A copper trispyrazolylborate complex catalyzes the direct oxidation of benzene to phenol. The oxidation of the catalyst may yield a copper-oxo active species, although superoxo and hydroperoxo active species cannot be excluded. The electronic structure and reactivity of these complexes have been studied at the DFT level. The computed Gibbs energies show that the generation of the oxo complex is exoergic, whereas the formation of the superoxo and hydroperoxo species is not spontaneous. In addition, the latter two species involve very high energy pathways. The oxo active species, which has radical electrophilic character, promotes the reaction through two distinct mechanisms: OH rebound and electrophilic aromatic substitution (see Figure). Both mechanisms are stepwise and require intersystem crossing between the singlet Cu(I) and triplet Cu(III) states. The lowest energy profile is associated with the electrophilic aromatic substitution pathway, in agreement with experiments. 

Mechanistic insight into copper-catalyzed C-H oxidation: A mixed experimental/theoretical study

244th National Meeting (2012)

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