Hexakis(1H-imidazole-κN)nickel(II) triaqua-tris(1H-imidazole-κN)nickel(II) bis-(naphthalene-1,4-dicarboxyl-ate).

The crystal structure of the title compound, [Ni(C(3)H(4)N(2))(6)][Ni(C(3)H(4)N(2))(3)(H(2)O)(3)](C(12)H(6)O(4))(2), contains uncoordinated naphthalene-dicarboxyl-ate dianions and two kinds of Ni(II) complex cations, both assuming distorted octa-hedral geometries. One Ni(II) ion is located on an inversion center and is coordinated by six imidazole mol-ecules, while the other Ni(II) ion is located on a twofold rotation axis and is coordinated by three water mol-ecules and three imidazole mol-ecules in a mer-NiN(3)O(3) arrangement. The naphthalene-dicarboxyl-ate dianion links both Ni(II) complex cations via O-H⋯O and N-H⋯O hydrogen bonding, but no π-π stacking is observed between aromatic rings in the crystal structure. One imidazole ligand is equally disordered over two sites about a twofold rotation axis; one N atom and one water O atom have site symmetry 2.