Synthesis and structure of cobalt (II) oxide halides -: Sr2CoO2X2 (X = Cl, Br)

The first layered cobalt (II) oxide halides, Sr2CoO2Cl2 and Sr2CoO2Br2, have been synthesized and their structures determined from Rietveld refinement of powder X-ray data. The materials are structural analogues of the K2NiF4 cuprate phase Sr2CuO2Cl2, crystallizing in space group I4/mmm. The compounds contain CoO2 square planes separated by SrX layers (X = Cl,Br). The bromide material displays the expected increase in cell dimensions, i.e., for Sr2CoO2Cl2, a = 4.06251(5) Angstrom, c = 15.1251(3) Angstrom and for Sr2CoO2Br2, a = 4.08891(7) Angstrom, c = 16.4077(4) Angstrom. (C) 2002 Elsevier Science (USA).