trans-Bis[(1-ammonio­pentane-1,1-di­yl)diphospho­nato-κ2 O,O′]diaqua­copper(II)

In the title compound, [Cu(C(5)H(14)NO(6)P(2))(2)(H(2)O)(2)], the Cu(II) atom occupies a special position on an inversion centre. It exhibits a distorted octa-hedral coordination environment consisting of two O,O'-bidentate (1-ammonio-pentane-1,1-di-yl)diphospho-nate anions in the equatorial plane and two trans water mol-ecules located in axial positions. The ligand mol-ecules are coordinated to the Cu(II) atom in their zwitterionic form via two O atoms from different phospho-nate groups, creating two six-membered chelate rings with a screw-boat conformation. The CuO(6) coordination polyhedron is strongly elongated in the axial direction with 0.6 Å longer bonds than those in the equatorial plane. Intra-molecular N-H⋯O hydrogen bonding helps to stabilize the mol-ecular configuration. The presence of supra-molecular -PO(OH)⋯O(OH)P- units parallel to (100) and other O-H⋯O and N-H⋯O hydrogen bonds establish the three-dimensional set-up.