi-phospho-nate (MDP) anion. The Pd^II atom has a square-planar coordination environment defined by the N atoms of a bidentate ethyl-enedi-amine (en) ligand and two O atoms of the bridging MDP anion. In the crystal structure, metal complexes are arranged in layers parallel (001) and are sandwiched between layers containing disordered water mol-ecules of crystallization. Extensive intra-layer hydrogen bonds of the type N-H⋯O in the metal complex layer and O-H⋯O in the water layer, as well as O-H⋯O hydrogen bonds between the two types of layers, lead to the formation a three-dimensional network structure. The two lattice water mol-ecules are each equally disordered over two positions.