Isotypic one-dimensional coordination polymers: catena-poly[[dichloridocadmium]-μ-5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylato-κ2N5:N6] and catena-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—Car bonds of the pyrazine ring. The metal ions are bridged by binding to the N atoms of the two pyridine rings and have an MN2Cl2 bisphenoidal coordination geometry. The metal–Npyrazine distances are much longer than the metal–Npyridine distances; 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 linked via pairs of C—H...Cl hydrogen bonds, forming corrugated slabs parallel to the ac plane.

Keywords

• crystal structure
• isotypic coordination polymer
• one-dimensional
• MN2Cl2 bisphenoidal coordination geometry
• dimethyl ester
• pyrazine
• pyridine
• C—H...Cl hydrogen bonding