Reversible Concerted Metalation–Deprotonation C–H Bond Activation by [Cp*RhCl2]2

The reversibility of the concerted metalation–deprotonation exchange of eight para-substituted phenylpyridines is examined with the parent Cp*RhCl­(κ-C,N-NC5H4–C6H4). Equilibrium constants are determined, and the free energies are used to extract the most important parameters that control the thermodynamics. Keq values are found to correlate best with heterolytic C–H bond strengths but in a way that is not obvious considering the electrophilic nature of these activations.