PdCl2(py)2 encaged in monodispersed zeolitic hollow spheres: a highly efficient and reusable catalyst for Suzuki-Miyaura cross-coupling reaction in aqueous media

By encaging the PdCl2(py)(2) complex (py = pyridine) in the interior space of silicalite-1 hollow spheres (SHS), a novel solid palladium catalyst, PdCl2(py)(2)@SHS, was successfully prepared. The structure and composition of the solid catalyst was characterized by SEM, TEM, XRD, N-2 sorption, FT-IR and XPS. This catalyst afforded fast conversions for the Suzuki-Miyaura cross-coupling reactions of various aryl halides and arylboronic acids even at Pd loadings of 0.0188 mol% in aqueous media. The turnover frequency (TOF) could be up to 63 210 h(-1) under mild conditions in air. In particular, because of the antileaching effect of the surrounding zeolitic shell toward the entrapped Pd species, PdCl2(py)(2)@SHS showed outstanding stability and reusability, which could be reused at least 10 times without appreciable loss of its activity. The developed solid catalyst combined with the mild conditions represented one of the most efficient heterogeneous systems for the Suzuki-Miyaura cross-coupling reactions of aryl halides.