An Abnormal N-Heterocyclic Carbene-Carbon Dioxide Adduct from Imidazolium Acetate Ionic Liquids: The Importance of Basicity
作者:Zsolt Kelemen、Barbara Péter-Szabó、Edit Székely、Oldamur Hollóczki、Dzmitry S. Firaha、Barbara Kirchner、József Nagy、László Nyulászi
DOI:10.1002/chem.201402912
日期:2014.9.26
[C2C1Im][OAc] ionic liquid with carbon dioxide at 125 °C and 10 MPa, not only the known N‐heterocyclic carbene (NHC)–CO2 adduct I, but also isomeric aNHC‐CO2 adducts II and III were obtained. The abnormal NHC‐CO2 adducts are stabilized by the presence of the polarizing basic acetate anion, according to static DFT calculations and ab initio molecular dynamics studies. A further possible reaction pathway
在125°C和10 MPa的条件下,乙酸1-乙基-3-甲基咪唑鎓[C 2 C 1 Im] [OAc]离子液体与二氧化碳的反应中,不仅存在已知的N-杂环卡宾(NHC)-CO 2加合物我获得了INH3和异构体aNHC-CO 2加合物II和III。根据静态DFT计算和从头算分子动力学研究,异常的NHC-CO 2加合物通过极化碱性乙酸根阴离子的存在得以稳定。系统的高碱性促进了进一步的反应途径,使最初形成的NHC-CO 2加合物I脱质子化,然后可以根据模型化合物的DFT计算,通过阴离子咪唑-2,4-二羧酸酯在过量的CO 2存在下将其转化为更稳定的2-去质子化的阴离子异常NHC-CO 2加合物。这暗示了异常NHC复合物形成的一般途径。