pH-metric Studies on Quaternary Mixed Ligand Complex Formation of Ni(ll)

Chemical Laboratories, Agra College, Agra Manuscript received 19 January 1979, accepted 29 December 1979 Mixed ligand complexes of the type MABC, where M =Ni(II), A=oxalic (OX), malonic (MALN) or phthalic (PHA) acids, B=ethylenediamine (en) or 1,2-diamino­propane (pn) and C= aminoacetic acid (gly) have been investigated by potentiometric titration technique. Evidence is given for the stepwise addition of B and C to the initially formed MA complex, resulting in ternary (MAB) and quaternary (MABC) com­plex formation respectively. Formation constants (log KMBAC) and the free energies of formation (∆F°) for the quaternary systems have been calculated at 25±1°. The order of stability in terms of diamine have been found to be as pn> en