Disorder in the anionic part of catena-poly[[(pyrazine-2-carboxyl-ato)copper(II)]-μ-pyrazine-2-carboxyl-ato].

The title compound, Cu(C(5)H(3)N(2)O(2))(0.88)(C(6)H(4)NO(2))(1.12), is characterized by disorder of the anion, resulting from a statistical occupation in a 0.44 (3):0.56 (3) ratio of pyrazine-2-carboxylate and pyridine-2-carboxylate. The compound was isolated during attempts to synthesize a mixed-ligand coordination polymer by solvothermal reaction between copper(II) nitrate and equimolar mixtures of pyrazine-2-carboxylic acid and pyridine-2-carb-oxy-lic acid in a mixture of water and EtOH. The difference in the two components of the compound is due to substitutional disorder of a CH group for one of the N atoms of the pyrazine ring which share the same site in the structure. In the crystal structure, the Cu(II) atom lies on an inversion centre and is six-coordinated in a distorted N(2)O(4) geometry. The carboxyl-ate group carbonyl O atoms are weakly coordinated to an equivalent Cu(II) atom that is translated one unit cell in the a-axis direction, thus forming a polymeric chain through carboxyl-ate bridges.