Addition of anilines to the [Fe(CO)3(1–5-η-C7H9)]BF4 complex, and the ‘Ordered Transition State Mechanism’

Abstract

Kinetic studies of the reversible addition of anilines to the complex [Fe(CO)₃(1–5-η-dienyl)]BF₄(1; dienyl = C₇H₉) have demonstrated the dependence of rate on the electronic and steric nature of the attacking nucleophile. A plot of ΔH_a^‡versusΔS_a^‡ for the reaction of aniline with the complexes [Fe(CO)₃(1–5-η-dienyl)] BF₄(1; dienyl = C₆H₇, 2-MeOC₆H₆, or C₇H₉) is linear, the slope of which gives an isokinetic temperature of 369 ± 23 K, indicating enthalpy control over the associative process. The reaction of aniline and other substituted anilines with complexes (1) clearly reveals the predominance of negative entropies of activation for the dissociative processes in these systems, thus providing strong support for the recently proposed ‘Ordered Transition State Mechanism.’