ChemInform Abstract: Polymorphism of In5S5Cl - X-Ray and HRTEM-Investigations

In5S5Cl belongs to the group of mixed valence indium compounds with indium occurring simultaneously in three oxidation states (In5S5Cl = In+(In2)4+2In3+5S2–Cl–). It was shown in an earlier work that In5S5Cl obtained from InCl3, indium and sulfur at 550 °C, crystallises in a monoclinic structure type in contrast to the orthorhombic bromide, In5S5Br. The main difference of both structure types is an ordered mutual exchange of In+ and (In2)4+ in specific crystallographic positions. This exchange is possible due to the almost identical coordination pattern of both ions. A closer inspection of the real structure of monoclinic In5S5Cl by High Resolution Transmission Microscopy (HRTEM) already showed the presence of small orthorhombic domains in the real structure of this compound. Now we also obtained macroscopic quantities of orthorhombic In5S5Cl by the reaction of InCl3, indium and sulfur at reaction temperatures below 500 °C (Pmn21, a = 3.907(1) A, b = 9.021(2) A, c = 14.866(3) A, Z = 2). The new polymorph is analysed by X-ray single crystal and X-ray powder diffraction and HRTEM investigations.