Investigation On The Reactions Of Lanthanide Bis (Trimethylsilyl) Amides With Oxygen-containing Reagents And Their Reaction Products

Oxygen is inevitably present in the fuel salt from thorium molten salt reactor during pyroprocessing,which causes the formation of oxides that influences the separation of actinides and fission products with lanthanide as representatives.Therefore,it is of great significance to investigate how oxygen behaves during the separation process,and particularly the reactions between oxygen and fission products such as lanthanides.In this thesis,the reaction of typical lanthanides with some oxygencontaining reagents were studied,and their reaction products were characterized mainly by crystallographic methods.At the same time,some special luminescence properties of lanthanum and cerium iodides discovered during the preparation of lanthanide bis（trimethylsilyl）amide precursors were also studied.The major results are as follows:（1）A series of trivalent lanthanide precursors Ln[N（SiMe₃）₂]₃（Ln=Eu,Sm,Nd,La,Ce,Yb）and divalent lanthanide precursors Ln[N（SiMe₃）₂]₂（THF）2（Ln=Eu,Yb）were synthesized from lanthanide chlorides or iodides,and the crystal structure of La[N（SiMe₃）₂]₃ that has never been reported was determined.The synthesis of these precursors serves as the starting point for the study of the reaction of lanthanides with oxygen-containing reagents.A rare photoluminescence phenomenon of LaI₃（THF）₄ complex was found in the process of preparing lanthanum（III）precursor.The complex can be easily prepared by immersing commercial anhydrous LaI₃ in THF.LaI₃（THF）₄ emit strong blue light when irradiated by ultraviolet light at 254 nm,and the absolute emission quantum yield is as high as 50.5%,which contrasts the non-luminescent character of either LaI₃ or THF.The photoluminescence of LaI₃ can be switched on and off by reversible THF association and dissociation.The experimental results show that anhydrous LaI₃ can be used as a convenient and rapid sensor to detect THF.It is found that CeI₃ has different photoluminescence phenomena in different organic solvents in the process of preparing cerium（III）precursor.Violet or blue emissions were observed for CeI₃ dissolved in THF,CH3 CN and Et2 O under ultraviolet irradiation.The luminescent properties are correlated with the structures of solvated complexes as exemplified in the CeI₃（THF）₄ case.The solvoluminescence is strongly affected by the presence of water which converts solvated Ce（III）into cerium hydrates.The results indicate the potential application of commercial CeI₃ as a convenient luminescent sensor for the detection of trace water in organic solvents.（2）The reactions of typical Ln（III）with the oxygen-containing reagents Me₃NO、Me₃PO and TEMPO were systematically investigated.It was found that the reaction of Ln（III）precursors with Me₃ NO lead to the simultaneous C-H bond activation and oxygen atom transfer（OAT）of Me₃ NO,and form the dinuclear lanthanide complexes Ln2（μ-OCH2NMe₂）₂[N（SiMe₃）2]4[Ln= Eu（T1）,Sm（T2）,Nd（T3）,Ce（T4）,La（T5）],while the metal center remained in the + 3 valence oxidation state.When the Ln（III）precursors reacted with Me₃ PO,simple 1:1 adducts Ln[N（SiMe₃）₂]₃（OPMe₃）[Ln= Eu（T7）,Sm（T8）,Nd（T9）,Ce（T10）,La（T11）,Yb（T12）] were obtained.Different from the Me₃ PO case,the reaction product of TEMPO is a Li Cl bridged binuclear adduct Nd[N（SiMe₃）₂]₃（μ-Cl）Li（TEMPO）3（T13）.The crystal structures of the above products were confirmed by X-ray single crystal diffraction and nuclear magnetic spectra analysis,and the relevant reaction mechanism was analyzed.The experimental results provide a new idea for the application of lanthanides in the activation and functionalization of C-H bonds in organic compounds.（3）The reactions of typical Ln（II）precursors with the oxygen-containing reagents Me₃ NO and TEMPO were investigated.A N,N,N’,N’-tetramethylethylenediamine（TMEDA）complex Eu[N（SiMe₃）₂]₂（TMEDA）（B1）of Eu（II）was synthesized via an uncommon self-aminomethylation reaction of Me₃ NO in the presence of Eu[N（SiMe₃）₂]₂（THF）2.It is proposed that the neutral TMEDA ligand is formed from the reaction of iminium ion and deprotonated Me₃ NO,both of which were generated from Me₃ NO.The Eu（II）precursor not only serves as a base,but also as a promoter that facilitates the generation of the iminium ion intermediate.In contrast,the reaction of Yb[N（SiMe₃）₂]₂（THF）2 and Me₃ NO led to the oxygen-bridged [Yb（NR₂）₂（ONMe₃）]2（μ-O）（R=SiMe₃）（B3）compound with a Yb（III）center,and Me₃NO acted as a regular oxygen-atom-transfer reagent as well as a neutral ligand.The higher reductive character of Yb[N（SiMe₃）₂]₂（THF）2 than Eu[N（SiMe₃）₂]₂（THF）2 should account for the absence of the TMEDA complex of Yb（II）via coupling of the carbon atoms from two Me₃ NO.When Eu[N（SiMe₃）₂]₂（THF）2 and Yb[N（SiMe₃）₂]₂（THF）2 reacted with TEMPO,mixed metal products [K（TEMPO）2Ln（NR₂）₂]（R=SiMe₃）[Ln=Eu（B4）,Yb（B5）] were produced,respectively,in which Ln（II）was oxidized to Ln（III）.The crystal structures of the above products were confirmed by X-ray crystallography.The experimental results demonstrate the capability of lanthanide（II）compounds in the aminomethylation reaction for the first time.