Copper(II) complexes supported by 8-hydroxyquinoline-imine ligands: Synthesis, characterization and catalysis in aerobic alcohols oxidation

Treatment of Cu(OAc)(2)middot4H(2)O with 8-hydroxylquinoline-imine ligands [2-(ArN = HC)-8-OH]C9H5N (Ar = 2,6-(Pr2C6H3)-Pr-i, L1H; Ar = 4-ClC6H4, L2H; Ar = 4-BrC6H4, L3H and Ar = 4-OMeC6H4, L4H) in refluxing EtOH gave the dual-ligand coordinated copper complexes [L2Cu] 1a-1d in good yields, respectively. All the four Cu complexes were characterized by IR, EPR, elemental analysis and HR-MS. Furthermore, the molecular structures of complexes 1a and 1d were further confirmed by X-ray crystallographic analysis. These complexes displayed high catalytic activity and good selectivity for aerobic oxidation of primary and secondary alcohols in the presence of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxyl) as the co-catalyst. The yields of desired aldehydes are decent (up to 84%) and the corresponding yields of ketones are in the range of 78-91%.

Automated summary

In this study, four dual-ligand coordinated copper complexes were successfully synthesized by reacting with different ligands, providing new options for catalyst research. These complexes exhibited high catalytic activity and good selectivity for the oxidation of primary and secondary alcohols.