Potentiometric Determination of the Formation Constants of Complexes of 3,3´ ,2"-Triaminodipropylethylamine with Co(II), Ni(II), Zn(II) and Cd(II)

Abstract

The tripodal tetraamine ligand N{(CH₂)₃NH₂}₂{(CH₂)₂NH₂} (ppe) has been investigated for the first time as asymmetrical tetraamine chelating agent for cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II). The protonation constants of this ligand and formation constants. of its complexes have been determined

potentiometrically in 0.1 M KCl at 25ºC. The successive protonation

constants (log K_n) are: 10.38,9.68,8.95 and 3.81 (n = 1-4).

One complex has the formula M(ppe)²⁺ is common to the all five

metal ions for which the formation constants {log β_ML, M = Co,

Ni, Cu, Zn, Cd} are:, 9.26, 11.95,15.98,12.01 and 8.33 respectively.

In additon to the simple complex; copper(II), cobalt(II) and zinc(II)

also give hydroxo complexes, Copper(II) and nickel(II) give the

mono protonated complexes and nickel(II) give the ML₂ complex.

The [Zn(ppe)](ClO₄)₂ and [Cd(ppe)Cl](ClO₄) complexes were also

isolated.