C-S Activation of CS₂ by Nb^{+ in Gas Phase}

The reaction of Nb⁺ with CS₂, producing cationic transition-metal sulfide and CS, was taken as a representative example to elucidate the overall mechanism of reactions of second-row early transition metal ions with CS₂. The reactions in both triplet and quintet state were studied by using the UB3LYP density functional method with the Stuttgart pseudo potentials and corresponding basis sets for Nb⁺ and the standard 6-311+G(2d) basis sets for C and S. The geometries for reactants, the transition states, and the products were completely optimized. All the transition states were verified by vibrational analysis and intrinsic reaction coordinate calculations. The results show that the reaction mechanism between niobium ion and CS₂ is an insertion-elimination mechanism. Intersystem crossing may occur in the reaction Nb⁺ with CS₂ and a minimum energy crossing point was found.