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]
imidazol-2-ylidene_(aka_IMes).png) | |
| 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 |
PubChem CID | |
CompTox Dashboard (EPA) | |
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| 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). | |
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
