A kinetic study on substitution reactions of tridentate ligands for acetylacetonate in bis(acetylacetonato)(tetrahydrofuran)dioxouranium(VI)

Kinetics of substitution reactions of tridentate Schiff base ligands [N-(2-hydroxy-phenyl)salicylidenimine and its derivatives] for acac in UO2(acac)2thf (acac=acetylacetonate, thf=tetrahydrofuran) have been studied spectrophotometrically in thf. It was found that the reaction rates show the first-order dependence on the concentrations of Schiff base ligands and are accelerated with the addition of water to solvent. Apparent second-order rate constant (at 25°C) and activation parameters (ΔH≠ and ΔS≠) are 7.52 M−1 s−1, 49.8±3.2 kJ mol−1, and −61.0±11.0 J K−1 mol−1, respectively. On the basis of these results, the reaction mechanisms will be discussed.