Oxonium (dihydrogen 1-amino-ethane-1,1-diyldiphospho-nato-κN,O)[hydrogen (1-amino-1-phosphono-ethyl)phospho-nato-κN,O]palladium(II) trihydrate.

The title compound, (H(3)O)[Pd(C(2)H(7)NO(6)P(2))(C(2)H(8)NO(6)P(2))]·3H(2)O, was synthesized by the reaction of [Pd(H(2)O)(4)](NO(3))(2) with 1-amino-ethane-1,1-diyldiphospho-nic acid in aqueous solution. The asymmetric unit contains one mol-ecule of the complex existing as an anion, an oxonium counter-ion and three solvent water mol-ecules. The Pd(II) ion occupies a position on a pseudo-twofold axis, which is not realized crystallographically. The slightly distorted square-planar coordination environment of the Pd(II) ion consists of the O atoms from two phospho-nic acid groups and two N atoms of the amino groups in cis positions. The crystal structure displays N-H⋯O and O-H⋯O hydrogen bonding, which creates a wide three-dimensional network.