Frustrated Lewis pair
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A frustrated Lewis pair (FLP) is a compound or mixture containing a Lewis acid and a Lewis base that, because of steric hindrance, cannot combine to form a classical adduct.[1] Many kinds of FLPs have been devised, and many simple substrates exhibit activation.[2][3]
The discovery that some FLPs split H2[4] triggered a rapid growth of research into FLPs. Because of their "unquenched" reactivity, such systems are reactive toward substrates that can undergo heterolysis. For example, many FLPs split hydrogen molecules. Thus, a mixture of tricyclohexylphosphine (PCy3) and tris(pentafluorophenyl)borane reacts with hydrogen to give the respective phosphonium and borate ions:
- PCy3 + B(C6F5)3 + H2 → [HPCy3]+ [HB(C6F5)3]−
This reactivity has been exploited to produce FLPs which catalyse hydrogenation reactions.[5]