Interaction of Bivalent ions Co (II), Ni (II), Cu (II) and Zn (II) reacts with 4,6 – dihydroxy – 2 – mercapto pyrimidine (DHMP) in presence of oxalic acid (Ox), malonic acid (Mal), o-phenylene diamine (OPDA), 2,2 – bipyridyl (Bipy), 1, 10 – phenanthroline (phen) and ethylene diamine (En) has been investigated by potentiometric studies. The tertiary complexes are formed in stepwise manner in which DHMP behaves as secondary ligand. The stability constants of tertiary complexes have been reported at 350 C and at μ=0.01 M KNO3 in aqueous solution. The perusal of the stability constants reveals that the order in terms of ligand (L) prefers O-O>N-N and the sequence is supported by the argument that M (II)Bipy/Phentertiary- interaction makes the complexes more stable.
