Mechanistic Studies of Magnetically Recyclable Pd-Fe3O4 Heterodimeric Nanocrystal-Catalyzed Organic Reactions

Recently, we have reported several catalytic applications of new PdFe3O4 heterodimeric nanocrystals as magnetically separable catalysts. Successful applications of the nanocrystals towards various useful organic reactions such as Suzuki, Heck, and Sonogashira coupling reactions, direct CH arylation, and Wacker oxidation have been recorded. However, detailed mechanistic courses of the reactions have not been delineated, and it was not clear whether these processes proceeded through a homogeneous or heterogeneous mechanism. Here, we report detailed mechanistic investigations of the reactions employing the PdFe3O4 nanoparticle catalysts. Suzuki coupling and Wacker oxidation reactions were chosen as two representative heterogeneous reactions employing the PdFe3O4 catalysts, and general kinetic studies, hot filtration tests, and three-phase tests were carried out for the two reactions. The studies showed that the reactions most probably proceed via a solution-phase mechanism.