Structure of the New Iron(ii) Oxalate Potassium Salt K2Fe[(C2O4)2(H2O)2]·0.18H2O.

The discovery of a new FeII oxalate framework of composition K2Fe[(C2O4)2(H2O)2]·0.18H2O is reported. Its crystal structure was solved by means of single crystal and powder X-ray diffraction. The new organic-inorganic hybrid compound crystallizes in the orthorhombic space group Pca21 with unit-cell parameters: a = 12.0351 (4) Å, b = 15.1265 (5) Å, c = 10.5562 (4) Å. This crystal structure, containing eight chemical formula, consists of a succession of FeO4(H2O)2 octahedra and K+ cations growing along b direction. Magnetization measurements indicate that the title compound is paramagnetic over the investigated temperature range (2-300 K). Both magnetization and 57Fe Mössbauer data indicate that Fe2+ is in a high-spin state.