1,3-BIS(2,4,6-TRIMETHYLPHENYL)IMIDAZOL-2-YLIDENE

Nucleophilic carbene that serves as a bulky, electron-rich "phosphine mimic" for metal-catalyzed reactions.
(a) Palladium-catalyzed Suzuki cross-coupling of aryl chlorides.
(b) Ruthenium-carbene complexes serve as more reactive catalyst for ring-closing metathesis.

1,3-Bis(2,4,6-trimethylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene (IMes) is a nucleophilic N-heterocyclic carbene (NHC) ligand.
It can be used to synthesize:

• IMes ligated-rhodium complex as a catalyst for the selective hydrogenation of substituted aryl and heteroaryl boronate esters to cis-substituted borylated cycloalkanes.
• IMes/ruthenium complex (Cp*Ru(IMes)Cl)(Cp* =η⁵-C₅Me₃) as a catalyst for olefin ring closing metathesis reaction.

IMes is also used as an ancillary ligand in Pd-catalyzed Suzuki-Miyaura cross-coupling reaction between aryl chlorides or aryl triflates and arylboronic acids.