title: Highly valence-diversified binuclear uranium complexes of a schiff-base polypyrrolic macrocycle: prediction of unusual structures, electronic properties, and formation reactions.
abstract: 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.
authors.affiliation: †Key Laboratory of Functional Inorganic Material Chemistry of Education Ministry, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Yao
authors.affiliation: †Key Laboratory of Functional Inorganic Material Chemistry of Education Ministry, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080, China.
authors.forename: Xiu-Jun
authors.initials: XJ
authors.lastname: Zheng
authors.affiliation: †Key Laboratory of Functional Inorganic Material Chemistry of Education Ministry, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080, China.
authors.forename: Qing-Jiang
authors.initials: QJ
authors.lastname: Pan
authors.affiliation: ‡Department of Chemistry, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada.
authors.forename: Georg
authors.initials: G
authors.lastname: Schreckenbach