Density functional theory (DFT) calculations have been performed to explore the potential energy surfaces of C–O bond activation in CO2 molecule by gas-phase Mo + cation and Mo atom, in order to better understanding the mechanism of second-row metal reacting with CO2. The minimum energy reaction path is found to involve the spin inversion in the different reaction steps. This potential energy curve-crossing dramatically affects reaction exothermic. The present results show that the reaction mechanism is insertion-elimination mechanism along the C–O bond activation branch. All the theoretical results not only support the existing conclusions inferred from early experiment, but also complement the pathway and mechanism for this reaction.

The potential energy surfaces for the La + CO2 and La+ + CO2 reactions have been theoretically investigated by using the DFT (B3LYP/ECP/6–311+G(2d)) level of theory. To obtain an accurate evaluation of the activation barrier and reaction energy, the QCISD(T) single-point calculations using the B3LYP structures were performed. Both ground and excited state potential energy surfaces are discussed. These results show that the reaction mechanism is insertion mechanism along the C–O bond activation branch. The reaction of La atom with CO2 was shown to occur preferentially on the ground state (doublet) PES throughout the reaction process, and the experimentally observed species, has been explained according to the mechanisms revealed in this work. As for the reaction between La+ cation with CO2, it involves potential energy curve-crossing which dramatically affects reaction mechanism, and the crossing points (CPs) have been localized by the approach suggested by Yoshizawa et al. Due to the intersystem crossing existing in the reaction process of La+ with CO2, the intermediate (OLa(η2-CO))+ may not form. This mechanism is different from that of La + CO2 system. All our theoretical results not only support the existing conclusions inferred from early experiment, but also complement the pathway and mechanism for this reaction.

Density functional theory (DFT) calculations have been performed to explore the sextet, quartet, and doublet potential energy surfaces of C–X (X=S, O) bond activation in CS2 and SCO molecules by gas-phase Mo+ cation, in order to better understanding the reaction mechanism of second-row metal cations reacting with SCX (X=S, O). The minimum energy reaction path is found to involve the spin inversion in the different reaction steps. The crossing points (CPs) of the different potential energy surfaces (PESs) have been localized with the approach suggested by Yoshizawa et al. [K. Yoshizawa, Y. Shiota, T. Yamabe, J. Chem. Phys. 111 (1999) 538]. The potential energy curve-crossing dramatically affects reaction mechanism. The present results show that the reaction mechanism is insertion–elimination mechanism both along the C–S and C–O bond activation branches, but the C–S bond activation is much more favorable than the C–O bond activation in energy. All theoretical results not only support the existing conclusions inferred from early experiment, but also complement the pathway and mechanism for this reaction.