First time exploration and characterization of key-intermediates in palladium-catalysed coupling reactions

Abstract

Abstract The oxidative addition of a bromoporphyrin onto in situ formed highly active Pd(0) complex allowed us to characterize the Pd(II) intermediate by X-ray crystallography. In addition, after the heterobidentate coordination of Xantphos hemioxide ( Xantphos: 4,5-bis(diphenylphosphino)-9,9-dimethyl-xanthene), the oxidized product responsible for Pd(II)-Pd(0) reduction, was also proved. The species isolated by us is the product of oxidative addition, the first step of the suggested catalytic cycle. Earlier only the structure of the dichloro complex of palladium with (P-P(O)) ligand was known. The isolated Pd(P-P(O))X(porphyrinyl) complex can be considered as a new example of catalytic intermediates of important cross-coupling and carbonylation reactions giving further strong proof for their mechanism.