Density functional theory calculations were performed to investigate the reaction mechanism of the aerobic oxidation of benzyl alcohol to benzaldehyde catalyzed by Au and Au–Pd clusters. Two consecutive reaction mechanisms were examined with Au₈ and Au₆Pd₂ clusters: (1) the oxidation of benzyl alcohol with dissociated O atoms on metal clusters generating benzaldehyde and H₂O; and (2) oxidation with adsorbed oxygen molecules generating benzaldehyde and H₂O₂. The calculations show that the aerobic oxidation of benzyl alcohol energetically prefers to proceed in the former mechanism, which agrees with the experimental observation. We demonstrate that the role of Au centers around the activation of molecular oxygen to peroxide-like species, which are capable of the H–abstraction of benzyl alcohol. The roles of Pd in the Au₆Pd₂ cluster are: (1) increasing the electron distribution to neighboring Au atoms, which facilitates the activation of O₂; and (2) stabilizing the adsorption complex and transition states by the interaction between positively charged Pd atoms and the π-bond of benzyl alcohol, both of which are the origin of the lower energy barriers than those of Au₈.

Density functional theory calculations have been used to investigate the mechanism of intramolecular hydroamination of unactivated alkenes by using primary amines on gold nanoclusters (NCs) under aerobic conditions. By examining the activation modes in the cyclization process, the olefin activation mechanism was calculated to be the most energetically feasible of the three possible pathways. The amine activation pathway suffered from a high activation barrier, which means that this pathway is unlikely to take place on gold NCs. The catalytic cycle comprises five elementary steps: (1) adsorption of O₂ on Au NCs results in superoxo‐like species and provides Lewis acidic sites that allow the nucleophilic substrate, 2,2‐diphenyl‐4‐penten‐1‐amine, to be adsorbed effectively; (2) intramolecular cyclization (C−N bond formation) takes place on the Au NCs through anti‐addition of the amino group; (3) hydroperoxy moiety formation by hydrogen transfer from the cyclic intermediate to superoxo‐like species; (4) the formation of hydrogen peroxide and (5) product involves hydrogen transfer from a hydrated formic acid. Natural bond orbital analysis of the transition states that arise during C−N bond formation reveals that anti‐addition of the substrate is preferred over the syn‐addition mechanism. A possible side reaction, the formation of 2‐methylene‐4,4‐diphenylpyrrolidine through β‐hydrogen elimination, is also discussed.