title: Isotypic one-dimensional coordination polymers: catena-poly[[di-chlorido-cadmium]-μ-5,6-bis-(pyridin-2-yl)pyrazine-2,3-di-carboxyl-ato-κ(2) N (5):N (6)] and catena-poly[[di-chlorido-mercury(II)]-μ-5,6-bis-(pyridin-2-yl)pyrazine-2,3-di-carboxyl-ato-κ(2) N (5):N (6)].
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-di-carb-oxy-lic acid. In both compounds, the metal ions are located on a twofold rotation axis and a second such axis bis-ects 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.
authors.affiliation: Institute of Chemistry, University of Neuchâtel, Av. de Bellevaux 51, CH-2000 Neuchâtel, Switzerland.
authors.forename: Montserrat
authors.initials: M
authors.lastname: Alfonso
authors.affiliation: Insitute of Physics, University of Neuchâtel, rue Emile-Argand 11, CH-2000 Neuchâtel, Switzerland.
authors.forename: Helen
authors.initials: H
authors.lastname: Stoeckli-Evans
keywords: C—H⋯Cl hydrogen bonding; MN2Cl2 bisphenoidal coordination geometry; crystal structure; di­meth­yl ester; isotypic coordination polymer; one-dimensional; pyrazine; pyridine