Mechanisms for the Ni-mediated oxidation of benzene to phenol by N2O

The gas-phase Ni⁺-mediated benzene oxidation by N₂O on both quartet and doublet potential energy surfaces are surveyed using density functional theory (DFT). Geometries and energies for all relevant intermediates are calculated. The initial N₂O reduction for forming NiO⁺ takes place only via reaction with the excited Ni⁺(⁴F) through the N–O insertion mechanism. The second step of the oxidation can involve two mechanisms: ‘nonradical’ through benzene H migration following the formation of the boat complex of benzene–NiO⁺ or ‘oxygen-insertion’ via rearrangement to an arenium intermediate from the chair-type benzene–NiO⁺ encounter complex. Both mechanisms are energetically available.