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A combined experimental and computational study on the reaction of fluoroarenes with Mg-Mg, Mg-Zn, Mg-Al and Al-Zn bonds

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Title: A combined experimental and computational study on the reaction of fluoroarenes with Mg-Mg, Mg-Zn, Mg-Al and Al-Zn bonds
Authors: Bakewell, C
Ward, BJ
White, AJP
Crimmin, MR
Item Type: Journal Article
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 SNAr-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, DG‡ 298 K(experiment) ¼ 21.3 kcal mol1 is modelled by DFT with the uB97X functional, DG‡ 298 K(DFT) ¼ 25.7 kcal mol1 . 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/Fortho 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 ¼ Mg, Zn, Al) on C–F activation has been investigated. A series of highly novel b-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/Fortho interactions which in turn lower the energy of the transition states for C–F bond activation.
Issue Date: 23-Jan-2018
Date of Acceptance: 19-Jan-2018
URI: http://hdl.handle.net/10044/1/58305
DOI: https://dx.doi.org/10.1039/c7sc05059c
ISSN: 2041-6520
Publisher: Royal Society of Chemistry
Start Page: 2348
End Page: 2356
Journal / Book Title: Chemical Science
Volume: 9
Issue: 8
Copyright Statement: Open Access Article. This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence (https://creativecommons.org/licenses/by-nc/3.0/).
Sponsor/Funder: The Royal Society
The Leverhulme Trust
Commission of the European Communities
Funder's Grant Number: UF090149
RPG-2015-248
677367
Keywords: Science & Technology
Physical Sciences
Chemistry, Multidisciplinary
Chemistry
C-F ACTIVATION
METAL-CARBONYL ANIONS
OXIDATIVE ADDITION
CATALYZED BORYLATION
BUILDING-BLOCKS
BASIS-SETS
CHEMISTRY
FLUORINE
COMPLEX
FUNCTIONALIZATION
Publication Status: Published
Open Access location: http://pubs.rsc.org/en/content/articlepdf/2014/SC/C7SC05059C?page=search
Appears in Collections:Chemistry



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