Functionalized N-heterocyclic carbene nonspectator ligands upon internal alkyne activation reactions.

When studying the activation of 3-arylpropiolates by [TpRu(picolyl-(R)I)Cl]/NaBAr(F)4 (picolyl-(Me)I = 3-methyl-1-(2-picolyl)imidazol-2-ylidene (1); picolyl-(Me)BI = 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(κ(3)-C,N,N'-═C(Ph)-C(CH2Py)(CO2Me)((Me)I)][BAr(F)4] 3a and 4a and [TpRu(κ(3)-C,N,N'-═C(4-CF3Ph)-C(CH2Py)(CO2Me)((Me)I)][BAr(F)4] 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-(Me)I)Cl] complex (1) and NaBAr(F)4 led to isolation and characterization of the corresponding disubstituted vinylidene complexes. Also, structures of [TpRu(picolyl-(Me)I)(═CC(COR)(Ph)][BAr(F)4] (R = Me (6a); Ph (6b)) are reported.