Exploring the Frontiers of Heterometallic Systems: the {FeW 5 } 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 [FeW 5 Br 14 ] (TBA = tetrabutylammonium), exhibits selective ligand substitution reactions at the iron site when exposed to various solvents. Several {FeW 5 }-type anions, namely, [FeW 5 Br 14 ] 2- , [FeW 5 Br 13 (L)] - (L = H 2 O, DMSO, CH 3 CN), and [(FeW 5 Br 13 ) 2 O] 4- , were revealed and characterized by single-crystal X-ray diffraction analysis. The redox properties of [FeW 5 Br 14 ] 2- were studied and compared with those of [W 6 Br 14 ] 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 {M 6 } clusters.