Metal Insertion Route of the Ni + CO2 → NiO + CO Reaction

The gas-phase reaction of the nickel atom with CO 2 molecule is investigated at the B3LYP and CCSD(T) levels of theory. The insertion−elimination route to NiO ( 3 Σ - ) + CO ( 1 Σ + ) 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 Σ - ) + CO ( 1 Σ + ) 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 Π). The Ni + CO 2 → NiO + CO reaction is found to be endothermic by 37.4 kcal/mol in good agreement with experiment (36.6 kcal/mol).