Complex formation in aqueous-organic mixed solvents

Approaches to the interpretation of complex-formation data in mixed aqueous-organic solvents based on the analysis of log-log plots of stability constants versus water molarity have been substantiated and developed. The near-integer values of the coefficients of these locally linear plots might serve as a base for determining the ligand denticities. As a result of the entrance of organic molecules into the inner sphere around the central atom, of the stoichiometrically determinate interaction of ligand species with solvent molecules, and of the simultaneous formation of inner- and outer-sphere complexes, the integer coefficients deviate to smaller values. The rearrangement of the coordination sphere can induce either positive or negative deviations. Specific effects can occur, such as the simultaneous expression of various denticities by some ligands and the addition of cosolvent molecules to the complex.