Chapter 9: NHC–Palladium Complexes in Catalysis

In the past 10 years, the field of NHC–Pd catalysis has grown at an impressive rate. Early studies largely focussed on catalyst design for a limited number of reactions (e.g. C–C coupling reactions). However, the opportunities unveiled by these early studies initiated many and varied research efforts, and a large number of research teams are involved in the field. As a consequence, the range of reactions catalysed by NHC–Pd complexes is now substantial: in addition to the traditional C–C coupling reactions, which still remains the most comprehensively investigated field, it encompasses such reactions as direct C–H arylation, telomerisation, hydrogenation and Buchwald-Hartwig amination (to name a few). A number of catalytic systems are now active enough that they can be considered for pilot or industrial scale production in the fine chemicals and pharmaceutical industry. Yet limitations remain, in particular regarding catalyst deactivation/decomposition. In this chapter, these various aspects are critically examined, with an emphasis on catalyst design for each class of transformation.