Isolated and edge-sharing interstitially stabilized metal tetrahedra {M(4)Z} in La(4)ZBr(7), M(9)Z(4)I(16), and BaM(4)Z(2)I(8) (M = La,Ce). The nature of Z

摘要

Metallothermic reductions of LaBr3, LaI3 and CeI3 with barium metal resulted in single crystals of La(4)ZBr(7), M(9)Z(4)I(16) and BaM(4)Z(2)I(8) (M = La,Ce) as by-products, subject to apparently ubiquitous "oxygen" and/or "nitrogen" (= Z) impurities. The crystal structure of La(4)ZBr(7) (1, orthorhombic, Prima, Z = 4, a = 1212.4(1), b = 1404.8(2), c = 804.7(1) pm, R-1 = 0.0358 for I > 2 sigma I with N:O = 0.91:0.09) is determined by isolated {La(4)Z} tetrahedra surrounded by and connected through bromide ligands. In the crystal structure of Ce(9)Z(4)I(16) (2, orthorhombic, Fddd, Z = 8, a = 890.0(1), b = 2264.1(2), c = 4279.5(4) pm, R-1 = 0.0262 for I > 2 sigma I with N:O 0.75:0.25), {Ce(4)Z} tetrahedra are connected to {Ce(4/2)Z} chains via common edges and further to layers by iodide ligands. The layers are stacked and connected via the ninth cerium atom according to Ce[{Ce(4/2)Z}I-4](4). Similar {La(4/2)Z} chains and BaI8/4 chains run perpendicularly to each other and are connected via common iodide ions in the crystal structure of BaLa(4)Z(2)I(8) = Ba-2[{La(4/2)Z}I-4](4) (3, monoclinic, C2/c, Z = 4, a = 897.5(1), b = 2162.4(3), c = 1229.3(2), beta = 110.32(1)degrees, R-1 = 0.0261 for I > 2 sigma I with N:O = 0.54:0.46). The nature of the interstitial Z, oxygen and/or nitrogen, is evaluated.