Structure And Reactivity Study Of Metal Complexes Based On In-situ Characterization Tools

In 1968,Prof.Heck used lithium tetrachloropalladate to catalyze the coupling reaction between ethylene and phenylmercury acetate.This work became the first discoverer of the palladium-catalyzed coupling reaction.Since then,the curtain of transition metal complexes catalysis has been opened.A large number of names reactions were discovered in the 1970 s,and this research frenzy continues to this day.Transition metal have a variety of coordination configurations and can be easily coordinated with ligands.This allows various ligands to easily adjust the property of transition metals’ front d orbits,allowing us to improve the selectivity and efficiency of transition metal catalyst through the ligand.Many achievements have been made due to various reactions catalyzed by transition metals.This article first briefly introduces several common reactions catalyzed by palladium,then focusing on research that trying to find the real palladium catalysts in the name reaction catalyzed by metal palladium.Next,a relatively sweeping of four new methods for the synthesis of zinc reagent.Cobalt,copper and iron catalyzed Negishi coupling were mentioned.Finally,the article introduces the research of electrocatalytic water splitting,expounds the advantages of alkaline water electrolysis cell,and introduces several representative catalysts of HER and OER.The main contents of the thesis research are as follows.1.We probed the DMF solution of palladium acetate by synchrotron radiation spectroscopy,and studied the coordination changes caused by the addition of halogen salts.X-ray near-edge spectroscopy showed that the oxidation state of Pd would not be affected by excess halogen.As for the data of the extended edge spectrum,the fitting of the first shell around the Pd atom shows that it is basically completely coordinated by the halogen ion,and only a small amount of oxygen is coordinated in a few cases.By analyzing the bond length data obtained by fitting,we found that there is a certain relationship between the coordination number of halogen atoms and the bond length.Cyclic voltammetry experiments show that the cation of the halide salt will also affect the Pd anion clusters in the solution.Theoretical calculations show that zinc salts tend to dimerize due to strong covalency,while bromine salts tend to form ionic clusters due to high solvation stabilization energy.2.We achieved the photocatalytic Negishi coupling reaction without an external catalyst.In the control experiment,we found that the presence of DMF is very important for the reaction,and only 4 times the equivalent of Zn DMF is needed to obtain the ideal yield.The free radical trapping experiment confirmed that the zinc reagent would produce phenyl radicals under blue light,while the switching light experiment proved that the reaction is not a free radical chain reaction.Adding a small amount of DMF to the zinc reagent dissolved in THF can precipitate a solid zinc reagent,NMR showed that the solid zinc reagent contains DMF in it,and the solid can also react well in pure THF solution.XAS experimental data show that the zinc reagent in THF exists as dimers,while in DMF,is in the form of monomers,indicating that DMF can cause the depolymerization of the Zn reagent in solution.Combining the existing data,we give a reasonable mechanism circle.The zinc reagent produces phenyl radicals and zero-valent zinc under the action of blue light.The phenyl radicals self-couple to produce biphenyl by-product,and zero-valent zinc species act as catalyst.The on-line generated zero-valent zinc species catalyzed the entire Negishi coupling reaction,and some evidences in the experiment prove that the zinc reagent has a Schlenk equilibrium in the reaction.3.We synthesized a two-dimensional carbon-nitrogen material supported composite metal-oxide nanoparticle catalyst by the high-temperature calcination onepot method,and further determined its structure through a variety of analysis and characterization methods,including electron microscopy,XRD,EDX,etc.Through these tests,we understand the formation process of the carrier carbon-nitrogen materials and the damage process at high temperature,and also determine the formation temperature and agglomeration laws of composite metal oxide nanoparticles.These findings point us to the best catalyst.The electrochemical oxygen evolution test found that the catalyst that keeps the support material undamaged and the oxide does not agglomerate has the best electrochemical activity.Combined with the characterization data,we explain the advantages of the composite structure.With the help of other electrochemical tests to understand the various electrochemical properties of the catalyst,we finally controlled the production of a two-dimensional carbon materialsupported composite oxide catalyst through in-depth structural research,and achieved good OER reaction activity.