Constants for complexation reactions - Determination and applications

Complexation reactions are useful in a wide range of industrial applications, such as the large-scale production of reducing metals, wet surface treatment or the processing of ores to extract metals. These same reactions are also very useful in analytical chemistry, either for separations or for masking interfering species during quantitative determinations. Mastering complexation reactions relies on a good understanding of the nature of complex bonds and the equilibria associated with the corresponding reactions. A systematic method of calculation provides access to the distribution of species in a given medium. In the absence of complications due, for example, to parasitic reactions whose progress is poorly understood, this approach provides a better understanding of the phenomena involved, and enables us to predict the behavior of systems. Several applications of practical interest are discussed, and numerous values of equilibrium constants are made available to the reader. In addition, the determination of equilibrium constants is discussed, as the values of equilibrium constants needed to treat new practical cases have not necessarily been determined or have simply not been published.

In this article, we limit our reasoning to the case of complexes in aqueous phase. Moreover, hydration is not specified in the structures. As a result, the complex formation discussed here results from substitution reactions of one or more water molecules by one or more ligands whenever the complexed species is hydrated. Finally, we do not deal with lanthanides or actinides, whose specificity is such that they merit a separate study in their own right.