Reactivity of cationic (pi-allyl)Pd(II) complexes with olefins and dienes Public Deposited

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  • Reactivity of cationic (pi-allyl) Pd(II) complexes with olefins and dienes
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  • March 21, 2019
  • Urbin, Stephanie A.
    • Affiliation: College of Arts and Sciences, Department of Chemistry
  • The use of transition metal catalysts for 1,3-diene polymerization is desirable due to the ability to control the microstructure, polydispersity, and molecular weight of the resulting polymer by easily tuning the ligand and metal used. Previously, progress has been made through the development of highly active, nickel(II) ligand-free catalysts for 1,3-diene polymerizations, which has also provided significant insight into the mechanism for these reactions. While highly active, these catalysts are relatively unstable and difficult to generate, and hence development of stable, initiator-free complexes is desirable. This dissertation focuses on the synthesis of (allyl)Pd(II) catalysts and their reactivity with olefins and 1,3-dienes. Particular attention is given towards the observation and, in some cases, isolation of intermediates for the mechanism of 1,3-diene polymerizations. Chapter 2 describes the successful synthesis of [(allyl)Pd(arene)][SbF?6?] complexes with highly labile arene ligands. The reactivity of these complexes with olefins and alkynes results in formation of bis-olefin and bis-alkyne Pd(II) species at low temperatures and is thoroughly discussed. A comparison of the reactivity of these Pd(II) complexes with the analogous [(allyl)Ni(arene)][B(Ar?F?)?4?] complexes is a feature of this work. Chapter 3 presents the reactivity of the [(allyl)Pd(arene)][SbF6] complexes with a variety of dienes. For the first time, a diene complex exhibiting an s-trans-eta4-binding mode to a d8 metal center has been synthesized and characterized. Additionally, a variety of [(allyl)Pd(eta4-diene)]+ species have been spectroscopically observed at low temperatures. This chapter also focuses on the direct observation of insertion intermediates as models for the polymerization of 1,3-butadiene, including an eta3, eta2-wrap-around species. Chapter 4 describes the synthesis of stable eta3,eta2wrap-around complexes as models for the first insertion product in the polymerization of 1,3-dienes. The binding affinity of the eta2-olefin can be quantitatively measured and controlled by tuning different electronic factors of the wrap-around complexes. Furthermore, reactions of the Pd(II) wrap-around complexes with 1,3-dienes were explored with the goal of gaining further insight into the chain transfer and polymerization mechanism for (allyl)Pd(II) complexes.
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  • Brookhart, Maurice
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  • University of North Carolina at Chapel Hill
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