In order to elucidate the mechanism of reaction M^＋＋SCO, the reactions of Cu^＋＋SCO and Zn^＋＋SCO have been investigated at the B3LYP level of density functional theory with the standard 6-311＋＋G** basis set. The geometries for reactants, transition states and products were completely optimized. All the transition states were verified by the vibrational analysis and the intrinsic reaction coordinate calculations. For the reaction of Cu^＋＋SCO, the involved potential energy curve-crossing dramatically affected reaction mechanism, and the reaction rate has been discussed detailedly, the crossing point are localized by means of the Hammond postulate and the intrinsic reaction coordinate approach. The results show that the reaction took 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. The main reaction channel was detected for the title reaction. All theoretical results are in line with early experiments.

Key words: transition-metal ion, reaction mechanism, density functional theory