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Base-Promoted, Remote C−H Activation at a Cationic (η5‐C5Me5)Ir(III) Center Involving Reversible C−C Bond Formation of Bound C5Me5

IIQ

Juan J. Moreno, María F. Espada, Jesús Campos, Joaquín López-Serrano, Stuart A. Macgregor, Ernesto Carmona J. Am. Chem. Soc. 2019, Vol. 141, 2205-2210

C−H bond activation at cationic [(η5-C5Me5)Ir(PMe2Ar′)] centers is described, where PMe2Ar′are the terphenyl phosphine ligands PMe2ArXyl2 and PMe2ArDipp 2. Different pathways are defined for the conversion of the five-coordinate complexes [(η5-C5Me5)-IrCl(PMe2Ar′)]+, 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, [(η5-C5Me5)Ir- (PMe2Ar′)]2+, is proposed. When NEt3 is present, the PMe2ArDipp2 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 C5Me5 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.

Juan José Moreno