Theoretical study of hydrogenolysis termination processes in ethylene polymerization

The reaction of molecular hydrogen with the active species of a model metal locene catalyst is investigated through quantum mechanical calculations. Th e results art: compared to ethylene insertion in the corresponding polymeri zation reaction. Hydrogenolysis and ethylene insertion exhibit both frontsi de and backside mechanisms. However, while ethylene insertion proceeds pref erably through frontside mechanism, hydrogenolysis occurs mainly through th e backside one. The activation energies are close but hydrogenolysis is sli ghtly more favorable than ethylene insertion, in agreement with experimenta l findings. Agostic interactions have been found to play an important role, like in the chain propagation process. (C) 2001 Elsevier Science Ltd. All rights reserved.