Preparation,Properties And Application Of New Palladium And Gold Nano Catalysts

With development of nano catalyst,nano catalysis becomes a cross-subject to research interpenetrating and intercross between nanoscience and catalysis.Heterogeneous catalysis is one of important research area in nano catalysis.Palladium nanoparticles(PdNPs),one of the efficient catalysts for the Suzuki-Miyaura reaction,have attracted considerable attentions over last decade.They exhibit high catalytic efficiency,easy recyclability and low palladium residue.General methods for fabrication of catalysts PdNPs are to immobilize the PdNPs on a support or involve a capping agent to stabilize the colloid PdNPs.Thus,the catalytic performance of PdNPs is not only depended on feature of nanoparticles but also affected by its supports or stabilizers.In most cases,the reactions catalyzed by the PdNPs were performed in organic media.In order to make the organic syntheses or reactions more environmentally friend or green,it is strongly desirable that the reactions can be performed in aqueous media.Metal-catalysed processes have been one of the most important tools for the synthesis of new fine chemicals,including pharmaceutical and natural products.N-heterocyclic carbene(NHC)has emerged as a group of promising materials for the design of a wide variety of highly active complexes because of their chemical and topological versatility.In recent years,the development of gold catalysis has attracted great interest.Gold complexes,especially gold species bearing an NHC ligand,have become very important in the synthetic chemist's arsenal and have allowed the design of numerous gold(?)complexes,which are precursors of active species in different catalysed reactions.(1)In the presence of protective agents,four kinds of reducing agents were used to investigate the preparation of nanoparticles like hydrazine hydrate,sodium borohydride,ascorbic acid,sodium formate.It was found that the smaller the size of Pd nanoparticles was synthesized by using weaker reducing ability of reducing agent.These nanoparticles showed varied performances for the reactions.PdNPs-NH2NH2 showed nearly no catalytic activity and only 2%conversion after 30 min was achieved.PdNPs-NaBH4 and PdNPs-Vc offered only 8%and 12%conversion,respectively.The best conversion was achieved when PdNPs-HCOONa was used as catalyst,which was 95%.These results indicated that the catalysis activity was depended on the size of palladium nanoparticles,the small size of nanoparticle PdNPs-HCOONa give the higher activity.The scope of substrate was further investigated,PdNPs-HCOONa were also high activity in catalyzing the electron withdrawing aromatic bromides at room temperature and>98%yield was gained for 4-nitrobromobenzene or ethyl 4-bromobenzoate as substrate in 4 h.2-bromonaphthalene is nearly full conversion to 2-phenylnaphthalene within 1 h.In addition,the catalysis activity of PdNPs-HCOONa for substituted arylboronic acid was also investigated,and found that reaction was also underway smoothly with 1-naphthylboronic acid and 4-methoxyphenylboronic acid as substrates.It was found that the catalyst has good stability which can be recycled more than 3 times.(2)In this thesis,N-heterocyclic carbene was functionalized with chiral reagent and hydrophilic group.The hydrophilic Au nanopaticle was synthesized by a reaction of the functionalized N-heterocyclic carbene with 1,3-Propanesultone.The catalyst was characterized by UV-vis and CD.