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Oxorhenium(V) complexes with phenolate-pyrazole ligands for olefin epoxidation using hydrogen peroxide
Niklas Zwettler1, Jörg A Schachner, Ferdinand Belaj
1Institute of Chemistry, University of Graz , Schubertstrasse 1, 8010 Graz, Austria.
Inorganic Chemistry
|December 3, 2014
Summary
New oxorhenium(V) complexes catalyze cyclooctene epoxidation with high efficiency. These stable catalysts demonstrate excellent activity using tert-butylhydroperoxide and hydrogen peroxide, offering greener catalytic options.
Area of Science:
- Inorganic Chemistry
- Organometallic Chemistry
- Catalysis
Background:
- Oxorhenium(V) complexes are valuable in catalysis.
- Developing stable and efficient catalysts for epoxidation is crucial.
- Exploring the use of greener oxidants and solvents is an ongoing challenge.
Purpose of the Study:
- To synthesize and characterize novel oxorhenium(V) complexes.
- To investigate the catalytic activity of these complexes in alkene epoxidation.
- To evaluate the performance of these catalysts with different oxidants and solvents.
Main Methods:
- Synthesis of oxorhenium(V) complexes with phenolate-pyrazole ligands.
- Characterization using spectroscopic methods and X-ray diffraction.
- Electrochemical studies (cyclic voltammetry) to understand redox properties.
- Catalytic epoxidation of cyclooctene using various oxidants and solvents.
Main Results:
- Six new oxorhenium(V) complexes were successfully prepared and characterized.
- Complexes showed high stability towards air and moisture.
- Electrochemical studies revealed ligand-dependent shifts in redox potentials.
- Excellent catalytic activity for cyclooctene epoxidation was observed with tert-butylhydroperoxide (quantitative conversion).
- Effective catalysis using hydrogen peroxide (up to 74% yield) and diethylcarbonate (up to 30% yield) was demonstrated.
Conclusions:
- The synthesized oxorhenium(V) complexes are stable and effective catalysts for alkene epoxidation.
- The electronic properties of the ligands influence the catalytic activity.
- These complexes offer promising alternatives for green epoxidation reactions using hydrogen peroxide or environmentally friendly solvents.
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