It is worth mentioning that Mirica and Chaplin had independently studied the reactions of [Pd(P t Bu3)2] + with aryl iodide and proposed the formation of Pd(III) intermediates via concerted oxidative addition reactions in their systems. Our calculation studies on a concerted oxidation addition pathway between 2 and the benzyl bromide, however, failed in locating its transition state probably due to high steric congestion. The mechanistic difference can be ascribed to the different steric and redox properties of the Pd(I) species and the organic halides. Cyclic voltammetry study on 2 indicates the redox event of 2 1-/0 has the half-wave potential E1/2 = -1.30 V (versus standard calomel electrode (SCE)), which is much lower than that of [Pd(P t Bu3)2] 0/1+ (E1/2 = 0.0 V vs SCE), and the redox process of 2 0/1+ with the potential of the oxidation peak Ep = 0.66 V is irreversible (Figure ). These potentials hint that the Pd(I) aryl species 2 is more reducing than [Pd(P t Bu3)2] + . On the other hand, the benzylic bromide is more oxidizing than aryl iodide. These two factors, in addition with sever steric hindrance around the Pd(I) center in 2 caused by its bulky NHC and aryl ligands, could thus lead to the preference of a stepwise oxidative addition mechanism.