The Preparation Of Polymeric Heterocyclic Carbene-Palladium (IPr-Pd) With Self-Catalysis And The Evaluation Of Its Catalytic Performance

Small molecular NHC-Pd catalysts have been widely applied in the catalysis of Suzuki-Miyaura coupling reaction depending on its high activity and good stability. However, the separation of these small molecular catalysts from the products becomes much difficult and tedious. Thus, the immobilization of these small molecular catalysts are being rapidly developed to solve this problem. But, in process of the immobilization, the structure damage of catalysts was inevitable leading to the loss of catalystic activity. Furthermore, the low loading of catalyst on the supports is another important factor to restrict the catalytic activity. Thus, in this work, the self-catalysis was employed to prepared the responding catalysts. Namely, the NHC ligand was modified not only as the catalysts but also as the monomer. Depending on its catalysis, the monomer was polymerized and cross-linked to prepare the responding solid catalysts.This paper mainly contains the following points:(1) The final high purity I-IPr ligand was prepared with iodoaniline by the amine aldehyde condensation of the ring-closing reaction.(2) Two different sources of palladium were employed to chelate with I-IPr to obtain the small molecular ctalysts of(I-NHC)Pd(acac)Cl) and( I-NHC)PdCl2-3-chloropyridine.(3)T he above two small molecule palladium catalysts and tris(4-aminophenyl) amine were polymerized by Buchwald-Hartwig coupling reaction occurred by itself.The final cross-linked polymer were the catalyst C1( the specific surface area was 7.5894 m2 / g, an average particle diameter of 1.540μm) and the catalyst C2(specific surface area of 13.09m2 / g, an average particle diameter of 2.086μm).(4) The catalytic behavior of the two catalysts were evaluated in the coupling reaction of aryl bromides, iodides aromatic with aryl boronic acid.The catalyst C1 and the catalyst C2 showed high activity and stability. The substrate adaptability of the catalyst C2 was better than that of the catalyst C1.(5) It was found that the ancillary ligand and flexible steric hindrance were much important to influence its the stability and activity of macromolecular polymer catalyst.