Introduction
Carbon-donor ligands are a class of ligands that contribute carbon atoms in chemical reactions and they are usually referred to as carbene ligands. Carbon monoxide is the simplest carbon-donor ligands, and N-Heterocyclic carbenes are an important class of compounds that are indeed regarded as most versatile carbon-donor ligands in transition metal and organometallic catalysis. A N-Heterocyclic carbene contains a nonbonded singlet lone pair and is an electron-rich neutral donor ligand, these neutral two-electron donors show pronounced σ-donor ability with only little to no π-back-bonding. Due to their strong σ-electron-donating properties, N-Heterocyclic carbenes ligands usually form strong bonds with most metal centers and are therefore highly resistant toward decomposition. Beyond that, their facile availability, synthetic flexibility, and beneficial impact on (catalytic) reactivity of the metal center have bring many advantages in research of carbene metal complexes. Because of the advantages mentioned above, N-Heterocyclic carbenes has disclosed highly diverse fields of applications.

Applications
N-Heterocyclic carbenes have become one of the most widely studied class of ligands in molecular chemistry and have found applications in fields as varied as catalysis, photophysical, and biochemistry[1].
Fig.1 Some structure of N-Heterocyclic carbenes complexes
Alfa Chemistry can offer all kinds of carbon-donor ligands, especially N-Heterocyclic carbenes ligands and related technical advices and services, please don't hesitate to contact us if you are in need of assistance.
Reference
- Vivancos A.; et al. Mesoionic and related less heteroatom-stabilized N heterocyclic carbene complexes: synthesis, catalysis, and other applications[J]. Chemical Reviews. 2018, 120, 9493-9586.