mer-Trichloridotris(tetrahydrothiophene-κS)-iridium(III): preparation and comparison with other mer trichloridotris(tetrahydrothiophene-κS)metal complexes

The title complex, [IrCl₃(C₄H₈S)₃], was prepared according to a literature method. A suitable crystal was obtained by diffusion of pentane into a di­chloro­methane solution and analyzed by single-crystal X-ray diffraction at 100 K. The title complex is isotypic with mer-tri­chlorido­tris­(tetra­hydro­thio­phene-κS)rhodium(III). However, the orientation of the tetra­hydro­thio­phene rings is different from an earlier report of mer-tri­chlorido­tris­(tetra­hydro­thio­phene-κS)iridium(III) deposited in the Cambridge Structural Database. The IrS₃Cl₃ core shows a nearly octa­hedral structure with various bond angles within 1-2° of the perfect 90 or 180° expected for an octa­hedron. The structure of the title compound is compared with the previous iridium complex as well as the rhodium and other octa­hedral metal tris-tetra­hydro­thio­phene compounds previously structurally characterized. DFT calculations were performed, which indicate the mer isomer is significantly lower in energy than the fac isomer by 50.1 kJ mol⁻¹, thereby accounting for all compounds in the CSD being of the mer geometry. Powder X-ray diffraction of the bulk material showed that the preparation method yielded only the isomorph reported in this communication.