An abnormal N-heterocyclic carbene-carbon dioxide adduct from imidazolium acetate ionic liquids: The importance of basicity

Zsolt Kelemen, Barbara Péter-Szabõ, Edit Székely, Oldamur Hollõczki, Dzmitry S. Firaha, Barbara Kirchner, Jõzsef Nagy, Lászlõ Nyulászi

Research output: Contribution to journalArticle

47 Citations (Scopus)

Abstract

In the reaction of 1-ethyl-3-methylimidazolium acetate [C2C1Im][OAc] ionic liquid with carbon dioxide at 125 C and 10MPa, 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.

Original languageEnglish
Pages (from-to)13002-13008
Number of pages7
JournalChemistry - A European Journal
Volume20
Issue number40
DOIs
Publication statusPublished - Sep 26 2014

Keywords

  • N-heterocyclic carbenes
  • basicity
  • density functional calculations
  • ionic liquids
  • supercritical CO

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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