IMes

IMes

Names
Other names 1,3-bis(2,4,6-trimethylphenyl)-imidazolium, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene
Identifiers
CAS Number	141556-42-5
ChemSpider	9298886
Jmol interactive 3D	Image
PubChem	11123757
InChI 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
SMILES Cc1cc(c(c(c1)C)N2C=CN([C]2)c3c(cc(cc3C)C)C)C
Properties
Chemical formula	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 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, this diimine condenses with formaldehyde to give the dimesitylimidazolium cation. This cation is the conjugate acid of the NHC.^[3]

Related compounds

Related to IMes another popular NHC ligand is IPr, featuring diisopropylphenyl groups in place of the mesityl groups, IPr is even bulkier.^[4]

Important variants of IMes and IPr have saturated backbones, these ligands are called SIMes and SIPr.^[1] They are prepared by alkylation of substituted anilines with dibromoethane followed by ring closure and dehydrohalogenation of the dihydroimidazolium salt.^[5]

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

References

1. Steven P. Nolan "N-Heterocyclic Carbenes in Synthesis" Wiley-VCH, 2006. ISBN 978-3-527-60940-6.
2. Arduengo, Anthony J., III; Dias, H. V. Rasika; Harlow, Richard L.; Kline, Michael "Electronic Stabilization of Nucleophilic Carbenes" Journal of the American Chemical Society 1992, volume 114, pp. 5530-4. doi:10.1021/ja00040a007
3. Elon A. Ison, Ana Ison "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" J. Chem. Educ., 2012, volume 89, pp 1575–1577. doi:10.1021/ed300243s
4. Morgan Hans and Lionel Delaude "Microwave-Assisted Synthesis of 1,3-Dimesitylimidazolium Chloride" Org. Synth. 2010, vol. 87, 77. doi:10.15227/orgsyn.087.0077
5. Arnaud Gautier, Federico Cisnetti, Silvia Díez-González, Clémentine Gibard "Synthesis of 1,3–bis(2,4,6–trimethylphenyl)–imidazolinium salts : SIMes.HCl, SIMes.HBr, SIMes.HBF₄ and SIMes.HPF₆" Protocol Exchange 2012. doi:10.1038/protex.2012.048. http://www.nature.com/protocolexchange/protocols/2488#/procedure

Further reading

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