title: Mixed pentele-chalcogen cationic chains from aluminum and gallium halide melts.
abstract: The reactions of tellurium or selenium with bismuth or antimony in chloridogallate and iodidoaluminate melts in the presence of group 15 trihalides as weak oxidants yielded the compounds (Sb2Te2)[GaCl4] (1), (Sb2Te2)I[AlI4] (2), (Bi2Te2)Cl[GaCl4] (3a), (Bi2Se2)Cl[GaCl4] (3b), (Sb3Te4)[GaCl4] (4), and (SbTe4)[Ga2Cl7] (5). In the crystal structures one-dimensional polymeric cations (Sb2Te2(+))n (1), (Sb2Te2(2+))n (2), (Bi2Te2(2+))n (3a), (Bi2Se2(2+))n (3b), (Sb3Te4(+))n (4), and (SbTe4(+))n (5) are present. The polymeric cationic strands in 2, 3a, 3b, and 4 consist of pentele/chalcogen dumbbells, which are connected to ladder-shaped bands. The strands in 1 and 5 consist of condensed rings that involve four-membered Sb2Te2 rings for 1, and five-membered SbTe4 rings for 5. The counteranions are the weakly coordinating [GaCl4](-), [AlI4](-), and [Ga2Cl7](-) in addition to Cl(-) and I(-) anions, which are coordinated to the atoms of the cations. The crystal structures of 1-4 are characterized by a statistical disorder in the anions with alternatively occupied positions for the Al and Ga atoms. For 4 superstructure reflections appear in the diffractions patterns, indicating a partial order. A correct assignment of the Sb and Te positions in the cation of 5 was achieved by periodic quantum-chemical calculations, which were performed via a Hartree-Fock density functional theory hybrid method. A clear preference of the 4-fold coordinated site was obtained for Sb.
authors.affiliation: Institute for Inorganic Chemistry, University of Bonn , Gerhard-Domagk-Strasse 1, 53121 Bonn, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Eich
authors.forename: Thomas
authors.initials: T
authors.lastname: Bredow
authors.forename: Johannes
authors.initials: J
authors.lastname: Beck