Having established that SIPr and SIMes ligand-controlled divergent selectivity is general to a variety of chloroaryl triflates and arylboronic acids, we next turned to density functional theory (DFT) calculations to understand the origin of selectivity in this system. Calculations were performed at the CPCM(THF) M06/BS2//M06L/BS1 level of theory (seeComputational Methods for details). Neutral transition structures were located using monoligated [Pd(SIPr)] for oxidative addition at both C−Cl and C−OTf of1(Figure 2A, top). Consistent with the experiment, [Pd(SIPr)] is predicted to favor reaction at C−Cl by 4.6 kcal mol−1(compareTS31aandTS31b). However, the same computational method predicts that [Pd(SIMes)] should also favor reaction at C−Cl, by 9.5 kcal mol−1(compare TS32aandTS32b). The latter result strongly contradicts the observed experimental preference for cross-coupling at C−OTf using SIMes. A variety of other DFT methods were evaluated (see theSupporting Information), and nearly all provide the same prediction that reaction at C−OTf is disfavored with [Pd(SIMes)].