Different Reactivities of Pyrid-2-yl- and 6-Picol-2-yl-Functionalized NHC Ligands with [Ru3(CO)12]: C(sp2)−H and Double C(sp3)−H Bond Activation Reactions

While both the direct and silver-mediated reactions of the bidentate NHC-pyridine ligand 1-[(pyrid-2-yl)methyl]-3-methylimidazol-2-ylidene (HpyCH2ImMe) lead to [Ru3(μ-H)(μ-κ3C2,N-pyCH2ImMe)(CO)9] (1), which contains a bridging ligand that arises from the metalation of the pyridine ring at the 6-position, similar reactions with 1-[(6-picol-2-yl)methyl]-3-methylimidazol-2-ylidene (MepyCH2ImMe), which has a methyl group at the same ligand position, afford either [Ru3(κC-MepyCH2ImMe)(CO)11] (2), which is a mere CO-substitution product, or [Ru3(μ-H)2(μ3-κ3C2,N-HCpyCH2ImMe)(CO)8] (3), in which that methyl group has been transformed into a CH fragment through a double C−H bond activation process.