Design And Synthesis Of Nnn Pincer Ligands Bearing Remote Auxiliary Acid Center(S),and Applications Of Their Ru(?) Complexes In Transfer Hydrogenation Reaction

In this thesis,a new family of pyridyl-based NNN pincer ligands bearing remote auxiliary acid center?s?and their ruthenium???complexes were synthesized,and their crystal structures were characterized by single crystal X-ray diffraction.Later on,the application of the obtained pincer Ru?II?complexes in transfer hydrogenation of ketones was investigated.The experimental results?as shown in Scheme 1?disclosed that the activity of34,35 and 36 bearing a remote hydroxyl group are superior to 14 possessing the a indenyl methylene moiety,wherein the catalyst 35 showed the highest activity.These results demonstrate that introducing a CH₂OH group to the 4?-position of the pyrazolyl moiety is an appropriate choice.Hydroxymethylation of the catalyst 35,obtaining catalyst 37,greatly impede the catalytic activity.???Employing the complex 35 as the catalyst,other parameters,such as the loading of the catalyst,and the type and loading of bases were further investigated.Under the optimized reaction conditions,the complex 35 exhibited high catalytic activity in transfer hydrogenation of ketones.Most of the tested ketones were reduced with 99%conversion in30 seconds,offering the highest final TOFs up to 59400 h^-1 under refluxing conditions.Additionally,the mechanism of this reaction was also preliminarily studied and a reasonable catalytic cycle was proposed.The metal-ligand cooperation exists in the catalytic process of the complex 35,which promotes the transfer hydrogenation of ketones.The remote hydroxyl group in the complexes providing metal-ligand cooperation was found for the first time,which provides a new strategy for exploring bifunctional ligands to construct effective new catalysts.