Copper(II) complexes of N-octylated bis(benzimidazole) diamide ligands and their peroxide-dependent oxidation of aryl alcohols.

New N-octylated benzimidazole-based diamide ligands N,N'-bis(N-octylbenzimidazolyl-2-ethyl)hexanediamide (O-ABHA), possessing a chiral center, and N,N'-bis(N-octylbenzimidazolyl-2-methyl)hexanediamide (O-GBHA) have been synthesized and utilized to prepare Cu(II) complexes of general composition [Cu(L)X]X, where L = O-ABHA or O-GBHA and X = Cl(-) or NO(3)(-) . The X-ray structure of one of the complexes, [Cu(O-GBHA)NO(3)]NO(3), has been obtained. The Cu(II) ion is found to possess a distorted octahedral geometry with a highly unsymmetrical bidentate nitrate group. The N(2)O(2) equatorial plane comprises an amide carbonyl O, a nitrate O, and the two benzimidazole imine N atoms while another amide carbonyl O and nitrate O take up the axial positions. The complexes carry out the oxidation of aromatic alcohols to aldehydes in the presence of cumenyl hydroperoxide at 40-45 degrees C and act as catalyst with turnovers varying between 13- and 27-fold. The percentage yields of the respective products have been obtained which vary from 32% to 65% with respect to the catalyst turnover.