Electron transfer reactions of bis[dicarbonyl(pentamethylcyclopentadienyl)iron] with organic compounds

[(C5Me5)Fe(CO)2]2 (A) reacts with one equivalent of tetracyanoethylene (TCNE) and tetracyanoquinodimethane (TCNQ) to give the compounds {2[(C5Me5)Fe+(CO)2]·TCNE2-} (B) and {2[(C5Me5)Fe+(CO)2]·TCNQ2-} (D) respectively. The reaction of A with two equivalents of TCNE gives the polymeric compound [(C5Me5)Fe(CO)2TCNE]n (C) in which the TCNE2- anion is coordinated to the metal through nitrogen of the CN group. Electronic, IR and ESR spectra indicate that compounds B and D are formed by two one-electron steps involving the rather elusive [(C5Me5)Fe(CO)2{radical dot}] radicals. The electron transfer processes are discussed on the basis of the thermodynamic redox potentials of donor A and of two acceptors TCNE and TCNQ. © 1987.