Silver–N-heterocyclic carbenes in π–Activation: Synergistic effects between the ligand ring size and the anion

Frith, Abigail, Clarke, Aimee K., Heyam, Alex, Lynam, Jason M., Newman, Paul D. ORCID: https://orcid.org/0000-0002-1808-1211, Unsworth, William P. and Willans, Charlotte E. 2024. Silver–N-heterocyclic carbenes in π–Activation: Synergistic effects between the ligand ring size and the anion. Organometallics 43 (5) , pp. 598-604. 10.1021/acs.organomet.3c00476

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Abstract

A series of 12 silver­(I)–N-heterocyclic carbene (NHC) complexes were prepared featuring five- (both saturated and unsaturated backbone), six-, and seven-membered ring ligand scaffolds. The N-substituents of the NHCs were diisopropylphenyl in all cases, while the anion was varied between bromide, acetate, and triflate. The complexes were evaluated as catalysts in the spirocyclization of 1-(1H-indol-3-yl)-4-phenylbut-3-yn-2-one to give a spirocyclic indolenine product. To our knowledge, it is the first time that a systematic study has been conducted to examine the effects of both NHC ring size and anion in this type of silver-catalyzed reaction. While the acetate and triflate complexes catalyzed the reaction to 100% conversion, the bromide complexes exhibited a significant ligand/anion effect. Reactions catalyzed by both complexes bearing the five-membered ring NHC ligands and the complex bearing the seven-membered ring NHC ligand stalled after approximately two turnovers. However, the bromide complex bearing the six-membered ring NHC ligand catalyzes the reaction to almost full conversion, similarly to the acetate and triflate complexes. This demonstrates that the NHC ligand ring size can have a dramatic effect in these types of reactions and does not necessarily display a linear correlation.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Chemistry
Additional Information:	License information from Publisher: LICENSE 1: URL: https://creativecommons.org/licenses/by/4.0/, Start Date: 2024-02-27
Publisher:	American Chemical Society
ISSN:	0276-7333
Date of First Compliant Deposit:	13 March 2024
Date of Acceptance:	13 February 2024
Last Modified:	13 Mar 2024 10:15
URI:	https://orca.cardiff.ac.uk/id/eprint/167175

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