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.
© 1990 American Chemical Society. Received December 15, 1989. Published in print 25 June 1990. This work has been funded by the National Science Foundation through Grant No. CHE87-11567 (JLB) and CHE85-12711 (MTB) and a Shell Foundation graduate fellowship (DVD). In addition we thank the donors of the Petroleum Research Fund, administered by the American Chemical Society, for additional support. This manuscript is contribution number 8069 from the Division of Chemistry and Chemical Engineering at the California Institute of Technology.