(μ-2,2′,2′′,2′′′-{[Pyrazine-2,3,5,6-tetra­yltetra­kis(methyl­ene)]tetra­kis(sulfanedi­yl)}tetra­acetato)bis­[aqua­nickel(II)] hepta­hydrate

Reaction of the ligand 2,2′,2′′,2′′′-{[pyrazine-2,3,5,6-tetra­yltetra­kis­(methyl­ene)]tetra­kis­(sulfanedi­yl)}tetra­acetic acid (H(4)L1), with NiCl(2) leads to the formation of a binuclear complex, (μ-2,2′,2′′,2′′′-{[pyrazine-2,3,5,6-tetra­yltetra­kis­(methyl­ene)]tetra­kis­(sulfanedi­yl)}tetra­acetato-κ(5) O,S,N (1),S′,O′:κ(5) O′′,S′′,N (4),S′′′,O′′′)bis[aqua­nickel(II)] hepta­hydrate, {[Ni(2)(C(16)H(16)N(2)O(8)S(4))(H(2)O)(2)]·7H(2)O} (I). It crystallizes with two half mol­ecules in the asymmetric unit. The complete mol­ecules are generated by inversion symmetry, with the center of the pyrazine rings being located at crystallographic centres of inversion. The ligand coordinates two Ni(II) ions in a bis-penta­dentate manner and the sixfold coordination sphere of each nickel(II) atom (NiS(2)O(3)N) is completed by a water mol­ecule. The complex crystallized as a hepta-hydrate. The binuclear complexes are linked by O(water)—H⋯O(carbon­yl) hydrogen bonds, forming layers parallel to the (101) plane. This layered structure is additionally stabilized by weak C—H⋯O hydrogen bonds. Further O—H⋯O hydrogen bonds involving binuclear complexes and solvent water mol­ecules, together with weak C—H⋯S hydrogen bonds, link the layers to form a supra­molecular framework. [Image: see text]