Effect of Excess Concentration of Secondary Ligand on Stability of Mixed Ligand Complexes

Abstract

The formation constants of ternary complexes MAL where
M = Ni(II), Cd(II) or Zn(II), A = 2,2' -bipyridyl amine as primary
ligand and L = 1,2-diaminopropane or ethylene diamine have, been
determined in aqueous solution by potentiometric method at constant
ionic strength,   μ= 0.2 M at 30 ± 0.1 °C. The stability of the
complexes is explained in terms of M→L π iriteraction, size of
the chelate ring and steric factors. The effect of higher molar concentration
of secondary ligand (1 : 1 : 2.5) on stability constants
of complexes is compared with optimum molar concentration of L
(1 : 1 : 1).