Single Atom Catalysts Catalyzed Fluorination Of Acyl Chlorides And Hydrogermylation Of Alkynes

With the continuous development of economy and society,green chemistry continues to be concerned by individuals.Over the past period,single atom catalysis has aroused the interest of many chemists and physicists since it was proposed.Compared with traditional metal catalytic reaction,single atom catalysis has the advantages of low metal loading,high atom utilization,rich catalytic sites,high catalytic efficiency,and good recoverability,which make single atom catalysis a good model reaction for studying the chemical reaction mechanism and exploring the structure-activity relationship of the catalyst.At present,in the process of design,synthesis and application of single atom catalysts,how to maintain the monoatomic form of metal catalytic centers and prevent them from clusterization and then deactivation in the reaction process is a pinch point that researchers urgently need to solve.Through continuous attempts and exploration,researchers have developed many suitable metal-support,metal-ligand and other catalyst construction systems to achieve the stable application of single atom catalysts through physical and chemical methods,as well as the strategy of reactivating catalyst clusters to atomically dispersing catalysts,so that single atom catalysts can not only have good catalytic effect at the initial stage,but also have catalytic activity after recovering from the clusters.In this thesis,we mainly studied the use of porous organic ligand polymers to stabilize single atoms and the application in the hydrogermylation of alkynes.Moreover,we have constructed a stable monoatomic-support active center to enable the efficiently catalysis of the fluorination of acyl chlorides.The two different strategies we designed can make the single atom catalyst stable and efficient in the reaction and have certain reference value for the design and synthesis of single atom catalysts in the future.This dissertation is mainly divided into three parts to elaborate the relevant research contents:Part Ⅰ:This chapter gives a brief overview of the existing synthesis methods and stabilization strategies of single atom catalysts.Through the analysis of design and synthesis methods of different single atom catalysts,we can provide reference and basis for the subsequent design and synthesis of the supports and ligands for stabilizing the monoatomic state of the metal center.Part Ⅱ:Improving the stability of sensitive catalytic systems is an emerging research topic in the catalysis field.However,the current design of heterogeneous catalysts mainly improves their catalytic performance.In this chapter,a single-atom catalyst（SAC）strategy was presented to improve the cobalt-catalyzed fluorination of acyl chlorides.A stable Co-F intermediate can be formed through the oxidative fluorination of Co₁-N₄@NC SAC,which can replace the unstable high-valent cobalt catalytic system.In the SAC system,KF can be employed as a fluorinating reagent to replace the Ag F,which can be applied to various substrates and scale-up conversion with high turnover numbers（TON=1.58×10⁶）.This work also shows that inorganic SACs have tremendous potential for organofluorine chemistry,and it provides a good reference for the follow-up studies on the structure–activity relationship between catalyst design and chemical reaction mechanisms.Part Ⅲ:Organogermanium reagents have the advantages of good stability,low toxicity,and high reactivity.In addition to participating in electrophilic substitution and cross-coupling reactions as intermediates,organogermanium reagents also have certain physiological activities and participate in the physiological regulation processes.Therefore,the development of simple and efficient synthetic methods of organogermanium compounds has a great impact and practical significance.Especially for the transition metal catalyzed hydrogermylation of alkynes,products are usuallyα-/β-and Z/E mixtures with low selectivity.Based on the full study of the traditional catalytic system and the charge of the palladium,we have developed a highly active single atom palladium supported porous organic phosphine ligand polymer through metal ligand exchange.This single atom catalyst can efficiently realize the highly selective hydrogermylation of alkynes even after recycled for 5 runs,and the reaction selectivity can reach up to E/Z>100:1.