Turning Frustration into Bond Activation: A Theoretical Mechanistic Study on Heterolytic Hydrogen Splitting by Frustrated Lewis Pairs

摘要

It has long been noted that the strength of the dative bond in a Lewis acid-base pair is strongly influenced by steric factors, which can even preclude the formation of a donor-acceptor adduct. These systems remained only exotic textbook examples until quite recently, when Stephan et al. brought into sharp focus their inherent synthetic potential. In their landmark experiments, they demonstrated that the incapability of adduct formation in a "frustrated Lewis pair is a key element to remarkable chemical transformations. For instance, mixtures of frustrated phosphines (PR3, R = C6H2Me3 or tBu) and boranes (BR'3, R' = C6F5) can easily cleave molecular hydrogen (H2) in a heterolytic manner under very mild conditions, and they can undergo addition reactions with olefins as well.