Catalytic two-electron reduction of dioxygen by ferrocene derivatives with manganese(V) corroles

Jieun Jung, Shuo Liu, Kei Ohkubo, Mahdi M. Abu-Omar, Shunichi Fukuzumi

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33 Scopus citations

Abstract

Electron transfer from octamethylferrocene (Me8Fc) to the manganese(V) imidocorrole complex (tpfc)MnV(NAr) [tpfc = 5,10,15-tris(pentafluorophenyl)corrole; Ar = 2,6-Cl2C6H3] proceeds efficiently to give an octamethylferrocenium ion (Me8Fc+) and [(tpfc)MnIV(NAr)]- in acetonitrile (MeCN) at 298 K. Upon the addition of trifluoroacetic acid (TFA), further reduction of [(tpfc)MnIV(NAr)]- by Me8Fc gives (tpfc)MnIII and ArNH2 in deaerated MeCN. TFA also results in hydrolysis of (tpfc)MnV(NAr) with residual water to produce a protonated manganese(V) oxocorrole complex ([(tpfc)MnV(OH)]+) in deaerated MeCN. [(tpfc)MnV(OH)]+ is rapidly reduced by 2 equiv of Me8Fc in the presence of TFA to give (tpfc)MnIII in deaerated MeCN. In the presence of dioxygen (O2), (tpfc)MnIII catalyzes the two-electron reduction of O2 by Me8Fc with TFA in MeCN to produce H2O2 and Me8Fc+. The rate of formation of Me8Fc+ in the catalytic reduction of O2 follows zeroth-order kinetics with respect to the concentrations of Me8Fc and TFA, whereas the rate increases linearly with increasing concentrations of (tpfc)MnV(NAr) and O2. These kinetic dependencies are consistent with the rate-determining step being electron transfer from (tpfc)MnIII to O2, followed by further proton-coupled electron transfer from Me8Fc to produce H2O2 and [(tpfc)MnIV]+. Rapid electron transfer from Me8Fc to [(tpfc)MnIV]+ regenerates (tpfc)MnIII, completing the catalytic cycle. Thus, catalytic two-electron reduction of O2 by Me8Fc with (tpfc)MnV(NAr) as a catalyst precursor proceeds via a MnIII/MnIV redox cycle.

Original languageEnglish
Pages (from-to)4285-4291
Number of pages7
JournalInorganic Chemistry
Volume54
Issue number9
DOIs
StatePublished - 4 May 2015

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© 2015 American Chemical Society.

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