Palladium(II) Halide Complexes II. Acid Hydrolysis and Halide Anations of Palladium(II) Chloro and Bromo Aqua Complexes

The rate constants for the chloride and bromide anations of Pd(H2O)42+, the chloride anations of PdCl3H2O−, the bromide anation of PdBr3H2O− and the acid hydrolysis of PdCl(H2O)3+, PdBr(H2O)3+, PdCl42−, and PdBr42− have been determined at 15, 25 and 35 °C using a stopped-flow technique. The ionic strength was 1.00 M and the supporting electrolyte perchloric acid. The obtained rate constants and the activation enthalpies and entropies are given. A comparison with the corresponding reactions for platinum(II) complexes indicates that the acid hydrolyses are 1×105 to 2×105 times faster and the halide anations 4×101 to 6×104 times faster for palladium. The increased rates of reaction are due to a decrease in activation enthalpies. The reactions are typically square planar substitutions with respect to entering and leaving groups. The mechanism appears to be associative in nature.