Potentiometric determination of the formation constants for complexes of 3,2',2''-triaminopropyldiethylamine with cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II)

• Published in: Transition metal chemistry (Weinheim) 2003-05, Vol.28 (4), p.425
• Main Authors: Keypour, Hassan, Dehdari, Masoud, Salehzadeh, Sadegh, Wainwright, Kevin P
• Format: Article
• Language: English
• ISSN: 0340-4285; 1572-901X
• DOI: 10.1023/A:1023670918923

The tripodal tetraamine ligand N{(CH^sub 2^)^sub 3^NH^sub 2^}{(CH^sub 2^)^sub 2^NH^sub 2^}^sub 2^ (pee), has been investigated as an asymmetrical tetraamine chelating agent for Co^sup II^, Ni^sup II^, Cu^sup II^, Zn^sup II^ and Cd^sup II^. The protonation constants for this ligand and the formation constants for its complexes have been determined potentiometrically in 0.1 M KCl at 25 °C. The successive protonation constants (log K^sub n^) are: 10.22, 9.51, 8.78 and 1.60 (n = 1-4). One complex with formula M(pee)^sup 2+^ (M = Co, Ni, Cu, Zn and Cd) is common to all five metal ions and the formation constant (log β^sub ML^) is: 12.15, 14.17, 16.55, 13.35 or 9.74, respectively. In addition to the simple complexes, Co^sup II^, Cu^sup II^ and Zn^sup II^ also give hydroxo complexes, and Cu^sup II^ and Ni^sup II^ give complexes with monoprotonated pee. [Zn(pee)](ClO^sub 4^)^sub 2^ and [Cd(pee)Cl](ClO^sub 4^) complexes were isolated and are believed to have tetrahedral and trigonal-bipyramidal structures, respectively.[PUBLICATION ABSTRACT]