Redox Reactions in Palladium Catalysis: On the Accelerating and/or Inhibiting Effects of Copper and Silver Salt Additives in Cross‐Coupling Chemistry Involving Electron‐rich Phosphine Ligands

Challenging a catalytic cycle : Pd 0 catalysts are readily oxidized by Cu and Ag salts to give dinuclear Pd I complexes and Cu I or Ag I cubanes (see scheme). The reactivities of the resulting Pd I dimers are consistent with several observations of additive effects in cross‐coupling chemistry. The results indicate the possibility for alternative catalytic cycles involving dinuclear Pd I complexes over the currently accepted synergistic cycles involving Pd 0 /Pd II intermediates and Cu or Ag.