31P-NMR study of the organophosphorous complexes of uranium(VI)

The intermolecular ligand exchange in uranyl nitrate complexes with TBP and TOPO is studied by³¹P-NMR. The constant rates at 25°C in CCl₄ are: (8.47±1.86)·10³ s^?1 for U-TBP and (1.3±0.04)·10⁴M^?1·s^?1 for U-TOPO system. The very similar activation parameters values of the ligand exchange suggest the same mechanism for both systems, namely an one-step interchange mechanism. The differences between the systems regarding the rate equations and the extraction properties are discussed.