IMes

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
CAS Number	141556-42-5  Y
3D model (JSmol)	Interactive image
ChemSpider	9298886
ECHA InfoCard	100.154.201
PubChem CID	11123757
CompTox Dashboard (EPA)	DTXSID70456010
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 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]}

Related compounds

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. 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 .

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. S2CID   30604456.