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)CENTER-DOT-NH2O

Synthesis of the polymeric complex [Cd(OH)(H3L)(H2O)3]n . nH2O (1) [H4 L = piperazine-1,4-diylbis(methylene)bis(phosphonic acid), (II)] and X -ray crystal structures of I and II.HCl are reported. In I, the phosph onic acid coordinates as a monoanionic zwitterion through one oxygen a tom of each phosphonate group to give polymeric chains of Cd atoms bri dged through the organic function of the ligands. Three water molecule s and one hydroxo ligand complete the approximately octahedral coodina tion sphere around cadmium. The piperazine ring has the chair conforma tion in both I and II . HCl, and II can be regarded as doubly zwitteri onic.