One-dimensional structure of catena-poly[tetraethylammonium [tetracyanoiron(III)-μ-cyano-[bis(ethylenediamine)cadmium(II)]-μ-cyano] tetrahydrate]

The title compound, {(C8H20N)[CdFe(CN)(6)(C2H8N2)(2)]center dot-4H(2)O}(n), was isolated from the aqueous system Cd2+/ethylenediamine (en)/[Fe(CN)(6)](3-) in the presence of [Et4N]Br. The crystal structure is dominated by a one-dimensional motif, viz. a negatively charged 2,2-CT (cis-trans) [-Cd(en)(2)-NC-Fe(CN)(4)-CN-](n)(n-) chain. The Cd and Fe atoms of the anion and the N atom of the cation all lie on twofold axes. The ethyl groups of the cation are equally disordered over two orientations. The cationic building block of the chain consists of a Cd-II atom coordinated by two chelating en ligands, and the distorted octahedral coordination is completed by two bridging cyano ligands in cis positions. The anionic building block is an [Fe(CN)(6)](3). anion in which the Fe-III atom is octahedrally coordinated by six cyano ligands; two of the cyano ligands, in trans positions, are bridging. The uncoordinated water molecules link neighbouring chains through O - H center dot center dot center dot N and N - H center dot center dot center dot O hydrogen bonds.