Synthesis, Crystal Structures, Characterization and Catalytic Property of Copper(II) Complexes Derived from Hydrazone Ligands

Yao Tan,Yan Lei

doi:10.17344/acsi.2020.6044

Abstract

A new bromido-coordinated mononuclear copper(II) complex [Cu(HL1)Br2] (1), and a new mononuclear copper(II) complex [CuL2(HL2)]ClO4·0.5H2O (2), with the hydrazone ligands 4-tert-butyl-N'-(1-(pyridin-2-yl)ethylidene)benzohydrazide (HL1) and 4-bromo-N'-(pyridin-2-ylmethylene)benzohydrazide (HL2), have been synthesized and structurally characterized by physico-chemical methods and single crystal X-ray determination. X-ray analysis indicates that the Cu atom in complex 1 is in distorted square pyramidal coordination, and that in complex 2 is in octahedral coordination. The catalytic property for epoxidation of styrene by the complexes was evaluated.

Highlights

Hydrazone compounds, containing the typical -CH=N-NH-C(O)- groups, represent one of the most attractive series of ligands in coordination chemistry
In pursuit of new copper(II) complexes with mono-anionic hydrazone ligands, we report the syntheses, X-ray crystal structures, and catalytic properties of a new bromido-coordinated mononuclear copper(II) complex [Cu(HL1)Br2] (1), and a new mononuclear copper(II) complex [CuL2(HL2)]ClO4 · 0.5H2O (2), with the hydrazone ligands 4-tert-butyl-N’-(1-(pyridin-2-yl)ethylidene)benzohydrazide (HL1) and 4-bromo-N’-benzohydrazide (HL2) (Scheme 1)
The hydrazones were readily prepared by condensation reaction of 2-acetylpyridine with 4-tert-butylbenzohydrazide, and 2-pyridinecarboxaldehyde with 4-bromobenzohydrazide, respectively, in methanol

Summary

Introduction

Hydrazone compounds, containing the typical -CH=N-NH-C(O)- groups, represent one of the most attractive series of ligands in coordination chemistry. The hydrazone ligands are capable of binding various transition and rare earth metal atoms to form complexes with versatile structures and properties.[1] To date, most hydrazone complexes have been reported to have interesting catalytic properties, such as asymmetric epoxidation, oxidation of sulfides, and various type of polymerization.[2] Among the complexes, those with Cu centers are of particular interest for their catalytic properties.[3] To date, a large number of metal complexes with the hydrazones derived from salicylaldehyde and its analogues are reported.

Experimental

Results and Discussion

Conclusion