Solvent coordination to palladium can invert the selectivity of oxidative addition.

Reaction solvent was previously shown to influence the selectivity of Pd/P Bu-catalyzed Suzuki-Miyaura cross-couplings of chloroaryl triflates. The role of solvents has been hypothesized to relate to their polarity, whereby polar solvents stabilize anionic transition states involving [Pd(P Bu)(X)] (X = anionic ligand) and nonpolar solvents do not. However, here we report detailed studies that reveal a more complicated mechanistic picture.