REINVESTIGATION OF THE OXIDATIVE ADDITION OF MEI, H2, AND O2 TO IR(CO)(CL)L2 - QUANTITATIVE-ANALYSIS OF LIGAND EFFECTS (QALE)

Kinetic data for the oxidative addition of Mel and H-2 to Ir(CO)(Cl)L2, as well as the data for the association and dissociation of O2, were analyzed satisfactorily in terms of the three stereoelectronic parameters chi, theta, and E(ar) of the phosphine ligands according to the following equation: log k = a(chi) + btheta + cE(ar) + d. Literature data for MeI and H-2 addition have been supplemented with data from our laboratories. The addition of MeI involves the most polar transition state of the group, whereas the addition of H-2 involves the least polar transition state based on the size of the coefficients of chi. All the reactions show a significant dependence on E(ar), including the addition of H-2, which shows little dependence on chi. The steric sensitivity (coefficient of theta) is greatest for the addition of MeI and least for H-2. The coefficients of both chi and E(ar) for the MeI reaction are smaller in acetone compared to those in benzene, whereas the steric sensitivity shows a smaller variation on changing solvent. The addition of H-2 is insensitive to the nature of the solvent. The dissociation of O2 from Ir(CO)(Cl)L2(02) is insensitive to both theta and chi but does show a statistically significant dependence on E(ar).