Theoretical investigation on the mechanism of Ni0(acetylide carbanion)-ate complex-catalyzed C(sp2)–F bond activation and the origin of the counterion effect on reactivity

Abstract

This study employs density functional theory (DFT) calculations to elucidate the mechanism and alkali metal-dependent reactivity in the Ni⁰-catalyzed C(sp²)–F bond activation of fluoronaphthalenes, assisted by lithium acetylides. The results reveal that the energy barrier for C(sp²)–F bond activation initiated by the acetylide carbanion is 30.1 kcal mol⁻¹, significantly higher than that (18.5 kcal mol⁻¹) for the ethide carbanion-initiated one, due to the notably weaker nucleophilicity of the acetylide carbanion. Interestingly, the reaction between lithium acetylides and the pre-catalyst Ni⁰(cod)₂ generates a Ni⁰(acetylide carbanion)-ate complex, in which high nucleophilicity is localized at the Ni⁰-center. Significantly, the energy barrier for C(sp²)–F bond activation catalyzed by the Ni⁰(acetylide carbanion)-ate complex via an inner-sphere nucleophilic aromatic substitution (S_NAr) pathway is considerably lowered to 25.3 kcal mol⁻¹. Theoretical analysis clarifies that the distinct reactivity of the ate complex stems from coordination of the acetylide carbanion to the Ni⁰ center, with strong Li⋯F interactions serving as a key driving force to stabilize the transition state. This work provides a comprehensive insight into transition metal-catalyzed C–F bond activation with the assistance of an acetylide carbanion, which is expected to offer a theoretical perspective for the rational design of C–F functionalization strategies.