Crystal structure of -di-aqua-(1,4,8,11-tetra-aza-undeca-ne)nickel(II) bis-(pyridine-2,6-di-carboxyl-ato)nickel(II).

The asymmetric unit of the title compound, -di-aqua-(1,4,8,11-tetra-aza-undecane-κ , , , )nickel(II) bis-(pyridine-2,6-di-carboxyl-ato-κ ,, )nickel(II) {[Ni()(HO)][Ni(pdc)] where = 1,4,8,11-tetra-aza-undecane (CHN) and pdc = the dianion of pyridine-2,6-di-carb-oxy-lic acid (CHNO )} consists of an [Ni()(HO)] complex cation and a [Ni(pdc)] anion. The metal ion in the cation is coordinated by the four N atoms of the tetra-amine ligand and the mutually O atoms of the water mol-ecules in a tetra-gonally elongated octa-hedral geometry with the average equatorial Ni-N bond length slightly shorter than the average axial Ni-O bond [2.087 (4) 2.128 (4) Å]. The ligand adopts its energetically favored conformation with five-membered and six-membered chelate rings in and conformations, respectively. In the complex anion, the Ni ion is coordinated by the two tridentate pdc ligands their carboxyl-ate and nitro-gen atom donors in a distorted octa-hedral -NiON geometry with nearly orthogonal orientation of the planes defining the carboxyl-ate rings and the average Ni-N bond length [1.965 (4) Å] shorter than the average Ni-O bond distance [2.113 (7) Å]. In the crystal, the NH donor groups of the tetra-amine, the carb-oxy-lic groups of the pdc anion and the coordinated water mol-ecules are involved in numerous N-H⋯O and O-H⋯O hydrogen bonds, leading to electroneutral sheets oriented parallel to the (001) plane.