A carbon-13 nuclear magnetic resonance investigation of the ring exchange in (1–4-η4-cyclo-octatetraene)(1–6-η6-cyclo-octatetraene)iron

Abstract

The site exchange between the η⁴- and η⁶-C₈H₈ rings in [Fe(η⁴-C₈H₈)(η⁶-C₈H₈)] is shown to occur via a mechanism where the transition state retains the differentiation between the four different types of CH groups in the η⁶-C₈H₈ ring with ΔG₃₀₀‡= 10.9 kcal mol^–1 No evidence is found for any shifts within the η⁶-C₈H₈ ring, while the shifts of the η⁴-C₈H₈ ring have ΔG‡ < 5.4 kcal mol^–l, and the reasons for this are discussed.