Stable cyclopropenylvinyl ligands via insertion into a transient cyclopropenyl metal bond.

Treatment of the rhodium pincer complexes [RhCl(RPm)] (RPm = N , N '-bis(di-R-phosphinomethyl)perimidinylidene, R = Ph, Cy) with triphenylcyclopropenium hexafluorophosphate affords rhodacyclobutadiene complexes. These in turn react with activated alkynes (RCCCO 2 Me, R = H, CO 2 Me) to afford unusually stable cyclopropenylvinyls, implicating the intermediacy of σ-cyclopropenyl isomers. In contrast, treatment of [RhCl{py(NHP t Bu 2 ) 2 -2,6}] with the same reagent instead results in double functionalisation ( S E Ar) at the pincer backbone.