Characterization of a Paramagnetic Mononuclear Nonheme Iron-Superoxo Complex

O2 bubbling into a THF solution of FeII(BDPP) (1) at −80 °C generates a reversible bright yellow adduct 2. Characterization by resonance Raman and Mössbauer spectroscopy provides complementary insights into the nature of 2. The former shows a resonance-enhanced vibration at 1125 cm–1, which can be assigned to the ν­(O–O) of a bound super­oxide, while the latter reveals the presence of a high-spin iron­(III) center that is exchange-coupled to the superoxo ligand, like the FeIII–O2– pair found for the O2 adduct of 4-nitro­catechol-bound homo­proto­catechuate 2,3-dioxy­genase. Lastly, 2 oxidizes dihydro­anthracene to anthracene, supporting the notion that FeIII–O2– species can carry out H atom abstraction from a C–H bond to initiate the 4-electron oxidation of substrates proposed for some nonheme iron enzymes.