A seven-coordinate pyridine-2,6-dicarboxylate-bridged cadmium(II) complex, at 110 K

The reaction of cadmium(II) chloride monohydrate with a self-assembling pyridine-containing ligand, LH2 {LH2 is [H2pyda]2+[pydc]2−, where pyda = 2,6-di­amino­pyridine and H2pydc = pyridine-2,6-di­carboxyl­ic acid}, in water leads to the formation of a centrosymmetric dinuclear CdII complex, di-μ-pyridine-2,6-di­carboxyl­ato-bis­[tri­aqua­cadmium(II)], [Cd(pydc)(H2O)3]2·2H2pydc or [Cd2(C7H3NO4)2(H2O)6]·2C7H5NO4. Each Cd atom is seven-coordinate and has a distorted pentagonal-bipyramidal geometry. The two metal fragments are linked via the central four-membered Cd2O2 ring and there is no [Hpyda]+ moiety in the structure of the complex. The structure self-assembles into layers via hydrogen bonds.