| Summary: | The iridium cyclooctadiene complex incorporating a tricyclopentyl phosphine ligand (PCyp₃), Ir(η²:η²-C₈H₁₂) (PCyp₃)Cl, has been prepared. Removal of the chlorine from this complex using Na[BAr₄<sup>f</sup>][Ar<sup>f</sup> = C₆H₃(CF₃)₂] in CH₂Cl₂/arene solvent results in dehydrogenation (C-H activation followed by β-H transfer) of one of the alkyl phosphine rings and formation of the complexes [Ir(η⁶-C₆H₅X){PCyp₂(η²-C₆H₇)}] [BAr₄<sup>f</sup>] (X=H,F) which contain a hybrid phosphine-alkene ligand. These complexes are formed alongside another product (5-20% yield) that has been identified as [Ir(η²:η²-C₈H₁₂){PCyp₂(η²-C₆H₇)}] [BAr₄<sup>f</sup>], which can be prepared in high yield by an alternative, and slightly modified, route. This complex is with a minor isomer that has been tentatively identified as [Ir(η²:η³-C₈H₁₁) (H){PCyp₂(η²-C₆H₇)}] [BAr₄<sup>f</sup>], which results from allylic C-H activation of cyclooctadiene. Addition of H₂ to [Ir(η²:η²-C₈H₁₂){PCyp₂(η²-C₆H₇)}] [BAr₄<sup>f</sup>] and its isomer in arene solvent (C₆H₅X, X=F,H) forms the dihydrido η⁶-arene Ir (III) complexes [Ir(H)₂(η⁶-C₆H₅X)(PCyp₃)][BAr₄<sup>f</sup>]. In contrast, hydrogenation in CH₂Cl₂ alone results in the formation of Ir(H)₂(PCyp₃){η⁶-(C₆H₅(CF₃)₂[BAr₃<sup>f</sup>} in which the [BAr₄<sup>f</sup>]⁻ anion is now acting as a ligand through one of its aryl rings. The fluorobenzene complex [Ir(H)₂(η⁶-(C₆H₅F){PCyp₂(η²-C₅H₇)}[BAr₄<sup>f</sup>] by addition of the hydrogen acceptor tert-butylethene (tbe).
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