Preparation of NHC–ruthenium complexes and their catalytic activity in metathesis reaction

A detailed overview on the synthesis of four-, five- and six-membered, saturated and unsaturated N-heterocyclic carbenes used in the preparation of their corresponding ruthenium complexes (Grubbs’ second-generation, Fischer-type, Hoveyda–Grubbs, homo and hetero-bimetallic) is presented both in solution and on solid support. The catalytic activity of the different complexes in ruthenium-catalyzed metathesis reaction is compared and explained by their structural features.