Potentiometric Determination of the Formation Constants of Complexes of 3,3´ ,4´ ´ -Triaminodipropylbutylamine with Co(II), Ni(II), Cu(II) and Zn(II)

Abstract

The tripodal 3,3,4-tetraamine ligand N{CH₂)₃NH₂}₂(CH₂)₄NH₂ (L = ppb) has been investigated for the first time as asymmetrical tetraamine chelating agent for cobalt(II), nickel(II), copper(II) and zinc(II). The protonation constants of ppb and formation constants of ppb and formation constants
of its complexes have been determined potentiometrically in 0.1 M
KCl at 25ºC. The successive protonatoin constants (log K_n) are:
10.69, 10.12,9.49,6.72 (n = 1–4). Two complexes having the formulae
ML, MHL (where L = ppb) are common to all the four metal
ions for which the formation constants {log β_ML, M = Co²⁺, Ni²⁺
Cu²⁺, Zn²⁺) are: 6.70, 6.79,12.98 and 9.37 and {log β_MHL, M=
Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺) are: 14.94, 16.09,22.20 and 17.24 respectively.
In addition to the simple and protonated complexes,
cobalt(II), copper(II) and zinc(II) give the hydroxo complexes and
nickel(II) gives the ML₂ complexes. The nickel(II) complex,
Ni(ppb )·(ClO₄)₂·1.5H₂O and zinc(II) complex, Zn(ppb)·(ClO₄)·H₂O,
have been isolated.