The treatment of 2-(ArNC(H))C6H4-HNC9H6N with n-BuLi and the subsequent addition of CuCl2 afforded the anilido-aldimine Cu(II) complexes 1-5 Cu[{2-[ArN=C(H)]C6H4}N(8-C9H6N)]Cl (Ar = 2,6-iPr2C6H3 (1), 2,4,6-(CH3)3C6H2 (2), 4-OCH3C6H4 (3), 4-BrC6H4 (4), 4-ClC6H4 (5)), respectively. All the copper complexes were fully characterized by IR, EPR and HR-MS spectra. The X-ray diffraction analysis reveals that 2 and 4 are mononuclear complexes, and the Cu atom is sitting in a slightly square-planar geometry. These Cu(II) complexes have exhibited excellent catalytic activity in the Chan-Lam coupling reactions of benzimidazole derivatives with arylboronic acids, achieving the highest yields of up to 96%.
Keywords: Chan–Lam coupling; anilido-imine ligands; benzimidazole; copper complexes.