Mononuclear Manganese(III) Superoxo Complexes: Synthesis, Characterization, and Reactivity
| Autor: | Maurice van Gastel, Chi-Yi Chu, Hanna H. Cramer, Shengfa Ye, Eckhard Bill, I-Ren Lee, Yen Hao Lin, Way Zen Lee, Ting-Shen Kuo, Yi-Hsuan Tsai |
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| Rok vydání: | 2019 |
| Předmět: |
Ligand
chemistry.chemical_element Manganese Resonance (chemistry) Medicinal chemistry Article law.invention Inorganic Chemistry chemistry.chemical_compound chemistry Transition metal Catalytic cycle law Pyridine Reactivity (chemistry) Physical and Theoretical Chemistry Electron paramagnetic resonance |
| Zdroj: | Inorganic Chemistry |
| ISSN: | 1520-510X 0020-1669 |
| DOI: | 10.1021/acs.inorgchem.9b00767 |
| Popis: | Metal–superoxo species are typically proposed as key intermediates in the catalytic cycle of dioxygen activation by metalloenzymes involving different transition metal cofactors. In this regard, while a series of Fe–, Co–, and Ni–superoxo complexes have been reported to date, well-defined Mn–superoxo complexes remain rather rare. Herein, we report two mononuclear MnIII–superoxo species, Mn(BDPP)(O2•–) (2, H2BDPP = 2,6-bis((2-(S)-diphenylhydroxylmethyl-1-pyrrolidinyl)methyl)pyridine) and Mn(BDPBrP)(O2•–) (2′, H2BDPBrP = 2,6-bis((2-(S)-di(4-bromo)phenylhydroxyl-methyl-1-pyrrolidinyl)methyl)pyridine), synthesized by bubbling O2 into solutions of their MnII precursors, Mn(BDPP) (1) and Mn(BDPBrP) (1′), at −80 °C. A combined spectroscopic (resonance Raman and electron paramagnetic resonance (EPR) spectroscopy) and computational study evidence that both complexes contain a high-spin MnIII center (SMn = 2) antiferromagnetically coupled to a superoxo radical ligand (SOO• = 1/2), yielding an overall S = 3/2 ground state. Complexes 2 and 2′ were shown to be capable of abstracting a H atom from 2,2,6,6-tetramethyl-1-hydroxypiperidine (TEMPO-H) to form MnIII–hydroperoxo species, Mn(BDPP)(OOH) (5) and Mn(BDPBrP)(OOH) (5′). Complexes 5 and 5′ can be independently prepared by the reactions of the isolated MnIII-aqua complexes, [Mn(BDPP)(H2O)]OTf (6) and [Mn(BDPBrP)(H2O)]OTf (6′), with H2O2 in the presence of NEt3. The parallel-mode EPR measurements established a high-spin S = 2 ground state for 5 and 5′. Two mononuclear MnIII−superoxo complexes, synthesized by bubbling O2 into solutions of their MnII precursors at −80 °C and well-characterized spectroscopically and computationally, were shown to be capable of abstracting a H atom from TEMPO-H to form MnIII−hydroperoxo species. |
| Databáze: | OpenAIRE |
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