Intramolecular C−H Activation Involving a Rhodium−Imidazol-2-ylidene Complex and Its Reaction with H₂ and CO

An orthometalated rhodium−carbene complex Rh(IMes)(H)(IMes‘)Cl (2) was obtained in high yield by reacting 2 equiv of a nucleophilic carbene, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) with [Rh(COE)2Cl]2 (1). The X-ray structure of 2 shows an intramolecular C−H activation of one aryl ortho methyl group. Complex 2 reacts rapidly with H2 and CO at room temperature, leading to the formation of Rh(IMes)2(H)2Cl (3) and Rh(IMes)2(CO)Cl (4), respectively.