Isotypic one-dimensional coordination polymers:catena-poly[[dichloridocadmium]-μ-5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylato-κ2N5:N6] andcatena-poly[[dichloridomercury(II)]-μ-5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylato-κ2N5:N6]

Abstract

The isotypic title one-dimensional coordination polymers, [CdCl2(C18H14N4O4)]n, (I), and [HgCl2(C18H14N4O4)]n, (II), are, respectively, the cadmium(II) and mercury(II) complexes of the dimethyl ester of 5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylic acid. In both compounds, the metal ions are located on a twofold rotation axis and a second such axis bisects the Car—Carbonds of the pyrazine ring. The metal ions are bridged by binding to the N atoms of the two pyridine rings and have anMN2Cl2bisphenoidal coordination geometry. The metal–Npyrazinedistances are much longer than the metal–Npyridinedistances; the difference is 0.389 (2) Å for the Cd—N bonds but only 0.286 (5) Å for the Hg—N bond lengths. In the crystals of both compounds, the polymer chains are linkedviapairs of C—H...Cl hydrogen bonds, forming corrugated slabs parallel to theacplane.