Crystal structure of poly[(2,2'-bipyridine-κ2N,N')-tetrakis(μ-cyanido-κ2N:C)dinickel(II)]

Abstract

The polymeric title complex, [Ni2(CN)4(C10H8N2)]n, was obtained serendipitously under hydrothermal conditions. The asymmetric unit consists of one half of an [Ni(CN)4]2- anion with the Ni2+ 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 Ni2+ cation situated on a twofold rotation axis. The two Ni2+ 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 Ni2+ 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.