ELEMENTARY PROCESSES OF THE ZIEGLER CATALYSIS .7. ETHYLENE, ALPHA-OLEFIN AND NORBORNENE COPOLYMERIZATION WITH THE STEREORIGID CATALYST SYSTEMS IPR[FLUCP]ZRCL2 MAO AND ME2SI[IND]2ZRCL2/MAO/

The stereorigid ansa-metallocene catalysts lidene(isopropylidene)-fluo ren-9-ylidene]zirconium dichloride/methylaluminoxane (iPr[FluCp]ZrCl2/ MAO) and methylsilylene)bis(eta5-inden-1-ylidene)]zirconium dichloride /methylaluminoxane (Me2Si[Ind]2-ZrCl2/MAO) are different in respect to the symmetry and, therefore, to the behaviour of the stereospecifity, in the size of the angle between the planes of the pi-ligand systems and in the homopolymerization behaviour of ethylene and propene. The p resent paper concerns itself with comparing the investigations of the ethylene/alpha-olefin and the ethylene/cycloolefin copolymerization wi th both catalyst systems. The main kinetic result for both catalysts i s that the alpha-olefins show an accelerating effect on the ethylene p olymerization rate during the copolymerization whereas norbornene show s exclusively a rate-decreasing effect. The acceleration effect can be explained by an increase in the concentration of active centres and/o r an increase of the rate constant of the ethylene insertion. The anal ysis of the microstructures of the formed copolymers by the use of sta tistical models demonstrates that in copolymers with a high content of alpha-olefins, the experimental trial distributions can only be descr ibed satisfactorily with second-order Markovian statistics. That means that in this case the last two monomers have influence on the inserti on of the subsequent monomer. A further main result of all investigate d copolymerizations is that the r-parameters for the alpha-olefin inse rtion are more favourable for the system iPr[FluCp]ZrCl2/MAO than for the system Me2Si[Ind]2ZrCl2/MAO; the reason for this is the different size in the coordination gap aperture of the pi-ligands. Furthermore, the r-parameters show only a small dependence on the chain length of t he alpha-olefin. Finally, it is remarkable that the stereospecifity (s yndiotactic or isotactic alpha-olefin blocks) remains intact in the co polymers.