EPR spectroscopy has been used to monitor changes occurring at the molecular level upon adsorption of N2O on grafted Mo/SiO2 catalysts using naturally abundant and Mo-95-enriched molybdenum. The tetracoordinated Mo-4c(5+) surface species produced upon reduction with d(x2-y2) SOMO coordinates N2O at 298 K and rearranges into a pentacoordinated complex of apparent C-4v symmetry With d(xy) ground state indicating attachment of the N2O ligand in equatorial position. Upon temperature-induced metal to ligand electron transfer (MLET) between 3 pi* and d(xy) redox orbitals, O- radicals are produced with an activation energy of 20 +/- 4 kJ/mol measured in the 323-393 K range. The mechanism of this process and the hindrance to electron transfer are discussed in terms of intrinsic barriers and within the framework of potential energy surfaces. From the spin Hamiltonian parameters of O-, the unpaired electron density on molybdenum and the splitting of energy levels of O- species were calculated to be 4.3% and Delta E(x,y-z)=1.5 eV, respectively. The crystal field approach was used to discuss the O--Mo6+ bonding.