Alkyne Insertion Induced Regiospecific C-H Activation with [Cp*MCl2]2 (M = Ir, Rh)

Regiospecific ortho-C2(pyrene)-H bond activation of a pyrene-based imine ligand was first promoted by sodium acetate with [Cp*IrCl2](2) to form a half-sandwich cycloiridation complex. Internal and terminal alkynes were then found to insert into the Ir-C-2pyrene bond of a cycloiridation complex, which induced another regiospecific peri-C8'(naphthyl)-H bond activation: different coordination modes of the alkynes group were captured. Unlike the iridium-based insertion complex, which is very stable, the rhodium-catalyzed oxidative coupling of an aromatic imine with an internal alkyne effectively proceeds via regioselective C-H bond activation to produce an indenone imine product. All the intermediate compounds following C-H activation, alkyne insertion and reduction, as well as indenone imine product were fully characterized, including the determination of X-ray structures.