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NMRによるCMPO/TBP系におけるランタニド錯体の構造解析

Study of lanthanide(III) nitrate complexes in CMPO/TBP systems by nuclear magnetie resonance

佐野 雄一   ; 青瀬 晋一; 岡本 文敏; 田中 康正

not registered; Aose, Shinichi; not registered; not registered

TRUEX(transuranium extraction)プロセスにおいて使用される抽出剤CMPO(octyl(phenyl)‐N,N‐diisobutylcarbamoylmethylphosphine oxide)及び相改質剤TBP(tributylphosphate)と軽ランタニド元素(La,Ce,Pr,Nd,Sm,Eu)との反応について、NMR(核磁気共鳴吸収)測定を用いて検討を行った。NMR測定の結果より、ランタニド/TBP系においては2分子のTBPが、ランタニド/CMPO系においては3分子のCMPOが、それぞれランタニドイオンに単座配位及び2座配位することが示された。また、ランタニド/CMPO/TBP系においては、CMPOのみが直接ランタニドイオンに2座配位し、TBPは第一配位圏には存在しないことが確認された。ランタニド/TBP系及びランタニド/CMPO系における配位子交換反応については、CBS(complete bandshape)法から求められた活性化パラメータの値から、会合機構あるいは第1配位圏外での溶媒などとの相互作用を伴う解離機構により配位子交換反応が進むものと推測された。一方、ランタニド/CMPO/TBP系におけるCMPOの交換反応は、第1配位圏外でのTBPによる影響を伴った反応で進行することが示唆された。

THe coordination properties of the lanthanide (La, Ce, Pr, Nd, Sm and Eu) complexes in lanthanide/TBP (tributylphosphate), lanthanide/CMPO (octyl(phenyl)-N, N-diisobutylcarbamoylmethylphosphine oxide) and lanthanide/CMPO/TBP systems were investigated by the NMR (nuclear magnetic resonance) measurements. The numbers of the coordinated CMPO and TBP to the lanthanide ion were estimated about three and two in the lanthanide/CMPO and lanthanide/TBP systems, respectively. It is considered that TBP and CMPO coordinate to the lanthanide (III) ion in the monodentate and the bidentate manners, respectively. In the lanthanide/CMPO/TBP system, $$^{31}$$P-NMR spectra suggested that CMPO coordinates to lanthanide(III) ion directly in the bidentate mode, but TBP doesn't exist within the first coordination sphere and coordinates to the lanthanide(III) ion from beyond the first coordination sphere. The activation parameters for the ligand exchange reactions calculated by the CBS (complete bandshape) method suggest that the ligand exchange reactions in the lanthanide (Pr and Eu)/TBP and lanthanide (La, Pr and Sm)/CMPO systems proceed through either the associative (A) mechanism or the dissociative (D) mechanism with an ordering into the second coordination sphere. In the lanthanide (Pr and Sm)/CMPO/TBP systems, it was shown that the CMPO exchange reactions proceed through the mechanism with an ordering into the second coordination sphere, which is caused by TBP in the systems.

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