Aryl halides are commonly employed as aryl radical precursors, through activation by single
electron-transfer (SET) or halogen atom transfer (XAT). For over a century alkali metal
alkoxides alone have been shown to activate aryl halides to form aryl radials, but the
mechanism by which this occurs has not been clear. Many authors have proposed that
alkoxides undergo ground-state SET to the aryl halide, but key evidence for this has been
missing. In Chapter 2 of this thesis, this proposal is refuted, and instead evidence is
presented that alkali metal alkoxides initiate chain reactions through the formation of
benzynes. Substrates including I, II, and III were investigated, along with their deuterated
analogues, and removal of H+ or D+
is shown to control the formation of aryl radicals from
aryl halides.
[see figure in thesis]
The high reactivity of aryl radicals makes their identification in organic reactions
challenging, particularly where products could alternatively arise from competing twoelectron transition metal-mediated pathways. In Chapter 3, a recently developed aryl
radical assay employing substrate IV is used to directly probe radical formation from aryl
halides in the presence of nickel species under ground-state conditions. Formation of aryl
radicals in benzene with a suitable base produces a characteristic VI : V product ratio of ca.
4, providing a clear diagnostic signature. Air-stable Ni(COD)(DQ) is shown to promote the
efficient coupling of aryl halides with benzene via aryl radical intermediates.
[see figure in thesis]
In Chapter 4, the assay is extended to palladium systems under both thermal and
photoexcited conditions. Under thermal conditions, evidence is obtained that Pd⁰
complexes generate aryl radicals from aryl halides, with ligand-dependent control over
radical formation. Under visible light irradiation, the results of the assay further support the
activation of aryl halides to form “Pd-radical hybrid” species, in line with recent
photochemical cross-coupling studies.
| Date of Award | 22 May 2026 |
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| Original language | English |
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| Awarding Institution | - University Of Strathclyde
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| Sponsors | EPSRC (Engineering and Physical Sciences Research Council) |
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| Supervisor | John Murphy (Supervisor) & Tell Tuttle (Supervisor) |
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