text: Since mesoionic carbene ligands are very strong σ-donors and make it easier for a metal center to undergo oxidative addition, MIC ligands have the potential to be useful in catalysis.  MIC transition metal complexes have been tested as catalysts in olefin metathesis, ring closure metathesis, and ring opening polymerization metathesis.  The MIC complexes work very well, and in many cases, they outperform their NHC counterparts.  MIC complexes have been successful as catalysts for Suzuki-Miyaura and Heck-Mizoroki cross-coupling reactions.  Again, in many cases, MIC catalysts are superior to their NHC counterparts.  For example, in olefin metathesis, MIC catalysts are active at room temperature after simply addition of a Brønsted acid, such as hydrochloric acid or trifluoroacetic acid, compared to the large amount of thermal activation required for NHC catalysts.  MIC complexes have found use as catalysts in olefin hydrogenation.  They have been shown to hydrogenate terminal and cis-alkenes.  They work better than their NHC counterparts due to the MIC ligand’s stronger electron-donating properties.  They are better able to provide electron density to promote hydrogen gas oxidative addition to the metal.  MIC complexes have been used in transfer hydrogenation reactions.  For example, they have been used to hydrogenate a diaryl ketone using isopropanol as a hydrogen source.,  MIC complexes are being considered as green chemistry catalysts.  They act as catalysts for base- and oxidant-free oxidation of alcohols and amines.  Some complexes have also been shown to synthesize certain aryl amides.  Other MIC complexes have been used in hydroarylation, involving the addition of an electron-rich aryl group and a hydrogen across a multiple bond.  The reactions that mesoionic carbene complexes catalyze will continue to expand as more research is done.