IMes

IMes

IMes

Chemical compound

IMes is an abbreviation for an organic compound that is a common ligand in organometallic chemistry. It is an N-heterocyclic carbene (NHC). The compound, a white solid, is often not isolated but instead is generated upon attachment to the metal centre.[1]

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First prepared by Arduengo,[2] the heterocycle is synthesized by condensation of 2,4,6-trimethylaniline and glyoxal to give the diimine. In the presence of acid, the resulting glyoxal-bis(mesitylimine) condenses with formaldehyde to give the dimesitylimidazolium cation. This cation is the conjugate acid of the NHC.[3][4]

Bulkier than IMes is the NHC ligand IPr (CAS 244187-81-3). IPr features diisopropylphenyl in place of the mesityl substituents.[5]

Some variants of IMes and IPr have saturated backbones, two such ligands are SIMes and SIPr.[1] They are prepared by alkylation of substituted anilines with dibromoethane followed by ring closure and dehydrohalogenation of the dihydroimidazolium salt.[6]

SIMes is a popular NHC ligand with a more flexible backbone compared to IMes

References

  1. [1]
    Steven P. Nolan (2006). N-Heterocyclic Carbenes in Synthesis. Wiley-VCH. ISBN 978-3-527-60940-6.
  2. [2]
    Arduengo, Anthony J.; Dias, H. V. Rasika; Harlow, Richard L.; Kline, Michael (1992). "Electronic stabilization of nucleophilic carbenes". Journal of the American Chemical Society. 114 (14): 5530–5534. doi:10.1021/ja00040a007.
  3. [3]
    Ison, Elon A.; Ison, Ana (2012). "Synthesis of Well-Defined Copper N-Heterocyclic Carbene Complexes and Their Use as Catalysts for a "Click Reaction": A Multistep Experiment That Emphasizes the Role of Catalysis in Green Chemistry". Journal of Chemical Education. 89 (12): 1575–1577. Bibcode:2012JChEd..89.1575I. doi:10.1021/ed300243s.
  4. [4]
    Chen, Junting; Ritter, Tobias (2019). "Late-Stage Deoxyfluorination of Phenols with PhenoFluorMix". Org. Synth. 96: 16. doi:10.15227/orgsyn.096.0016.
  5. [5]
    Morgan Hans; Lionel Delaude (2010). "Microwave-Assisted Synthesis of 1,3-Dimesitylimidazolium Chloride". Org. Synth. 87: 77. doi:10.15227/orgsyn.087.0077.
  6. [6]
    Arnaud Gautier, Federico Cisnetti, Silvia Díez González, Clémentine Gibard (10 October 2012). "Synthesis of 1,3–bis(2,4,6–trimethylphenyl)–imidazolinium salts: SIMes·HCl, SIMes·HBr, SIMes·HBF4 and SIMes·HPF6". Protocol Exchange. doi:10.1038/protex.2012.048 (inactive 31 January 2024).{{cite journal}}: CS1 maint: DOI inactive as of January 2024 (link) CS1 maint: multiple names: authors list (link)

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