THE ION-PAIR ASSOCIATION CONSTANT OF OXALATE WITH FAC-TRIS(2-AMINOMETHYLPYRIDINE)COBALT(III)

The equilibrium constant K for the ion-pair formation fac-[Co(pic)(3)] (3+) + C2O42- reversible arrow fac-[Co(pic)(3)](3+)/C2O42- where pic = 2-aminomethylpyridine, has been determined spectrophotometrically at 0.35 M (KCl) ionic strength and 25.0 degrees C, using four different c alculation approaches; The best results were obtained when the concent ration of the minor component (the cobalt complex ion) was not neglect ed in comparison with the oxalate ion concentration. The value of K (5 .3 M(-1)) increases when the supporting electrolyte is LiCl (K = 8.2 M (-1)). The effect of the ionic strength variation from 0.35 to 2.0 M ( LiCl) was also investigated. Copyright (C) 1996 Elsevier Science Ltd