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

PubChem CID

* 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 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. ↑ 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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Organometallic chemistry

Principles|

* crystal field theory
* ligand field theory
* 18-electron rule
* polyhedral skeletal electron pair theory
* isolobal principle
* π backbonding
* hapticity
* d electron count
* spin states

Reactions|

* oxidative addition / reductive elimination
* migratory insertion
* β-hydride elimination
* transmetalation
* carbometalation

Types of compounds|

* Gilman reagents
* Grignard reagents
* cyclopentadienyl complexes
* metallocenes
* sandwich compounds
* half sandwich compounds
* transition metal carbene complexes
* transition metal carbyne complexes

Applications|

* Monsanto process
* Ziegler–Natta process
* Shell higher olefin process
* olefin metathesis

Related branches of chemistry|

* organic chemistry
* inorganic chemistry
* bioinorganic chemistry

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