The reaction of nickel(II) nitrate hexahydrate with the protontransfer compound piperazinediium 4-hydroxypyridine-2,6- dicarboxylate, (pipzH2)(hypydc), where pipz is piperazine and hypydcH2 is 4-hydroxypyridine-2,6-dicarboxylic acid, in aqueous solution leads to the formation of the title complex, [Ni(C7H3NO5)(H2O)3]1.5H2O. Nickel(II) is coordinated by three donor atoms of the tridentate dianionic ligand, and three water molecules, in a slightly distorted octahedral geometry. The range of H A and D A distances, and D—H A angles indicates the presence of strong hydrogen bonding in this complex, which involves the coordinated and uncoordinated water molecules (one of which lies on a twofold rotation axis), giving a three-dimensional network.
