Synthese und Kristallstruktur einer Neuen hexagonalen Modifikation von Al2S3 mit fünffach koordiniertem Aluminium

Synthesis and Crystal Structure of a Novel Hexagonal Modification of Al₂S₃ with Five-coordinated Aluminum A new hexagonal high temperature modification of Al₂S₃ could be prepared by chemical vapour transport with iodine (860 → 750°C) or by annealing of α -Al₂S₃ at 550°C. According to the single crystal X-ray structure determination the novel form of Al₂S₃ crystallizes in space group P 6₁ (No. 169) with a = 6.491(1), c = 17.169(4) Å, V = 626.5 ų, Z = 6; R = 0.0253. In this modification one half of the aluminum atoms are tetrahedrally coordinated d(Al? S): 2.226–2.267 Å], whereas the other half are in trigonal bipyramidal coordination of five S atoms with bond lengths of 2.272–2.315 Å (equatorial) and 2.495–2.521 Å (axial). Aluminum in AlS₅ coordination is observed for the first time in this compound. The crystal structure is isotypic to In₂Se₃ and AlInS₃. In addition, results of a refinement of the α -Al₂S₃ crystal structure are reported which were obtained on crystals prepared also by chemical vapour transport with iodine.