NHC–Nickel and Platinum Complexes in Catalysis
This chapter summarizes the recent impact of the use of N-heterocyclic carbene (NHC) ligands in the field of Ni- and Pt-mediated processes. This family of ligands have allowed the development of novel nickel-based catalysts of increased reactivity and selectivity compared to previous Ni-phosphine reagents. These NHC–Ni catalysts are active in hydrogenation, hydrogen transfer properties and C–S or C–F bond activation. Conversely, they efficiently catalyze arythiolation, hydrothiolation and also cross-coupling reactions, as well as various cycloadditions of alkynes, isomerization of vinylcyclopropanes, polymerization or carboxylation reactions. In most of these processes, nitrogen- or oxygen-containing heterocycles can be efficiently produced. New features in the design of more efficient NHC–Ni are specifically examined for these catalytic applications. On the other hand, the application domain of NHC–Pt analogues appears still restricted. Indeed, recent studies are, above all, focused on preparation of new families of Pt complexes for particular applications in light emitters or in medicine. Apart from hydrogenations or hydrosilylations (covered in Chapter 13), some miscellaneous reactions such as diborilation, and cycloisomerisation of enynes or polyenes, are described.