Acta Crystallographica Section C

Crystal Structure Communications

Volume 64, Part 6 (June 2008)

metal-organic compounds

gd3207 scheme

Acta Cryst. (2008). C64, m221-m223 [ doi:10.1107/S0108270108011694 ]

Poly[diaqua(-4,4'-bipyridine-²N:N')bis(-cyanido-²C:N)bis(cyanido-C)nickel(II)copper(II)]: a metal-organic cyanide-bridged framework

O. Sereda and H. Stoeckli-Evans

Abstract: The structure of the title compound, [NiCu(CN)₄(C₁₀H₈N₂)(H₂O)₂]_n or [{Cu(H₂O)₂}( [mu] -C₁₀H₈N₂)( [mu] -CN)₂{Ni(CN)₂}]_n, was shown to be a metal-organic cyanide-bridged framework, composed essentially of -Cu-4,4'-bpy-Cu-4,4'-bpy-Cu- chains (4,4'-bpy is 4,4'-bipyridine) linked by [Ni(CN)₄]^2- anions. Both metal atoms sit on special positions; the Cu^II atom occupies an inversion center, while the Ni^II atom of the cyanometallate sits on a twofold axis. The 4,4'-bpy ligand is also situated about a center of symmetry, located at the center of the bridging C-C bond. The scientific impact of this structure lies in the unique manner in which the framework is built up. The arrangement of the -Cu-4,4'-bpy-Cu-4,4'-bpy-Cu- chains, which are mutually perpendicular and non-intersecting, creates large channels running parallel to the c axis. Within these channels, the [Ni(CN)₄]^2- anions coordinate to successive Cu^II atoms, forming zigzag -Cu-N [triple bond] C-Ni-CN-Cu- chains. In this manner, a three-dimensional framework structure is constructed. To the authors' knowledge, this arrangement has not been observed in any of the many copper(II)-4,4'-bipyridine framework complexes synthesized to date. The coordination environment of the Cu^II atom is completed by two water molecules. The framework is further strengthened by O-HN hydrogen bonds involving the water molecules and the symmetry-equivalent nonbridging cyanide N atoms.

Formula: [NiCu(CN)₄(C₁₀H₈N₂)(H₂O)₂]