The stability constants of the complexes of chlorosubstituted pyrazoles and pyrazoline in 70 % (v/v) dioxane-water mixture have been determined by PH-Meter. The proton-ligand and metal-ligand stability constants of Cu(II),Ni(II),Co(II) and Nd(III) metal ions with 3-(2-hydroxy-3,5-dichlorophenyl)-4-anisoyl-5-(4’-methoxyphenyl)- 1-phenylpyrazole(L1),3-(2-hydroxy-3,5-dichlorophenyl)-4-anisoyl-5-(4’-methoxyphenyl)-1-phenylpyrazoline (L2) and 4-(2-chlorophenyl)-3-(3-furanoyl-5-(2-hydroxyphenyl) pyrazole(L3) have been performed pH metric method at 0.1 M ionic strength at 27± 0.10C. The value of Log K1 and Log K2 were used to determined the stepwise and simultaneous complex formation and to verify the validity of Log K= a. pK + b relation.
