Bis[(1-ammonio­ethane-1,1-di­yl)diphospho­nato-κ(2) O,O′]diaqua­nickel(II) nona­hydrate

The title compound, [Ni(C(2)H(8)NO(6)P(2))(2)(H(2)O)(2)]·9H(2)O, exhibits a slightly distorted octa­hedral coordination environment around the Ni(II) atom. It contains two mol­ecules of 1-amino­­ethyl­idenediphospho­nic acid in the zwitterionic form, coord­inated via O atoms from two phospho­nate groups and creating two six-membered chelate rings. Two water mol­ecules in cis positions complete the coordination environment of the Ni(II) atom. The title compound contains nine partly disordered solvent water mol­ecules, which create a three-dimensional network of strong O—H⋯O and N—H⋯O hydrogen bonds.