Kinetics and mechanism of cyclo- and decyclo-metallation of some iridium triaryl phosphite complexes. Evidence for the electrophilic displacement mechanism

Abstract

The formation of [IrH(P–C)(cod)L]X [P–C = P(OC₆H₃Me-o)(OC₆H₄Me-o)₂, cod = cyclo-octa-1,5-diene, L = P(OC₆H₄Me-o)₃ or PMe₂Ph] from [Ir(P–C)(cod) L] and HX (X = ClO₄, PF₆, or BF₄) is proposed to occur by a mechanism involving direct proton attack at the metallated carbon for ring opening, followed by electrophilic displacement of a proton from an ortho-C–H by a preformed iridium(III) hydride in the ring closing step; a similar mechanism is proposed for the ring opening in the reaction of [Ir(P–C)(cod)L] with halogen acids HX (X = Cl, Br, or I) to give [IrHX₂(cod)L].