β‐[SbI₂][AlI₄] – A Second Polymorph of Diiodidoantimony‐Tetraiodido Aluminate with a Polymeric Structure

Abstract

The reaction of antimony triiodide and aluminum triiodide at 160 °C yields orange crystals of β‐[SbI2][AlI4] (1) via gas phase deposition. This second polymorph of [SbI2][AlI4] crystallizes monoclinic in space group P21/n and is built of [SbI2]+ and [AlI4]– ions connected via long Sb–I bonds. Sb is coordinated in form of a distorted square pyramid. These SbI5 polyhedra are connected alternately by edges and corners by almost regular tetrahedral tetraiodido aluminate units to undulated [SbI2AlI4]n chains. This stands in contrast to the molecular structure of the α polymorph consisting of molecular, tetranuclear units ([SbI2][AlI4])2. The Raman vibrational spectra were calculated at density‐functional (DFT) level and compared to the experimental spectrum. Additionally, the normal modes were analysed.