Design,Synthesis And Application Research Of Novel Iridium Catalysts Based On Nitrogen,Phosphorus-Containing Ligands

Precious metal catalysts have received great attention from scientific research and industrial production due to their unique chemical properties and outstanding catalytic performance in some fields.Iridium is a precious metal with unique properties.In recent years,it has been gradually developed into a variety of important functions and applications.Hydrogen borrowing reaction is a type of green reaction with high application value because the by-product is mainly water and the conversion of a variety of inactive organic compounds can be achieved through this strategy.The iridium catalysts have a good catalytic effect on this type of reaction.Most commonly used iridium catalysts were homogeneous catalysts,which caused waste of metal and some pollution to the environment.To solve these problems,this paper designed,synthesized and optimized several iridium catalysts containing N or P ligands,which not only reduced the use of iridium,but also achieved the recycling of the catalyst.The more specific research contents and results are as follows:(1)Several novel pyridine-oxadiazole iridium complexes were synthesized and the structures were characterized through X-ray crystallography.The iridium catalyst had a high catalytic activity for the reaction borrowing hydrogen reactions of amides with benzyl alcohols.N,N'-(phenylmethylene)dibenzamide products were unexpectedly isolated under non-coordinating anion conditions.The mechanism explorations excluded the possibility of "silver effect"(silver-assisted or bimetallic catalysis)and revealed that the reactivity of iridium catalyst was varied by non-coordinating anions.(2)Iridium on phosphorus?doped porous organic polymers(POP-Ir)was developed by anchoring the simple iridium onto the skeleton of porous organic polymers through coordination bonds.This POP-Ir catalyst was thoroughly characterized by means of EDS,SEM,TEM,XRD,XPS and FT-IR.The catalyst revealed excellent catalytic activity for the reaction of diphenyl phosphinamide with benzyl alcohol through borrowing hydrogen strategy with wide functional group tolerance.Meanwhile,it has good catalytic effect for the reaction of biguanides and benzyl alcohols through acceptorless dehydrogenation.The mechanism explorations were conducted to further understand this POP-Ir catalytic system and these transformations.Moreover,this POP-Ir catalyst could be simply recovered and reused for at least five times without a significant loss of activity and revealed considerable application prospects.(3)Polypyridine-oxadiazole(PPO),which was a new kind of porous organic polymer,was synthesized with further improvements and analysis of the previous two chapters.The new catalyst PPO-Ir was obtained after the iridium complex supported on the PPO,and the POP-Ir catalyst was successively characterized by the use of EDS,SEM,TEM,XRD,XPS and FT-IR.The catalyst maintained good catalytic activity for the reaction of amides with benzyl alcohol through borrowing hydrogen strategy and had the same result for reaction of Dimethyl-6-aminouracil and benzyl alcohol.The possible reaction mechanism was deduced through kinetic exploration experiments.Through the recycling experiments of the above two reactions,it was proved that the catalyst had recyclability and provided a sustainable development route.