Aquation Kinetics of the Aquoammine Complexes of Palladium(II)

Abstract

Upon treatment with excess aqueous HClO₄, Pd(NH₃)₄²⁺ is converted through four consecutive steps to Pd(OH₂)₄²⁺. Correlation of observed rate constants with actual mechanistic steps is based primarily on reconstruction of the absorption spectra of the intermediate species; it was thus found that the rate constants decrease steadily from one step to the next. At 50°, µ = 1, rate constants found are respectively 0.020, 0.008, 9.2 X 10ˉ³ and 2.2 X 10ˉ⁴ secˉ¹. Activation enthalpies range from 21 to 24 kcal/mol and activation entropies from +4 to -4 eu. Substituent effects are compared with those in chloride-containing complexes and with those for the reverse reactions.