Ziegler-Natta catalyst activation. Thermodynamic and kinetic aspects of metallocenium ion-pair formation, dissociation, and structural reorganization

This contribution reviews thermochemical and dynamic NMR studies of metallocenium olefin polymerization catalyst formation from, and dissociation to, the neutral metallocene dimethyl precursors and either fluoroarylboranes or methylalumoxane (MAO), as well as the kinetics of ion pair separation/recombination/reorganization. Significant correlations are found between borane Lewis acidity, the enthalpy of catalyst formation, catalyst NMR spectral parameters, the free energy of activation of catalyst ion pair separation/recombination/reorganization, and ethylene polymerization activity.