Stability of Supported Pincer Complex-Based Catalysts in Heck Catalysis

Several studies question the stability of palladated pincer complexes under Heck catalysis conditions. Through a series of poisoning tests, kinetic and spectroscopic studies, and computational experiments, these studies prove that any supported as well as small molecule Pd-pincer complexes decompose during the Heck catalysis. Furthermore, no experimental proof could be obtained with regard to the proposed Pd(II)/Pd(IV) catalytic cycle, which is a requirement for the Heck promoted by stable Pd(II) pincer complexes. The decomposition results may be applicable to other Pd-coupling chemistry because they follow similar catalytic cycles. Despite the detailed kinetic and poisoning studies, recent literature still show a plethora of articles that use palladated pincer complexes as catalysts for coupling chemistry where no studies to investigate the stability of the Pd pincer complexes are carried out.