title: Lead rare-earth oxyhalides: syntheses and characterization of Pb6LaO7X (X = Cl, Br).
abstract: Yellowish elongated crystals of the two new compounds Pb6LaO7Br (1) and Pb6LaO7Cl (2) have been obtained by the method of solid-state reactions. Both structures can be described in the terms of oxo-centered tetrahedra. The structures of 1 and 2 consist of [O7Pb6La]+ chains that are built from oxocentered OA4 (A = Pb, La) tetrahedra. The halogen ions connect the chains through weak Pb-X bonds. An arrangement of eight OA4 tetrahedra that all share the same central La atom forms a [O8Pb10La3]13+ cluster. The clusters are linked into chains, and additional OPb4 tetrahedra are attached to the chains. Incorporation of Cl atoms instead of Br atoms into the structure causes a lowering of the symmetry from Cmcm to C2/m.
authors.affiliation: Department of Crystallography, St. Petersburg State University, University Emb. 7/9, 199034 St. Petersburg, Russia.
authors.forename: Oleg I
authors.initials: OI
authors.lastname: Siidra
authors.forename: Sergey V
authors.initials: SV
authors.lastname: Krivovichev
authors.forename: Thomas
authors.initials: T
authors.lastname: Armbruster
authors.forename: Wulf
authors.initials: W
authors.lastname: Depmeier
mesh_terms: D018360:Crystallography, X-Ray; D006219:Halogens / Q000737:chemistry*; D007854:Lead / Q000737:chemistry*; D008674:Metals, Rare Earth / Q000737:chemistry*; D008958:Models, Molecular
chemical_list: D006219:Halogens; D008674:Metals, Rare Earth; D007854:Lead