Synthesis And Catalytic Performance Of Nitrogen Heterocyclic Carbene Noble Metal Complexe

Nitrogen heterocyclic carbene is a strong donor ofσelectrons.Because it is easy to control the spatial coherence and electronic effect by adjusting the branched chain on the nitrogen atom,and the carbene C atom can acts on theπbond,the electron density of the metal central can be increased.Therefore,nitrogen heterocyclic carbene-metal complexes can exist in a relatively stable manner.The wide applications of these metal complexes in catalytic reactions,which show excellent catalytic activity,have made N-heterocyclic carbene complexes become the most concerned class of catalysts in the field of organic catalytic reactions.Suzuki coupling reaction is one of most important method to construct the carbon-carbon bonds（C-C）.The coupling reaction has outstanding advantages such as high conversion efficiency,wide substrate applicability,and wide source of boronic acid reagents.It is widely used in many fields such as organic synthesis and medical pesticides.In this thesis work,three novel benzyl-functionalized nitrogen-heterocyclic carbene ligands were synthesized,and coordinated with palladium and ruthenium precursor to form a series of nitrogen-heterocyclic palladium complexes and Ruthenium complexes.Their catalytic activity in coupling reaction were investigated and the reaction conditions were optimized.The main findings are:Firstly,three new benzyl-functionalized nitrogen heterocyclic carbene ligand were synthesized.The structure of the target compound was characterized by ¹H NMR and ¹³C NMR,and its purity was determined for the next reaction.Second,three different benzyl-functionalized nitrogen heterocyclic carbene ligands were reacted with three precursor,namely potassium tetrachloropalladate,dichloro（4-methylisopropylbenzene）ruthenium（II）dimer,and triphenylphosphine dichloride ruthenium respectively.Three novel azacyclic carbene palladium complexes and two novel azacyclic carbine ruthenium complexes were successfully synthesized by solvothermal method.Their structure and stability were determined by X-ray single crystal diffraction,infrared analysis（FT-IR）,thermogravimetric analysis（TG）,X-ray powder diffraction（PXRD）and other characterization methods.Finally,three synthesized nitrogen-heterocyclic palladium complexes were used as catalysts in the Suzuki-Miyaura coupling reaction.The optimal reaction conditions of the three catalysts were studied,and various influencing factors such as substrate,solvent,catalyst dosage,reaction time and reaction temperature were optimized.The research shows that under normal temperature and pressure,using green solvent,the three catalysts have good catalytic performance,and the yield is above 95%;Na₂CO₃ is used as the base,DMF-H₂O is used as the reaction solvent,the temperature is 80℃,and the reaction time is 6h the cross-coupling reaction of halogenated aromatic hydrocarbons and phenylboronic acid can be carried out efficiently.The experimental dehydrogenation of alcohols was initially investigated using two nitrogen-heterocyclic carbene ruthenium complexes as catalysts.The reaction is carried out without solvent,thus reducing the use of harmful solvents and adverse environmental impact.It turns out that both ruthenium catalysts have some catalytic efficiency under solvent-free conditions.