Synthesis, Characterization And Catalytic Properties Of Amine-bis(phenolate) Iron Complexes

Copolymerization of carbon dioxide?CO₂?with epoxy alkane to produce a series of environmentally friendly high polymer materials attracets a wide spread attention because of its feature of environmental protection.Amine-bis?phenolate?ligand is a ligand type which can be easily synthesized and decorated.Iron is a green metal element which is easily reachable,toxic free and safe.Rarely people use these two chemicals as catalyst in the copolymerization of CO₂ with epoxy alkane,also,there is seldom research on this.This paper studied a series of reactions by use of 3,5-di-tert-butylphenol to synthesis four kinds of amine-bis?phenolate?ligands.To obtain the other four kinds of iron amine-bi s?phenolate?complexes,the complex reaction between our previous production,amine-bis?phenolate?ligands and iron ions are achieved.Characterization analyze by nuclear magnetic resonance spectroscopy?NMR?,elemental analysis and high resolution mass spectrometry?HRMS?give the evidence that the obtained ligands match our targeted ones.For the first time,the synthesized amine-bis?phenolate?complexes are used as the catalyst in the copolymerization of CO₂ with CHO.¹H-NMR,FT-IR and GPC are used to characterized the polymers.The influence from different ligand structures,cocatalysts,ratio of catalyst and cocatalyst,temperature,pressure,time,ratio of CHO and catalyst were discussed.We found that when it comes to amine-bis?phenolate?iron base catalyst,complexes with benzene ring present a better catalytic activity and selectivity.As the main catalyst,Fe-L₁,catalytic activity can be obviously raised by choosing PPNCl as the cocatalyst.Moreover,the catalytic activity increases when the reaction temperature raises,but moves higher and drop lower as the pressure changes to be higher.The relation between catalytic activity and ratio of catalyst and CHO is positive correlation.Also,the conversion of CHO and the molecular weight of the polymer keep growing following the time's raising.Besides,the catalyst system consisted of Fe-L₁ and PPNCl has a pretty strong heat stability.Under a higher temperature,this system can also maintain a good selectivity.When the reaction condition reached 120?,TOF value of the reaction will be 225.5 h^-1,which is dramatically good in comparison to the reported single core iron base catalyst in previous studies.