High-valent transition metal-oxo intermediates play a significant role in the catalytic cycle of the ubiquitous cytochrome P450 enzymes and in biomimetic catalytic systems. In this work, manganese(III) porphyrin and corrole systems (2) were synthesized and characterized by UV-vis absorbance and 1H-NMR, matching literaturereported spectroscopic data. Manganese(V)-oxo corroles (3) and a manganese(IV)-oxo porphyrin (4) were successfully generated by chemical oxidation using mchloroperoxybenzoic acid (m-CPBA), and their oxidation reactions with organic reductants were comparatively investigated. Results from single-turnover kinetic studies indicate that in the tris(pentafluorophenyl)corrole system (3a), the active oxidizing intermediate differs in different solvents. The active oxidizing intermediate in acetonitrile is likely the manganese(V)-oxo species 3a. However, in dichloromethane, the active oxidant is suspected to be a putative manganese(VI)-oxo species generated by disproportionation of the manganese(V)-oxo species.
Tris(pentafluorophenyl)corrolato manganese(III) (2a) was shown to selectively catalyze sulfoxidation and epoxidation with iodobenzene diacetate [PhI(OAc)2] as a mild oxygen source. 2a exhibited higher conversions than triphenylcorrolato manganese(III) (2b), most likely because of the higher stability of 2a compared to 2b. In contrast, tetramesitylporphyrinato manganese(III) (2c) was more efficient in catalytic oxidations than 2a, resulting in much higher conversions, but much less selectivity. Other reported metalloporphyrin and metallocorrole systems show an accelerating effect upon addition of small amounts of water; however, neither corrole systems exhibited a positive water effect. This is attributed to the strong coordination between the manganese center and water, preventing the oxygen source from coordination.
| Identifer | oai:union.ndltd.org:WKU/oai:digitalcommons.wku.edu:theses-2954 |
| Date | 01 April 2017 |
| Creators | Jeddi, Haleh |
| Publisher | TopSCHOLAR® |
| Source Sets | Western Kentucky University Theses |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Masters Theses & Specialist Projects |
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