Article · Wikipedia archive · Last revised Jun 6, 2026

IMes

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.

Last revised
Jun 6, 2026
Read time
≈ 2 min
Length
421 w
Citations
7
Source
Wikipedia ↗
IMes
source ↗
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
ECHA InfoCard 100.154.201
  • InChI=1S/C21H24N2/c1-14-9-16(3)20(17(4)10-14)22-7-8-23(13-22)21-18(5)11-15(2)12-19(21)6/h7-12H,1-6H3
    Key: JCYWCSGERIELPG-UHFFFAOYSA-N
  • InChI=1/C21H24N2/c1-14-9-16(3)20(17(4)10-14)22-7-8-23(13-22)21-18(5)11-15(2)12-19(21)6/h7-12H,1-6H3
    Key: JCYWCSGERIELPG-UHFFFAOYAJ
  • Cc1cc(c(c(c1)C)N2C=CN([C]2)c3c(cc(cc3C)C)C)C
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).

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.34

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 source ↗
References

References

  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. Bibcode:1992JAChS.114.5530A. 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. Bibcode:2012JChEd..89.1575I. doi:10.1021/ed300243s.
  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.{{cite journal}}: CS1 maint: multiple names: authors list (link)
Further reading

Further reading