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      Synthesis, characterization, electrochemistry, and ring-opening polymerization of heavier group 13 bridged metallocenophanes

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      PhDThesisJAS.pdf (1.485Mb)
      Date
      2007
      Author
      Schachner, Joerg Anton
      Type
      Thesis
      Degree Level
      Doctoral
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      Abstract
      The synthesis of two types of metallocenophanes is described: strained, ring-tilted [1]metallocenophanes with Al and Ga in bridging positions and Fe and Ru as transition elements and unstrained [1.1]ferrocenophanes with Al, Ga and In in bridging positions. [1]Metallocenophanes are potential monomers for the synthesis of organometallic polymers via ring-opening polymerization (ROP). After the successful synthesis of various starting monomers using the concept of intramolecular coordinating ligands, four different pathways of ROP were investigated. However, only one of these pathways proved successful in obtaining polymeric material. The starting monomers showed a surprising stability against commonly used initiators. This was attributed to an overly steric protection by the intramolecular coordinating ligands, thereby blocking the initiators, and a reduced ring strain, a consequence of the size of the bridging element.[1.1]Ferrocenophanes belong to a class of dinuclear complexes where the two redox-active iron atoms are in close proximity with restricted flexibility. [1.1]Ferrocenophanes with Al, Ga and In in bridging positions were investigated. The redox properties of previously published [1.1]ferrocenophanes showed a fully reversible, stepwise, one-electron oxidation (FeII/FeII → FeII/FeIII → FeIII/FeIII). After the initial oxidation of the first iron center, a stable, mixed-valent monocationic species is created. The removal of a second electron from the second iron center therefore is more difficult, and occurs at higher potential to create the dicationic species. The difference in potential for the stepwise oxidation is directly related to the delocalization of the charge in the mixed-valent species. This delocalization mainly depends on the electronic properties of the bridging element. Depending on the bridging group 13 element, very different electrochemical properties were observed. For the alumina[1.1]ferrocenophane, no delocalization was detected, and a one-step, two-electron oxidation at the same potential was observed. For the inda[1.1]ferrocenophane, a more complex electrochemistry was observed that we attributed to an isomerization of the compound in solution. Only the investigated galla[1.1]ferrocenophane showed the expected stepwise oxidation-reduction behavior.
      Degree
      Doctor of Philosophy (Ph.D.)
      Department
      Chemistry
      Program
      Chemistry
      Supervisor
      Mueller, Jens
      Committee
      Foley, Stephen R.; Bowles, Richard K.
      Copyright Date
      2007
      URI
      http://hdl.handle.net/10388/etd-08272007-135338
      Subject
      inorganic polymers
      Robin and Day
      strained sandwich complexes
      Strained organometallic complexes
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      • Graduate Theses and Dissertations
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