Copper(II) Schiff base complexes derived from 2,2′-dimethyl-propandiamine: Synthesis, characterization and catalytic performance in the oxidation of styrene and cyclooctene

Two new mononuclear copper(II) complexes ([CuL1]·CHCl3 (1) and [CuL2] (2)) have been prepared by the reaction of two ONNO type Schiff base ligands, ([bis(2-hydroxy-propiophenone)2,2′-dimethylpropan-diamine] (H2L1) and [bis(5-bromosalicylaldehyde)2,2′-dimethyl-propandiamine] (H2L2)) with Cu(OAc)2·H2O in 1:1 molar ratios. The complexes have been characterized by elemental analyses, IR and UV–Vis spectroscopy. The structures have been confirmed by X-ray single crystal analysis at 100 K. The Cu(II) atom in 1 is coordinated equatorially by a N2O2 donor set of the tetradentate, dinegative Schiff-base (L1)2− in a distorted square planar arrangement. While in [CuL2] (2), the Cu(II) ion possesses an additional weak intermolecular contact with one bromine atom of the ligand, thus the coordination sphere of 2 can be described as strongly distorted square pyramidal. The catalytic performance of the prepared copper complexes for the oxidation of styrene and cyclooctene with tert-butyl hydroperoxide has been evaluated.

Graphical abstractThe oxidation of styrene and cyclooctene by CuL1 and CuL2.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Crystal structure determination of two new mononuclear copper(II) complexes. ► Catalytic performance of the complexes in the oxidation of cyclooctene and styrene. ► The maximum conversion was obtained with tert-butyl hydroperoxide as the oxidant.