The reaction of Fe+ with CS2, which was selected as a representative system of the reactions of transition metals with CS2, has been investigated using density functional theory at B3LYP/6-311+G(d) level of theory. The geometries, energies and frequencies of reactant, intermediates, transition states and products were explored in detail on both the quartet and sextet potential energy surfaces of [Fe, C, S-2](+). Our calculations indicate the reaction proceeds via an insertion-elimination mechanism but not a direct abstract mechanism. All of the observed products in the early experiment has been explained according to the cleavage of different bonds in the insertion intermediate S-Fe+-C-S. The connectivity in [Fe, C, S](+), which cannot be specified by experiment, was revealed as [S-C-Fe](+) in our study. By comparing the Fe+ + CS2 and V+ + CS2, we suppose all the reactions of first-row transition metal ions with CS2 could proceed according to the similar insertion-elimination mechanism. (C) 2002 Elsevier Science B.V. All rights reserved.