Organometallic Uranium(V)−Imido Halide Complexes: From Synthesis to Electronic Structure and Bonding

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• 作者：Christopher R. Graves ; Ping Yang ; Stosh A. Kozimor ; Anthony E. Vaughn ; David L. Clark ; Steven D. Conradson ; Eric J. Schelter ; Brian L. Scott ; J. D. Thompson ; P. Jeffrey Hay ; David E. Morris ; Jaqueline
• 刊名：Journal of the American Chemical Society
• 出版年：2008
• 出版时间：April 16, 2008
• 年：2008
• 卷：130
• 期：15
• 页码：5272 - 5285
• 全文大小：1839K
• 年卷期：v.130,no.15(April 16, 2008)
• ISSN：1520-5126

文摘

Reaction of (C₅Me₅)₂U(ages/entities/dbd_2.gif">N-2,4,6-^tBu₃-C₆H₂) or (C₅Me₅)₂U(ages/entities/dbd_2.gif">N-2,6-ⁱPr₂-C₆H₃)(THF) with 5 equiv of CuX_n (n = 1, X = Cl, Br, I; n = 2, X = F) affords the corresponding uranium(V)−imido halide complexes, (C₅Me₅)₂U(ages/entities/dbd_2.gif">N-Ar)(X) (where Ar = 2,4,6-^tBu₃-C₆H₂ and X = F (3), Cl (4), Br (5), I (6); Ar = 2,6-ⁱPr₂-C₆H₃ and X = F (7), Cl (8), 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, ¹H 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)₂U(ages/entities/dbd_2.gif">N-2,4,6-^tBu₃-C₆H₂)(Cl) (4) was analyzed to obtain structural information, and the Uages/entities/dbd_2.gif">N_imido (1.97(1) Å), U−Cl (2.60(2) Å), and U−C₅Me₅ (2.84(1) Å) 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(ages/entities/dbd_2.gif">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 ~1.50 V. The electronic spectra are comprised of π→π* and π→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 5f¹ 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 5f¹ actinide coordination complexes. Temperature-dependent magnetic susceptibilities are reported for all complexes with μ_eff values ranging from 2.22 to 2.53 μ_B. The onset of quenching of orbital angular momentum by ligand fields is observed to occur at ~40 K in all cases. Density functional theory results for the model complexes (C₅Me₅)₂U(ages/entities/dbd_2.gif">N-C₆H₅)(F) (11) and (C₅Me₅)₂U(ages/entities/dbd_2.gif">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 σ and two π interactions with variable participation of 5f and 6d orbitals from the uranium center.