Triaqua(4-hydroxypyridine-2,6-dicarboxylato)nickel(II) sesquihydrate

The reaction of nickel( II) nitrate hexahydrate with the proton-transfer compound piperazinediium 4-hydroxypyridine-2,6dicarboxylate, (pipzH(2))(hypydc), where pipz is piperazine and hypydcH(2) is 4-hydroxypyridine-2,6-dicarboxylic acid, in aqueous solution leads to the formation of the title complex, [Ni(C7H3NO5)(H2O)(3)] center dot 1.5H(2)O. 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 center dot center dot center dot A and D center dot center dot center dot A distances, and D - H center dot center dot center dot 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.