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) ?, c=15.1251(3) ? and for Sr2CoO2Br2, a=4.08891(7) ?, c=16.4077(4) ?.