Cycloaliphatic polyolefins with functional groups were obtained by Pd(II)-catalyzed homo- and copolymerizations of norbornene derivatives. Bicyclo[2.2.1]hept-5-ene-2-carboxylic acid, the corresponding methyl ester, 2-(hydroxymethyl)bicyclo[2.2.1]hept-5-ene, and the corresponding octanoate and decanoate were used as the monomers in these addition polymerizations. Pd(II)−nitrile catalysts [Pd(RCN)4][BF4]2 (with R = CH3 and C2H5) quite selectively polymerized the exo isomers of the esters of 2-(hydroxymethyl)bicyclo[2.2.1]hept-5-ene. Monomer mixtures containing an 80/20 ratio of endo/exo isomers were converted into polymers containing more than 50% of exo units. 1H NMR studies showed that the predominant fraction of the endo isomer remained unreacted. The nitrile based Pd catalysts were not sufficiently active to polymerize the monomers with electron-withdrawing substituents linked to the bicyclic unit at ambient temperature. In-situ prepared (η3-allyl)palladium complexes with associated tetrafluoroborate and hexafluoroantimonate ions were found to be substantially more active. They were able to catalyze the addition polymerization of norbornene derivatives containing a large proportion of endo isomers. Quantitative monomer conversions were achieved for aliphatic esters of 2-(hydroxymethyl)bicyclo[2.2.1]hept-5-ene. Random copolymers of norbornene and the latter esters with molecular weights M n(GPC) above 100 000 were prepared. The (η3-allyl)palladium compounds were suitable for the polymerization of bicyclo[2.2.1]hept-5-ene-2-carboxylic acid methyl ester; high molecular weight materials were obtained via copolymerization with norbornene. Furthermore, addition polymers containing 0.2 carboxylic acid group per repeating unit were prepared by the copolymerization of norbornene and bicyclo[2.2.1]hept-5-ene-2-carboxylic acid. The hexafluoroantimonate-based (η3-allyl)Pd(II) catalyst had a higher polymerization activity than the Pd compound with the smaller BF4 - counterion which was rationalized by a slightly stronger association of BF4 - with the (η3-allyl)Pd(II) unit.

ansa-Metallocene derivatives XVII *. Racemic and meso diastereomers of group IV metallocene derivatives with symmetrically substituted, dimethylsilanediyl-bridged ligand frameworks. Crystal structure of R ,S-Me 2 Si(3-t.Bu-5-MeC s H 2) 2ZrCI2

67Isotactic polypropene was prepared using rac-dimethyl-silylbis(2-methyl-4-t-butyl-cyclopentadienyl)zirconiumdichloride (1) and methyla!umoxane (MAO) at temperatures between 0 and 80°C and with Al/Zr ratios of 300 and 1500. The polymers, prepared at temperatures below 30°C had melting points of 162°C and above. The chain ends were determined by means of distortionless enhancement by polarization transfer (DEPT)-NMR spectroscopy. The pentad intensities were corrected according to the chemical shifts of the end groups. The intensity distributions are shown to arise from enantiomorphic site control of the chiral catalyst species.

Cycloaliphatic polyolefins with functional groups were prepared by the Pd(II)‐catalyzed addition polymerization of norbornene derivatives. Homo‐ and copolymers containing repeating units based on bicyclo[2.2.1] hept‐5‐en‐2‐ylmethyl decanoate (endo/exo‐ratio = 80/20), bicyclo[2.2.1]hept‐5‐ene‐2‐carboxylic acid methyl ester (exo/endo = 80/20), bicyclo[2.2.1]hept‐5‐ene‐2‐methanol (endo/exo = 80/20), and bicyclo[2.2.1]hept‐5‐ene‐2‐carboxylic acid (100% endo) were prepared in 49–99% yields with {(η3‐allyl)Pd(BF4)} and {(η3‐allyl)Pd(SbF6)} as catalysts. The catalyst containing the hexafluoroantimonate ion was slightly more active than the tetrafluoroborate based Pd‐complex.

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