Highly efficient and recyclable amorphous Pd(Ⅱ)/crystal Pd(0) catalyst for boosting Suzuki reaction in aqueous solution

Ultrafine and highly dispersed Pd nanoparticles have drawn considerable attention with high activity, selectivity and atomic efficiency. In this paper, amorphous Pd(Ⅱ)-complex solid spheres with ~ 5 nm Pd nanoparticles loaded on were successfully achieved through a simple and gentle one-pot solution method with vitamin B1 simultaneously as complexing agent and reducing agent. An ultrathin mesoporous SiO₂ shell was then coated at the surface of Pd(Ⅱ-0) spheres as the armor which could prevent the dissolution of Pd(Ⅱ) during the catalytic process. The combination of Pd(Ⅱ) and Pd(0) endowed Pd(Ⅱ-0)@m-SiO₂ catalyst an excellent performance in eco-friendly aqueous media Suzuki reactions. The high activity, productivity and recyclability were all comparable with the best Pd catalysts ever reported. The ingenious formation of amorphous Pd(Ⅱ)/crystal Pd(0) with enhanced catalytic performances provides a new, scalable strategy to practical promotion of Suzuki cross-coupling reactions.