A Density Functional Theory Study on Comparing the Reactivity of [Mn(13-TMC)(OOH)]2+ and [Mn(13-TMC)(O2)]+ for the Sulfoxidation of Thioanisole: Elucidation of Substrate and Non-Redox Metal Ion Effects
The reactivities of [Mn(13-TMC)(OOH)]2+ (1) and [Mn(13-TMC)(O2)]+ (2) in the sulfoxidation of thioanisole have been compared using density functional theory methods. The orientation of the 13-TMC ligand and substrate and non-redox metal ion effects have been considered to improve the oxidation e...
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| Published in: | Inorganic chemistry Vol. 60; no. 17; pp. 13615 - 13625 |
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| Main Authors: | , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
American Chemical Society
06-09-2021
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| Online Access: | Get full text |
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| Summary: | The reactivities of [Mn(13-TMC)(OOH)]2+ (1) and [Mn(13-TMC)(O2)]+ (2) in the sulfoxidation of thioanisole have been compared using density functional theory methods. The orientation of the 13-TMC ligand and substrate and non-redox metal ion effects have been considered to improve the oxidation efficiency of 1 and 2. In 1, the syn- and anti-orientation of the 13-TMC ligand do not change the coordination of the Mn ion. In contrast, the orientation of the 13-TMC ligand regulates the geometry of 2, wherein the syn-13-TMC ligand exhibits the MnIII-peroxo (2hs and 2ls ) species, while the anti-13-TMC shows the MnII-superoxo (2′hs and 2′ls ) species. However, the MnII-superoxo species are found to be less stable than the MnIII-peroxo complexes by around +26.6 kcal/mol. The ground state geometries of 1 and 2 with the syn-13-TMC ligand are found to be more stable in the high- (S = 2) spin states (1hs and 2hs ) than the low- (S = 1) spin complexes (1ls and 2ls ), by +15.6 and +25.5 kcal/mol, respectively. The computed mechanistic pathways clearly indicate that the sulfoxidation of thioanisole by 1hs is kinetically (by +16.6 to +46.1 kcal/mol) and thermodynamically (+14.4 to +56.1 kcal/mol) more preferred than 1ls , 2hs , and 2ls species. This is mainly due to the feasible heterolytic O1-O2 bond cleavage followed by the proton transfer step. In addition, the molecular electrostatic potential analysis indicates that the higher oxidation efficacy of 1hs than 2hs is due to the −OOH moiety. The reactivity of 1hs is further enhanced by incorporating electron donating substituents in thioanisole, wherein the p-NH2 thioanisole decreases the ΔG ‡ of 1hs by 28%. Interestingly, the incorporation of non-redox metal ions (M n+ = Sc3+, Y3+, Mg2+, and Zn2+) improves the reactivity of 2hs , wherein the non-redox metal ions tend to bind with the oxygen atoms of 2hs and subsequently shift the one-electron reduction potential (E 0 (red) vs SCE) toward the positive side. The positive shift in the E 0 (red) is more evident in 2hs-Y 3+ that significantly decreases the ΔG ‡ of 2hs by 58.7%, which is in fact lower than the ΔG ‡ of 1hs by +2.0 kcal/mol. Hence, in the presence of Y3+, the reactivity of 2hs is comparable with 1hs in the sulfoxidation of thioanisole. |
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| Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
| ISSN: | 0020-1669 1520-510X |
| DOI: | 10.1021/acs.inorgchem.1c01915 |