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

Abstract

Treatment of Cu(OAc)2·4H2O with 8-hydroxylquinoline-imine ligands [2-(ArN = HC)-8-OH]C9H5N (Ar = 2,6-iPr2C6H3, 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%.