Pyridinium diaqua­bis­(methyl­enediphospho­nato-κ(2) O,O′)chromate(III) tetra­hydrate

In the title complex, (C(5)H(6)N)[Cr(CH(4)O(6)P(2))(2)(H(2)O)(2)]·4H(2)O, the Cr(III) atom, lying on an inversion centre, is coordinated by two bidentate methyl­ene diphospho­nate ligands and two water molecules in a distorted octa­hedral coordination geometry. The pyridinium cation is located on an inversion centre, with an N atom and a C atom sharing a position each at a half occupancy. A three-dimensional network is constructed by O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds between the pyridin­ium cation, complex anion and uncoordinated water mol­ecules.