Tetra-aqua-(ethane-1,2-di-amine-κ 2 N , N ')nickel(II) naphthalene-1,5-di-sulfonate dihydrate.

The reaction of ethane-1,2-di-amine (en, C 2 H 8 N 2 ), the sodium salt of naphthalene-1,5-di-sulfonic acid (H 2 NDS, C 10 H 8 O 6 S 2 ), and nickel sulfate in an aqueous solution resulted in the formation of the title salt, [Ni(C 2 H 8 N 2 )(H 2 O) 4 ](C 10 H 6 O 6 S 2 )·2H 2 O or [Ni(en)(H 2 O) 4 ](NDS)·2H 2 O. In the asymmetric unit, one half of an [Ni(en)(H 2 O) 4 ] 2+ cation and one half of an NDS 2- anion, and one water mol-ecule of crystallization are present. The Ni 2+ cation in the complex is positioned on a twofold rotation axis and exhibits a slight tetra-gonal distortion of the cis -NiO 4 N 2 octa-hedron, with an Ni-N bond length of 2.0782 (16) Å, and Ni-O bond lengths of 2.1170 (13) Å and 2.0648 (14) Å. The anion is completed by inversion symmetry. In the extended structure, the cations, anions, and non-coordinating water mol-ecules are connected by inter-molecular N-H⋯O and O-H⋯O hydrogen bonding, as well as C-H⋯π inter-actions, forming a three-dimensional network.