Performance of Density Functionals for Activation Energies of Re-Catalyzed Organic Reactions

By employing high-level coupled cluster CCSD(T)-F12 calculations as reference, we herein systematically assessed the performance of 16 popular density functional theory (DFT) approximations for typical rhenium-catalyzed reactions. The reactions under study cover those catalyzed by low-valent rhenium(I)/(III) carbonyl complexes as well as high-valent organorhenium(VII) bisperoxo complex. Without DFT dispersion correction, the four best-performing functionals for the barrier heights are B2GP-PLYP, TPSSh, B3LYP, and PBEO with the mean unsigned deviations (MUDs) under kcal/mol. Among these four functionals, B2GP-PLYP generates more accurate barrier heights, while B3LYP and TPSSh behave more reliably in the barrier trend description for these Re-catalyzed reactions. In general, herein the hybrid functionals are better choices than pure GGA or pure meta-GGA functionals. DFT empirical dispersion corrections were found to have beneficial effects on MUDs only for four tested functionals of BMK, CAM-B3LYP, LC-omega PBE, and omega B97X. Often associated with very large errors up to about 15 kcal/mol in barrier height for many tested functionals, the reaction catalyzed by high-valent rhenium(VII) bisperoxo is apparently different from the ones catalyzed by low-valent rhenium(I)/(III) carbonyl complexes. For reactions catalyzed by Re(I)/(III) carbonyl complexes, omega B97XD with dispersion correction performs excellently (MUD = 0.63 kcal/mol) and hence is highly recommended for these Re(I)/Re(III)-mediated reactions.