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

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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 1521-3765 (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.

ORCID iDs

Rae, Annabel, Byrne, Keelan M., Brown, Scott A., Kennedy, Alan R. ORCID logoORCID: https://orcid.org/0000-0003-3652-6015, Krämer, Tobias, Mulvey, Robert E. ORCID logoORCID: https://orcid.org/0000-0002-1015-2564 and Robertson, Stuart D. ORCID logoORCID: https://orcid.org/0000-0002-9330-8770;
  • 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:19 Dec 2024 12:53
    URI:https://strathprints.strath.ac.uk/id/eprint/79644
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