Intramolecular Hydroamination by a Primary Amine of an Unactivated Alkene on Gold Nanoclusters: A DFT Study

Abstract

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.

Importance of the Pd and Surrounding Sites in Hydrosilylation of Internal Alkynes by Palladium–Gold Alloy Catalyst

“…The M06-L functional has been employed for all calculations. The spin states and structures of large Pd–Au clusters were simulated by using M06-L functional, for which the functional dependence was previously examined. ,, We have used the scalar relativistic effective core potential (ECP) with double-ζ basis sets [3s3p3d] and the Lanl2dz basis set for Au and Pd atoms which approximately takes care of the relativistic effects relevant in the calculation of Au or Pd clusters. The valence electrons were explicitly treated for Au (19) and Pd (18) atoms.…”

Gold‐Palladium Nanocluster Catalysts for Homocoupling: Electronic Structure and Interface Dynamics

“…Therefore, to examine this catalytic reaction, we adopted Au 10 Pd 10 NC model whose composition accords with the best Au−Pd ratio of 1 : 1 ,,. In Au−Pd:PVP system, the previous theoretical works,, as well as XPS measurements suggest that the Au−Pd NC supported by PVP is negatively charged. Various structural isomers are possible regarding the topology of the Au and Pd atoms in Au 10 Pd 10 NC model .…”

“…Theoretically, we have extensively investigated the NC catalysts both in colloidal phase stabilized by polymer matrix and supported on metal oxides. For the colloidal phase Au NC catalysts stabilized by PVP, we clarified the mechanism of some catalytic reactions using DFT calculations; for example aerobic oxidation of alcohols,, homocoupling of phenylboronic acid, and intramolecular hydroamination by a primary amine of an unactivated alkene . We have also worked on the mechanistic crossover in the CO oxidation on nucleobases tagged Au NC .…”

“…For the colloidal phase Au NC catalysts stabilized by PVP, we clarified the mechanism of some catalytic reactions using DFT calculations; for example aerobic oxidation of alcohols, [33,34] homocoupling of phenylboronic acid, [35] and intramolecular hydroamination by a primary amine of an unactivated alkene. [36] We have also worked on the mechanistic crossover in the CO oxidation on nucleobases tagged Au NC. [37] In these theoretical works, the systems of NC catalysts with multi-step reactions are large in size and complicated and therefore, reliable calculation as well as high-throughput computation is required.…”

C–H Bond Activation Mechanism by a Pd(II)–(μ-O)–Au(0) Structure Unique to Heterogeneous Catalysts

“…Because the mechanism for molecular transformations by heterogeneous catalysts is still analogous and based on the understanding of homogeneous catalysts, theoretical approaches are necessary for elucidation. Many heterogeneous catalysts have been calculated through the use of cluster or slab models, − but most of these were focused on gas-phase reactions − such as CO oxidation. − Some liquid-phase fundamental organic reactions − have been evaluated such as alcohol oxidation, , coupling reactions, − and hydrogenation, , but other important elementary mechanisms in liquid-phase organic reactions including C–H bond activation have been rarely considered. This may be because experimentally determining the exact active site structures of supported catalysts is quite difficult, which forces calculations to consider various active site models as possibilities.…”