LAUSR

Palladium and nickel catalysed cross-coupling reactions are used extensively in organic synthesis, with state-of-the-art cross-coupling methodology enabling access to diverse building blocks in an efficient and selective manner. In recent years, there has been growing interest in using nickel-based catalysts for cross-coupling reactions, in place of the more commonly used palladium catalysts. This is motivated by both the unique reactivity that can be accessed when using nickel catalysts, and due to nickel being cheaper and more earth abundant than palladium. Despite these advantages, larger catalyst quantities and higher reaction temperatures are often required when using nickel, increasing cost and environmental impact. As such, in order to design more efficient nickel-catalysed cross-coupling reactions, a greater understanding of how these catalysts operate is required. In this review, mechanistic studies on the key transmetalation step of typical palladium and nickel-catalysed cross-couplings are discussed, with a focus on how catalyst structure affects the efficiency of transmetalation at palladium(II) and nickel(II).