A Nuclear Magnetic Resonance Study on Ligand Exchange Reactions in U(VI) Nitrato Complexes with Ligands Containing Phosphoryl Group in Non-aqueous Solvents.

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  • HATAKEYAMA Koh
    Research Laboratory for Nuclear Reactors Tokyo Institute of Technology Naka Energy Research Center Mitsubishi Materials Corp.,
  • PARK Yoon-Yul
    Research Laboratory for Nuclear Reactors Tokyo Institute of Technology Pusan Junior College
  • TOMIYASU Hiroshi
    Research Laboratory for Nuclear Reactors Tokyo Institute of Technology
  • IKEDA Yasuhisa
    Kashiwa Laboratory Institute of Research and Innovation

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  • Nuclear Magnetic Resonance Study on Lig

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Abstract

The exchange reactions of tributyl phosphate (TBP) and dihexyl-N, N-diethylcarbamoylmethylphosphonate (CMP) in U(VI) nitrato complexes with TBP or CMP (abbreviated as U(VI)-TBP or U(VI)-CMP) have been studied by means of 31P NMR method in CD3COCD3 or CD2Cl2. The number of TBP coordinated to uranyl nitrate was directly determined to be 1 in CD3COCD3 and 2 in CD2Cl2 by the area integrations of 31P NMR signals of free and coordinated TBP. Similarly, the number of coordinated CMP was evaluated as 1 in CD3COCD3. The exchange rate constants of TBP and CMP in U(VI)-TBP and U(VI)-CMP complexes were calculated by the two-site exchange model. The exchange rate of TBP in U(VI)-TBP is independent of the free TBP concentrations ([TBP]f ), while that in U(VI)-CMP is dependent on [CMP]f. From these results, the dissociative (D) and interchange (I) mechanisms were proposed for the exchange reactions of TBP in U(VI)-TBP and CMP in U(VI)-CMP, respectively. Kinetic parameters are as follows: rate constant (25°C), ΔH≠(kJ-mol-1), ΔS≠(J•K-1•mol-1); 9.9×103s-1, 33.7, -55.4 (U(VI)-TBP system), 2.3×104 m-1•s-1 (apparent second-order), 25.2, -75.9 (U(VI)-CMP system).

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