Iodine-mediated substitution of terminal ligands in [{M6I8}I6]2– (M = Mo, W) by DMSO

Abstract

The family of octahedral iodide cluster complexes of molybdenum and tungsten – [{M6I8}L6]n – exhibit a unique set of properties with significant practical potential. Due to the strong influence of terminal ligands L on these properties, the search for new simpler, more convenient and cheaper approaches for their substitution is an urgent task. This work demonstrates a new one-step method for terminal ligand substitution using well-known and readily available complexes [{M6I8}I6]2–. The synthetic technique involves the addition of molecular iodine to the reaction mixture in order to bind the released I– ions, thereby facilitating the reaction process. As a result, two new cluster complexes with dimethyl sulfoxide ligands [{M6I8}(DMSO)6](I3)4 (M = Mo (1), W (2)) have been obtained and structurally characterized. The optical properties of the obtained compounds have been studied both in solid state and in solution, and Eg values have been calculated from the solid-state absorption spectra. The presence of I3– anions has been shown to quench the emission of the cluster complexes, explaining the absence of luminescence in the obtained compounds.