文摘
A variety of palladated PCP pincer complexes are covalently tethered onto polymeric andsilica supports via either amide or ether linkages and are evaluated in the Heck reaction ofiodobenzene and n-butyl acrylate. The decomposition under reaction conditions of allcomplexes studied is established through poisoning and kinetic studies. Furthermore, theinitial steps of the decomposition pathway of PCP as well as SCS pincer Pd(II) complexesare proposed and validated using in situ NMR, mass spectroscopy, and XAS as well ascomputational methods. These findings together with our previous reports strongly suggestthat all Pd(II) pincer complexes are simply precatalysts during the Heck reaction thatdecompose to form catalytically active Pd(0) species.