Application of transition metal fluorides in catalysis

Transition metal (TM)-based catalysts are indispensable tools in modern organic synthesis. Although many efficient catalysts based on TMs are already known, further improvement of catalytic system activity remains one of the major goals of transition metal coordination chemistry. A large number of TM-based catalysts contain halide ligands, mostly chlorides and bromides. Transition metal fluorides have received less attention due to their relatively low stability or more difficult synthesis. However, their performance in many processes considerably differs from other halides. Insertion of fluoride in coordination sphere of metal can significantly improve the activity of the catalyst or even shift the reaction selectivity. In this review, we have collected applications of TM fluorides as catalysts for organic reactions and attempted to shed light on the nature of their remarkable activity compared to other TM halides. The review also covers a recently proposed strategy for activation of catalytic systems with fluoride, which can significantly simplify further application of capricious metal fluorides in catalysis. Finally, prospects for the development of fluoride catalysts are suggested.