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Synthesis of Magnetically Recyclable Core-shell Nanocatalysts for Epoxidation of Alkenes and Reduction of Sulfoxide to Sulfides and Oxygen Atom transfer by Mo(VI) Complexes

Haghdoost Manjili, Mohammad Mehdi | 2014

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 46712 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Bagherzadeh, Mojtaba
  7. Abstract:
  8. In the first part of this thesis, the application of core-shell magnetic nanoparticles supported V(V), Mo(VI) and Mn(III) complexes in the catalytic oxidation and reduction reactions was discussed. A magnetically recyclable vanadium(V) catalyst was synthesized by covalent anchoring of VO(salen)Cl on silica coated Fe3O4 nanoparticles. These nanoparticles were efficient catalysts for selective oxidation of sulfides to corresponding sulfoxides with urea hydrogen peroxide in excellent yields. Leaching and recycling experiments revealed that the nanocatalyst can be applied for nearly complete oxidation of sulfides for at least five successive cycles. A manganese(III) complex was immobilized on silica-coated magnetic Fe3O4 nanoparticles through the amino propyl linkage. The resulting nanoparticles are used as efficient and recyclable catalysts for selective oxidation of thiols to disulfides using urea-hydrogen peroxide as the oxidant. The recycling of the nanocatalyst in six consecutive runs afforded a total turnover number of more than 10,000.
    In the second part, the oxygen atom transfer by Mo(VI) complexes was investigated. The catalytic activity of a molybdenum(VI) oxo–peroxo complex through the oxidation and reduction of sulfur-based compounds was evaluated. The catalytic and oxidation activities of the complex were compared with those of other Mo(VI) oxo-peroxo complexes. The difference in the reactivity of complexes was explained by DFT calculations in terms of the natural atomic charge of the peroxooxygens and the Mo-peroxo distance. The preparation and catalytic activity of a new molybdenum(VI) dioxido complex were reported. By using the AIM analysis, topological properties of the electron density were analyzed to define the bond path between atoms. In addition, two new chiral Mo(VI) complexes, ((R,R)-1,1'-(cyclohexane-1,2-diylbis ((nitrilo) methylylidene ))bis(2-naphtholato)) dioxo molybdenum(VI) and (S,S)-((R,R)-1, 1'-(cyclohexene-1,2-diylbis((imino)methylene))bis(2-naphtholato)) dioxo molybdenum(VI), have been tested as catalysts in the enantioselective epoxidation of alkenes and sulfides. The molecular structure in the solid state of these complexes was confirmed by single-crystal X-ray diffraction analysis. Using these chiral complexes, catalytic oxidation of methylphenyl sulfides in methanol solvent resulted in formation of (S)-methylphenyl sulfoxide in 95% yield and 9.4% enantiomeric excess
  9. Keywords:
  10. Nano Catalyst ; Oxygen Transfer ; Molybdenum Schiffbase Complex ; Magnetic Recyclability ; Alkenes Epoxidation ; Sulfoxides Reduction

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