SYNTHESES AND CRYSTAL-STRUCTURES OF PIPERAZINE-1,4-DIYLBIS(METHYLENE)BIS(PHOSPHONIC ACID)HYDROCHLORIDE, [H5L]CL, AND ITS COMPLEX WITH CADMIUM(II), [CD(OH)(H3L)(H2O)3](N).NH2O

Synthesis of the polymeric complex [Cd(OH)(H3L)(H2O)3]n . nH2O (1) [H4L = piperazine-1,4-diylbis(methylene)bis(phosphonic acid), (II)] and X-ray crystal structures of I and II.HCl are reported. In I, the phosphonic acid coordinates as a monoanionic zwitterion through one oxygen atom of each phosphonate group to give polymeric chains of Cd atoms bridged through the organic function of the ligands. Three water molecules and one hydroxo ligand complete the approximately octahedral coodination sphere around cadmium. The piperazine ring has the chair conformation in both I and II . HCl, and II can be regarded as doubly zwitterionic.