Azide/thiocyanate incorporated cobalt(III)-Schiff base complexes: Characterizations and catalytic activity in aerobic epoxidation of olefins

• Azide/thiocyanate incorporated cobalt(III)-Schiff base complexes are synthesized.
• Characterized by different physicochemical methods.
• Metal ions exhibits different degrees of distortions in spite of similar geometries.
• Act as catalyst in aerobic epoxidation of alkenes under homogeneous condition.
• Azido complex shows greater epoxide selectivity compared to thiocyanato counterpart.

Reaction of cobalt(II) perchlorate hexahydrate with a potentially tetradentate Schiff base ligand, HL (2-methoxy-6-[(2-diethylaminoethylimino)methyl]phenol) in presence of sodium azide and sodium thiocyanate yields two complexes [Co(L)(HL)(N3)]·ClO4 (1) and [Co(L)(HL)(NCS)]·ClO4 (2); both being characterized by different physicochemical methods. Crystal structure of 1 was determined by single crystal X-ray diffraction while that of 2 was reported earlier. In 1, the central cobalt(III) adopts slightly distorted octahedral geometry with same donor set to that of 2. Catalytic efficacy of the complexes towards epoxidation of different alkenes under aerobic condition were investigated in homogeneous medium which reveals that 1 is better catalyst than 2 with respect to alkene oxidation, reflected from the turn over frequencies (TOF) measured at an optimum temperature of 60 °C in acetonitrile.

Two azide/thiocynate incorporated cobalt(III)-Schiff complexes have been synthesized and characterized and employed as catalysts in the aerobic epoxidation of alkenes under homogeneous condition which reveals that azido complex exhibits greater epoxide selectivity compared to thiocyanato complex though both shows excellent performance at an optimum temperature of 60 °C in acetonitrile.Figure optionsDownload as PowerPoint slide