Crystal structure of poly[(2,2'-bi-pyridine-κ(2) N,N')tetra-kis-(μ-cyanido-κ(2) N:C)dinickel(II)].

The polymeric title complex, [Ni2(CN)4(C10H8N2)] n , was obtained serendipitously under hydro-thermal 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'-bi-pyridine), 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 octa-hedron 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 inter-actions 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 inter-action between adjacent sheets is also observed.