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[摘要]：was studied by means of in situ FTIR method with monitoring of the n(CO2) region of the IR spectra under various conditions. shows higher thermal stability compared with 1,3-bis(2,6-diisopropylphenyl)imidazolium-2-carboxylate (IPr-CO2). The presence of free CO2 can significantly inhibit the decompn. of NHC-CO2 adducts, while the addn. of an epoxide such as propylene oxide has a neg. effect on stabilizing these adducts. As zwitterionic compds., NHC-CO2 adducts were also proved to be effective org. catalysts for the coupling reaction of CO2 and epoxides to afford cyclic carbonates, for which a possible mechanism was proposed. Among these NHC-CO2 adducts, the relatively unstable IPr-CO2 exhibits the highest catalytic activity. The presence of an electrophile such as SalenAlEt could greatly improve the catalytic activity of IPr-CO2 due to intermol. cooperative catalysis of the binary components. |
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