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IMes

Topic: Chemistry

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IMes
Names
Preferred IUPAC name
1,3-Bis(2,4,6-trimethylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene
Other names
1,3-Dimesitylimidazol-2-ylidene, 1,3-bis(2,4,6-trimethylphenyl)-imidazolium, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene
Identifiers
3D model (JSmol)
ChemSpider
Properties
C21H24N2
Molar mass 304.43
Appearance white solid
Melting point 150 to 155 °C (302 to 311 °F; 423 to 428 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

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]

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. ↑ 1.0 1.1 Steven P. Nolan (2006). N-Heterocyclic Carbenes in Synthesis. Wiley-VCH. ISBN 978-3-527-60940-6. 
  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. ↑ 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. doi:10.1021/ed300243s. Bibcode: 2012JChEd..89.1575I. 
  4. ↑ Chen, Junting; Ritter, Tobias (2019). "Late-Stage Deoxyfluorination of Phenols with PhenoFluorMix". Org. Synth. 96: 16. doi:10.15227/orgsyn.096.0016. 
  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. ↑ 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. http://www.nature.com/protocolexchange/protocols/2488#/procedure. 

Further reading

  • Bantreil, Xavier; Nolan, Steven P. (2011). "Synthesis of N-heterocyclic carbene ligands and derived ruthenium olefin metathesis catalysts". Nature Protocols 6 (1): 69–77. doi:10.1038/nprot.2010.177. PMID 21212784. 



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