Benzimidazolic complexes of methyltrioxorhenium(VII): Synthesis and application in catalytic olefin epoxidation

Seven new Lewis base adducts of methyltrioxorhenium(VII) (MTO) with the general formula CH3ReO3·L (L = bidentate benzimidazolic ligands, namely (L = 2-(2-Pyridinyl)-1H-benzimidazole, 5-methyl-2-(2-pyridyl)benzimidazole, 5-Chloro-2-(2-pyridyl)benzimidazole, 2-(2-Pyridyl)-1H-imidazo-[4,5-b]-pyridine, 2-(2-Quinolyl)benzimidazole, 2-(5-methyl-1H-benzimidazol-2-yl)-quinoline, and 2-(5-chloro-1H-benzimidazol-2-yl)-quinoline)) were prepared. All the complexes were characterized by IR, 1H, 13C NMR, MS and elemental analysis as well as tested as catalysts for olefin epoxidation using 35% aqueous hydrogen peroxide as oxidant under mild condition. The influence of different ligand concentrations was also examined. The results show that the complexes are highly selective in olefin epoxidation and good yields can be obtained when excess ligand is applied.

Graphical abstractSeveral new methyltrioxorhenium (MTO)-benzimidazolic complexes were prepared, characterized and applied for the epoxidation of olefins with aqueous hydrogen peroxide as oxidant at room temperature.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Seven new MTO-benzimidazolic complexes were prepared and characterized. ► All the complexes were tested as catalysts for olefin epoxidation with hydrogen peroxide as oxidant. ► The results show that all the complexes give excellent selectivity in olefin epoxidation. ► Good yields can be obtained when ligands are applied in significant excess.