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A Structurally Characterized Nonheme Cobalt-Hydroperoxo Complex Derived from Its Superoxo Intermediate via Hydrogen
Chun-Chieh Wang1,2, Hao-Ching Chang1, Yei-Chen Lai2
1Department of Chemistry and Instrumentation Center, National Taiwan Normal University , Taipei 11677, Taiwan.
Journal of the American Chemical Society
|October 12, 2016
Summary
Cobalt(III)-superoxo complexes activate molecular oxygen, forming hydroperoxo species. This oxygen activation mechanism is crucial for understanding cobalt-catalyzed aerobic oxidations and the action of Co-bleomycin.
Area of Science:
- Inorganic Chemistry
- Bioinorganic Chemistry
- Catalysis
Background:
- Cobalt complexes are known catalysts for aerobic oxidation reactions.
- The mechanism of oxygen activation by cobalt species is not fully understood.
- Understanding these mechanisms is vital for applications in catalysis and medicine, such as with Co-bleomycin.
Purpose of the Study:
- To investigate the formation and reactivity of cobalt-oxygen adducts.
- To elucidate the mechanism of oxygen activation by cobalt complexes.
- To explore the role of cobalt-superoxo intermediates in hydrogen atom abstraction.
Main Methods:
- Reaction of cobalt(II) complex with oxygen at low temperature.
- Spectroscopic characterization using resonance Raman and Electron Paramagnetic Resonance (EPR).
- Structural characterization of cobalt-hydroperoxo complex.
Main Results:
- Formation of a cobalt(III)-superoxo adduct (Co(BDPP)(O2)) from cobalt(II) precursor.
- Characterization of the adduct as a low-spin cobalt(III) ion bound to a superoxo ligand.
- Demonstration that the cobalt(III)-superoxo species can abstract hydrogen atoms, forming a cobalt(III)-hydroperoxo complex.
Conclusions:
- Cobalt(III)-superoxo complexes are capable of hydrogen atom abstraction.
- A stepwise oxygen activation process involving cobalt-superoxo intermediates is proposed.
- This mechanism provides insight into cobalt-catalyzed aerobic oxidations and Co-bleomycin's function.
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