N-Heterocyclic carbene complexes of rhodium: structure, stability and reactivity

The organometallic chemistry of N-heterocyclic carbene complexes of the transition metals has received significant attention over the past ten years, especially with respect to complexes of Pd and Ru. The present Perspective highlights the chemistry of NHC complexes of another important transition metal, Rh. The application of Rh-NHC complexes in the industrially significant reactions of hydrogenation and hydroformylation is described. In order to accurately assess the activity of these complexes, their stability must be carefully determined. Various synthetic routes to Rh-NHC complexes are also described.