A theoretical analysis of the haptotropic rearrangements involving thiophene and [Rh(PH3)3]+ is presented. This haptotropic rearrangement is involved in the C-S bond activation of thiophene by d8-ML3 fragments. In this study, two theory levels, the second order Moller-Plesset perturbation theory (MP2) and density-functional theory (DFT-B3LYP), are employed. The pathway discussed in this paper connects an η4 coordination mode with an η3 one. The results suggest that for the fragment studied in this work, an η3 precursor of the C-S cleavage is preferred over the other one proposed in the literature.