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    SELECTIVITY OF METATHESIS REACTIONS CATALYZED BY SUPPORTED COMPLEXES OF GROUP VI

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    Dissertation_WiebkeWackerow.pdf
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    Description:
    Wiebke Wackerow - Final Dissertation
    Embargo End Date:
    2021-11-12
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    Type
    Dissertation
    Authors
    Wackerow, Wiebke cc
    Advisors
    Basset, Jean-Marie cc
    Committee members
    Huang, Kuo-Wei cc
    Ruiz-Martinez, Javier cc
    Astruc, Didier
    Program
    Chemical Science
    KAUST Department
    Physical Science and Engineering (PSE) Division
    Date
    2020-11
    Embargo End Date
    2021-11-12
    Permanent link to this record
    http://hdl.handle.net/10754/666031
    
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    Access Restrictions
    At the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation will become available to the public after the expiration of the embargo on 2021-11-12.
    Abstract
    The general objective of this thesis is the analysis of selective reactions for group VI grafted metal complexes via methods and principles of SOMC. For this objective, three approaches have been chosen. The first chapter is an introduction to the topic of selectivity in catalysis, emphasizing heterogeneous catalysis and more specifically the different approaches to support catalysts on surfaces. The concept of catalysis by design is introduced as a new way to use the surface as a ligand. Chapter 2 presents the results of a library of well-defined catalysts of group VI with identical catalytic functionality, but different ligand environment. The results reveal, that metal-carbynes are able to switch their catalytic reactivity based on the substrate that they are contacted with. The difference in reaction mechanisms and the differing reactivities towards the substrates are presented. It can be concluded that the classical ROMP is selectively achieved with cyclic alkene substrates leading to polymers whereas cyclic alkanes yield exclusively higher and lower homologues of the substrate without polymeric products. Chapter 3 presents the study of olefin metathesis of cis-2-pentene with metal-carbynes of group VI, where the selectivity of the catalyst library towards yield of cis-/trans products is analyzed. It is presented, that the ligand environment of the catalysts is showing an influence in the selectivity. Rates of cis/trans isomerization of the products are high and are approaching thermodynamic equilibrium at high conversion. Product isomerization, thermodynamic equilibrium and reactivity differences between liquid phase and gas phase products are analyzed. Chapter 4 presents the full characterization of tungsten-hydrides by selective transformation into tungsten-hydroxides. These newly discovered well-defined tungstenhydroxides are fully characterized by ICP, TEM, DRIFT, double quantum and triple quantum solid-state NMR. The presented results allow to predict that tungsten-hydrides on KCC-1700 are present as two distinct species. Catalysis results with cyclooctane show, that due to burial of the complexes in the KCC-1700 surface the tungsten-hydrides are less active towards cyclic alkane metathesis reactions with bulky cyclooctane than the metalcarbyne complexes. Chapter 5 is giving a conclusion of results and an outlook for catalytic applications of the generated tungsten-hydroxides of chapter 4.
    Citation
    Wackerow, W. (2020). SELECTIVITY OF METATHESIS REACTIONS CATALYZED BY SUPPORTED COMPLEXES OF GROUP VI. KAUST Research Repository. https://doi.org/10.25781/KAUST-4Z682
    DOI
    10.25781/KAUST-4Z682
    ae974a485f413a2113503eed53cd6c53
    10.25781/KAUST-4Z682
    Scopus Count
    Collections
    Dissertations; Physical Science and Engineering (PSE) Division; Chemical Science Program

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