Functionalized N‑Heterocyclic Carbene Nonspectator Ligands upon Internal Alkyne Activation Reactions

When studying the activation of 3-arylpropiolates by [TpRu­(picolyl-RI)­Cl]/NaBArF4 (picolyl-MeI = 3-methyl-1-(2-picolyl)­imidazol-2-ylidene (1); picolyl-MeBI = 3-methyl-1-(2-picolyl)­benzoimidazol-2-ylidene (2)) a migratory insertion of the NHC into a ruthenium–carbon bond and an unprecedented C–N bond activation of the chelating picolyl-NHC ligand take place to give the new ruthenium metallacycles [TpRu­(κ3-C,N,N′-C­(Ph)C­(CH2Py)­(CO2Me)­(MeI)]­[BArF4] 3a and 4a and [TpRu­(κ3-C,N,N′-C­(4-CF3Ph)C­(CH2Py)­(CO2Me)­(MeI)]­[BArF4] 3b and 4b. X-ray crystal structures of 3a and 3b are reported, and a mechanistic pathway is proposed. In contrast, activation of internal alkynones by a mixture of [TpRu­(picolyl-MeI)­Cl] complex (1) and NaBArF4 led to isolation and characterization of the corresponding disubstituted vinylidene complexes. Also, structures of [TpRu­(picolyl-MeI)­(CC­(COR)­(Ph)]­[BArF4] (R = Me (6a); Ph (6b)) are reported.