Evidence for 'cocktail'-type catalysis in Buchwald-Hartwig reaction. A mechanistic study

摘要

The mechanism of the C-N cross-coupling reaction, catalyzed by palladium complexes with N-heterocyclic carbene ligands (Pd/NHC), was evaluated in detail at the molecular and nanoscale levels. For the first time, the formation of a "cocktail"-type catalytic system was proven for the Buchwald-Hartwig reaction. The unique ability of the Pd/NHC system to generate several types of catalytic centers (Pd complexes, clusters and nanoparticles) and the involvement of complementary pathways (homogeneous and heterogeneous) were discovered to take place in a "one pot" manner directly in the reaction vessel. Access to various catalytic centers from a single and readily available Pd/NHC complex is the key to designing a universal catalytic system with adaptive tuning capability.