Structure of the new iron(II) oxalate potassium salt K2Fe[(C2O4)2(H2O)2]·0.18H2O

The discovery of a new Fe II oxalate framework of composition K 2 Fe[(C 2 O 4 ) 2 (H 2 O) 2 ]·0.18H 2 O 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 Pca 2 1 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 FeO 4 (H 2 O) 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 57 Fe Mössbauer data indicate that Fe 2+ is in a high-spin state.