The adsorption of NO onto Ni/SiO2 catalyst has been investigated at 77 and 296 K at various pressures by EPR spectroscopy. The principal steps of NO disproportionation involve coordination of NO molecule with concomitant formation of paramagnetic mono {Ni-3c(II)-NO.}(9)/SiO2 and diamagnetic dinitrosyl species {Ni-2c-(NO)(2)}(10)/SiO2, reduction of nickel through inner-sphere ligand-to-metal electron transfer leading to {Ni-3c(I)-NO+}(9)/SiO2, formation of {Ni-3c-NO2}(9)/SiO2 Complex via metal-oxo intermediate, and spillover of the NO2 ligand onto silica. The key reaction intermediates have been isolated and identified. Their assignment and molecular structure have been ascertained by DFT calculations. (c) 2006 Elsevier B.V. All rights reserved.