Kinetic Studies of the Ligand Substitution Reaction of Some New Uranyl Schiff Base Complexes with Tri‐n‐butylphosphine. Issue 12 (5th October 2013)

• Record Type: Journal Article
• Authors: Asadi, Zahra; Asadi, Mozaffar; Firuzabadi, Fahimeh Dehghani
• Is Part Of: International journal of chemical kinetics. Volume 45:Issue 12(2013:Dec.)
• Page Start: 795
• Page End: 802
• Publication Date: 2013-10-05
• Subjects: Chemical kinetics -- Periodicals; 541.394
• DOI: 10.1002/kin.20815
• Languages: English
• ISSNs: 0538-8066

Abstract

<abstract abstract-type="main"> <title>ABSTRACT</title> <p>Kinetics of the substitution reaction of solvent molecule in uranyl(VI) Schiff base complexes by tri‐<italic>n</italic>‐butylposphine as the entering nucleophile in acetonitrile at 10–40°C was studied spectrophotometrically. The second‐order rate constants for the substitution reaction of the solvent molecule were found to be (8.8 ± 0.5) × 10⁻³, (5.3 ± 0.2) × 10⁻³, (7.5 ± 0.3) × 10⁻³, (6.1 ± 0.3) × 10⁻³, (13.5 ± 1.6) × 10⁻³, (13.2 ± 0.9) × 10⁻³, (52.9 ± 0.2) × 10⁻³, and (88.1 ± 0.6) × 10⁻³ M⁻¹ s⁻¹ at 40°C for [UO₂(Schiff base)(CH₃CN)], where Schiff base = L1–L8, respectively. In a temperature dependence study, the activation parameters Δ<italic>H</italic>^# and Δ<italic>S</italic>^# for the reaction of uranyl complexes with PBu₃ were determined. From the linear rate dependence on the concentration of PBu₃, the span of <italic>k</italic>₂ values and the large negative values of the activation entropy, an associative (A) mechanism is deduced for the solvent substitution. By comparing the second‐order rate constants <italic>k</italic>₂_, it was concluded that the steric and the electronic properties of the complexes were important for the rate of the reactions.</p> </abstract>