Synthesis, Characterization, and Reactivity of Low-Valent Iron Corroles

Studies of metallocorroles in low formal oxidation states are quite rare as the trianionic ligand has traditionally been utilized for stabilizing high oxidation states. To address this deficiency, we have examined the stepwise reduction of iron complexes containing the triphenylcorrolate ligand (TPC). Reaction of [Fe(THF)(TPC)] with KC8 generates the iron corrole anion, [Fe(TPC)]−. Isolation and crystallographic characterization of [Fe(TPC)]− represents the first instance of a fully characterized corrole complex of divalent iron. Treatment of this species with molecular oxygen at -78 °C generates the spectroscopically observed iron(III) superoxo correlate, [Fe(O2-·)(TPC)]-. Treatment of [Fe(TPC)]- with alkyl halides results formal oxidative addition to form the tetravalent alkyl species [Fe(R)(TPC)] (R = Me, Et, i-Pr, Cy, 1-Ad, t-Bu, Bn). These unique iron(IV) organometallic compounds are resistant to β-H elimination and demonstrate stabilities that correlate with the ease of Fe−C homolysis. The iron corrole anion activates organic azides forming a reactive iron nitrene species, [Fe(NR)(TPC)]-. Boc2O assisted intramolecular C-H amination of (4-azidobutyl)benzene resulted in the Boc-protected amine products, 2-phenylpyrrolidine and 4-phenylbutan-1-amine. One electron reduction of the iron(II) corrole anion generates a dianionic corrole species, [Fe(TPC)]2-, capable of CO2 activation.