Bakewell, C;
Ward, BJ;
White, AJP;
Crimmin, MR;
(2018)
A combined experimental and computational study on the reaction of fluoroarenes with Mg–Mg, Mg–Zn, Mg–Al and Al–Zn bonds.
Chemical Science
, 9
(8)
pp. 2348-2356.
10.1039/C7SC05059C.
Preview |
Text
Bakewell_A combined experimental and computational study on the reaction of fluoroarenes with Mg–Mg, Mg–Zn, Mg–Al and Al–Zn bonds_VoR.pdf - Published Version Download (921kB) | Preview |
Abstract
Through a combined experimental and computational (DFT) approach, the reaction mechanism of the addition of fluoroarenes to Mg–Mg bonds has been determined as a concerted S_{N}Ar-like pathway in which one Mg centre acts as a nucleophile and the other an electrophile. The experimentally determined Gibbs activation energy for the addition of C₆F₆ to a Mg–Mg bond of a molecular complex, ΔG‡_{₂₉₈K}(experiment) = 21.3 kcal mol⁻¹ is modelled by DFT with the ωB97X functional, ΔG‡₂₉₈ {K}_(DFT) = 25.7 kcal mol⁻¹. The transition state for C–F activation involves a polarisation of the Mg–Mg bond and significant negative charge localisation on the fluoroarene moiety. This transition state is augmented by stabilising closed-shell Mg⋯F_{ortho} interactions that, in combination with the known trends in C–F and C–M bond strengths in fluoroarenes, provide an explanation for the experimentally determined preference for C–F bond activation to occur at sites flanked by ortho-fluorine atoms. The effect of modification of both the ligand coordination sphere and the nature and polarity of the M–M bond (M = Mg, Zn, Al) on C–F activation has been investigated. A series of highly novel β-diketiminate stabilised complexes containing Zn–Mg, Zn–Zn–Zn, Zn–Al and Mg–Al bonds has been prepared, including the first crystallographic characterisation of a Mg–Al bond. Reactions of these new M–M containing complexes with perfluoroarenes were conducted and modelled by DFT. C–F bond activation is dictated by the steric accessibility, and not the polarity, of the M–M bond. The more open coordination complexes lead to enhanced Mg⋯F_{ortho} interactions which in turn lower the energy of the transition states for C–F bond activation.
| Type: | Article |
|---|---|
| Title: | A combined experimental and computational study on the reaction of fluoroarenes with Mg–Mg, Mg–Zn, Mg–Al and Al–Zn bonds |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1039/C7SC05059C |
| Publisher version: | http://dx.doi.org/10.1039/C7SC05059C |
| Language: | English |
| Additional information: | © The Royal Society of Chemistry 2018. This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence (https://creativecommons.org/licenses/by-nc/3.0/). |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10057624 |
Archive Staff Only
 |
View Item |
