Abstract
This paper discusses the relationship between the intermolecular oxidative addition reaction of carbon-hydrogen bonds in organic molecules to transition metal centres, and the dissociation energies of the CH, MH and MR bonds that undergo changes during this process. Earlier studies of transition metal MH and MR bond energies are reviewed, followed by a summary of relative and absolute bond energies measured more recently for the (η
5-C
5Me
5)(PMe
3)Ir(X)(Y) system. The MH and MR energies are unusually large in this system compared with most others that are presently known; an important exception are those in the thorium series, where intermolecular CH activation is also observed. The IrC and IrH bond energy values are utilized in discussing the propensity of iridium for intermolecular CH insertion, and in predicting thermochemistries for its RH insertion and M(H)(R) reductive elimination reactions. Finally, the physical basis for the strong metal-carbon and -hydrogen bonds in the iridium system is discussed.
