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+(F-4) 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. (c) 2008 Elsevier B.V. All rights reserved.