Characterization of a Paramagnetic Mononuclear Nonheme Iron-Superoxo Complex

摘要

O_2 bubbling into a THF solution of Fe~Ⅱ(BDPP) (1) at -80 ℃ generates a reversible bright yellow adduct 2. Characterization by resonance Raman and Moessbauer 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 υ(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 Fe~Ⅲ-O_2~- pair found for the O_2 adduct of 4-nitrocatechol-bound homoprotocatechuate 2,3-dioxygenase. Lastly, 2 oxidizes dihydroanthracene to anthracene, supporting the notion that Fe~Ⅲ-O_2~- 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.