Affiliation:
1. Faculty of Chemistry and Food Chemistry Technische Universität Dresden 01062 Dresden Germany
2. Würzburg-Dresden Cluster of Excellence ct.qmat Technische Universität Dresden 01062 Dresden Germany
3. Max Planck Institute for Chemical Physics of Solids Nöthnitzer Straße 40 01187 Dresden Germany
Abstract
AbstractBlack needle‐shaped crystals of the bismuth‐rich mixed halogenide Bi21Rh4Cl6I7were obtained by slow cooling of a melt of Bi, RhI3and BiCl3. Single‐crystal X‐ray diffraction revealed an orthorhombic structure that consists of infinite intermetallic rodsBi9Rh2]3+and discrete anionic groups [BiII2Cl2I5]3−and [BiIIICl4I2]3−. The rods consist of Rh‐centered [RhBi8] polyhedra that alternately share triangular and rectangular faces. Using traditional electron counting rules, the rod can be interpreted as a covalent polymer with Rh2dumbbells bonded to molecular Bi2and Bi5units. However, a quantum‐chemical bonding analysis shows that the bonds involving Rh atoms are largely diffuse, while two‐center bonds dominate in the bismuth units. The below 240 K observed semiconducting behavior of Bi21Rh4Cl6I7is consistent with a complete localization of the valence electrons. Above 240 K, the resistance along the needle axis is largely independent of temperature.