Enhanced Catalytic Activity of High-Index Faceted Palladium Nanoparticles in Suzuki–Miyaura Coupling Due to Efficient Leaching Mechanism

Abstract

The structure−property relationship of palladium (Pd) catalysts in Suzuki−Miyaura cross-coupling reactions was investigated using Pd nanocrystals of uniform size and shape. Superior catalytic reactivity was observed for Pd nanoparticles with high-index {730} surface facets compared to low-index {100} facets. Although the nanocrystal morphologies were maintained during the reaction, the presence of Pd clusters, identified by high-resolution transmission electron microscopy (TEM), indicates a leaching mechanism. The nature of the surface facets on the nanoparticles was observed to influence the rate of Pd leaching during the Suzuki coupling reaction. The enhanced reactivity observed for the high-index facet catalysts stems from the greater number of leachable atoms of low abstraction energy available on high-index planes.

Simple preparation of Pd-NP/polythiophene nanospheres for heterogeneous catalysis

“…Pd-NPs are a very important class of catalyst for numerous organic transformations. Among others, the Suzuki-Miyaura cross-coupling reaction between various organic halides and boronic acids is arguably the most valuable reaction for synthetic chemists [24][25][26][27]. The Pd-NP/polythiophene nanospheres contain sub-20 nm Pd-NPs which are known to be very effective catalyst for Suzuki-Miyaura cross-coupling reaction under mild reaction conditions.…”

“…The Pd-NP/polythiophene nanospheres contain sub-20 nm Pd-NPs which are known to be very effective catalyst for Suzuki-Miyaura cross-coupling reaction under mild reaction conditions. For instance, Collins and co-workers recently reported Pd-NP shape-/size-dependent catalytic activities for SuzukiMiyaura cross-coupling reaction, comparing the catalytic activities of 10 nm and 20 nm cube-shaped Pd-NPs and concave cubic Pd-NPs with faceted with high-index {730} facets with a dimension similar to 20 nm Pd-NP cubes [24]. Interestingly, 20 nm Pd-NP (0.5 mol%) did not exhibit any catalytic activity for a prolonged reaction period ($30 h) under very similar reaction conditions compared to this study.…”

Engineering Metallic Nanoparticles for Enhancing and Probing Catalytic Reactions

“…NPs with high index surface facets were also useful catalytic probes for Suzuki coupling. [13] Concave Pd nanocubes exhibited a nearly 7-fold increase in the surface normalized turn over frequency compared to the cubic counterparts. Analysis of the catalysts post reaction showed that the structural integrity of the concave catalysts appeared well preserved at high catalysts loadings, but only at lower catalysts loadings was dissolution of the NP and morphological evolution to small diameter NPs was apparent as shown in Figure. 1 (e)-(h).…”

Halide-Enhanced Catalytic Activity of Palladium Nanoparticles Comes at the Expense of Catalyst Recovery

“…According to Gaikwad et al [56] Pd 0 atom and Pd II ion leach simultaneously and this simultaneous leaching underpins the catalysis in the SMXR. High-index surface facets have also been correlated with high catalytic activity as a result of increased Pd leaching [57,58].…”