抄録
Transition metal complexes containing a metal–metal bond have received considerable attention not only due to fundamental understanding of their bonding nature but also their potential applications. In this report, the first example of a Werner-type Fe2 dinuclear complex containing an unsupported metal–metal bond will be introduced, which was reported by Wieghardt's group this year. The use of a redox-active ligand may be a key factor to obtain this unprecedented complex. The reduction of the reported complex, [FeII(tim0)(MeCN)2]2+, gave the Fe2 dimeric complex, [{Fe(tim)}2], having an unsupported Fe–Fe bond with a relatively long bond distance of 2.69 Å. The bonding nature was determined by magnetic measurements, Mössbauer and absorption spectra, and DFT calculation. As a result, they concluded that the dimeric complex is represented by a mixed-valent species with respect to both the metal and ligand, described as [{Fe2.5(tim2.5-)}2]. The Fe–Fe bond is accounted for by the dz2–dz2 interaction between the two Fe ions, and the presence of a doubly occupied σ orbital and a singly occupied σ* orbital indicates a formal metal–metal bond order of 0.5.
