Synthesis, structural analysis and evaluation of the catalytic activity of a non-symmetric N-(salicylidene)diethylenetriamine complex of copper(II)

A new copper(II) complex of a non-symmetric Schiff base, [CuII(saldien)(H2O)]+ (1), has been synthesized and characterized by elemental analysis and several other spectroscopic methods (Hsaldien = N-(salicylidene)diethylenetriamine). The crystal structure of 1 has also been determined by X-ray crystallography. The geometry of the complex cation in 1 was found to be distorted square pyramidal with the mononegative Schiff base coordinating to the copper in a tetradentate mode via the O,N,N', and N”-donor atoms. The remaining coordination site was occupied by the O atom of a H2O molecule in the axial position. The catalytic potential of 1 was tested in the oxidation reactions of cyclooctene and cyclohexene with aqueous 30% H2O2/NaHCO3 in acetonitrile. These reactions proceeded smoothly to give the corresponding epoxides with selectivity levels greater than 99%. This catalytic system also showed high levels of activity and selectivity towards the oxidation of cyclohexane (i.e., cyclohexanol 37% and cyclohexanone 54%) in comparison with most of the other Cu-based systems reported in the literature.

Graphical abstractSynthesis and crystal structural analysis of a new copper(II) complex of a non-symmetric Schiff base have been reported. The complex showed high levels of catalytic activity and selectivity towards the oxidation of cycloalkenes and cyclohexane by H2O2 and NaHCO3.Figure optionsDownload full-size imageDownload as PowerPoint slide