Kinetic and mechanistic studies on the interaction of thiosemicarbazide with cis-diaquaethylenediamine platinum (II) ion

Kinetics of interaction of thiosemicarbazide with [Pt(en)(H2O)(2)](2+) has been studied spectrophotometrically as a function of [Pt(en)(H2O)(2)](2+), [thiosemicarbazide] and temperature at a particular pH(4.0) where the subst rate complex exists predominantly as the diaqua species and the ligand thio semicarbazide as a neutral molecule. The interaction reaction shows distinc t two step consecutive process, the first step is the ligand assisted anati on and the second step is the chelation step. The activation parameters for both the steps are evaluated (Delta H-1(not equal) =35.69 +/- 0.80 k J mol (-1), Delta S-1(not equal) = -166 +/- 2.54 JK(-1) mol(-1) and Delta H-2(not equal) = 44.54 +/- 1.32 k J mol(-1), Delta S-2(not equal) = -182 +/- 4.18 JK(-1) mol(-1)).