N-Heterocyclic Carbenes

This chapter presents an overview of N-heterocyclic carbenes (NHCs) as chemical species. The electronic characteristics of these ligands are discussed, detailing how pπ–pπ delocalization and σ electron withdrawal stabilizes the carbene center. The bonding to metal centers is also discussed, whereby the potential for σ donation, π donation, and π backbonding is highlighted. The chapter presents a brief introduction to how these species can be classified. In addition, an overview is also presented of how these compounds, and stable adducts thereof, can be prepared in the laboratory. The chapter provides the reader with a foundation from which the myriad applications of NHCs can be appraised and understood, en route to stimulating or developing the use of NHCs in the reader's chemical research.