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 tr ialkyl and silicon alkoxide compounds. The choice of the basis set ind icated that the 6-3iG basis set is the best for aluminium-, oxygen- a nd silicon-containing compounds. Examination of the interaction energi es of the complexes showed that the aluminium compounds determine the stability of the cocatalyst complexes. The silicon alkoxides have a sl ight effect on the interaction energies, which are to some degree depe ndent on the size and number of the alkoxy groups of the silicon alkox ides.