Volumes of activation for the anation of Pd(II) substituted dien complexes by chloride ion in aqueous solution. A high pressure stopped-flow instrument for studying the kinetics of fast reactions under pressure

Abstract

The kinetics of anation of Pd(1,1,7,7-Et 4dien)OH 2+ 2 and Pd(1,1,4-Et 3dien)OH 2+ 2 by chloride ion were studied under pressures up to 1 kbar using a high pressure stopped-flow system. The construction and testing of the latter system are discussed in detail. The rate and activation parameters for the above reactions are: k(25 °C) = 4.2 ± 0.1 and 1558 ± 68 M −1 sec −1; ΔH≠ = 13.4 ± 0.4 and 10.5 ± 0.7 kcal mol −1; ΔS≠ = −10.7 ± 1.2 and −8.7 ± 2.3 cal K −1 mol −1; and ΔV≠ = −3.0 ± 0.2 and −2.7 ± 0.2 cm 3 mol −1, respectively. These are considered as evidence for an associative type of anation process.