C–Cl Bond Activation on Au/Pd Bimetallic Nanocatalysts Studied by Density Functional Theory and Genetic Algorithm Calculations

Abstract

The C–Cl bond activation by Au/Pd bimetallic alloy nanocatalysts has been investigated with regard to the oxidative addition of chlorobenzene (PhCl). Fifteen stable structures of the Au10Pd10 nanocluster (NC) obtained by a genetic algorithm were examined by DFT calculations using the M06-L, TPSS, and B3LYP functionals. Triplet states of cage-like C1 and Cs structures are found to be relevant reflecting the quasi-degenerate nature of the Pd moiety, while several other low-lying structures and spin states may also contribute to the oxidative addition. For all examined cluster structures, the oxidative addition step is exothermic, and internal conversion and/or spin crossing are expected to occur as several states are close in energy and geometry. Based on an energetic analysis of a model system consisting of the Au10Pd10 NC surrounded by four poly(n-vinylpyrrolidone) (PVP) molecules, the PVP units activate the system as electron donors and stabilize it. While a neutral NC model overestimates the energy barrier slightly, the opposite holds for an anionic NC model. In the oxidative addition, the interaction between the phenyl group and the Pd atom on the NC surface as well as a dissociation taking place at the Pd site are found to be essential. This indicates the importance of direct coordination effects in the Au/Pd bimetallic NC. NBO analysis shows that a π back-donation of the M(dπ) to σ*(C–Cl) orbital is relevant for the C–Cl bond activation and the interaction energy explains the favorable dissociation at the Pd site compared to the Au site.

Catalytic Activation of PVP-Stabilized Gold/Silver Cluster on p- Nitrophenol Reduction: A DFT

“…LaNL2DZ for Ag/Au and 6-31G++(d,p) basis set for C, H, N and O atoms was used while performing DFT calculation. B3LYP functional calculations give the stable cluster and also reproduce the experimental results [17,18,24]. Calculations are carried out for ground state geometry optimization in gaseous phase.…”

“…Finally, the most important question that in a catalytic reaction how does the interaction between the catalyst surface and the reactant/substrate change in presence of stabilizer. Very few reports are available regarding this topic [18,19]. The catalytic reduction of nitroarenes to aminoarenes by transfer hydrogenation methodologies is an important class of organic transformations.…”

Gold/Palladium Bimetallic Nanoclusters for C-X Bond Activation: A Unique Effect of Gold

“…23,27 The density functional theory with M06 or M06 L functional 28 was utilized, and the geometry optimization was performed in fully relaxed manner without any restriction of coordinates. For calculating the stable NC structures, the Genetic Algorithm (GA) approach (Birmingham Cluster Genetic Algorithm) 29 was adopted.…”

“…It is relevant to consider the involvement of these various stable structures and spin states in the C X bond activation on Au/ Pd NC, and this was explored by GA calculations followed by DFT calculations. 27 Even for the relatively small NCs like Au 10 Pd 10 NC, several stable structures and spin states exist. These states are closely located in energy and cross over each other along the oxidative addition pathway of phenyl chloride as shown in Figure 14; for example, low lying triplet ( 3 C 1 , 3 C s ) and singlet ( 1 C 1 , 1 C s ) states in Au 10 Pd 10 NC.…”

Catalytic activation of nitrobenzene on PVP passivated silver cluster: A DFT investigation

“…Finally, the most important question that in a catalytic reaction how does the interaction between the catalyst surface and the reactant/substrate change in presence of stabilizer. Very few reports are available regarding this topic …”