Mechanistic insights into dioxygen activation by a manganese corrole complex: a broken-symmetry DFT study

• Published in: RSC advances Vol. 11; no. 4; pp. 24852 - 24861
• Main Authors: Yu, Jiangfeng, Lai, Wenzhen
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 16.07.2021; The Royal Society of Chemistry
• Subjects: Cartesian coordinates; Chemistry; Density functional theory; Donors (electronic); Electron transfer; Endothermic reactions; Hydrogen; Ligands; Manganese; Oxidation; Oxidizing agents; Substrates
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/d1ra02722k

The Mn-oxygen species have been implicated as key intermediates in various Mn-mediated oxidation reactions. However, artificial oxidants were often used for the synthesis of the Mn-oxygen intermediates. Remarkably, the Mn( v )-oxo and Mn( iv )-peroxo species have been observed in the activation of O 2 by Mn( iii ) corroles in the presence of base (OH − ) and hydrogen donors. In this work, density functional theory methods were used to get insight into the mechanism of dioxygen activation and formation of Mn( v )-oxo. The results demonstrated that the dioxygen cannot bind to Mn without the axial OH − ligand. Upon the addition of the axial OH − ligand, the dioxygen can bind to Mn in an end-on fashion to give the Mn( iv )-superoxo species. The hydrogen atom transfer from the hydrogen donor (substrate) to the Mn( iv )-superoxo species is the rate-limiting step, having a high reaction barrier and a large endothermicity. Subsequently, the O-C bond formation is concerted with an electron transfer from the substrate radical to the Mn and a proton transfer from the hydroperoxo moiety to the nearby N atom of the corrole ring, generating an alkylperoxo Mn( iii ) complex. The alkylperoxo O-O bond cleavage affords a Mn( v )-oxo complex and a hydroxylated substrate. This novel mechanism for the Mn( v )-oxo formation via an alkylperoxo Mn( iii ) intermediate gives insight into the O-O bond activation by manganese complexes. DFT calculations revealed a novel mechanism for the formation of Mn( v )-oxo in the dioxygen activation by a Mn( iii ) corrole complex involving a Mn( iii )-alkylperoxo intermediate.