Water and proton Exchange Processes on Metal Ions

Publisher Summary The simplest reaction on a metal ion in aqueous solution is the exchange of a water molecule between the first and second coordination shells. This reaction is fundamental in understanding not only the reactivity of metal ions in chemical and biological systems but also the metal–water interaction. The replacement of a water molecule from the first coordination shell represents an important step in complex-formation reactions of metal cations and in many redox processes. This chapter presents the concepts of solvent exchange reactions and how exchange reaction mechanisms can be assigned from variable pressure experiments. The chapter describes the oxygen-17 NMR techniques available to measure water exchange rates over 18 orders of magnitude. Water exchange rate constants and activation parameters measured directly by 17 O NMR on aqua-ions and on some metal complexes with an inert ligand and water molecules in the first shell are also discussed in the chapter.