**4. Catalytic applications of NHC-metal complexes**

In 1962, Wanzlick et al. made the early reports on the stability and reactivity of NHCs [55]. Later in 1968, the first NHC-mercury complex was isolated [56]. Despite this isolation, the studies related to the NHCs as ligands thrived only after the first isolation report by Arduengo et al. in 1991 [1]. This easy synthetic strategy facilitated the extensive studies of NHC-metal complexes and their catalytic applications. The catalytic applications of NHCs as ligands can be broadly classified into three types, and they are (a) NHCs for organocatalysis [57–59], (b) NHCs as ligands for transition metal catalysis, and (c) NHCs and main group elements-based adducts for catalysis [60]. The following section of this chapter focuses on few selective and important NHC-transition metal catalyzed reactions (**Figure 15**), since the complete details are beyond the scope of this chapter.

#### **Figure 15.**

*Catalytic applications of NHC-transition metal complexes [14].*

*Imidazolium-Based N-Heterocyclic Carbenes (NHCs) and Metal-Mediated Catalysis DOI: http://dx.doi.org/10.5772/intechopen.102561*
