Synthesis And Application Of Palladium Complexes By Ring-Opening Of Pyridine-bridged Imidazolium

Pd complexes have made great contributions in the fields of medicine,materials,catalysis and other related fields,and the selection and design of palladium complexes are worthy of attention.The N-heterocyclic palladium complex stability of excellent in heat,in water and in air are recognized in most areas of metal,but usually people in the preparation of the N-heterocyclic ligand or N-heterocyclic metal palladium complexes when it will inevitably generate a certain amount of heterocyclic hydrolysis by-products,the phenomenon of early researchers ignore.In recent years,due to the unique structure of the ring-opening products and the uncertainty of the coordination,that have attracted the attention of scientists.Based on this,this paper mainly focused on the hydrolysis and ring opening of imidazolium salt,the coordination mode of palladium and its catalytic activity in Suzuki-Miyaura coupling reaction.1.The hydrolysis of pyridine bridged benzimidazolium salt ring opening products is a pair of rotamers.In order to control the stereochemistry of hydrolysis products,we use changing the substituent groups on the ring products.We find that the steric effect of regulation rotational isomer ratio,so as to achieve the high selective control of open ring product space structure objective.It is found that when the steric hindrance group is introduced onto the amino group,the product with high spatial distortion is dominant.When the steric hindrance group is introduced onto the aldehyde group,the product with low spatial distortion is 99%.2.An anionic controlled benzimidazolium salt hydrolysis ring opening Pd coordination method has been developed.A series of benzimidazolium salt hydrolyzed ring opening Pd complexes and a conventional pyridine bridged benzimidazole Pd complex have been obtained.When benzimidazolium salt anion is chlorine,bromine,iodine ions,silver oxide selectively promote the hydrolysis of benzimidazolium salt with Pd open ring,and metal coordination so as to obtain a class of open-ring Pd complexes;When benzimidazolium salt anions are nitrate,three fluorine sulfonic groups,six fluorine phosphate,tetrafluoroboric acid root silver,salt and benzimidazole reaction is first generated silver complexes,and then metal replacement reaction with Pd metal to obtain a kind of conventional Pd complexes.3.The above synthesized Pd complexes are applied to the Suzuki-Miyaura coupling reaction of methanol and water respectively.In methanol solution,Suzuki-Miyaura reaction can be carried out smoothly at room temperature,and in pure water solution,the reaction temperature needs to increase to 90~oC.Under the same reaction conditions,bromobenzene ether and benzene boric acid as a model reaction,the open-ring Pd complexes than conventional Pd complexes exhibit higher catalytic activity,and this kind of catalyst containing different electronic effect of aryl boric acid and aryl bromide showed a good substrate universality.In order to investigate the open-ring stability and reaction mechanism of Pd with the help of mercury poisoning experiments show that the open-ring Pd complexes in the reaction process showed a good stability,the catalyst showed that the catalyst mainly experienced homogeneous catalysis,and the catalytic effect of nanoscale Pd was not shown.4.Acetonitrile adduct is usually synthesized by free carbene,but the reaction conditions are demanding.We found for the first time that benzimidazolium salt hydrolyzed ring opening products and acetonitrile were used to prepare acetonitrile addition products.This method is simple,and provides a simple and efficient new method for the synthesis of acetonitrile adducts.