source: Coordination Chemistry Review year: 2007 volume: 251 first page: 765 last page: 794 doi: 10.1016/j.ccr.2006.09.002
Abstract: N-heterocyclic carbenes are now commonly encountered in organometallic and inorganic coordination chemistry. The increasing attention they enjoy is due to their ability to act as ancillary ligands in a growing number of transition metal catalysts or even to play the role of nucleophilic reagents and catalysts in diverse organic transformations. As a fine addition to the NHC-Ru-alkylidenes, popular for their tremendous success in metathesis chemistry, an array of robust and stable Ru-NHCs have proven their utility in non-metathetical reactions. The present review surveys different classes of Ru-NHCs and their applications as efficient catalysts (or precatalysts) in several types of fundamental organic processes e.g. hydrogenation, hydrogen transfer, isomerization, cycloisomerization, cyclopropanation, hydrosilylation, allylation and deallylation, enol-ester synthesis, heterocycle synthesis, C-C alkyne coupling, Kharasch addition and ATRP. A special section is devoted to tandem processes some of which include concurrent or sequential metathesis steps. Relevant mechanistic and stereochemical aspects related to NHC-Ru catalysis will be highlighted.
Keywords: N-Heterocyclic Carbenes, Ruthenium Complexes, Non-Metathesis, Catalysis, Radical Reactions, Tandem Processes