- Manipulating radicals
- Using cobalt to steer radical reactions
- Award date
- 2 November 2017
- Number of pages
- Document type
- PhD thesis
- Faculty of Science (FNWI)
- Van 't Hoff Institute for Molecular Sciences (HIMS)
This thesis describes research aimed at understanding and exploiting metallo-radical reactivity and explores reactions mediated by square planar, low-spin cobalt(II) complexes. A primary goal was to uncover novel reactivity of discrete cobalt(III)-bound carbene radicals generated upon reaction of the cobalt(II) catalysts with carbene precursors. Another important goal was to replace cobalt(II)-porphyrin catalysts with cheaper and easier to prepare metallo-radical analogues. Therefore the catalytic activity of planar, low-spin cobalt(II) complexes based on the dibenzotetraazaannulene (MeTAA) ligand scaffold was investigated. Besides the easier synthetic procedure, these complexes are also more active in catalysis than the corresponding cobalt(II)-porphyrins in a variety of ‘carbene transfer’ reactions. The work described in this thesis shows that, like in enzymes, controlled metal-catalysed reactions proceeding via radical-type pathways are certainly possible using well-defined metallo-radical complexes of cobalt(II). Generating ‘carbene-radicals’ upon activation of carbene precursors with these catalysts leads to fascinating new reactivities, taking advantage of the preferred one-electron reactivity of cobalt. The intrinsic reactivity of these species can be controlled by changing the ligand, and the reactions lead to interesting products such as cyclopropanes, ketenes and indenes.
Thesis (complete) (Embargo up to and including 2 November 2019)
Chapter 3: Mechanistic investigations into the cyclopropanation of electron deficient alkenes with ethyl diazoacetate using [Co(MeTAA)] (Embargo up to and including 2 November 2019)
Chapter 5: [Co(MeTAA)] metalloradical catalytic route to ketenes via carbonylation of carbene radicals (Embargo up to and including 2 November 2019)
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