Bis[(1-ammonio-ethane-1,1-di-yl)diphospho-nato-κO,O']diaqua-nickel(II) nona-hydrate.

The title compound, [Ni(C(2)H(8)NO(6)P(2))(2)(H(2)O)(2)]·9H(2)O, exhibits a slightly distorted octa-hedral coordination environment around the Ni(II) atom. It contains two mol-ecules of 1-amino--ethyl-idenediphospho-nic acid in the zwitterionic form, coord-inated via O atoms from two phospho-nate groups and creating two six-membered chelate rings. Two water mol-ecules in cis positions complete the coordination environment of the Ni(II) atom. The title compound contains nine partly disordered solvent water mol-ecules, which create a three-dimensional network of strong O-H⋯O and N-H⋯O hydrogen bonds.