Insights on the Anion Effect in N-heterocyclic Carbene Based Dinuclear Gold(I) Catalysts

Filippo Campagnolo; Matteo Bevilacqua; Marco Baron; Cristina Tubaro; Andrea Biffis; Daniele Zuccaccia

doi:10.1002/cplu.202300421

Insights on the Anion Effect in N-heterocyclic Carbene Based Dinuclear Gold(I) Catalysts

Chempluschem. 2024 Mar;89(3):e202300421. doi: 10.1002/cplu.202300421. Epub 2023 Nov 21.

Authors

Filippo Campagnolo¹, Matteo Bevilacqua², Marco Baron², Cristina Tubaro², Andrea Biffis², Daniele Zuccaccia¹

Affiliations

¹ Dipartimento di Scienze Agroalimentari, Ambientali e Animali, Università di Udine, Via Cotonificio 108, 33100, Udine, Italy).
² Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131, Padova, Italy.

PMID: 37902252
DOI: 10.1002/cplu.202300421

Abstract

Dinuclear bisNHC (bis(N-heterocyclic carbene)) gold(I) complexes 3 a and 4 a of general formula [Au₂ Br₂ (bisNHC)] were tested as catalysts in the cycloisomerization of N-(prop-2-yn-1-yl)benzamide and in the hydromethoxylation of 3-hexyne in the presence of silver(I) activators bearing different counteranions. The catalytic performance of mononuclear NHC complexes (1 a, 2 a) in the same reactions was also studied. The results highlighted the fundamental role of both NHC ligand and counterion in the catalytic cycles and activation process: dinuclear catalysts exhibit higher initial activity even under milder conditions but suffer in terms of stability with respect to mono NHCs. Furthermore, a new dinuclear bisNHC gold(I) complex 4 b of general formula [Au₂ (OTs)₂ (bisNHC)] (OTs=p-toluenesulfonate) was successfully synthesized and characterized by means of NMR and ESI-MS analyses.

Keywords: carbenes; counterion effect; dinuclear catalyst synthesis; gold; homogeneous catalysis; kinetics.