A Tale of Two Complexes: Electro-Assisted Oxidation of Thioanisole by an "O 2 Activator/Oxidizing Species" Tandem System of Non-Heme Iron Complexes.

We report two new Fe III complexes [L 1 Fe III (H 2 O)](OTf) 2 and [L 2 Fe III (OTf)], obtained by replacing pyridines by phenolates in a known non-heme aminopyridine iron complex. While the original, starting aminopyridine [(L 5 2 )Fe II (MeCN)](PF 6 ) complex is stable in air, the potentials of the new Fe III/II couples decrease to the point that [L 2 Fe II ] spontaneously reduces O 2 to superoxide. We used it as an O 2 activator in an electrochemical setup, as its presence allows to generate superoxide at a much more accessible potential (>500 mV gain). Our aim was to achieve substrate oxidation via the reductive activation of O 2 . While L 2 Fe III (OTf) proved to be a good O 2 activator but a poor oxidation system, its association with another complex (TPEN)Fe II (PF 6 ) 2 generates a complementary tandem couple for electro-assisted oxidation of substrates, working at a very accessible potential: upon reduction, L 2 Fe III (OTf) activates O 2 to superoxide and transfers it to (TPEN)Fe II (PF 6 ) 2 leading in fine to the oxidation of thioanisole.