Kinetic and mechanistic studies on the interaction of DL-methionine with di-mu-hydroxobis(bipyridyl)dipalladium(II) ion

Kinetics of interaction between DL-methionine with the titled complex has b een studied spectrophotometrically as a function of [Pd-2(bipy)(2)(OH)(2)(2 +)], [DL-methionine], pH and temperature. The reaction has been monitored a t 270 nm, the lambda (max) of the substituted complex where the spectral di fference between the reactant and the product is maximum. The reaction rate increases linearly with increase in [DL-methionine]. The second order rate constants have been calculated from the slope of k(obs) versus [ligand] pl ot. From the experimental findings an associative mechanism for the substit ution process is suggested. The activation parameters (DeltaH(not equal) = 46.0 +/- 1.5 kJ mol(-1), AS(not equal) = -101 +/- 5 J K-1 mol(-1)) support the proposition.