Synthesis and crystal structure of a new isomer of poly[di-μ3-cyanido-μ-2,6-di­methyl­pyrazine-dicopper(I)]

In the crystal structure of the title compound, the copper(I) cations are linked by the cyanide anions into layers that are additionally connected by the 2,6-di­methyl­pyrazine ligands into a 3D network. The title compound represents a new isomer of Cu₂(CN)₂(2,6-di­methyl­pyrazine), which has already been reported in the literature.

The title compound, [Cu₂(CN)₂(C₆H₈N₂)]_n or Cu₂(CN)₂(2,6-di­methyl­pyrazine), was prepared by the reaction of copper(I) cyanide with 2,6-di­methyl­pyrazine in water. Its asymmetric unit consists of two crystallographically independent copper(I) cations and cyanide anions as well as one crystallographically independent 2,6-di­methyl­pyrazine ligand in general positions. Each copper cation is fourfold coordinated by one N atom of the 2,6-di­methyl­pyrazine ligand and three cyanide anions, that are disordered so that each C and N position has mixed occupancy with a ratio between N and C of 94:6 and 77:23. The copper cations are linked by the cyanide atoms into layers that are further connected into a 3D network by the 2,6-di­methyl­pyrazine ligands. Powder X-ray diffraction (PXRD) proves that a pure crystalline phase has been obtained. It is noted that this crystal structure represents a new isomer of Cu₂(CN)₂(2,6-di­methyl­pyrazine), which has already been reported in the literature [Chesnut et al. (2001#). J. Chem. Soc. Dalton Trans. pp. 2567–2580].