Pentagonal Bismuth Antiprisms with Endohedral Palladium or Platinum Atoms by Low‐Temperature Syntheses

Abstract

We present the syntheses, crystal structures, and properties of five metal‐rich salts containing the Bi104+ pentagonal antiprism with an endohedral palladium or, for the first time, platinum atom. Tetragonal [Pt@Bi10](AlBr4)4 [P42/n at 296(1) K; P4 at 150(2) K] was obtained by reacting platinum, bismuth, and bismuth tribromide in [BMIm]Br·4.1AlBr3 at 140 °C (BMIm = 1‐butyl‐3‐methylimidazolium). Monoclinic [Pt@Bi10](AlBr4)2(Al2Br7)2 [P21/n] occurs as by‐product. The two corresponding palladium compounds result from the dissolution of Bi16PdCl22 in [BMIm]Br·4.1AlBr3. [Pd@Bi10](AlBr4)4 [P42/n] adopts a disordered structure homeotypic to its platinum analog. [Pd@Bi10](AlBr4)2(Al2Br7)2 [P21/n] is isostructural to [Pt@Bi10](AlBr4)2(Al2Br7)2. In all structures, the [M@Bi10]4+ cations are well separated by the bromido‐aluminate anions with inter‐cluster Bi···Bi distances longer than 520 pm. This is not the case in [Pd@Bi10][Bi2Sn6Cl22], which crystallized from a tin‐containing melt of the metals and BiCl3. In its monoclinic structure [P21/c], the cluster cations are arranged in chains along [001] with an inter‐cluster distance of only 357 pm. Despite further structural evidence, DFT‐based quantum chemical analysis gave no hint on inter‐cluster bonding. According to the calculated band structure as well as resistivity and magnetic susceptibility measurements, the black compound is a diamagnetic semiconductor.