Recent advances in S-functionalized N-heterocyclic carbene ligands: From the synthesis of azolium salts and metal complexes to applications

•The combination of NHC and S donor groups within the same hybrid ligand imparts enhanced chemical versatility.•Diversity of coordination modes for the S-functionalized NHC ligands.•Hemilability and reactivity of S,CNHC-metal systems.•Applications of S,CNHC-metal systems in homogeneous catalysis.

This review summarizes the recent progress in the field of S-functionalized N-heterocyclic carbene ligands and their metal complexes. The syntheses of the azolium precursors and of the corresponding metal complexes are discussed as a function of the five different S-containing chemical groups examined here: thiolate, thioether, thiophene, sulfonate and thione. In addition to an example of application of dithienyl-functionalized NHC acting as a switchable organocatalyst, the properties of the S-functionalized NHC metal complexes are discussed for each category of ligand, and are mostly related to applications in homogeneous catalysis.

Graphical abstractN-Heterocyclic carbene ligands can be associated with one or more S-containing functional groups, such as thiolates, thioethers, thiophenes, sulfonates or thiones. Their ligand properties are examined and the applications of their metal complexes are discussed for each category of ligand, and are mostly related to homogeneous catalysis.Figure optionsDownload full-size imageDownload as PowerPoint slide