Synthesis of half-sandwich iron carboxyalkyls and iron (thiocarboxy)alkyls: Reaction of cyclopentadienyldicarbonyliodoiron with O- and S-based nucleophiles in the presence of triphenylphosphine

Article abstract of DOI:10.1021/om00008a048

One equivalent of NaOMe is added to an equimolar mixture of (η-C₅H₅)Fe(CO)₂I (1) and PPh₃ after the addition of a few drops of n-BuLi, to take advantage of the catalytic formation of [(η⁵-C₅H₅)Fe(CO)₂(PPh) ₃]⁺I^- (3), which, upon formation, becomes the virtual reactant with OMe^-. The OMe^- reaction yields the methyl carboxylate (η⁵-C₅H₅)Fe(CO)(PPh)₃C(O)OMe (8Me). A similar pattern is observed in the OPh^-, SMe^-, and SPh^- reactions, resulting in the derivatives (η⁵-C₅H₅)Fe(CO)(PPh)₃C(O)OPh (8Ph), (η⁵-C₅H₅)Fe(CO)(PPh)₃C(O)SMe (9Me), and (η⁵-C₅H₅)Fe(CO)(PPh)₃C(O)SPh (9Ph), respectively. The metalloesters exist simultaneously in the molecular form (8R) and the ionic form [(η⁵-C₅H₅)Fe(CO)₂(PPh) ₃]⁺ OR^- (10R; R = Me, Ph) in solutions of medium polarity (CHCl₃, CH₂Cl₂, and MeCN), whereas the S analogs exist only in the ionic form. In CHCl₃, CH₂Cl₂, and MeCN solutions, the ratio of neutral 8Me to ionic 10Me is ca. (6.0-8.4):1, as judged from the NMR measurements. Nonetheless, the ratio of neutral 8Ph to ionic 10Ph is ca. (0.17-0.25):1.