title: An abnormal N-heterocyclic carbene-carbon dioxide adduct from imidazolium acetate ionic liquids: the importance of basicity.
abstract: In the reaction of 1-ethyl-3-methylimidazolium acetate [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 is facilitated by the high basicity of the system, deprotonating the initially formed NHC-CO2 adduct I, which can then be converted in the presence of the excess of CO2 to the more stable 2-deprotonated anionic abnormal NHC-CO2 adduct via the anionic imidazolium-2,4-dicarboxylate according to DFT calculations on model compounds. This suggests a generalizable pathway to abnormal NHC complex formation.
authors.affiliation: Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Szt. Gellért tér 4. Budapest, 1111 (Hungary).
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Kelemen
authors.forename: Barbara
authors.initials: B
authors.lastname: Péter-Szabó
authors.forename: Edit
authors.initials: E
authors.lastname: Székely
authors.forename: Oldamur
authors.initials: O
authors.lastname: Hollóczki
authors.forename: Dzmitry S
authors.initials: DS
authors.lastname: Firaha
authors.forename: Barbara
authors.initials: B
authors.lastname: Kirchner
authors.forename: József
authors.initials: J
authors.lastname: Nagy
authors.forename: László
authors.initials: L
authors.lastname: Nyulászi
keywords: N-heterocyclic carbenes; basicity; density functional calculations; ionic liquids; supercritical CO2