Mechanistic insights into C-C cross coupling activities of Pd/Ni-doped heterofullerenes

Abstract

Mechanistic insights into Heck and Suzuki-Miyaura cross coupling reactions with C 59 M (M = Pd/Ni) catalysts were developed. Density functional theory was used for the analysis of all the intermediates and transition states possible during C-C cross coupling reactions over the catalysts under study. Oxidative addition, a step common to both Heck and Suzuki-Miyaura cross coupling reactions, was observed to proceed with smaller activation barriers over C 59 Pd. Heck coupling of iodobenzene with styrene was observed to proceed via oxidative addition, migratory insertion, and reductive elimination steps. The free energy barriers for oxidative addition, migratory insertion, and reductive elimination steps were 14.8, 11.6, and 4.8 kcal/mol, respectively, over C 59 Pd, and 17.4, 79.3, and 17.4 kcal/mol, respectively, over C 59 Ni,ing oxidative addition and migratory insertion to be the rate-determining steps over C 59 Pd and C 59 Ni, respectively. Similarly for Suzuki-Miyaura coupling reaction, activation barriers for oxidative addition, transmetalation, and reductive elimination steps were 14.8, 52.4, and 7.9 kcal/mol, respectively, over C 59 Pd, and 17.4, 64.7, and 60.2 kcal/mol, respectively, over C 59 Ni, indicating transmetalation step to be the rate-determining step over both the heterofullerenes.