Selective Catalytic Oxidation of Organic Sulfides by Iron (III) Porphryin Catalysts and Generation of Iron (IV)-OXO Prophyrin Radical Cations

Authors

Nawras A. Asiri, Western Kentucky UniversityFollow

Publication Date

8-2013

Advisor(s) - Committee Chair

Rui Zhang (Director), Chad Snyder, Eric Conte

Degree Program

Department of Chemistry

Degree Type

Master of Science

Abstract

Macrocyclic ligand-complexed transition metal-oxo intermediates are the active oxidizing species in a variety of important biological and catalytic oxidation reactions. Many transition metal catalysts have been designed to mimic the predominant oxidation catalysts in nature, namely the cytochrome P450 enzymes. Iron porphyrin complexes have been the center of research as catalysts. In this study 5,10,15,20- tetramesitylporphyrin (H₂TMP) and its corresponding iron complexes Fe^III(X)TMP (X= Cl, ClO₄, ClO₃, NO₃, NO₂, and BrO₃) have been successfully synthesized and fully characterized by UV-vis and NMR spectroscopies. For the catalytic selective oxidation of organic sulfides, the potential of iron(III) porphyrin complexes with iodobenzene diacetate [PhI(OAc)₂] have been investigated. Iodobenzene diacetate was found to be an efficient oxygen source in the iron(III) porphyrin-catalyzed oxidation of sulfides to sulfoxides. Iron(III) porphyrin catalysts show an excellent conversion and selectivity for the sulfoxidation reactions. Reaction conditions and environments that effect the catalytic sulfoxidation including solvent, catalytic amount, axial ligand, water, and thioanisole substrates, have been investigated to identify the optimal conditions and the substrate scope. Under optimized conditions, excellent substrate conversions (up to 100%) as well as product selectivies (sulfoxide:sulfone > 95:5) have been achieved. To probe the nature of the oxidizing species in above catalytic sulfoxidations, iron(IV)-oxo porphyrin radical cations model of Compound I were chemically produced from the corresponding iron(III) tetramesitylporphyrin precursors with excess amounts of PhI(OAc)₂ (20-50 equivalents) in CH₃CN solvent. All O=Fe^IV(X)TMP·⁺ (X= Cl, ClO₄, ClO₃, and NO₃) show weaker Soret band and broader Q band that are characteristic of Compound I analogues. A new photochemical method that led to generation of the iron(IV)-oxo porphyrin radical cations was also successfully developed. Iron(IV)-oxo porphyrin radical cations were generated by irradiation of iron(III) porphyrin chlorate or bromate complexes that result in heterolytic cleavage of the O-X bond in the axial ligand.

Disciplines

Chemistry | Inorganic Chemistry | Medicinal-Pharmaceutical Chemistry | Organic Chemistry

Recommended Citation

Asiri, Nawras A., "Selective Catalytic Oxidation of Organic Sulfides by Iron (III) Porphryin Catalysts and Generation of Iron (IV)-OXO Prophyrin Radical Cations" (2013). Masters Theses & Specialist Projects. Paper 1290.
https://digitalcommons.wku.edu/theses/1290