The reactions of organometallic compounds play a central role in a great variety of important reactions. As examples, the actions of coenzyme B12 depend on the Co-C bond strength and new organic molecules which may have potential as drugs may be prepared from routes which depend upon transition metal mediated hydrogenation or asymmetric epoxidation. Understanding fundamental organometallic reactions can have a direct impact on understanding these processes. While in recent years, substantial progress has been made towards understanding organometallic reactions, many unanswered questions about the energetics of most organometallic reactions remain. Even basic questions about bond strengths heats of formation and enthalpies of reaction are often difficult to address in anything more than a qualitative context. Clearly, this information is central to any fundamental understanding of how organometallic precesses occur, what types of transformations are possible and predicting the synthesis and reactivity of new compounds. The goal of this research is to measure the enthalpic and rate data necessary to understanding basic reactions. Mechanistically significant steps will be examined which cover a broad range of reactivity. Metal-ligand bond strengths will be investigated as a function of the electronic nature of the metal complex as well as structure of the ligand itself. The role which bifunctionality plays in binding of CO2 to metals will also be examined. Activation of aliphatic C-H bonds and Si-H bonds will be examined. The strain inherent in the formation of small rings which contain a metal center will also be looked at. Finally, the energetics of ring slip reactions will be compared to the metal ligand bond strength information. This comparison will help ascertain which reaction si the generally preferred mode of introducing a site of coordinative unsaturation. Enthalpic data will be obtained with time-resolved photoacoustic calorimetry while kinetic data will be obtained from the photoacoustic experiment and with a nanosecond flash photolysis apparatus with detection in the visible region. The long term aims of this research are to obtain the thermochemical data which can be used to increase our understanding and predictive abilities of organometallic reactions. In turn, this information can be applied to understanding catalytic activity and selectivity and how metals influence chemical reactivity in general. The applications of this may be useful in a broad range of areas from peteroleum chemistry to biological systems.
