title: Structure and bonding of Bi4Ir: a difficult-to-access bismuth iridide with a unique framework structure.
abstract: Crystals of Bi(4)Ir, a new intermetallic compound, were obtained by the reaction of an iridium-containing intermetallic precursor with liquid bismuth. X-ray diffraction on a single crystal revealed a rhombohedral structure [R3̅m, a = 2656.7(2) pm, and c = 701.6(4) pm]. Bi(4)Ir is not isostructural to Bi(4)Rh but combines motifs of the metastable superconductor Bi1(4)Rh(3) with those found in the weak topological insulator Bi1(4)Rh(3)I(9). The two crystallographically independent iridium sites in Bi(4)Ir have square-prismatic and skewed-square-antiprismatic bismuth coordination with Bi-Ir distances of 283-287 pm. By sharing common edges, the two types of [IrBi(8)] units constitute a complex three-dimensional network of rings and helices. The bonding in the heterometallic framework is dominated by pairwise Bi-Ir interactions. In addition, three-center bonds are found in the bismuth triangles formed by adjacent [IrBi(8)] polyhedra. Density functional theory based band-structure calculations suggest metallic properties.
authors.affiliation: Department of Chemistry and Food Chemistry, Technische Universität Dresden , 01062 Dresden, Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Isaeva
authors.forename: Michael
authors.initials: M
authors.lastname: Ruck
authors.forename: Konrad
authors.initials: K
authors.lastname: Schäfer
authors.forename: Ute Ch
authors.initials: UCh
authors.lastname: Rodewald
authors.forename: Rainer
authors.initials: R
authors.lastname: Pöttgen