Sigma/pi bonding preferences of solvated alkali-metal cations to ditopic arylmethyl anions

Rae, Annabel and Byrne, Keelan M. and Brown, Scott A. and Kennedy, Alan R. and Krämer, Tobias and Mulvey, Robert E. and Robertson, Stuart D. (2022) Sigma/pi bonding preferences of solvated alkali-metal cations to ditopic arylmethyl anions. Chemistry - A European Journal, 28 (18). e202104260. ISSN 0947-6539 (https://doi.org/10.1002/chem.202104260)

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Abstract

Arylmethyl anions allow alkali-metals to bind in a σ-fashion to the lateral carbanionic centre or a π-fashion to the aryl ring or in between these extremities, with the trend towards π bonding increasing on descending group 1. Here we review known alkali metal structures of diphenylmethane, fluorene, 2-benzylpyridine and 4-benzylpyridine. Next, we synthesise Li, Na, K monomers of these diarylmethyls using polydentate donors PMDETA or Me 6TREN to remove competing oligomerizing interactions, studying the effect that two aromatic rings has on negative charge (de)localisation via NMR, X-ray crystallographic and DFT studies. Diphenylmethyl and fluorenyl anions maintain C(H)−M interactions regardless of alkali-metal, although the adjacent arene carbons engage in interactions with larger alkali-metals. Introducing a nitrogen atom into the ring (at the 2- or 4-position) encourages relocalisation of negative charge away from the deprotonated carbon and onto nitrogen. Phenyl(2-pyridyl)methyl moves from an enamide formation at one extremity (lithium) to an aza-allyl formation at the other extremity (potassium), while C- or N-coordination modes become energetically viable for Na and K phenyl(4-pyridyl)methyl complexes.

  • Item type:Article
    ID code:79644
    Dates:
    Date
    Event
    28 March 2022
    Published
    8 March 2022
    Published Online
    16 February 2022
    Accepted
    Subjects:Science > Chemistry
    Department:Faculty of Science > Pure and Applied Chemistry
    Depositing user: Pure Administrator
    Date deposited:16 Feb 2022 16:34
    Last modified:09 Apr 2024 03:03
    URI:https://strathprints.strath.ac.uk/id/eprint/79644
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