Reactions catalyzed by N-heterocyclic carbene-metal complexes, such as olefin metathesis, coupling reaction, hydrosilylation reaction, etc. were reviewed. Ruthenium(Ⅱ) complexes bearing one or two imidazolin-2-ylidene ligands are highly active catalysts for all types of ring closing metathesis reactions. Importantly, they even allow the formation of tetrasubstituted alkenes that were not previously achieved by ruthenium-phosphine metathesis catalysts. In addition, functionalized olefins were synthesized by intermolecular cross- metathesis and ring-closing metathesis. Palladium(O) complexes of imidazolin-2-ylidenes (19) could not catalyze the coupling of p- chlorotoluene and phenylboronic acid. However, a system consists of a Pd(O) precursor and dihydroimidazoline carbene ligand, which is generated in situ, showed high activity for Suzuki cross-coupling reaction of aryl chlorides with arylboronic acids, Kumada cross- coupling reaction of aryl chlorides with aryl Grignard reagents and amination of aryl chlorides. Complexes of the (NHC)Pd(PR3)I2-type with bulky N-heterocyclic carbenes (NHC) are efficient catalysts for the Suzuki and Stille cross-coupling reactions, etc. Imidazolidin-2- ylidene derivatives of rhodium(Ⅰ) and ruthenium(Ⅱ) catalyze the carbon-carbon coupling of terminal alkynes, the cyclopropanation reactions of diazoalkane derivatives with styrene, hydrosilylation of alkenes, alkynes, ketones and hydrogenation of olefins.

Key words: HETEROCYCLIC COMPOUNDS, LIGANDS, METAL COMPLEX, ORGANIC SYNTHESIS, METAL CATALYST, CATALYTIC REACTION