Base-Promoted, Remote C–H Activation at a Cationic (η(5)-C(5)Me(5))Ir(III) Center Involving Reversible C–C Bond Formation of Bound C(5)Me(5)

[Image: see text] C–H bond activation at cationic [(η(5)-C(5)Me(5))Ir(PMe(2)Ar′)] centers is described, where PMe(2)Ar′ are the terphenyl phosphine ligands PMe(2)Ar(Xyl)(2) and PMe(2)Ar(Dipp)(2). Different pathways are defined for the conversion of the five-coordinate complexes [(η(5)-C(5)Me(5))IrCl(PMe(2)Ar′)](+), 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(5)-C(5)Me(5))Ir(PMe(2)Ar′)](2+), is proposed. When NEt(3) is present, the PMe(2)Ar(Dipp)(2) 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 C(5)Me(5) 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.