Stepwise Formation of Metal Complexes in Non-Aqueous Solvents

Abstract

Stepwise complex formation in non-aqueous solvents is a much less frequent phenomena than in aqueous solutions, where the stepwise substitution of water molecules by mono-dentate ligands is a common process with hydrated metal ions. Experience from work with aqueous solutions demonstrates two essential factors for a study of stepwise complex formation: a) effective solvation, which dissociates the metalsalt MX_m into M(H₂O)n + and m_X , b) the possibility to vary the central ion and the ligand concentration over a wide range. These two conditions are not so easy to realize in non-aqueous solvents, and this may be one reason why most stability constants have been determined in aqueous solutions. However, the knowledge of a metalligand system will be more complete if it is studied in several different media (states). the stability of a complex in water, may, for example, be due to a mixed ligand stabilization of a complex ML₄ (H₂O)₂ , which is built into the water lattice. Two examples are taken here to illustrate this point and to demonstrate some techniques of studying stepwise complex formation in non aqueous solvents. Further material will be delivered at the conference.