Kinetic and Mechanistic Characterization of Low-Overpotential, H2O2-Selective Reduction of O2 Catalyzed by N2O2-Ligated Cobalt Complexes
| Autor: | Yu-Heng Wang, James B. Gerken, Soumya Ghosh, Zachary K. Goldsmith, Sharon Hammes-Schiffer, Shannon S. Stahl, Colin W. Anson, Patrick E. Schneider |
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| Rok vydání: | 2018 |
| Předmět: |
010405 organic chemistry
chemistry.chemical_element Protonation General Chemistry Overpotential 010402 general chemistry 01 natural sciences Biochemistry Combinatorial chemistry Catalysis 0104 chemical sciences Decamethylferrocene chemistry.chemical_compound Colloid and Surface Chemistry chemistry Catalytic cycle Selective reduction Differential pulse voltammetry Cobalt |
| Zdroj: | Journal of the American Chemical Society. 140:10890-10899 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/jacs.8b06394 |
| Popis: | A soluble, bis-ketiminate-ligated Co complex [Co(N2O2)] was recently shown to catalyze selective reduction of O2 to H2O2 with an overpotential as low as 90 mV. Here we report experimental and computational mechanistic studies of the Co(N2O2)-catalyzed O2 reduction reaction (ORR) with decamethylferrocene (Fc*) as the reductant in the presence of AcOH in MeOH. Analysis of the Co/O2 binding stoichiometry and kinetic studies support an O2 reduction pathway involving a mononuclear cobalt species. The catalytic rate exhibits a first-order kinetic dependence on [Co(N2O2)] and [AcOH], but no dependence on [Fc*] or [O2]. Differential pulse voltammetry and computational studies support CoIII-hydroperoxide as the catalyst resting state and protonation of this species as the rate-limiting step of the catalytic reaction. These results contrast previous mechanisms proposed for other Co-catalyzed ORR systems, which commonly feature rate-limiting protonation of a CoIII-superoxide adduct earlier in the catalytic cycle. Co... |
| Databáze: | OpenAIRE |
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