Relative reactivity of N, N-donor ligands in substitution reactions of cis-diaqua(2-aminomethylpiperidine)platinum(II): a detailed kinetic and mechanistic study

The reactivity of cis-[Pt(pipen)(H2O)(2)](2+) (pipen = 2-aminomethylpiperidine) was investigated by studying the interaction with some didentate N, N-donor ligands, namely, dimethylglyoxime (L1H), 1,2-cyclohexanedionedioxime (L2H) and alpha-furildioxime (L3H) in an aqueous medium. All the above substitution reactions have been monitored spectrophotometrically at 320, 308 and 290 nm, respectively, where the spectral difference between the reactants and the products are appreciable. The kinetic study has been substantiated by product isolation, UV, IR and ESI-MS spectroscopic analysis. The rate parameters have been evaluated under different reaction conditions. The reactions were found to occur in two consecutive steps. The mechanism of the substitution reactions appears associative in nature as supported by the large and negative values of Delta S-not equal.