Synthesis And Catalysis Of Mesoporous Molecular Sieves MCM-41 Immobilized Ruthenium Complexs

The oxidation of alcohols to their corresponding aldehydes and ketones is of crucial importance in organic chemistry.Ruthenium complexes performed very well in the alcohol oxidation.However,the difficult separation of the very expensive complexes from the reaction mixture makes them impossible to recycle directly.Heterogenization of the ruthenium complexes is expected to overcome this disadvantage.The ruthenium complex Ru?Terpy??Pydic?was successfully supported onto MCM-41using a multi-step grafting method,and an immobilized MCM-41/Ru?Terpy??Pydic?catalyst was obtained.The immobilized ruthenium complex was characterized thoroughly by FT-IR,Raman,UV-Vis,ICP,XRD,N₂ adsorption,SEM and TGA analysis.An efficient catalytic system for the oxidation of alcohols with TBHP as terminal oxidant has been developed from MCM-41/Ru?Terpy??Pydic?under solvent-free conditions.The reaction was optimized with 1-phenylethanol as a model substrate.Each component loading of the catalytic system and reaction temperature were investigated respectively.The final optimized conditions were:1-phenylethanol 2 mmol,MCM-41/Ru?Terpy??Pydic?0.019mol%,1-phenylethanol:TBHP=1:1.3,reaction temperature 70?.Under the optimized conditions,a conversion of 99%with a selectivity of 99%toward acetophenone was obtained after 2.2 h.This catalytic system also showed excellent performance in the oxidation of various secondary alcohols to their corresponding ketones.In addition,this immobilized ruthenium catalyst can be recycled four times without a large reduction of its activity.The ruthenium complex Ru?Terpy??PPh₃?Cl₂ was successfully supported onto MCM-41usingamulti-stepgraftingmethod,andanimmobilized MCM-41/Ru?Terpy??PPh₃?Cl₂ catalyst was obtained.The immobilized ruthenium complex was characterized thoroughly by FT-IR,UV–Vis,XRD,N₂ adsorption and ICP analysis.An efficient catalytic system for the oxidation of alcohols with TBHP as terminal oxidant has been developed from MCM-41/Ru?Terpy??PPh₃?Cl₂.The reaction was optimized with1-phenylethanol as a model substrate.Each component loading of the catalytic system,reaction temperature and solvents were investigated respectively.The final optimized conditions were:1-phenylethanol 2 mmol,MCM-41/Ru?Terpy??PPh₃?Cl₂ 0.016 mol%,1-phenylethanol:TBHP=1:1.5,reaction temperature 80?,without presence of solvent.Under the optimized conditions,a conversion of 99%with a selectivity of 99%toward acetophenone is obtained after 4 h.This catalytic system also showed excellent performance in the oxidation of other aromatic secondary alcohols,a certain catalytic activity in the oxidation of aliphatic secondary alcohols.Unfortunately,this immobilized ruthenium catalyst showed poor reusability.The activity of the catalyst decreased quikly in the recycle process due to the leaking of triphenylphosphine.