Layered ruthenium hexagonal perovskites: The new series [Ba2Br2-2x(CO3)x][Ban+1RunO3n+3] with n = 2, 3, 4, 5

Matthieu Kauffmann (1) , Pascal Roussel (1) , Francis Abraham (1)

1 UCCS - Unité de Catalyse et Chimie du Solide - UMR 8181

Single crystals of the title compounds were prepared by solid state reactions from barium carbonate and ruthenium metal using a BaBr2 flux and investigated by X-ray diffraction method using Mo(Ka) radiation and a Charge Coupled Device (CCD) detector. A structural model for the term n ¼ 2, Ba5Ru2Br2O9 (1) was established in the hexagonal symmetry, space group P63/mmc, a ¼ 5.8344(2)A ˚ , c ¼ 25.637(2)A ˚ , Z ¼ 2. Combined refinement and maximum-entropy method (MEM) unambiguously show the presence of CO3 2 ions in the three other compounds (2, 3, 4). Their crystal structures were solved and refined in the trigonal symmetry, space group P3ml, a ¼ 5.8381(1)A ˚ , c ¼ 15.3083(6)A ˚ for the term n ¼ 3, Ba6Ru3Br1.54(CO3)0.23O12 (2), and space group R3m, a ¼ 5.7992(1)A ˚ , c ¼ 52.866(2)A ˚ and a ¼ 5.7900(1)A ˚ , c ¼ 59.819(2)A ˚ for the terms n ¼ 4, Ba7Ru4Br1.46(CO3)0.27O15 (3), and n ¼ 5, Ba8Ru5Br1.64(CO3)0.18O18 (4), respectively. The structures are formed by the periodic stacking along [0 0 1] of (n+1) hexagonal closepacked [BaO3] layers separated by a double layer of composition [Ba2Br22x(CO3)x]. The ruthenium atoms occupy the n octahedral interstices created in the hexagonal perovskite slabs and constitute isolated dimers Ru2O9 of face-shared octahedra (FSO) in 1 and isolated trimers Ru3O12 of FSO in 2. In 3 and 4, the Ru2O9 units are connected by corners either directly (3) or through a slab of isolated RuO6 octahedra (4) to form a bidimensional arrangement of RuO6 octahedra. These four oxybromocarbonates belong to the family of compounds formulated [Ba2Br22x(CO3)x][Ban+1RunO3n+3] where n represents the thickness of the octahedral string in hexagonal perovskite slabs. These compounds are compared to the oxychloride series.

Domaines: Chimie inorganique

Matthieu Kauffmann, Pascal Roussel, Francis Abraham. Layered ruthenium hexagonal perovskites: The new series [Ba2Br2-2x(CO3)x][Ban+1RunO3n+3] with n = 2, 3, 4, 5. Journal of Solid State Chemistry, 2007, xx, pp.xx-xx. ⟨10.1016/j.jssc.2007.05.018⟩. ⟨hal-00187426⟩