Base-Promoted, Remote C-H Activation at a Cationic (η-CMe)Ir(III) Center Involving Reversible C-C Bond Formation of Bound CMe.

C-H bond activation at cationic [(η-CMe)Ir(PMeAr')] centers is described, where PMeAr' are the terphenyl phosphine ligands PMeAr and PMeAr. Different pathways are defined for the conversion of the five-coordinate complexes [(η-CMe)IrCl(PMeAr')], 2(Xyl) and 2(Dipp), into the corresponding pseudoallyls 3(Xyl) and 3(Dipp). In the absence of an external Brønsted base, electrophilic, remote ζ C-H activation takes place, for which the participation of dicationic species, [(η-CMe)Ir(PMeAr')], is proposed. When NEt is present, the PMeAr system is shown to proceed via 4(Dipp) as an intermediate en route to the thermodynamic, isomeric product 3(Dipp). This complex interconversion involves a non-innocent CMe ligand, which participates in C-H and C-C bond formation and cleavage. Remarkably, the conversion of 4(Dipp) to 3(Dipp) also proceeds in the solid state.