Organometallic uranium(V)-imido halide complexes: From synthesis to electronic structure and bonding
Organometallic uranium(V)-imido halide complexes: From synthesis to electronic structure and bonding
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DOI：
10.1021/ja711010h
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发表时间：
2008-04-16
影响因子：
15
通讯作者：
Kiplinger, Jaqueline L.
中科院分区：
文献类型：
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作者：
Graves, Christopher R.;Yang, Ping;Kiplinger, Jaqueline L.
(C5Me5)(2)U(=N-2,4,6-(BU3)-B-t-C6H2) 或 (C5Me5)(2)U(=N-2,6-Pr-i(2)-C6H3)(THF) 与 5 当量的 CuXn (n = 1, X = Cl, Br, I; n = 2, X = F) 反应得到相应的铀(V)-亚氨基卤化物络合物， (C5Me5)(2)U(=N-Ar)(X)（其中 Ar = 2,4,6-(BU3)-B-t-C6H2 且 X = F (3)、Cl (4)、Br (5)、I (6)；Ar = 2,6-Pr-i(2)-C6H3 且 X = F (7)、Cl (6)、Br (9)、I (10)），分离产率良好75-89%。这些化合物通过单晶 X 射线衍射、H-1 NMR 光谱、元素分析、质谱、循环伏安法、紫外-可见-近红外吸收光谱和变温磁化率的组合进行了表征。分析(C5Me5)(2)U(=N-2,4,6-(BU3)-B-t-C6H2)(Cl)(4)的铀L-III边X射线吸收光谱以获得结构信息，得到U=N-亚氨基(1.97(1)埃)、U-Cl(2.60(2)埃)和U-C5Me5(2.84(1)) 埃）距离与化合物 3、5、6、8-10 观察到的距离一致，这些化合物均通过单晶 X 射线衍射研究进行了表征。通过伏安法，所有 (C5Me5)2U(=N-Ar)(X) 配合物均表现出 U-V/U-IV 和 U-VI/U-V 氧化还原电对，这些金属基电对之间的电势分离基本保持恒定，约为 1.50 V。电子光谱由涉及金属亚氨基中电子的 pi ->pi* 和 pi -> nb(5f) 跃迁组成 键和以金属为中心的 f-f 带说明了自旋轨道和晶体场对 5f(1) 价电子构型的影响。两组不同的能带归因于源自该 5f1 配置的跃迁，并且这些能带中的强度比经典 5f(1) 锕系配位配合物的光谱中发现的强度显着增加。据报告，所有 mu(eff) 值范围为 2.22 至 2.53 mu B 的配合物均具有温度依赖性磁化率。在所有情况下，观察到配体场引起的轨道角动量猝灭发生在类似于 40 K 的温度。模型配合物 (C5Me5)(2)U(=N-C6H5)(F) (11) 和 (C5Me5)(2)U(=N-C6H5)(I) (12) 的密度泛函理论结果与实验结构和电化学数据表现出良好的一致性，并为光谱带的分配提供了基础。键合分析描述了铀金属中心和亚氨基氮之间的多重键合，该多重键合由一个 sigma 和两个 pi 相互作用组成，其中来自铀中心的 5f 和 6d 轨道的可变参与。
Reaction of (C5Me5)(2)U(=N-2,4,6-(BU3)-B-t-C6H2) or (C5Me5)(2)U(=N-2,6-Pr-i(2)-C6H3)(THF) with 5 equiv of CuXn (n = 1, X = Cl, Br, I; n = 2, X = F) affords the corresponding uranium(V)-imido halide complexes, (C5Me5)(2)U(=N-Ar)(X) (where Ar = 2,4,6-(BU3)-B-t-C6H2 and X = F (3), Cl (4), Br (5), I (6); Ar = 2,6-Pr-i(2)-C6H3 and X = F (7), Cl (6), Br (9), I (10)), in good isolated yields of 75-89%. These compounds have been characterized by a combination of single-crystal X-ray diffraction, H-1 NMR spectroscopy, elemental analysis, mass spectrometry, cyclic voltammetry, UV-visible-NIR absorption spectroscopy, and variable-temperature magnetic susceptibility. The uranium L-III-edge X-ray absorption spectrum of (C5Me5)(2)U(=N-2,4,6-(BU3)-B-t-C6H2)(Cl) (4) was analyzed to obtain structural information, and the U=N-imido (1.97(1) angstrom), U-Cl (2.60(2) angstrom), and U-C5Me5 (2.84(1) angstrom) distances were consistent with those observed for compounds 3, 5, 6, 8-10, which were all characterized by single-crystal X-ray diffraction studies. All (C5Me5)2U(=N-Ar)(X) complexes exhibit U-V/U-IV and U-VI/U-V redox couples by voltammetry, with the potential separation between these metal-based couples remaining essentially constant at similar to 1.50 V. The electronic spectra are comprised of pi ->pi* and pi -> nb(5f) transitions involving electrons in the metal-imido bond, and metal-centered f-f bands illustrative of spin-orbit and crystal-field influences on the 5f(1) valence electron configuration. Two distinct sets of bands are attributed to transitions derived from this 5f1 configuration, and the intensities in these bands increase dramatically over those found in, spectra of classical 5f(1) actinide coordination complexes. Temperature-dependent magnetic susceptibilities are reported for all complexes with mu(eff) values ranging from 2.22 to 2.53 mu B. The onset of quenching of orbital angular momentum by ligand fields is observed to occur at similar to 40 K in all cases. Density functional theory results for the model complexes (C5Me5)(2)U(=N-C6H5)(F) (11) and (C5Me5)(2)U(=N-C6H5)(I) (12) show good agreement with experimental structural and electrochemical data and provide a basis for assignment of spectroscopic bands. The bonding analysis describes multiple bonding between the uranium metal center and imido nitrogen which is comprised of one sigma and two pi interactions with variable participation of 5f and 6d orbitals from the uranium center.