Coordination chemistry concerns the interactions between metal centers and the ligands surrounding them. Descriptors such as stability constants tell us about the thermodynamics of these interactions but we have less information regarding the underlying kinetics, including the rates at which a donor atom binds and releases a metal. Understanding these processes will help us better understand hemilabile complexes − species in which chelate rings dynamically open and close. Hemilabile complexes are topical catalysts because the closed form is a protected resting state that can open when necessary to reveal a metal coordination site at which a substrate can convert into a product.
Many hemilabile complexes feature bidentate ligands with a strongly basic donor atom and a more weakly basic one. It is assumed that the less basic one releases its grip from the metal but how this happens is often not clear. We are also interested in the more challenging case of a symmetric bidentate ligand that binds a metal equally strongly at the two donor atoms. Breaking either the coordinate bonds is now degenerate and often takes quite some energy. This is a process that we will probe in the gas and solution phases.