Highly reactive transition metal-oxo intermediates are important active oxidant involved in numerous enzymes such as cytochrome P450 monooxygenases as well as in many useful metal-catalyzed oxidations. Many transition metal catalysts are designed for biomimetic studies of the predominant oxidation catalysts in Nature, the cytochrome P450 enzymes. In this work, a series of metalloporphyrin and metallocorrole complexes have been successfully synthesized and spectroscopically characterized by UV-vis, GCMS and 1H-NMR. The utilization of these complexes as catalysts for selective oxidation of sulfides and photocatalytic aerobic oxidations of activated hydrocarbons were investigated. Ruthenium(II) porphyrin complexes (2) and iron(III) corrole complexes (4) with iodobenzene diacetate [PhI(OAc)2] as a mild and excellent oxygen source efficiently catalyzed sulfides to sulfoxides under mild conditions. Ruthenium porphyrins (2) catalyzed the highly selective oxidation of para-substituted thioanisoles and allylic sulfides with PhI(OAc)2 in the presence of visible light. Over 95% conversion and 100% selectivity were achieved within 12 h. Results from competitive catalytic oxidations and spectra studies of the reaction of complexes (2) with PhI(OAc)2 in the absence of organic sulfide showed that the low-reactivity ruthenium(IV)-oxo intermediates (9) are most likely to be the active oxidant in the sulfoxidation reactions. An outstanding method for the highly selective oxidation of sulfides to sulfoxides was developed by using iron(III) corroles (4) and PhI(OAc)2 as mild oxygen source. Allylic thioanisoles and hydroxy sulfides could be successfully oxidized with good conversions and excellent selectivities within short time period. A significant accelerating effect on the rate of sulfoxidation reactions by small amount of water was noticed and will be understood by more studies. Fluorinated diiron(IV) μ-oxo biscorrole complex (5b) catalyzes alkenes and activated hydrocarbons using atmospheric oxygen and visible light (sunlight) with up to 1200 TONs. The observed photocatalytic oxidation is ascribed to a photodisproportionation mechanism to afford a highly reactive corrole-iron(V)-oxo species that can be directly observed by laser flash photolysis methods. It is noteworthy that the use of visible light (solar light) for activation of atmospheric oxygen without the consumption of a reducing agent in aforementioned photocatalysis is particularly relevant to realizing innovative and economically advantageous processes for conversion of hydrocarbons into oxygenates.
| Identifer | oai:union.ndltd.org:WKU/oai:digitalcommons.wku.edu:theses-2373 |
| Date | 01 May 2014 |
| Creators | Chen, Tse-Hong |
| 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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