Study On Preparation Of Palladium-carbon Covalent Bonds Stabilized Nanoparticles And Their Properties In Catalysis

Metal nanoparticles have become the hot research field and attracted extensive attention owing to the remarkably high surface area.They have been applied in various reactions successfully,such as hydrogenation reactions,oxidation reactions and carbon-carbon bond coupling reactions.However,enslaved to the uncertainty of reaction mechanism and the limitation of nanoparticles stability way,no breakthrough but coordination stabilizers(for instance,nitrogen and phosphine ligands)were realized to utilize.The reversibility of coordinated bonds leads to that the chiral induction mechanism of reaction is vulnerable to the interference of molecular complex chiral induction,especially when "leaching" exists in the metal nanoparticles to form molecular coplexes.In this work,the stabilizers were binded to the metal nanoparticles through covalent bonds,and the prepared nanocatalysts were applied into catalysis hydrogenation of N-heterocycles.In addition,the palladium nanoparticles stabilized by achiral precursors were synthesized and some preliminary investigations were carried out in the application in asymmertric catalysis hydrogenation of 2-methylquinoline.The thesis includes three research parts.Part ?:A series of modular palladium nanoparticles stabilized by single metal-carbon bond based on binaphthyl scaffolds which can be prepared from mono-substituted binaphthyl diazonium salts were synthesized in homogeneous system through direct reduction.TEM,ICP and 1H NMR were utilized to characterize the prepared nanocatalysts and the properties in catalysis hydrogenation were studied in detail when used in catalytic hydrohgenation of quinoline.The results showed that the electronic cloud density around the catalytic sites was affected by the structures of precursors,thus further affecting the catalytic activity of nanoparticles.With the optimized reaction conditions in hand,these nanocatalysts were successfully applied in the catalytic hydrogenation of quinoline derivatives with excellent selectivity and yields.Part ?:The double(palladium-carbon)covalent bonds stabilized nanoparticles were prepared from binapthyl diazonium in homogeneous system through in-situ reduction and the nanoparticles were characterized by TEM and ICPR The hydrogenation catalysis activity in N-heterocycles such as quinoline and derivatives in water was studied systematically.In addition,the catalysis activity of two kinds of nanocatalysts prepared from different methods was compared under the same reaction conditions.The diameter of nanoparticles prepared through homogeneous method focused on 2.5 ±0.5 nm which was less than that of two-phase reduction,and they performed synergistic effect of particle size and solvent when used in the catalytic hydrogenation in water.Part ?:In this part,the chiral binapthylamine was used as precursor to synthese the diazonium salt,and the chiral nanoparticles stabilized by palladium-carbon covalent bond which was characterzed by TEM and CD were also prepared through homogeneous reduction method.2-methylquinoline was utilized as model substrate to carry out the premilary investigation of chiral properties in asyumeriric hydrogenation.When external chiral source was added,low stereoselectivity was obtained by double(palladium-carbon)covalent bonds stabilized nanopartiles and this preliminary result deserved further extensive exploration.