X-ray powder structure of a new two-dimensional nickel(II) coordination polymer with pyrazine-2,3,5,6-tetracarboxylic acid

The new nickel(II) coordination polymer poly[diaquanickel(II)-μ-(pyrazine-2,3,5,6-tetracarboxylato) -tetraaquanickel(II)], {[{Ni(C8N2O8)(H2O) 2}Ni(H2O)4]}n, has been synthesized and characterized both spectroscopically and crystallographically, by X-ray powder diffraction analysis. In this two-dimensional coordination polymer, NiII ions are bridged by pyrazine-2,3,5,6-tetracarboxylic acid, coordinating in a bis-bidentate manner, so forming one-dimensional polymeric chains. The chains are linked by a second NiII ion, via an O atom of the coordinated carboxylate group, resulting in the formation of a two-dimensional layer-like polymer. The remaining coordination sites of the two independent octahedral NiII ions are occupied by water molecules. The layers are connected via hydrogen bonds involving all six coordinated water molecules.