Comparative analysis of palladium, nickel and copper phosphane/carbene catalysts in Suzuki–Miyaura couplings: Mechanistic insights and reactivity trends

Abstract

Suzuki–Miyaura coupling is a useful synthetic method of the formation of new car- bon–carbon bonds between an organic halide and a boronic acid (or boronate ester), generally catalyzed by palladium compounds in the presence of an external base. In the search of more sustainable and green chemistry processes, precious metals such as palladium are currently being replaced by base metal analogues, which produce more affordable and accessible catalytic platforms. In this work, the catalytic cycle of the Suzuki–Miyaura coupling reaction between phenyl bromide and phenylboronate has been studied by computational means for different combinations of metal/ligand systems. Three transition metals: palladium, nickel, and copper, and four monodentate ligands, including two phosphanes (PMe₃ and P(CF₃)₃) and two N-heterocyclic carbenes (1,3-bis(methyl)imidazol-2-ylidene and 1,3-bis(trifluoromethyl)limidazol-2-ylidene), have been used to construct and explore the reaction for monoligated catalytic species. Overall, the palladium systems display the lowest activation barriers for the Suzuki–Miyaura reaction, with nickel producing the second-best catalysts. On the other hand, copper seems to produce slightly worse systems, with reaction barriers over 25 kcal mol⁻¹ for all the ligands.