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One-electron chemistry of palladium, platinum, and gold bis(phosphine) complexes
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Sinclair, Matthew J. G. (2022) One-electron chemistry of palladium, platinum, and gold bis(phosphine) complexes. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3847887
Abstract
Complexes of the noble metals find extensive application in catalysis, with closed shell species that operate by two-electron redox processes the prevailing theme. The odd-electron configurations of metalloradical variants offer the possibility for unique and orthogonal reactivity, with intriguing implications for catalysis. However, well-defined examples are rare and their chemistry is correspondingly poorly developed. For heavily investigated palladium and platinum, for instance, complexes with the metal in a formal +I oxidation state are almost exclusively limited to transient monomers or diamagnetic dimers featuring metal–metal bonds. In this context, recent work in the Chaplin group involving the isolation and characterisation of bis(phosphine) palladium(I) and platinum(I) metalloradicals is notable, as these complexes provide a means to systematically study their onward reactivity.
The overarching aim of this thesis was to establish and thereafter exploit the capacity of linear d9-complexes of the noble metals to activate bonds by one-electron, “radical”, oxidative addition. The radical oxidative addition of aryl and alkyl iodides to palladium(I) metalloradicals has been investigated, with ensuing heterolytic C-I bond activation via three-coordinate palladium(II)-aryl intermediates consistent with a mechanism involving radical oxidative addition. Collaborator Dr J. F. Hooper identified catalytic applications of palladium(I) complexes in the oxidative cross-coupling of antimony and boron nucleophiles. Mechanistic investigation of the initial Sb-C bond cleavage is reported herein, with the presence of palladium(II)-aryl intermediates again consistent with a radical oxidative addition pathway. Additionally, reactions of palladium(I) and platinum(I) metalloradicals with nitric oxide were explored, resulting in isolatable diamagnetic palladium(II) and platinum(II) compounds, consistent with radical oxidative addition. Recognising the capacity of bulky electron donating phosphine-derived ligands to stabilise two-coordinate metalloradicals, linear gold(I) phosphido-borane complexes were prepared and their one-electron oxidation explored. Whilst the corresponding d9-metalloradicals were found to be unstable, these species form interesting adducts with Lewis acids.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QD Chemistry T Technology > TN Mining engineering. Metallurgy T Technology > TP Chemical technology |
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Library of Congress Subject Headings (LCSH): | Catalysis, Precious metals, Metal complexes, Free radical reactions | ||||
Official Date: | March 2022 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Department of Chemistry | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Chaplin, Adrian | ||||
Format of File: | |||||
Extent: | 247 leaves : illustrations | ||||
Language: | eng |
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