Narrow Results

The detailed singlet potential energy surface (PES) of the reaction of Ni(d^{10 1}S) + H₂ + CO₂→NiCO + H₂O is investigated at the CCSD(T)/6-311+G(2d,2p)//B3LYP/6-311+G(2d,2p) levels in order to explore possible reaction mechanism of CO₂ hydrogenation on Ni center. The calculation predicts that the co-interacted H₂ involved C–O bond cleavage of CO₂ molecule is prior to the dissociation of adsorbed H₂ molecule, and the entire reaction is exothermic by 297.3 kJ/mol with an energy barrier of 137.7 kJ/mol. The rate-determining step (RDS) for the overall reaction is predicted to be the insertion of Ni into the C–O bond of the CO₂ moiety.

The reaction mechanism of the activation of ethane by nickel atom has been investigated by density functional theory (DFT). The geometries and vibration frequencies of reactants, intermediates, transition states and products have been calculated at the B3LYP/6-311 + +G(d, p) level. Two main pathways, C–C bond activation and C–H bond activation, are identified. In former channel, the rate-limiting step is found to be hydrogen-transferring step with a high barrier of 227 kJ · mol^-1. In the C–H bond activation pathway, the second hydrogen-transferring step is the rate-determining step of the whole reaction. The barrier of the step is 71 kJ · mol^-1. Our results show that the studied reaction would undergo along C–H bond activation pathway to form the products H₂ molecule and Ni⋯ethene complex. The present theoretical work indicates that Ni atom is more active than Ni⁺ cation in activating ethane.