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

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.