Layered perovskite-related ruthenium oxychlorides: crystal structure of two new compounds Ba5Ru2Cl2O9 and Ba6Ru3Cl2O12

Single crystals of the title compounds were prepared using a BaCl₂ flux and investigated by X-ray diffraction methods using MoKα radiation and a charge coupled device (CCD) detector. The crystal structures of these two new compounds were solved and refined in the hexagonal symmetry with space group P6₃/mmc, a=5.851(1) Å, c=25.009(5) Å, ρ_cal=4.94 g cm⁻³, Z=2 to a final R₁=0.069 for 20 parameters with 312 reflections for Ba₅Ru₂Cl₂O₉ and space group , a=5.815(1) Å, c=14.915(3) Å, ρ_cal=5.28 g cm⁻³, Z=1 to a final R₁=0.039 for 24 parameters with 300 reflections for Ba₆Ru₃Cl₂O₁₂. The structure of Ba₅Ru₂Cl₂O₉ is formed by the periodic stacking along [001] of three hexagonal close-packed BaO₃ layers separated by a double layer of composition Ba₂Cl₂. The BaO₃ stacking creates binuclear face-sharing octahedra units Ru₂O₉ containing Ru(V). The structure of Ba₆Ru₃Cl₂O₁₂ is built up by the periodic stacking along [001] of four hexagonal close-packed BaO₃ layers separated by a double layer of composition Ba₂Cl₂. The ruthenium ions with a mean oxidation degree +4.67 occupy the octahedral interstices formed by the four layers hexagonal perovskite slab and then constitute isolated trinuclear Ru₃O₁₂ units. These two new oxychlorides belong to the family of compounds formulated as [Ba₂Cl₂][Ba_n+1Ru_nO_3n+3], where n represents the thickness of the octahedral string in hexagonal perovskite slabs.