Theoretical investigations on Ziegler-Natta catalysis: Models for the cocatalyst components

Theoretical ab-initio methods have been used to study the stability of the Ziegler-Natta cocatalyst complexes, which consist of aluminium trialkyl and silicon alkoxide compounds. The choice of the basis set indicated that the 6-3iG* basis set is the best for aluminium-, oxygen- and silicon-containing compounds. Examination of the interaction energies of the complexes showed that the aluminium compounds determine the stability of the cocatalyst complexes. The silicon alkoxides have a slight effect on the interaction energies, which are to some degree dependent on the size and number of the alkoxy groups of the silicon alkoxides.