The novel N2O2 unsymmetrical tetradentate Schiff bases complexes are used as catalysts for the selective aerobic oxidation of cyclohexene. In general, conversion percentages decrease with increasing DeltaE(p) and decreasing E-0'/(redox) Catalytic activity increases with decrease of the number of electron-donating groups and the catalytic selectivity varies according to the types of substituents in the ligands. The catalytic system described here is an inexpensive method for selective oxidation of olefins, with advantages of high activity, selectivity, re-usability and short reaction times. Analysing GC and redox potential results shows a moderate correlation between selectivity and activity. (C) 2004 Elsevier B.V. All rights reserved.