C-C Coupling Reactions Catalyzed By Palladium Supported On Metal-Organic Frameworks

C-C coupling reactions are the most practical and powerful methods for the construction of C-C bonds, which have been used in modern organic syntheses, such as natural products, pharmaceuticals, agrochemicals, functionalized materials, etc. Therefore, C-C coupling reactions possess great significance and value in academic research and practical application. Sonogashira reaction and Ullmann reaction are two of the most representative methods for forming C-C bonds among the C-C coupling reactions.In this work Pd/MOF-5, a novel catalyst with Pd nanoparticles supported on MOF-5, was synthesized at room temperature by a direct chemical recuding method. The morphology, structure and features of MOF-5 and Pd/MOF-5 were characterized by PXRD, N2-sorption, TGA, SEM, and TEM. The reaction conditions in this catalyst system such as solvent, base, loading amount of catalyst, reaction time and temperature have been optimized. The electronic and steric effect toward the reactivity of different substrates has been studied and the recyclability of the catalyst has been investigated as well. The results indicated that the Pd/MOF-5 can catalyze the Sonogashira cross-coupling reaction of iodoarenes very efficiently and its advantages of wide range of substrates, ease for separation, reuse of catalyst provide promising perspect for industry utilization. However the catalyst deactived from the third run due to the oxidation and aggregation of palladium. The Pd/MOF-5 can achieve the Sonogashira cross-coupling reaction of bromobenzene with mild yield, yet is not active enough for chlorobenzene. The Ullmann reaction catalyzed by Pd/MOF-5 was also investigated in this work. The coupling of iodoarenes can be carried smoothly but for bromoarens and chloroarens still require further investigation.