The new one-dimensional coordination polymercatena-poly[[diaquasodium(I)]-μ-oxalato-[diaquairon(III)]-μ-oxalato]

Abstract

The oxalate dianion is one of the most studied ligands and is capable of bridging two or more metal centres and creating inorganic polymers based on the assembly of metal polyhedra with a wide variety of one-, two- or three-dimensional extended structures. Yellow single crystals of a new mixed-metal oxalate, namelycatena-poly[[diaquasodium(I)]-μ-oxalato-κ4O1,O2:O1′,O2′-[diaquairon(III)]-μ-oxalato-κ4O1,O2:O1′,O2′], [NaFe(C2O4)2(H2O)4]n, have been synthesized and the crystal structure elucidated by X-ray diffraction analysis. The compound crystallizes in the noncentrosymmetric space groupI41(Z= 4). The asymmetric unit contains one NaIand one FeIIIatom lying on a fourfold symmetry axis, one μ2-bridging oxalate ligand and two aqua ligands. Each metal atom is surrounded by two chelating oxalate ligands and two equivalent water molecules. The structure consists of infinite one-dimensional chains of alternating FeO4(H2OW1)2and NaO4(H2OW2)2octahedra, bridged by oxalate ligands, parallel to the [100] and [010] directions, respectively. Because of thecisconfiguration and the μ2-coordination mode of the oxalate ligands, the chains run in a zigzag manner. This arrangement facilitates the formation of hydrogen bonds between neighbouring chains involving the H2O and oxalate ligands, leading to a two-dimensional framework. The structure of this new one-dimensional coordination polymer is shown to be unique among theAIMIII(C2O4)2(H2O)nseries. In addition, the absorption bands in the IR and UV–Visible regions and their assignments are in good agreement with the local symmetry of the oxalate ligand and the irregular environment of iron(III). The final product of the thermal decomposition of this precursor is the well-known ternary oxide NaFeO2.