Leaching of palladium atoms from small cluster models during Heck reactions – An experimental and theoretical study

Deconvoluting Substrates, Support, and Temperature Effects on Leaching and Deactivation of Pd Catalysts: An In Situ Study in Flow

“…By far, this appears to be the only system where the interaction with the aryl iodide is the only reaction component that causes leaching. The mechanisms by which ArX can cause leaching from surfaces of Pd nanoparticles have been extensively studied computationally by the research groups of Heinz, Ananikov, and Köhler . Based on these reports, we speculate that nature of these leached species is likely to be Pd clusters, which have greater catalyst activity and stability than the molecular species leaching from the polymer-supported PdEnCat and FC-1001.…”

“…Indeed, catalyst leaching in cross-coupling reactions, and the role of the leached species in catalytic turnover, have been topics for many debates. , Recently, there has been growing evidence to show that the mercury poisoning test is an unreliable method for discriminating between homogeneous and heterogeneous catalysis, , casting doubts on earlier studies. Discounting the mercury poisoning test, most leaching studies are conducted by corelating reaction conversions with the amount of Pd present in the reaction aliquot. − In comparison, there were fewer studies of catalyst leaching in situ, as these often required customized techniques and reactors. One of the earliest examples is a two-compartment reactor reported by Rothenberg and co-workers, , where a nanofiltration membrane was used to physically separate Pd catalyst nanoparticles in a separate compartment from other reaction components: iodobenzene, butyl acrylate, and a heterogeneous base (NaOAc).…”