Synthesis and structure of Ba6Co6ClO16, a new cobalt oxychloride with a layered perovskite-related structure

Well-developed single crystals of the title compound were prepared using a BaCl2 flux and investigated by X-ray diffraction methods using Mo(Kα) radiation and a Charge Coupled Device (CCD) detector. The crystal structure was solved and refined in the hexagonal symmetry with image space group, a=5.6698(2) Å and c=14.4654(5) Å to a final R1=0.022 for 44 parameters with 1418 individual reflections. The structure of Ba6Co6ClO16, which is related to the 6H-perovkite-type structure of BaMnO2.88, is formed by the periodic stacking along [001] of five [BaO3] layers separated by a [BaOCl] with a (hhhchc) stacking sequence. The [BaO3] stacking creates tetranuclear face sharing octahedra units Co4O15 containing Co(III) connected by dimers of corner-sharing CoO4 tetrahedra. This new oxychloride belongs to the family of compounds formulated as [BaOCl]M′2[Ban+1MnO3n+3] where n represents the thickness of the octahedral string in hexagonal perovskite slabs.