Elementarprozesse der Ziegler‐Katalyse, 6 Ethylen‐ und propenhomopolymerisation mit den stereorigiden katalysatorsystemen iPr[FluCp]ZrCl₂/MAO und Me₂Si[Ind]₂ZrCl₂/MAO

The ethylene and propene homopolymerization was investigated by means of the C s ‐symmetric [2,4‐cyclopentadien‐1‐ylidene(isopropylidene)fluoren‐9‐ylidene]zirconium dichloride/methylaluminoxane (iPr[FluCp]ZrCl 2 /MAO) and the C 2 ‐symmetric [(dimethylsilylene)bis(η 5 ‐inden‐1‐ylidene)]zirconium dichloride/methylaluminoxane (Me 2 Si[Ind] 2 ZrCl 2 /MAO) catalyst systems in toluene. Surprisingly, the C s ‐symmetric catalyst polymerizes propene faster than ethylene. The main results of the kinetic analysis are a first‐order dependence on the concentration of Zr but a bell‐shape in the plot of the polymerization rate versus log([Al]: [Zr]). This is true for both catalyst systems. Furthermore with increasing [Al]:[Zr] ratio the fraction of rmrr pentads is decreased continuously with the C s ‐symmetric catalyst; in the same direction the molecular weights are decreased. On the contrary with the C 2 ‐symmetric catalyst the stereospecificity and the molecular weights remain constant. The kinetic results reflect the complex role of the MAO, i.e. the existence of sterically more and more tight contact species between metallocene and MAO components with increasing [Al]: [Zr] ratio. The different behaviour of the two catalyst systems concerning stereospecificity and molecular weights of the polymers are due to different symmetry and different size of the angle between the planes of the π‐ligand systems.