@article{Leclerc1996Zralk-23759,
  year={1996},
  doi={10.1021/ja961157n},
  title={Zr-alkyl isomerization in ansa-zirconocene-catalyzed olefin polymerizations. Contributions to stereoerror formation and chain termination},
  number={38},
  volume={118},
  issn={0002-7863},
  journal={Journal of the American Chemical Society},
  pages={9024--9032},
  author={Leclerc, Margarete K. and Brintzinger, Hans-Herbert}
}

<rdf:RDF
    xmlns:dcterms="http://purl.org/dc/terms/"
    xmlns:dc="http://purl.org/dc/elements/1.1/"
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
    xmlns:bibo="http://purl.org/ontology/bibo/"
    xmlns:dspace="http://digital-repositories.org/ontologies/dspace/0.1.0#"
    xmlns:foaf="http://xmlns.com/foaf/0.1/"
    xmlns:void="http://rdfs.org/ns/void#"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema#" > 
  <rdf:Description rdf:about="https://kops.uni-konstanz.de/server/rdf/resource/123456789/23759">
    <dspace:isPartOfCollection rdf:resource="https://kops.uni-konstanz.de/server/rdf/resource/123456789/29"/>
    <dcterms:rights rdf:resource="https://rightsstatements.org/page/InC/1.0/"/>
    <dcterms:isPartOf rdf:resource="https://kops.uni-konstanz.de/server/rdf/resource/123456789/29"/>
    <dcterms:available rdf:datatype="http://www.w3.org/2001/XMLSchema#dateTime">2013-06-24T16:48:50Z</dcterms:available>
    <dc:rights>terms-of-use</dc:rights>
    <dc:contributor>Leclerc, Margarete K.</dc:contributor>
    <dc:creator>Brintzinger, Hans-Herbert</dc:creator>
    <dcterms:title>Zr-alkyl isomerization in ansa-zirconocene-catalyzed olefin polymerizations. Contributions to stereoerror formation and chain termination</dcterms:title>
    <void:sparqlEndpoint rdf:resource="http://localhost/fuseki/dspace/sparql"/>
    <dc:creator>Leclerc, Margarete K.</dc:creator>
    <dc:language>eng</dc:language>
    <dcterms:issued>1996</dcterms:issued>
    <bibo:uri rdf:resource="http://kops.uni-konstanz.de/handle/123456789/23759"/>
    <dcterms:bibliographicCitation>Journal of the American Chemical Society ; 118 (1996), 38. - S. 9024-9032</dcterms:bibliographicCitation>
    <dc:date rdf:datatype="http://www.w3.org/2001/XMLSchema#dateTime">2013-06-24T16:48:50Z</dc:date>
    <dc:contributor>Brintzinger, Hans-Herbert</dc:contributor>
    <foaf:homepage rdf:resource="http://localhost:8080/"/>
    <dcterms:abstract xml:lang="eng">In polymers made from (E)- or (Z)-[1-D]propene with methyl alumoxane (MAO)-activated ansa-zirconocene catalysts, signals of deuterium-labeled mrrm pentads document that stereoerrors arise mainly from an isomerization of the Zr-bound chain end. Reduced D-atom redistribution in poly([2-D]propene) indicates a kinetic isotope effect of k&lt;sub&gt;H&lt;/sub&gt;/k&lt;sub&gt;D&lt;/sub&gt; ≈ 3 for the β-H/D transfer associated with the isomerization reaction. In all poly([1- and [2-D]propenes) studied, D-labeled mmmm pentads occur with a probability similar to that of D-labeled mrrm pentads; this observation requires further mechanistic clarification. Olefinic chain ends of polymers obtained with C&lt;sub&gt;2&lt;/sub&gt;H&lt;sub&gt;4&lt;/sub&gt;(thind)&lt;sub&gt;2&lt;/sub&gt;ZrCl&lt;sub&gt;2&lt;/sub&gt;-MAO from (E)- or (Z)-[1-D]propene deviate in their D-label distributions from the expected stereochemistry. Isomerization of the Zr-bound chain end, probably via a Zr-bound tertiary alkyl intermediate, thus contributes also to chain-growth termination. With the sterically hindered catalyst Me&lt;sub&gt;2&lt;/sub&gt;Si(2-Me-4-tBu-C&lt;sub&gt;5&lt;/sub&gt;H&lt;sub&gt;2&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt;ZrCl&lt;sub&gt;2&lt;/sub&gt;-MAO, almost all chain terminations appear to occur via chain-end isomerization, which does not lead to stereoerrors here. With the high-performance catalyst Me&lt;sub&gt;2&lt;/sub&gt;Si(2-Me-benz[e]indenyl)&lt;sub&gt;2&lt;/sub&gt;ZrCl&lt;sub&gt;2&lt;/sub&gt;-MAO, finally, no D-label is found in the mrrm and mmmm pentad signals; here, Zr-alkyl isomerization can apparently not compete with the high rate of olefin insertion.</dcterms:abstract>
  </rdf:Description>
</rdf:RDF>