Metal insertion route of the Ni+CO2→NiO+CO reaction

The gas-phase reaction of the nickel atom with CO2 molecule is investigated at the B3LYP and CCSD(T) levels of theory. The insertion-elimination route to NiO ((3)Sigma(-)) + CO ((1)Sigma(+)) is found to be the most favorable mechanism. The insertion product on the (3)A surface is calculated to be about 15 kcal/mol higher in energy than the reactants. The insertion reaction is direct and needs to overcome an energy barrier of 34.6 kcal/mol. A second path, on the (3)A' surface, is similar but the insertion product is less stable with respect to the corresponding (3)A species and the transition state is higher in energy. The (3)A insertion product can dissociate to NiO ((3)Sigma(-)) + CO ((1)Sigma(+)) without exit barrier. This reaction is endothermic by 22 kcal/mol. The (3)A' insertion product can also dissociate without exit barrier but leads to an excited state of nickel oxide (A (3)Pi). The Ni + CO2 --> NiO + CO reaction is found to be endothermic by 37.4 kcal/mol in good agreement with experiment (36.6 kcal/mol).