**1.3 Late transition metals**

Late transition metals are on the right side of the d-block, from group 8 to 11 (and 12 if it is counted as transition metals) as shown in **Figure 2**.

**Figure 1.** *The structure and stabilization of the first persistent carbene and NHC's.*


**Figure 2.** *Late transition metals.*

*Late Transition Metal (LTM)-NHC Catalyzed Transformations of Renewable Chemicals… DOI: http://dx.doi.org/10.5772/intechopen.101164*

#### **Figure 3.**

*Transmetalation route for the synthesis of carbenes.*

#### **1.4 Free carbine route**

The general synthesis of carbene complexes involves the utilization of strong bases and harsh reaction conditions which involves high cost and more time.

#### **1.5 Transmetalation route**

It involves the transfer of the carbine fragment from a suitable metal center [generally Ag(I) or Cu(I)] to a precursor of the metal center of interest [19–22] as shown in **Figure 3**.

Even though, transmetalation method has operational simplicity but lacks atom economy. Hence, it is applied, in general, in scalable industrial processes.

### **2. Applications of late transition metal NHC's**

#### **2.1 CO2 as building blocks**

The exploitation of carbon dioxide as a renewable green source of carbon in organic synthesis is of continued interest. In this regard, late transition metal NHCs play a major role for the specified purpose.
