Exploring the Frontiers of Heterometallic Systems: the {FeW5} Octahedral Cluster Complex

This research presents the first examples of heterometallic octahedral cluster complexes incorporating both 5d and 3d metals, specifically, tungsten and iron. The key compound, (TBA)2[FeW5Br14] (TBA = tetrabutylammonium), exhibits selective ligand substitution reactions at the iron site when exposed to various solvents. Several {FeW5}-type anions, namely, [FeW5Br14]2–, [FeW5Br13(L)]− (L = H2O, DMSO, CH3CN), and [(FeW5Br13)2O]4–, were revealed and characterized by single-crystal X-ray diffraction analysis. The redox properties of [FeW5Br14]2– were studied and compared with those of [W6Br14]2–. Density functional theory calculations demonstrated that the bonding between Fe and W atoms is fundamentally different from the bonding between 4d (Mo–Mo) or 5d (W–W) metals in isotypic {M6} clusters.