Metal ion catalysis in acyl and phosphoryl transfer: Transition states as ligands

Interpretation of the role of metal ions in catalysis in terms of direct binding of the catalyst to the transition state of the uncatalyzed reaction allows one to view transition states as ligands and to apply the concepts elaborated for analysis of stability of coordination compounds to reactivity. This paper reviews recent results on kinetics of metal ion catalyzed hydrolysis of carboxylic acid and phosphate esters providing pseudo-equilibrium transition state complexation constants (KT≠) for approximately 130 reactions. General trends in KT≠ values, in particular, interrelations between ground state and transition state complexation for different groups of catalysts and reactions are discussed.