The kinetics of the thermal insertion reaction of tin(II) halides with cyclopentadienyliron dicarbonyl dimer

Abstract

The kinetics of the thermal insertion reaction of SnBr₂ and SnCl₂ with the metal–metal bonded dimer [π-C₅H₃Fe(CO)₂]₂ have been studied by following the change in the visible spectrum. The kinetic data are consistent with a two-stage mechanism involving the formation of a carbonyl-bridged intermediate followed by nucleophilic attack by the halides on this intermediate. The formation of the intermediate requires an activation enthalpy of 38.0 ± 1.0 kcal/mole, and an activation entropy of 45.5 + 1.5 cal mole⁻¹ deg⁻¹. The activation energy required to break the Fe—Fe bond is estimated to be about 32 kcal/mole.