We report the results of theoretical mechanistic studies on PH3-assisted migration of a coordinated aryl group to a coordinated CO in the complexes RhCpI(CO) (p-XC6H4). The X-substituent effect on thermodynamic and kinetic parameters was explored. The progress of the reaction was quantitatively studied using the bond orders of the Rh-CO bond, and the percentages of bond cleavage (BCij) of Rh-CO bond at the transition state were described. This theoretical study indicates good relationships between barrier energy (ΔE), bond distances variations (Rh-CO and Rh-Ph), activation energy (ΔH‡) , activation free energy (ΔG‡) values with Hammett constants of X-substituents. Linear relationship between ln(k) and the 103Rh magnetic shielding tensors of the product was explored.