Transformations of Pd/(N-Heterocyclic Carbene) Molecular Complexes into a Nanosized Catalytic Systems in the Mizoroki–Heck Reaction

The mechanism of the formation of catalytic species in the practically important Mizoroki–Heck reaction, which is in demand in modern fine organic synthesis, has been studied. It has been shown that catalysts based on palladium complexes with N-heterocyclic carbene ligands are transformed into a “ligand-free” form under the conditions of the Mizoroki–Heck reaction. Molecular modeling performed using quantum chemical methods showed that these processes compete with the target reaction at three of the six stages of the catalytic cycle. The presence of catalyst transformation products in the reaction system was confirmed by methods of nuclear magnetic resonance and mass spectrometry. Important mechanistic data have been obtained for the rational design of catalytic systems for cross-coupling reactions.