Bis(1-ammonio­ethane-1,1-diyl­diphos­phonato-κ(2) O,O′)diaqua­cobalt(II) nona­hydrate

In the title compound, [Co(C(2)H(8)NO(6)P(2))(2)(H(2)O)(2)]·9H(2)O, the Co(II) atom has a slightly distorted octa­hedral coordination environment consisting of four deprotonated phospho­nate O atoms of two independent 1-amino­ethyl­idendiphospho­nate anions and complemented by the O atoms of two water mol­ecules in cis positions. The anions exists in the zwitterionic form (protonated amino group and two deprotonated phospho­nate O atoms) and constitute two six-membered chelate rings. The crystal structure also contains nine partly disordered uncoordinated water mol­ecules, which create an extensive three-dimensional network of strong O—H⋯O and N—H⋯O hydrogen bonds.