Mechanistic insights into the transmetalation step of a Suzuki-Miyaura reaction of 2(4)-bromopyridines: Characterization of an intermediate

The mechanistic study of the palladium-catalyzed Suzuki-Miyaura cross-coupling between bromophenylpyridine compounds and phenylboronic acid led to the NMR identification of a transient intermediate in the transmetalation step. This species was identified by DFT calculations as a [Pd{Ph-B(OH)₃^–}{C₅H₂RN}(PR₃)₂] complex, containing a boronate ligand coordinated through an oxygen group to the metal center. The fitting of this intermediate within recent mechanistic proposals on the mechanism of transmetalation is discussed.