The catalytic properties of a series of cobalt complexes containing monodentate phosphorus, bidentate phosphorus, bidentate nitrogen ligand for displacement reaction of trialkylaluminum with ethylene is reported. Effect of reaction time, temperature and different ligands on catalyst performance has been investigated. The kinetics of the reaction of tri-isobutylaluminum with ethylene catalyzed by zerovalent cobalt complex has been studied. The displacement reaction rate shows first-order dependence with respect to trialkylaluminum concentration, cobalt complex concentration and ethylene pressure, respectively. The kinetics equation of displacement reaction rate is r = 1.4x10(6)[R3Al][Cat] [P-C2H4]. The activation energy for this reaction is E-a = 71.9 kJ/mol. (C) 2003 Elsevier Science B.V. All rights reserved.