Crystal structure of poly[(2,2′-bi­pyridine-κ(2) N,N′)tetra­kis­(μ-cyanido-κ(2) N:C)dinickel(II)]

The polymeric title complex, [Ni(2)(CN)(4)(C(10)H(8)N(2))](n), was obtained serendipitously under hydro­thermal conditions. The asymmetric unit consists of one half of an [Ni(CN)(4)](2−) anion with the Ni(2+) cation situated on an inversion centre, and one half of an [Ni(2,2′-bpy)](2+) cation (2,2′-bpy is 2,2′-bi­pyridine), with the second Ni(2+) cation situated on a twofold rotation axis. The two Ni(2+) cations exhibit different coordination spheres. Whereas the coordination of the metal in the anion is that of a slightly distorted square defined by four C-bound cyanide ligands, the coordination in the cation is that of a distorted octa­hedron defined by four N-bound cyanide ligands and two N atoms from the chelating 2,2′-bpy ligand. The two different Ni(2+) cations are alternately bridged by the cyanide ligands, resulting in a two-dimensional structure extending parallel to (010). Within the sheets, π–π inter­actions between pyridine rings of neighbouring 2,2′-bpy ligands, with a centroid-to-centroid distance of 3.687 (3) Å, are present. The crystal packing is dominated by van der Waals forces. A weak C—H⋯N inter­action between adjacent sheets is also observed.