Opening the CoIII,IV2(μ-O)2 Diamond Core by Lewis Bases Leads to Enhanced C–H Bond Cleaving Reactivity
| Autor: | Yan Li, Yisong Guo, Dong Wang, Marat R. Talipov, Suhashini Handunneththige, Jin Xiong |
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| Rok vydání: | 2020 |
| Předmět: |
biology
Chemistry Methane monooxygenase Diamond General Chemistry engineering.material Biochemistry Catalysis law.invention Delocalized electron Crystallography Colloid and Surface Chemistry Catalytic cycle law engineering biology.protein Reactivity (chemistry) Lewis acids and bases Electron paramagnetic resonance Isomerization |
| Zdroj: | Journal of the American Chemical Society. 142:21670-21678 |
| ISSN: | 1520-5126 0002-7863 |
| Popis: | The high-valent diiron(IV) intermediate Q is the key oxidant that cleaves strong C-H bonds of methane in the catalytic cycle of soluble methane monooxygenase (sMMO). sMMO-Q was previously reported as a bis-μ-oxo FeIV2(μ-O)2 diamond core but was recently described to have an open core with a long Fe···Fe distance. We recently reported a high-valent CoIII,IV2(μ-O)2 diamond core complex (1) that is highly reactive with sp3 C-H bonds. In this work, we demonstrated that the C-H bond cleaving reactivity of 1 can be further enhanced by introducing a Lewis base X, affording faster kinetic rate constants and the ability to cleave stronger C-H bonds compared to 1. We proposed that 1 first reacts with X in a fast equilibrium to form an open core species X-CoIII-O-CoIV-O (1-X). We were able to characterize 1-X using EPR spectroscopy and DFT calculations. 1-X exhibited an S = 1/2 EPR signal distinct from that of the parent complex 1. DFT calculations showed that 1-X has an open core with the spin density heavily delocalized in the CoIV-O unit. Moreover, 1-X has a more favorable thermodynamic driving force and a smaller activation barrier than 1 to carry out C-H bond activation reactions. Notably, 1-X is at least 4 orders of magnitude more reactive than its diiron open core analogues. Our findings indicate that the diamond core isomerization is likely a practical enzymatic strategy to unmask the strong oxidizing power of sMMO-Q necessary to attack the highly inert C-H bonds of methane. |
| Databáze: | OpenAIRE |
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