Study On SalenAlQ Complexes Containing Double Catalytic Centres For Cycloaddition Of Propylene Oxide With Carbon Dioxide

The cycloaddition of propylene oxide with carbon dioxide activated by catalysts is one of the industrial synthetic processes for the production of propylene carbonate (PC) and very attractive from the viewpoint of "green chemistry" and "atom economy".In this paper, a series of SalenAlQ complexes are designed and synthesized, which have double catalytic centres. Then, they were employed in the cycloaddition of propylene oxide with carbon dioxide as the catalyst. And the effects of molecular structure and condition of reaction on the catalytic activity are observed.First, a series of SalenAlEt with a unstable Al-C bond are synthesized. Then a kind quaternary ammonium containing a butul-hydroxy group was synthesized, which has an active hydrogen atom. The SalenAl and quaternary ammonium salt can be combined in one molecule through a steady Al-O bond. Thus, a series of new SalenAlQ complexes was synthesized, which contain both electrophilicity and nucleophilicity centres for the cycloaddition of propylene oxide with carbon dioxide. While the Structrues of SalenAlQ were characterized by ¹HNMR.These SalenAlQ complexes were employed in the cycloaddition of propylene oxide with carbon dioxide to catalyze the reaction. The effects of molecular structure on the catalytic activity are investigated. The result of experiments indicates that the catalytic activity is obviously affected by the substituent groups on the complexes. And the effect of substituent groups (for example tert-butyl) on benzene ring is stronger than that on amine's framework. Among the above synthesized complexes, the SalenAlQ complexe that is combined from ethylenediamine and salicylal is more effective catalytic activity, because it has smallest steric hindrance.The effects of temperature on the catalytic activity are also observed. It found that elevation of reaction temperature is effective for increasing catalytice activity. And as the increase of reaction temperature from 40℃to 120℃, catalytic activity of chosen SalenAlQ complexe was increased from 16.48 to 78.24 mol mol^-1h^-1.At last, the catalytic mechanism of cycloaddition of propylene oxide with carbon dioxide is discussed.