Félix-Massa, Tamara

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    Consecutive solvent – C60 exchange on (η2– C60) Ir(CO)Cl(PPh3)2 and catalytically significant organometallic reactions on Ir(CO)(PPh3)2Cl(Solvent)
    (2010) Félix-Massa, Tamara; Cortés-Figueroa, José E.; College of Arts and Sciences - Sciences; Cádiz, Mayra E.; Meléndez, Enrique; Department of Chemistry; Acevedo, Aldo
    The solvent/C60 exchange reactions on (η2 – C60)Ir(CO)(PPh3)2Cl (solvent = benzene and cyclohexane) are biphasic. Plots of absorbance values at 550 nm vs. time are biexponential. Experiments where the reactions were monitored by infrared spectroscopy and 1HNMR spectrometry permitted identification of the consecutive processes suggested by absorbance (550 nm) vs. time plots. The first segment of absorbance vs. time plots was assigned to C60/benzene exchange producing (benzene)Ir(CO)(PPh3)2Cl, whereas the corresponding second segment was attributed to a series of reactions involving C-H bond oxidative cleavage of η 2 -coordinated benzene followed by a series of catalytically-relevant reactions. Activation parameters for benzene/C60 exchange reactions on (η2 – C60)Ir(CO)(PPh3)2Cl suggested an interchange associative mechanism. This interpretation prompted kinetics studies of the reactions in benzene/cyclohexane mixtures to determine rate constant values without unresolved solvent concentration dependences. Interestingly, rate constant values obtained from the second segment of the plot were [solvent]-dependent, suggesting the existence of benzene-cyclohexane exchange on the solvated (benzene)Ir(CO)(PPh3)2Cl and (cyclohexane)Ir(CO)(PPh3)2Cl intermediates. The proposed mechanism was tested by monitoring the reactions by infrared spectroscopy and 1HNMR spectrometry of actual samples of commercially available Vaska’s compound. These experiments confirmed that once the solvated intermediates are produce they undergo C-H bond oxidative cleavage followed by a series of parallel PPh3 dissociation and σ-complexes formation.