Yao Jun, Zheng Xiu-Jun, Pan Qing-Jiang, Schreckenbach Georg
†Key Laboratory of Functional Inorganic Material Chemistry of Education Ministry, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080, China.
‡Department of Chemistry, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada.
Inorg Chem. 2015 Jun 1;54(11):5438-49. doi: 10.1021/acs.inorgchem.5b00483. Epub 2015 May 8.
On the basis of relativistic density functional theory calculations, homo- and heterovalent binuclear uranium complexes of a polypyrrolic macrocycle in a U-O-U bridging fashion have been investigated. These complexes show a variety of oxidation states for uranium ranging from III to VI, which have been confirmed by the calculated electron-spin density on each metal center. An equatorially 5-fold uranyl coordination mode is suitable for hexavalent uranium complexes, while silylation of the uranyl oxo is favored by pentavalent uranium. Uranyl oxo ligands are not required anymore for the coordination environment of tetra- and trivalent uranium because of their replacement by strong donors such as tetrahydrofuran and iodine. Optimization of binuclear U(VI)-U(III) complexes with various coordinating modes of U(III), donor numbers, and donor types reveals that 0.5-1.0 electron has been transferred from U(III) to U(VI). Consequently, U(V)-U(IV) complexes are more favorable. Electronic structures and formation reactions of several representative uranium complexes were calculated. For example, a 5f-based σ(U-U) bonding orbital is found in the diuranium(IV) complex, rationalizing the fact that it shows the shortest U-U distance (3.82 Å) among the studied binuclear complexes.
基于相对论密度泛函理论计算，研究了以U-O-U桥连方式存在的多吡咯大环的同价和异价双核铀配合物。这些配合物显示出铀的多种氧化态，范围从III到VI，这已通过计算每个金属中心的电子自旋密度得到证实。赤道面5重铀酰配位模式适用于六价铀配合物，而五价铀有利于铀酰氧的硅烷化。由于四氢呋喃和碘等强给体取代了铀酰氧配体，因此对于四价和三价铀的配位环境不再需要铀酰氧配体。对具有各种U(III)配位模式、给体数和给体类型的双核U(VI)-U(III)配合物进行优化后发现，有0.5 - 1.0个电子从U(III)转移到了U(VI)。因此，U(V)-U(IV)配合物更有利。计算了几种代表性铀配合物的电子结构和形成反应。例如，在二铀(IV)配合物中发现了一个基于5f的σ(U-U)成键轨道，这解释了它在所研究的双核配合物中显示出最短U-U距离(3.82 Å)这一事实。
