Structural, Electrochemical, and Magnetic Studies of Bulky Uranium(III) and Uranium(IV) Metallocenes
Structural, Electrochemical, and Magnetic Studies of Bulky Uranium(III) and Uranium(IV) Metallocenes
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DOI：
10.1021/acs.inorgchem.9b02719
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发表时间：
2019-12-16
影响因子：
4.6
通讯作者：
Arnold, John
中科院分区：
文献类型：
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作者：
Boreen, Michael A.;Lussier, Daniel J.;Arnold, John
添加大体积四氢呋喃的钾盐（异丙基）顺式（Cp-iPr 4）配体连接至UI 3（1，4-二氧六环）（1.5）导致形成弯曲的茂金属铀（III）络合物（Cp-iPr 4）（2）UI（1），然后用于获得铀（IV）和铀（III）二卤化物（Cp-iPr 4）（2）（UX 2）-X-IV（2-X）和[阳离子]-[（Cp-iPr 4）（2）（UX 2）-X-III]（3-X，[cation]（+）= [Cp*Co-2]（+），[Et 4 N]（+），or [Me 4 N]（+））作为单核的、无供体的配合物，对于X- = F-，Cl-，Br-，and I-.有趣的是，1与碱金属离子的氯化物和氰化物盐的反应导致分离氯化物-和氰化物-桥接的配位固体[（Cp-iPr 4）（2）U（mu-Cl）（2）Cs]（n）（4-Cl）和[（Cp-iPr 4）（2）U（mu-CN）（2）Na（OEt 2）（2）]（n）（4-CN）。从1中提取碘化物配体进一步使得能够分离“无碱”的双阳离子阳离子盐[（Cp-iPr 4）（2）U][B（C6 F5）（4）]（5）及其DME加合物[（Cp-iPr 4）（2）U（DME）][B（C6 F5）（4）]（5-DME）。固态结构的所有化合物，由X-射线晶体学确定，便于详细分析的影响，改变氧化态或卤化物配体的分子结构。2-X和3-X的NMR光谱学、X射线晶体学、循环伏安法和紫外可见光谱学研究进一步揭示，两个系列中的二氟化物物质表现出与在其他二卤化物中观察到的趋势显著不同的性质，例如[（Cp-iPr 4）（2）UX 2]铀（III/IV）氧化还原对的电势的显著负移。1和5的磁性表征表明，这两种化合物在施加磁场下表现出分子起源的缓慢磁弛豫;该过程由拉曼弛豫机制主导。
Addition of the potassium salt of the bulky tetra(isopropyl) cyclopentadienyl (Cp-iPr4) ligand to UI3(1,4-dioxane)(1.5) results in the formation of the bent metallocene uranium(III) complex (Cp-iPr4)(2)UI (1), which is then used to obtain the uranium(IV) and uranium(III) dihalides (Cp-iPr4)(2)(UX2)-X-IV (2-X) and [cation]-[(Cp-iPr4)(2)(UX2)-X-III] (3-X, [cation](+) = [Cp*Co-2](+), [Et4N](+), or [Me4N](+)) as mononuclear, donor-free complexes, for X- = F-, Cl-, Br-, and I-. Interestingly, reaction of 1 with chloride and cyanide salts of alkali metal ions leads to isolation of the chloride- and cyanide-bridged coordination solids [(Cp-iPr4)(2)U(mu-Cl)(2)Cs](n) (4-Cl) and [(Cp-iPr4)(2)U(mu-CN)(2)Na(OEt2)(2)](n) (4-CN). Abstraction of the iodide ligand from 1 further enables isolation of the "base-free" metallocenium cation salt [(Cp-iPr4)(2)U][B(C6F5)(4)] (5) and its DME adduct [(Cp-iPr4)(2)U(DME)][B(C6F5)(4)] (5-DME). Solid-state structures of all of the compounds, determined by X-ray crystallography, facilitate a detailed analysis of the effect of changing oxidation state or halide ligand on the molecular structure. NMR spectroscopy, X-ray crystallography, cyclic voltammetry, and UV-visible spectroscopy studies of 2-X and 3-X further reveal that the difluoride species in both series exhibit properties that differ significantly from trends observed among the other dihalides, such as a substantial negative shift in the potential of the [(Cp-iPr4)(2)UX2] uranium(III/IV) redox couple. Magnetic characterization of 1 and 5 reveals that both compounds exhibit slow magnetic relaxation of molecular origin under applied magnetic fields; this process is dominated by a Raman relaxation mechanism.