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 C59M (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 C59Pd. 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 C59Pd, and 17.4, 79.3, and 17.4 kcal/mol, respectively, over C59Ni, indicating oxidative addition and migratory insertion to be the rate-determining steps over C59Pd and C59Ni, 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 C59Pd, and 17.4, 64.7, and 60.2 kcal/mol, respectively, over C59Ni, indicating transmetalation step to be the rate-determining step over both the heterofullerenes.