Characterization of an Iron–Ruthenium Interaction in a Ferrocene Diamide Complex

Reaction of [fc­(NH2)2]­RuCl2(PPh3)2 (fc = 1,1′-ferrocenylene) with 2 equiv of KOtBu led to the formation of a diamido ruthenium complex, [fc­(NH)2]­Ru­(PPh3)2, whose solid-state molecular structure revealed a short Fe–Ru distance. A metal-to-metal charge transfer band was observed in the electronic absorption spectrum of [fc­(NH)2]­Ru­(PPh3)2. The Fe–Ru interaction was characterized by resonance Raman spectroscopy for the first time and also by 1H NMR, UV–vis, NIR, Mössbauer spectroscopy, and X-ray crystallography. Density functional theory (DFT) calculations including natural bond order analysis, Bader’s atom in molecules method, and time-dependent DFT (TDDFT) provided further support that the iron–ruthenium bond is a weak donor–acceptor interaction with iron acting as the Lewis base.