The Preparation,Characterization And Catalysis Of Thermoregulated Functionalized Ionic Liquid Containing Carbonyl Metal

In this paper, a novel polyether functioinalized ionic liquid1-butyl-3-polyethylene glycol-yl imidazole cobalt tetracarbonyl{[H(OCH2CH2)nbim]Co(CO)4}, was first synthesized, characterized, and used as the catalyst for the hydroesterification of1-(4-isobutylphenyl)ethanol(IBPE). We had investigated the solubility of these ionic liquids in water and different organic solvents under different temperature and developed a thermoregulated ionic liquid biphasic catalysis system, which provided a new way for making homogeneous catalysis and heterogeneous separation possible and separating catalyst from the reaction mixture.[H(OCH2CH2)nbim]Cl was prepared by alkylation from3-polyethylene glycolyl imidazole which was obtained by the reaction of ethylene oxide with imidazole.[H(OCH2CH2)nbim]Co(CO)4was prepared in a metathesis reaction between [H(OCH2CH2)nbim]Cl and KCo(CO)4obtained by potassium borohydride reduction method. The structure was characterized by FT-IR. It showed a strong band both at1886.3cm-1and1114.8cm-1indicating the formation of tetrahedral [Co(CO)4]-anion and-(CH2CH2O)nH functional group. The solubility of these ionic liquids in water and different organic solvents was investigated under different temperature. It was found that [H(OCH2CH2)nbim]Cl showed cloud point in the water and the cloud point increased with the increasing of the the value of n while decreased with the alkyl chain length increasing.[H(OCH2CH2)nbim]Co(CO)4showed neither cloud point in the water nor critical solution temperature(CST) in single organic solvent, nevertheless, it showed CST in1,4-dioxane-n-heptane mixtures that established the foundation for thermoregulated ionic liquid biphasic catalysis with the function of "mono-phase under high temperature, bi-phase under room temperature".We had studied the synthesis of2-(4-isobutylphenyl)methyl propionate by hydroesterification of IBPE catalyzed by [H(OCH2CH2)nbim]Co(CO)4. The optimum reaction conditions of the hydroesterification of IBPE were obtained by single-factor experiments. Under the pressure6.0MPa and temperature130℃, imidazole as promoter, butanone as solvent, hydrochloric acid as acidic medium, the conversion of IBPE reached100%, while the yield of2-(4-isobutylphenyl)methyl propionate reached54%in16h, the catalyst could be recycled five times with good catalytic performance. And a possible reaction mechanism had also been proposed according to experimental result.In this paper, a novel thermoregulated PEG biphasic system was proposed, which was composed of [H(OCH2CH2)nbim]Co(CO)4, PEG400, and1,4-dioxane-n-heptane mixtures. It was proved that the catalyst, IBPE and imidazole did not destroy PEG biphasic system while the hydrochloric did. The research priorities were the effects of temperature on the convertion of reaction and the recycling and utilization of the catalyst. The changes of the conversion of IBPE and the yield of product were significant when the temperature was raised to above CST. After reaction, the catalyst in PEG phase was recycled nine times without obvious loss of activity, which resolved the problem of the separation of catalyst.