Intramolecular C-H activation involving a rhodium-imidazol-2-ylidene complex and its reaction with H-2 and CO

An orthometalated rhodium-carbene complex Rh(IMes)(H)(lMes')Cl (2) was obtained in high yield by reacting 2 equiv of a nucleophilic carbene, 1,3-bis(2,4,6-trimethyphenyl)imidazol-2-ylidene (IMes) with [Rh(COE)(2)Cl](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 H-2 and CO at roam temperature, leading to the formation of Rh (IMes)(2)(H)(2)Cl (3) and Rh(IMes)(2)(CO)Cl (4), respectively.