A cobalt(II) complex with anionic and neutral N-donor ligands: synthesis, crystal structure, and application as a heterogeneous catalyst for olefin epoxidation with tert-BuOOH

Abstract

A cobalt(II) complex containing deprotonated mefenamic acid (Hmef) and imidazole (HIm), [Co(mef)₂(HIm)₂(CH₃OH)₂], has been synthesized and characterized by spectroscopic techniques (UV–vis, IR, and EPR), elemental analysis, and single-crystal X-ray diffraction analysis. The structure has distorted octahedral geometry around cobalt. The mefenamate is a monodentate ligand coordinated to the Co(II) through a carboxylate oxygen. This complex was tested as a catalyst for epoxidation of alkenes with tert-BuOOH in 1,2-dichloroethane solution. This catalyst was effective in epoxidation of various alkenes including non-activated terminal alkenes. The effects of solvent, oxidant, and temperature on the epoxidation of cyclohexene were investigated. In all cases, high yields of epoxidized alkenes were obtained.

Keywords:

• Heterogeneous catalysis
• tert-BuOOH
• Mefenamic acid
• Epoxidation
• Cobalt(II)

Acknowledgements

We are grateful for the financial support from the Department of Chemistry, Isfahan University of Technology (IUT). Also, the authors would like to thank the Raha Pharmacological Company for providing us with the required mefenamic acid.