The reaction of CO2 with (eta (2)-dioxygen)-transition metal complexes to give peroxocarbonates has been modelled using the Impulse Oscillation Model (IOM).(1) In accordance with our experimental findings concerning the reactivity of P3ClRh(eta (2)-O-2) (P = phosphane ligand) complexes towards carbon dioxide, application of the model to this reaction shows that the insertion of carbon dioxide into the O-O bond is the preferred pathway. In fact, the probability for CO2 insertion into the O-O bond equals maximum to 0.98 while into the M-O bond equals to 0.02. The concordance of calculated and experimental stretching frequencies indicates the possibility of identifying, through the vibration modes, proper ligands and metal systems that behave as selective catalysts at molecular level.