Mechanistic insights into Ni–Al co-catalyzed alkyne carbophosphination enabled by C–P bond activation

Abstract

Nickel–aluminum (Ni–Al) bimetallic catalysis has demonstrated remarkable efficiency in C–P bond activation, yet its underlying mechanism remains elusive. Key questions regarding the synergistic roles of Ni and Al, the advantages of the dual-catalyst system, and the effect of the substrate and ligand are critical for advancing this strategy. Here, we employ density functional theory (DFT) calculations to systematically investigate the Ni–Al cooperative catalysis mechanism, focusing on the interplay between Ni and Al, the impact of AlMe₂Cl, the role of PPh₃, and the effect of substituents on reaction efficiency. We explored two cooperative models for Ni–Al interactions and found that the uncommon Ni–LA interaction (Model A) is more favorable than the Ni–LA–L bridged system (Model B). This preference arises because the use of PPh₃ makes phenyl migration or phenyl dehydrogenation highly unfavorable, thereby directing the reaction toward Model A as the optimal pathway. Our results demonstrate that AlMe₂Cl plays a crucial role in stabilizing key transition states through non-covalent interactions, charge redistribution, electrostatic stabilization, and electron density distribution, as well as modulating HOMO and LUMO energies, effectively lowering activation barriers. Additionally, PPh₃ enhances reaction efficiency by facilitating stabilizing non-covalent interactions, strengthening Ni coordination through a Ni–P bond, and optimizing charge transfer. Furthermore, an analysis of substrate effects reveals that both steric congestion and electronic stabilization influence reaction efficiency, with smaller and more electronically favorable substituents facilitating charge transfer, lowering oxidative addition barriers, and leading to higher experimental yields. These findings provide a detailed mechanistic understanding of Ni–Al bimetallic catalysis in C–P bond activation and offer guiding principles for the rational design of more efficient catalytic systems. The study not only clarifies the synergistic roles of Ni and Al but also highlights the critical influence of ligands and substrate effects in optimizing reaction outcomes.