A two-dimensional Cd coordination polymer: poly[di-aqua-[μ-5,6-bis-(pyridin-2-yl)pyrazine-2,3-di-carboxyl-ato-κ::,,]cadmium].

The reaction of 5,6-bis-(pyridin-2-yl)pyrazine-2,3-di-carb-oxy-lic acid with cadmium dichloride leads to the formation of the title two-dimensional coordination polymer, [Cd(CHNO)(HO)] . The metal atom is sevenfold coordinated by one pyrazine and one pyridine N atom, two water O atoms, and by two carboxyl-ate O atoms, one of which bridges two Cd atoms to form a CdO unit situated about a centre of inversion. Hence, the ligand coordinates to the cadmium atom in an ,',-tridentate and an -monodentate manner.

Isotypic Mn and Fe binuclear complexes of the ligand 5,6-bis-(pyridin-2-yl)-pyrazine-2,3-di-carb-oxy-lic acid.

The title isotypic complexes, bis-[μ-5,6-bis-(pyridin-2-yl)pyrazine-2,3-di-carboxylato]-κ,,:;κ:,,-bis-[di-aqua-manganese(II)] tetra-hydrate, [Mn(CHNO)(HO)]·4HO, (I), and bis-[μ-5,6-bis-(pyridin-2-yl)pyrazine-2,3-di-carboxyl-ato]-κ,,:;κ:,,-bis-[di-aqua-iron(II)] tetrahydrate, [Fe(CHNO)(HO)]·4HO, (II), are, respectively, the mangan-ese(II) and iron(II) complexes of the ligand 5,6-bis-(pyridin-2-yl)-pyrazine-2,3-di-carb-oxy-lic acid. The complete mol-ecule of each complex is generated by inversion symmetry. Each metal ion is coordinated by a pyrazine N atom, a pyridine N atom, two carboxyl-ate O atoms, one of which is bridging, and two water O atoms.