Stability Constants of Metal(II) Complexes with Amines and Aminocarboxylates with Special Reference to Chelation

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Equations derived on the basis of mechanistic considerations have been utilized to calculate the stability constants of binary and ternary copper(II) complexes of amine(s) or aminocarboxylates. Calculated values of 185 copper(II) amine complexes have been compared with the observed. For 89 complexes including ammonia, ethylenediamine, cyclohexane-1,2-diamine, imidazole, pyridine, and some substituted analogs, the calculated values agree with the observed within 0.3 log unit. These complexes may be regarded as regular. Among the remaining non-regular complexes we find some complexes with lower stability constants due to steric hindrance, and some others with higher constants resulting from aromatic π–π interactions and/or hydrophobic interactions between coordinated ligands. Mechanistic considerations have also been successfully utilized to predict stability constants of polyamine and aminocarboxylate chelates of nickel(II), cobalt(II), and copper(II) according to Adamson’s approach.