N-Heterocyclic Carbene-Functionalized Gold Nanoclusters

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More recently, we have been working to expand the use of NHCs to the stabilization of gold nanoclusters. Following our initial report on the synthesis and isolation of [Au13(NHC)9Cl3]Cl2 clusters, we improved the isolation and purification procedures further in order to apply these clusters as catalysts in various reactions.And structures of clusters was confirmed by X-ray crystallographic analysis. After developing optimized procedures for the synthesis and purification of these clusters, we sought to test their activity in oxidation catalysis, along with our previously isolated NHC-phosphine ligated clusters. Towards this end we chose two model reactions, benzyl alcohol oxidation and photocatalytic benzyl amine oxidation as test cases. Benzyl alcohol oxidation using mixed phosphine/NHC Au13 clusters proceeds with moderate turnover frequency (average 7 h-1), producing benzaldehyde with high selectivity (average 95%). Due to the low stability of these clusters under catalytic conditions, we are currently investigating increasing their stability via solid supports and/or ligand modifications. We plan to also investigate other novel catalytic reactions using our family of NHC-functionalized gold nanoclusters in future research.