• Cluster compounds;
  • Polycations;
  • Phase transitions;
  • Raman spectroscopy;
  • 77Se NMR spectroscopy


The reactions of elemental antimony, tellurium, selenium and sulfur as well as antimony telluride and antimony sulfide in melts composed of GaCl3/SbCl3/ACl (A = Cu+, Ag+, PPh4+) yielded Ag(Sb7Te8)[GaCl4]6 (1), (Sb7Se8)[GaCl4]2[Ga2Cl7]3 (2), (Sb7Se8Cl2)[GaCl4]3 (3) and (Sb7S8Cl2)[GaCl4]3 (4). SbCl3 plays the role of the oxidant, and GaCl3 plays the role of the Lewis acidic chloride ion acceptor. All of the compounds form orange, air-sensitive crystals. The crystal structures consist of discrete, double-cube-shaped, mixed antimony–chalcogen cationic clusters (Sb7Te8)5+, (Sb7Se8)5+, (Sb7Se8Cl2)3+ and (Sb7S8Cl2)3+. The anions are discrete chloridogallate [GaCl4] and [Ga2Cl7] anions. All compounds were characterized by single-crystal X-ray diffraction, energy-dispersive electron-beam X-ray fluorescence spectroscopy, Raman vibrational spectroscopy and solid-state 77Se NMR spectroscopy. Supporting gas-phase and periodic DFT calculations allowed the assignments of the spectra and provided insights into the bonding situation of the hypervalent Sb atoms.