An explicit account of solvation is essential for modeling Suzuki-Miyaura coupling in protic solvents

We compared explicit and implicit solvation approaches in modeling the free energy profile of the final step of Suzuki-Miyaura coupling. Both approaches produced similar ΔG(≠) in all the studied solvents (benzene, toluene, DMF, ethanol, and water). Solvation free energies of individual reaction components reasonably correlated for explicit and implicit models in aprotic solvents (RMSE = 30-50 kJ mol(-1), R(2) > 0.71). However for ethanol and water the correlation was poor. We attributed this difference to the formation of the PdH-O hydrogen bond with Pd(PPh3)2 which was surprisingly observed in explicit modeling. Further QM calculations of the Pd(PPh3)2-H2O system confirmed the direction (PdH) and stability of this bonding. Therefore we stress the need for considering explicit solvation for modeling Pd-catalyzed reactions in protic solvents.