Synthesis of di-nitrogen Schiff base complexes of methyltrioxorhenium(VII) and their application in epoxidation with aqueous hydrogen peroxide as oxidant

Several di-nitrogen Schiff baseswere synthesized through the condensation of 2-pyridinecarboxaldehydewith primary amines. The Schiff bases as ligands coordinated with methyltrioxorhenium (MTO) smoothly to afford the correspondent complexes which were characterized by IR, H-1 NMR, C-13 NMR, MS and elemental analysis. One of the complexes was analyzed by X-ray crystallography as well. The results revealed that the complexes display distorted octahedral geometry in the solid state with a trans-position of Schiff base. Catalytic results indicated that the complexes as catalysts increased the selectivity of epoxides remarkably compared with MTO in the epoxidation of alkenes with 30% hydrogen peroxide as oxidant and the increasing rate depended on the structure of the Schiff base ligands of the complexes. The results indicated that the stronger the donating ability of the ligand, the higher selectivity of epoxides the complex gave in the epoxidation of alkenes with 30% hydrogen peroxide as oxidant. Copyright (C) 2010 John Wiley & Sons, Ltd.