Catalytically Active Gold Nanomaterials Stabilized byN‐heterocyclic Carbenes

Abstract

Solid supported or ligand capped gold nanomaterials (AuNMs) emerged as versatile and recyclable heterogeneous catalysts for a broad variety of conversions in the ongoing catalytic ′gold rush′. Existing at the border of homogeneous and heterogeneous catalysis, AuNMs offer the potential to merge high catalytic activity with significant substrate selectivity. Owing to their strong binding towards the surface atoms of AuMNs, NHCs offer tunable activation of surface atoms while maintaining selectivity and stability of the NM even under challenging conditions. This work summarizes well‐defined catalytically active NHC capped AuNMs including spherical nanoparticles and atom‐precise nanoclusters as well as the important NHC design choices towards activity and (stereo‐)selectivity enhancements.

Bottom‐up Synthesis of Water‐Soluble Gold Nanoparticles Stabilized by N‐Heterocyclic Carbenes: From Structural Characterization to Applications

“…Supports are often utilized in the synthesis of colloidal AuNPs to provide increased stability, as well as potentially improving their catalytic performance with increased selectivity, both directly or indirectly [23] . However, the use of a support in combination with surface stabilizing ligands requires careful optimization as both features can decrease the surface accessibility for catalytic reactions [3a] . Examples of supported NHC@AuNPs have been recently reviewed by Reithofer and co‐workers; [3a] however, the area is still very much in its infancy and only a few examples of metal NPs supported on carbon, silica or graphene oxide have been reported.…”

“…Recently, N‐heterocyclic carbenes (NHCs) have emerged as ‘smart’ surface ligands for metal NPs due to their ability to form strong covalent bonds to metallic surfaces and to their versatility with respect to functionalization [3] . In addition to the strong σ‐donor properties of NHC ligands, ligand surface adsorption and additional interactions of NHC wingtips seem to contribute to the overall stability of the NHC binding to Au(0) species [3a,4] . In this context, two main approaches have been applied for the synthesis of AuNPs stabilized by NHC ligands (NHC@AuNPs): either by reducing Au(I) NHC complexes (the ‘bottom‐up’ approach) or by replacing labile ligands at the AuNP surface with NHCs (the ‘top‐down’ approach).…”

Reactivity of Diamines in Acyclic Diamino Carbene Gold Complexes

“…Overall, this study shows that the product selectivity of primary versus secondary opens up new routes to ADC compounds, which might find application in catalysis and as gold nanomaterial precursors. 18 …”

“…Overall, this study shows that the product selectivity of primary versus secondary opens up new routes to ADC compounds, which might find application in catalysis and as gold nanomaterial precursors. 18 ■ EXPERIMENTAL SECTION Materials and Methods. All experiments were performed under ambient conditions unless stated otherwise.…”

“…Especially in recent years, diverse ADC gold chloride compounds have been explored in catalysis for biological applications and as gold nanomaterial precursors. ,− There are several examples of the reaction of isocyanide gold chloride with primary and secondary monoamines but only a few reports on the reactions of diamines with isocyanide gold chloride thus far. Such reactions are worth investigating as the expected products of bis-carbene complexes are not only advantageous for catalysis but could also serve as precursors for bis-carbene-stabilized nanomaterials, which may offer enhanced stability.…”