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 KO(t)Bu 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 (1)H 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.