Binary salt of a palladium(II) complex with (phosphonomethyl)phosphonic (medronic) acid comprising 'handbell-like' [Pd{μ-CH2(PO3)2}]3 units

Poly[[tri-μ-aqua-do-deca-aqua-tris-(μ3-1-hy-droxy-ethyl-idene-1,1-di-phospho-nato)tricalcium(II)tripalladium(II)] penta-hydrate]

The asymmetric unit of the title compound, {[CaPd{CH₃OHC(PO₃)₂}(H₂O)₅]·5/3H₂O}_n, consists of one half of the complex [Pd{CH₃OHC(PO₃)₂}]²⁻ anion (point group symmetry m..), one Ca²⁺ cation [site symmetry (.2.)] that is surrounded by three water mol­ecules (one of which is on the same rotation axis) and by three disordered lattice water mol­ecules. The anions form a trinuclear metallocycle around a crystallographic threefold rotation axis. The cations are related by a twofold rotation axis to form a [Ca₂(H₂O)₁₀]²⁺ dimer. The slightly distorted square-planar coordination environment of the Pd^II atoms in the complex anions is formed by O atoms of the bidentate chelating phospho­nate groups of the 1-hy­droxy­ethyl­idene-1,1-di­phospho­nate ligands. In the crystal, cations are bound to anions through —Ca—O—P—O— bonds, as well as through O—H⋯O hydrogen bonds, resulting in a three-dimensional polymer. The structure is completed by five disordered solvent mol­ecules localized in cavities within the framework.