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N-Heterocyclic carbenes as tunable ligands for catalytic metal surfaces


Heterogeneous catalysts represent the backbone of many industrial processes and thus have a considerable societal impact. The active sites of these heterogeneous catalysts are often metal surfaces, which consist of a large ensemble of metal atoms, and their properties differ significantly from metal complexes bearing highly developed ligands typically used in homogeneous catalysis. A highly interesting approach is the combination of these sophisticated ligand systems from homogeneous catalysis with metal surfaces to improve parameters such as stability, reactivity and selectivity. One class of these advanced ligands is N-heterocyclic carbenes (NHCs), which have been increasingly applied as molecular modifiers for metal surfaces. This review summarizes developments in this area, covering fundamental properties, preparation methods, important analytical techniques and reactions of NHC-modified metal surfaces. Emerging strategies for NHC design are categorized and future directions are outlined.

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Fig. 1: Overview of NHCs and their application in organometallic chemistry and surface modification.
Fig. 2: Synthetic accessibility, orientations and analysis of NHCs on surfaces.
Fig. 3: Categorization of reactions catalysed by NHC-modified metal surfaces.
Fig. 4: Design strategies by modulation of stability and solubility.
Fig. 5: Design strategies towards increased activity.
Fig. 6: Design strategies towards enantioselective transformations.


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This work was supported by the Deutsche Forschungsgemeinschaft (Leibniz Award, SFB 858). J. B. Ernst, M. Freitag and A. Heusler are gratefully acknowledged for helpful discussions.

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M.K., P.B. and M.D. conducted the literature search and wrote the manuscript. F.G. supervised the study and wrote the manuscript.

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Correspondence to Frank Glorius.

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Koy, M., Bellotti, P., Das, M. et al. N-Heterocyclic carbenes as tunable ligands for catalytic metal surfaces. Nat Catal 4, 352–363 (2021).

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