Reaction mechanisms of metal–metal-bonded carbonyls. Part 23. Thermal homolytic fission of decacarbonyldirhenium (Re–Re)

Abstract

The kinetics of thermal decomposition of [Re₂(CO)₁₀] in decalin under oxygen have been examined. Taken together with data for the substitution reaction with triphenylphosphine the results are qualitatively and quantitatively consistent with initial reversible homolytic fission followed by further reaction of the [Re(CO)₅] radicals. Activation enthalpies obtained from the data show that [Re(CO)₅] is considerably more stable than [Mn(CO)₅]. The substitution reaction of [Re₂(CO)₁₀] with PPh₃ must also occur via initial homolytic fission and evidence is presented to suggest that substitution of PPh₃ into [Re(CO)₅] can be much more rapid than reaction with O₂ and proceeds via an associative pathway.