Effect of Flexible Chain Length of Graphene‐Supported Palladium Complex Catalyst on Suzuki‐Miyaura Coupling Activity

Abstract

AbstractThree series of quasi‐homogeneous palladium catalysts (rGO‐L3‐nC‐Pd, n=4, 6, 8) for Suzuki‐Miyaura (S−M) coupling reactions were prepared by grafting organic palladium complexes with flexible chains of different lengths onto the surface of reduced graphene oxide (rGO) by covalent bonds. The Raman, FTIR, TGA, ICP‐MS, SEM and BET N2adsorption techniques were employed to characterize the catalysts. The three rGO‐L3‐nC‐Pd catalysts were used in various S−M coupling reactions. At room temperature (RT), in H2O/EtOH mixed solvents, they showed excellent catalytic activity and recyclability for various aromatic substrates with different substituents or substituent positions. The results indicated that the catalytic activities of rGO‐L3‐nC‐Pd were closely related to the length of the flexible chain of the organic palladium complex bonded to the surface of rGO, that is, the longer the length of the flexible chain, the greater the activity of the catalyst. The order of catalytic activity is rGO‐L3‐8C‐Pd>rGO‐L3‐6C‐Pd>rGO‐L3‐4C‐Pd. This activity sequence did not change with different solvents, bases and substrates, even if the catalyst was recycled ten times. Our results may provide a new idea for the design of quasi‐homogeneous catalysts.