Organometallic Reaction Energetics from Product Kinetic Energy Release Distributions

Product kinetic energy release distributions reveal important features of the potential energy surfaces associated with the formation and rupture of H-H, C-H and C-C bonds at transition metal centers. For processes in which there is no barrier for the reverse reaction (loose transition state), experimental distributions can be reproduced with phase space theory. The single important parameter in fitting theory and experiment is the reaction exothermicity, which in turn yields bond dissociation energies for organometallic reaction intermediates. Two distinct experiments are discussed. In the first, the systems are chemically activated with reaction intermediates having well defined internal energies. The second, potentially more general method, involves investigations of ions with a broad range of internal energies. In this case the temporal constraints of the experiment lead to preferential detection of ions with a narrow range of internal energies. The results obtained to date in these studies are summarized, and several cautions are discussed which must be exercised if accurate bond energies are to be obtained