Research On Preparation And Catalytic Properties Of The IB Group Nanoparticles

Much attention has been devoted to the problem of environmental pollution recently. Enormouspotential savings compared with conventional chemistry, for example, the minimization of wastes, theuse of recyclable heterogeneous catalysts, and the use of oxygen as an oxidant or of hydrogen as areductant, are needed. Accordingly, the conception of green chemistry is put forward in recent years.Catalysis increasingly holds the key to green chemistry. The nanomaterial possessed an essence ofhigh surface area and insufficient coordination number. As a result, the nanocatalyst is regarded as anunmatchable advantage compared with traditional catalyst. The introduction of nanocatalyst becomesthe new growth point of green catalysis. Because of their easy preparation and relative stabilities in air,the nanoparticles of coinage metals, such as copper and silver, were widely reported, and there aremany excellent examples on their applications as catalysts in organic reactions. In most cases, thenanoparticles of coinage metals worked as dehydrogenation catalysts, few reports were concernedwith the construction of carbon-carbon bonds or carbon-hetero bonds. In this thesis, the preparation ofcoinage metal nanoparticles and its applications in the construction of carbon-carbon bonds orcarbon-hetero bonds was studied.1. Screening of the preparation methods for coinage metal nanoparticles with a good reproducibility(1) Research on the preparation of silver and copper nanoparticles by liquid phase reduction. Duringthe process, the effects of the type of metal source, protective reagent, and reducing agent etc. on thesize and shape of nanoparticles were investigated. We describe the synthesis of silver particles withnarrow size distribution by reducing silver nitrate with trisodium citrate dehydrate in the aqueoussolution of PVP. The average size of Ag nanoparticles is ca.30nm. In the preparation procedure ofcopper nanoparticles, copper acetate are reduced by sodium borohydride in the presence of PVP. Theaverage size of Cu nanoparticles is ca.30nm. The cuprous oxide particles can be prepared usingglucose as reducing agents and PVP as capping agents for the control of particle sizes, where ashexagonal particles with diameters of700nm were prepared.(2) Silver nanoparticles supported on carbon and metal oxide were prepared by liquid phasereduction. A narrow size distribution is observed for the supported silver nanoparticles. The diametersof the silver nanoparticles are estimated to be20-30nm.(3) Silver nanoparticles supported on carbon were prepared by template method. In compared withliquid phase redutioin, the narrow size distribution was obtained by template method. The averagesize of silver nanoparticles is ca.25nm. 2. Titanium dioxide-supported silver nanoparticles were utilized as a highly efficient catalyst for theaddition of terminal alkynes to aldehydes to prepare propargylic alcohols with the promotion bytriphenylphosphine in water. Both a significant support effect and a ligand effect were observed in thecatalytic reaction. The result of “hot separation” experiment indicated that the reaction should takeplace on the surface of the solid catalyst rather than by the presence of soluble silver-phosphinecomplex in the solution. Furthermore, the catalyst could be recovered and reused effectively withoutobvious decrease in catalytic activity.3. A highly efficient alkynylation-cyclization of terminal alkynes with salicylaldehydes leading tosubstituted2,3-dihydrobenzofuran-3-ol derivatives was developed by using Cy3P-silver complex ascatalyst in water. Counter anions in the silver complex proved to be the key factor to Z/Estereoselectivity control.4. A highly efficient addition of O-containing nucleophiles to triple bond leading to the keyintermediates to synthesize aurones was catalyzed by silver nanoparticles/carbon black-supportedsilver nanoparticles. In the presence of phosphine ligand, both the catalysts show excellent catalyticactivities in the reaction and give the products with good yields as well as excellent regio-andstereo-selectivities in a water-toluene mixed solvent. Furthermore, the catalysts can be recovered andrecycled effectively several times.5. A efficient oxidation-cyclization of2-(1-hydroxy-3-phenylprop-2-yn-1-yl)phenol was developedby using copper nanoparticles or cuprous oxide particles as catalyst in a water-toluene mixed solvent.The bifunctional catalytic system was established for copper nanoparticles and cuprous oxide particles.A significant ligand effect was observed in the catalytic reaction. Molecular oxygen could be used asa clean and mild oxidant.