The cube-shaped main group element clusters (Bi4S4)4+ and (Bi4Se4)4+ synthesis from chloroaluminate melts, crystal structures and vibrational spectra

The reaction of bismuth and bismuth trichloride with sulfur or selenium, respectively, in a AlCl3/NaCl melt at 130 degreesC leads to (Bi4S4)[AlCI4](4) 1 and (Bi4Se4)[AlCl4](4) 2 in the form of red and amber colored crystals. Both crystallize isotypically in the tetragonal space group 14 with the lattice constants a = 1181.60(2), c = 1104.75(2) pm for I and a = 1199.32(2), c = 1118.64(3) pin for 2. Besides the nearly regular tetrahedral [AlCl4](-) ions the structures contain (Bi4S4)(4+) and (Bi4Se4)(4+) cations. These ions are actually of crystallographic S-4 symmetry but deviate only slightly from the ideal cubic symmetry. Bi and chalcogen atoms occupy alternatingly the corners of the cubes. 1 and 2 are isotypical to the already known (Bi4Te4)[AlCl4](4), so the series of the cube-shaped (Bi4E4)(4+) ions (E = S, Se, Te) is now complete. Infrared und Raman spectra of I und 2 show the vibration modes of both kinds of ions in the region 50 - 600cm(-1). Symmetry analysis and normal mode calculations of the vibrational spectra confirm the local symmetry of the (Bi4E4) clusters and the [AlCl4] groups.