Tetra-aqua-bis[(1-ammonio-1-phosphono-ethyl)phospho-nato]zinc(II) tetra-hydrate.

The title compound, [Zn(C(2)H(8)NO(6)P(2))(2)(H(2)O)(4)]·4H(2)O, was synthesized by the reaction of ZnCl(2) with 1-amino-ethane-1,1-diyldiphospho-nic acid in aqueous solution. The asymmetric unit contains one-half of the complex and two water mol-ecules of solvation. The Zn atom occupies a special position on an inversion centre. This results in a slightly distorted octa-hedral coordination environment, which consists of the O atoms from two phospho-nic acids and four water mol-ecules. The crystal structure displays N-H⋯O and O-H⋯O hydrogen bonding, which creates a three-dimensional network.