KINETIC AND MECHANISTIC STUDIES ON SUBSTITUTION-REACTIONS OF AQUA-LIGANDS FROM CIS-DIAQUA-BIS(BIGUANIDE)COBALT(III) WITH PYRIDINE-2-ALDOXIME IN VARIOUS ETHANOL-WATER MIXTURES

Kinetic studies on the substitution of aqua ligand of cis-diaqua-bis(b iguanide)cobalt(III) by pyridine-2-aldoxime in various ethanol water m edia (20, 30, 40% v/v) have been carried out spectrophotometrically. T he reaction rate is found to be pH-dependent in the pH range of 3.5 to 6.0 and compared with those of analogous systems. Low DELTAH(double d agger) and high negative DELTAS(double dagger) values are indicative o f a common mechanism involving outersphere association between the tit led complex and the entering ligand followed by transformation of the outersphere complex into product by an associative interchange process (I(a)). The effect of variation of dielectric constant of the reactio n medium on the rate has been used to verify the mechanistic conclusio n.