Design Of Ruthenium-based Complexes And Their Catalytic Performance For The Alcohols Accceptorless Dehydrogenation

Carbonyl compounds produced by dehydrogenation and oxidation of alcohol are important intermediates in the synthesis of fine chemicals such as spices and medicines,and are widely used in industrial production and organic synthesis.However,the traditional dehydrogenation and oxidation reaction needs to consume a lot of oxidants,which is prone to side reactions and environmental pollution.Metal-based molecular catalysts can catalyze the direct dehydrogenation of alcohol to carbonyl compounds and hydrogen.The acceptorless dehydrogenation reaction has a high utilization rate of atoms,which meets the requirements of green chemistry and is a hot research topic.In this paper,a series of ruthenium-based molecular catalysts were designed and synthesized based on the regulating effect of ligands on active centers,and pyrrole groups were selected to replace the traditional pyridine ligands.The catalytic activity of active centers on the anaerobic dehydrogenation of alcohols was regulated from three aspects of electronic structure,conjugated structure and weak interaction,and the catalytic mechanism was further explored.The main conclusions of this paper are as follows.（1）RuHCl（CO）（PPh₃）₃react with 2-（1-H-pyrrol-2-yl）pyridine ligands and their derivative ligands（HL1-6）in alkaline or neutral environments to obtain Ru（L1-6）（H）（CO）（PPh₃）₂（1-7）or Ru（L1）Cl（CO）（PPh₃）₂（8）、Ru（L6）Cl（CO）（PPh₃）₂（9）respectively.Ru（L1）Cl（PPh₃）₃（10）and Ru（L6）Cl（PPh₃）₃（11）was formed when these ligands react with RuCl₂（PPh₃）₃.Under the heating condition,the high yield of 7 is converted into 1.These eleven complexes were characterized by NMR,IR,UV-vis absorption spectra and X-ray single crystal diffraction,and the HOMO-LOMO orbit of complex 1 and 7 was caculated.（2）The effects of solvent,temperature,base and other factors on the anaerobic dehydrogenation of alcohols catalyzed by Ru-Cl and Ru-H complexes were investigated by the method of controlled variables,and the optimal reaction conditions were obtained.Under the optimum conditions,the catalytic activities of complexes 1-7 with different modification groups were compared,and the effects of different modification groups on the catalytic performance of complexes were compared.The reaction mechanism of RuH complex 1 catalyzing the anaerobic dehydrogenation of alcohol was explored and summarized through the detection of intermediate products and the toxicity test of catalyst.Compounds 1,4,5,6 and 8 were used to catalyze the dehydrogenation of phenylethanol to acetophenone.It was found that these complexes had catalytic effects,and 5 showed the best catalytic efficiency.However,when KOH was used as base,the yield decreased instead of increasing.It was found that acetophenone would further react and form acyl compounds through aldol condensation.These results indicate that pyrrolyl complexes have the potential to catalyze the anaerobic dehydrogenation of alcohols.