Nothing frustrating about “Frustrated Lewis pairs”

In the six short years following our initial report, the areas impacted by the chemistry of “frustrated Lewis pairs” (FLPs) continue to grow most dramatically. While the use of FLPs in stoichiometric and catalytic hydrogenations of imines was the first application to emerge, the development of such metal-free hydrogenations continues to surprise. The evolution of FLPs has resulted in an extended range of hydrogenation substrates including silylenol ethers, enamines, enones, anilines and heterocycles. In addition, beautiful developments in the hydrogenation of challenging organometallic substrates have been demonstrated. In a further evolution, important work on asymmetric selectivity has also emerged. While aspects and applications of dihydrogen activation continue to be of experimental and theoretical interest, the chemistry of FLPs is certainly not a “one-trick pony”.

FLPs have also been shown to activate a widening variety of small molecules, including olefins, alkynes, disulfides, B–H and C–H bonds, CO₂, N₂O, cyclopropanes, enynes, enones and diynes, among others. This variety of reactivity foreshadows applications of FLPs in synthetic organic chemistry. In addition, the timely work on greenhouse gas capture and reduction may provide new strategies to these issues. The insightful use of FLPs in acrylate polymerizations, and, most recently, in the radical polymerization of styrenes, are brilliant examples of creative new developments that target real-world utility. It is also clear that the concept of FLPs is not being limited to main group systems. Indeed, the advent of all-carbon- and metal-based FLPs demonstrates a broadening scope of impact. There is no doubt that exciting new developments will emerge as a more diverse cross-section of the chemical community embraces and applies the concept of FLPs.

The collection of papers presented in this issue of Dalton Transactions is focused on FLP chemistry. This collection illustrates a series of clever innovations from creative chemists. A variety of FLPs incorporating new group 13/15 combinations, and carbon- or metal-based FLP systems demonstrate new reactivity of FLPs, while computational studies provide insight, understanding and stimuli for further synthetic work. These contributions make this volume an exciting one, as they reflect the broadening impact and excitement of the new field of FLP chemistry.

---