Recent Advances in the Chemistry of N‐Heterocyclic‐Carbene‐Functionalized Metal‐Nanoparticles and Their Applications

Abstract

Metal-nanoparticles (M-NPs) have been widely applied in catalysis, imaging, sensing and medicine. One particularly active area of this research is the modification of the surface of the nanoparticles to prevent aggregation through the coordination of ligands. N-Heterocyclic carbenes (NHCs) have emerged as suitable ligands for this purpose due to their affinity to the metals and their strongly electron donating nature. A number of rationally designed NHC-modified M-NPs have been developed using strategies based on metal complex decomposition and ligand exchange. Herein, NHC-stabilized M-NPs based on a range of transition metals, especially the recent advances, were summarized.

Template Synthesis of Metal Nanoparticles within Organic Cages

“…On the other hand, although M‐NPs synthesized within cage templates have proven to be more stable and efficient catalysts than their conventional counterparts in a few catalytic reactions, a large number of catalytic reactions remain to beexplored, as well as a range of other potential applications. Furthermore, given recent high‐profile progress made in N ‐heterocyclic carbene (NHC)‐modified M‐NPs, we look forward to the future use of a range of porous NHC‐precursor cages as templates in the controlled synthesis of M‐NPs.…”

“…Metal nanoparticles (M‐NPs) have attracted tremendous interest in recent years due to their unique physical and chemical properties resulting from their size reduction and shape variation . In particular, the use of ultra‐small M‐NPs as efficient catalysts in various reactions is a rapidly growing area of research as a consequence of their synthetic accessibility and superior catalytic efficiency . However, due to their high surface energy, small M‐NPs are prone to aggregation during reactions and associated loss of their catalytic activities.…”

Synthesis and Electrocatalytic HER Studies of Carbene-Ligated Cu3-xP Nanocrystals

“…It has been demonstrated that NHC ligands have the ability to enhance nanocrystal catalyst stability and increase nanocrystal catalyst activity and/or selectivity. [9][10][11][12] NHC-stabilized nanocrystals have been shown to display catalytic activity toward, for example, hydrogenations and semihydrogenations, 9,[12][13][14] lactonization, 10 asymmetric arylations, 15 Buchwald-Hartwig aminations, 16 and cross-coupling reactions. 15 NHC-stabilized nanocrystals have also been shown to be competent electrocatalysts for CO2 reduction.…”

“…[9][10][11][12] NHC-stabilized nanocrystals have been shown to display catalytic activity toward, for example, hydrogenations and semihydrogenations, 9,[12][13][14] lactonization, 10 asymmetric arylations, 15 Buchwald-Hartwig aminations, 16 and cross-coupling reactions. 15 NHC-stabilized nanocrystals have also been shown to be competent electrocatalysts for CO2 reduction. 11,17 For example, Cao et al investigated the use of NHC-stabilized Au nanocrystals as electrocatalysts for the reduction of CO2 to CO. Interestingly, the Au nanocrystal catalyst with surface-bound carbene ligands exhibited a higher Faradaic efficiency for CO2 reduction to CO than did bare (or ligand-less) Au nanoparticles; it was further shown that the NHC affected the mechanistic pathway of catalysis.…”

“…17 Despite the proven benefits of applying NHC ligands to nanocrystal catalysts, they have thus far only been supported on metal nanocrystal catalysts (e.g., Ru, Au, Pt, Pd, Cu). [9][10][11][12][13][14][15][16][17][18] Therefore, the potential utility of NHC ligands as supporting ligands for other types of nanocrystal catalysts is currently unknown. Certain metal phosphide nanocrystals have emerged as an important class of catalysts for reactions such as hydrodesulfurization, [19][20][21] hydrodeoxygenation, 22 and the hydrogen evolution reaction (HER).…”