The kinetics of interaction between glycylglycine and cis-[Ru(bipy) 2 (H 2 O) 2 ] 2+ have been studied spectrophotometrically as a function of [Ru(bipy) 2 (H 2 O) 2 2+ ], [diglycine] and temperature at a particular pH (4.8), where the substrate complex exists predominantly as the diaqua species and diglycine as the zwitter ion. The reaction has been found to proceed via two consecutive steps. The first step involves the ligand-assisted anation, while the second step involves chelation when the second aqua ligand is displaced. Rate constants have been evaluated and activation parameters calculated. The low enthalpy of activation and large negative values of entropy of activation indicate an associative mode of activation for both steps.