COMPOSITIONS AND STRUCTURES OF COPPER HEXACYANOFERRATE(II) AND HEXACYANOFERRATE(III) - EXPERIMENTAL RESULTS

The preparation, composition and structure of copper hexacyanoferrates have been investigated. Three methods were used: precipitation, local growth in an aqueous solution, and growth in a gel. Four compounds we re obtained, either in powdered form or as single crystals: (Cu2FeII)- Fe-II(CN)(6) . xH(2)O, Cu-3(II)[Fe-III(CN)(6)](2) . xH(2)O, (Na2CuFeII )-Fe-II(CN)(6) . 10H(2)O and (K2CuFeII)-Fe-II(CN)(6). Powders of (Cu2F eII)-Fe-II(CN)(6) . xH(2)O and Cu-3(II)[Fe-III (CN)(6)](2) . xH(2)O ar e easily prepared by precipitation and can also be obtained by local g rowth. They crystallise generally with cubic symmetry, in space group Fm(3) over bar m, and are structurally disordered. The mixed copper he xacyanoferrates of general formulae M(2)(I)Cu(II)Fe(II)(CN)(6) or M(I) Cu(II)Fe(III)(CN)(6) (here M(I) is Na, K) were not obtained by precipi tation. The appropriate method was local growth for the preparation of powders of (K2CuFeII)-Fe-II(CN)(6). Single crystals of (Na2CuFeII)-Fe -II(CN)(6) were obtained by growth in a gel, and their study using sin gle crystal X-ray diffraction revealed a new monoclinic structure.