Electronic effects of substituents on the oxidation potentials of vanadyl complexes with tetradentate Schiff base ligands derived from 1,2-propylenediamine

Two tetradentate Schiff base ligands (H(2)L(1-2)) (H(2)L(1) = bis(2-hydroxy-3-methoxy-benzaldehyde)-1,2-propandiimine, H(2)L(2) = bis(2-hydroxy-4-methoxy-acetophenone)-1,2-propandiimine) were prepared by reaction of 1,2-propylenediamine and o-hydroxycarbonyls compounds containing a methoxy group and characterized by elemental analysis, FT-IR, (1)H and (13)C NMR. The vanadyl complexes were synthesized and characterized. The catalytic potential of these complexes was tested for the oxidation of cyclooctene and styrene using tert-butylhydroperoxide (TBHP) as oxidant. It has been shown that the presence of electron-donating substituents on the aromatic ring as well as the imine bond can effectively improve the catalytic activity and the product selectivity of catalysts. (C) 2010 Elsevier B.V. All rights reserved.