Tetra-aqua-diimidazole-nickel(II) naphthalene-1,5-disulfonate.

The triclinic unit cell of the title compound, Ni(C(3)H(4)N(2))(2)(H(2)O)(4), contains one centrosymmetric cation and one centrosymmetric anion. In the cation, the Ni(II) ion is six-coordinated by two imidazole ligands [Ni-N = 2.0568 (14) Å] and four water mol-ecules [both independent Ni-O distances are 2.098 (1) Å] in a distorted octa-hedral geometry. Inter-molecular O-H⋯O and N-H⋯O hydrogen bonds form an extensive three-dimensional network, which consolidates the crystal packing.