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Abstract
The novel cobalt(II) crown carbene complex 12(II) has been prepared and characterised by X-ray crystallography. This complex is reduced in a one-electron process to a cobalt(I) complex that acts as a powerful single electron donor, reducing aryl halides, including aryl chlorides and demonstrating the strong electron-enriching effect on cobalt of the crown carbene ligand. The metal ion is tightly held in a tetrahedral conformation by its enveloping crown liganddthis prevents what would otherwise be expected to be an easy oxidation to cobalt(III) under standard electrochemical conditions. Complex 12 is shown to be an effective catalyst in mediated electrochemical reductions of aryl iodides at room temperature and aryl bromides at 90 C. The electrochemically produced catalyst [from 10 mol % of added Co(II) complex] also triggers reduction of aryl chlorides, although this seems at the limit of its reactivity. However, when the cobalt(II) complex is reduced by sodium amalgam, this affords stoichiometric quantities of the active cobalt reducing agent, which affords reduction of aryl iodides and bromides as above, but also reduces aryl chlorides at elevated temperatures.
Original language | English |
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Pages (from-to) | 10756-10761 |
Number of pages | 6 |
Journal | Tetrahedron |
Volume | 65 |
Issue number | 52 |
DOIs | |
Publication status | Published - 26 Dec 2009 |
Keywords
- electron transfer activity
- cobalt
- cobalt crown carbene
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Dive into the research topics of 'Electron transfer activity of a cobalt crown carbene complex'. Together they form a unique fingerprint.Projects
- 1 Finished
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Physical Organic Chemistry: Opportunities In Synthesis, Materials And Pharmaceuticals (Science And Innovation Award)
Murphy, J. (Principal Investigator), Coombs, G. (Co-investigator), Ferguson, A. (Co-investigator) & Florence, A. (Co-investigator)
Scottish Funding Council SFC, EPSRC (Engineering and Physical Sciences Research Council)
1/09/07 → 30/10/12
Project: Research