Abstract: The evolution of catalytic systems based on transition metal complexes under catalytic reaction conditions leads to the formation of a catalyst cocktail, i.e., an ensemble of species with different structures, each capable of exhibiting catalytic activity. Transformation of molecular Pd(II)–NHC complexes into a catalytically active cocktail form involves R–NHC coupling, which results in the formation of low-coordinated metal centers and [R–NHC](+)[X](−) salt (X = halogen). In this work, using DFT methods, it is demonstrated that one factor influencing the R–NHC coupling process is substituent effects within the pyridine or phosphine ligand of the Pd(II) complex (R = Me, Ph; NHC = IMe, IPr, IMes). The presence of electron-donating (–OMe) or electron-withdrawing (–CN; –F) substituents in the ligand molecule significantly influences both the activation energy and the reaction energy of the R–NHC coupling process. In particular, electron-accepting substituents reduce the potential barrier for this process and completely shift the equilibrium toward the product of the R–NHC coupling, whereas electron-donating substituents possess the opposite effect. Thus, the effect of substituents can act as a “switch” facilitating the transition from molecular catalysis to “cocktail-type” catalysis.

Cite: Naumovich V.O. , Gordeev E.G. , Ananikov V.P.
Substituent Effects on the Stability of Pd– NHC Complexes: Switching From Molecular to “Cocktail‐Type” Catalysis
Journal of Computational Chemistry. 2026. V.47. N24. e70500 . DOI: 10.1002/jcc.70500 WOS Scopus OpenAlex

Dates:

Submitted:	Jul 8, 2026
Published online:	Sep 11, 2026

Identifiers:

≡ Web of science:	WOS:001875958300005
≡ Scopus:	2-s2.0-105050273241
≡ OpenAlex:	W7212297608

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