Alkene epoxidation by homogeneous and heterogenised manganese(II) catalysts with hydrogen peroxide

Three Schiff base ligands derived from three different 1,3-diones and diethylenetriamine have been synthesized and subsequently grafted on a silica surface via covalent bonds. The organic ligands as well as the heterogenised ligands reacted with manganese(II) ions leading to the formation of the corresponding metal complexes. Supported and non-supported manganese complexes have been evaluated as catalysts for alkene epoxidation with hydrogen peroxide in the presence of ammonium acetate as an additive. Both homogeneous and heterogeneous systems are able to activate hydrogen peroxide towards epoxide formation presenting remarkable catalytic properties. This catalytic ability of the immobilised manganese complexes is further highlighted, since they present efficient systems overcoming competitive H2O2 dismutation, in conjunction with advantages of the heterogeneous catalysts. In this context, they gave high yields for limonene epoxidation, significantly higher than the corresponding homogeneous catalysts.

Graphical abstractThree Schiff base ligands derived from three different 1,3-diones and diethylenetriamine have been synthesized and subsequently grafted on a silica surface via covalent bonds. Supported and non-supported manganese complexes have been evaluated as catalysts for alkene epoxidation with hydrogen peroxide. The observed high catalytic activity of the immobilised manganese complexes is highlighted, since they present efficient systems overcoming competitive H2O2 dismutation, in conjunction with advantages of the heterogeneous catalysts. Figure optionsDownload full-size imageDownload as PowerPoint slide