Some remarks about 5f → 6d and charge transfer transitions in uranium(IV) and plutonium(IV) complexes

Poturaj-Gutniak, S.; Taube, M.

doi:10.1016/0022-1902(68)80319-7

Cited by 6 publications

(4 citation statements)

References 7 publications

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“…A 5f 2 f 5f 1 6d 1 assignment for this unresolved band in the uranium bis(ketimide) complexes seems potentially attractive because such transitions should have large oscillator strengths and fairly broad bandwidths. Previous studies of classical U IV coordination complexes place this transition at higher energy; [21][22][23][24][25] however, the stronger σ-and π-interactions of the ketimide ligands with the metal center may stabilize some subset of metal 6d orbitals as well, thereby lowering the energy of the interconfiguration transition relative to that in, for example, the (C 5 Me 5 ) 2 U(CH 3 ) 2 complex. The ultimate uncertainty in assigning this transition is exacerbated by the much greater potential for mixing of excited states in these ketimide complexes as a result of more favorable metalligand orbital energy matching and greater metal-ligand bonding interactions.…”

Section: Uranium(iv) Fluoroketimidesmentioning

confidence: 99%

Systematic Studies of Early Actinide Complexes: Uranium(IV) Fluoroketimides

et al. 2007

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The reaction of (C5Me5)2U(CH3)2 with 2 equiv of N[triple bond]C-ArF gives the fluorinated uranium(IV) bis(ketimide) complexes (C5Me5)2U[-N=C(CH3)(ArF)]2 [where ArF=2-F-C6H4 (4), 3-F-C6H4 (5), 4-F-C6H4 (6), 2,6-F2-C6H3 (7), 3,5-F2-C6H3 (8), 2,4,6-F3-C6H2 (9), 3,4,5-F3-C6H2 (10), and C6F5 (11)]. These have been characterized by single-crystal X-ray diffraction, 1H and 19F NMR, cyclic voltammetry, UV-visible-near-IR absorption spectroscopy, and variable-temperature magnetic susceptibility. Density functional theory (DFT) results are reported for complexes 6 and 11 for comparison with experimental data. The most significant structural perturbation imparted by the F substitution in these complexes is a rotation of the fluorinated aryl (ArF) group out of the plane defined by the N=C(CMe)(Cipso) fragment in complexes 7, 9, and 11 when the ArF group possesses two o-fluorine atoms. Excellent agreement is obtained between the DFT-calculated and experimental crystal structures for 11, which displays the distortion, as well as for 6, which does not. In 7, 9, and 11, the out-of-plane rotation results in large angles (phi=53.7-89.4 degrees) between the planes formed by ketimide atoms N=C(CMe)(Cipso) and the ketimide aryl groups. Complexes 6 and 10 do not contain o-fluorine atoms and display interplanar angles in the range of phi=7-26.8 degrees. Complex 4 with a single o-fluorine substituent has intermediate values of phi=20.4 and 49.5 degrees. The distortions in 7, 9, and 11 result from an unfavorable steric interaction between one of the two o-fluorine atoms and the methyl group [-N=C(CH3)] on the ketimide ligand. All complexes exhibit UV/UIV and UIV/UIII redox couples, although the distortion in 7, 9, and 11 appears to be a factor in rendering the UIV/UIII couple irreversible. The potential separation between these couples remains constant at 2.15+/-0.03 V. The electronic spectra are dominated by unusually intense f-f transitions in the near-IR that retain nearly identical band energies but vary in intensity as a function of the fluorinated ketimide ligand, and visible and near-UV bands assigned to metal (5f)-to-ligand (pi*) charge-transfer and interconfiguration (5f2-->5f16d1) transitions, respectively. Variable-temperature magnetic susceptibility data for these complexes indicate a temperature-independent paramagnetism (TIP) below approximately 50 K that results from admixing of low-lying crystal-field excited states derived from the symmetry-split 3H4 5f2 manifold into the ground state. The magnitude of the TIP is smaller for the complexes possessing two o-fluorine atoms (7, 9, and 11), indicating that the energy separation between ground and TIP-admixed excited states is larger as a consequence of the greater basicity of these ligands.

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Section: Uranium(iv) Fluoroketimidesmentioning

confidence: 99%

Systematic Studies of Early Actinide Complexes: Uranium(IV) Fluoroketimides

et al. 2007

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“…The number of articles reporting on the investigation of complexes by ultraviolet spectrophotometry is increasing, but the complexes investigated are becoming more exotic and of less potential use in analysis. Studies on metal complexes of possible interest include fluoro complexes of vanadium(V) (193) and molybdenum(VI) (209), tellurium(IV) with hydrochloric acid (344), iron(III) with sodium triphosphate (13), iron(III) chloro complexes in dimethylformamidestyrene (83), complex formation by iron(III) chloride and ammonia in an alcohol-dioxane mixture (317), peroxide complexes of niobium (V) and tantalum (V) in sulfuric acid (65), complexes of uranium (IV) and plutonium (IV) with chloride and oxygen containing ligands (316), nickel ß-ketoenolates (117), complexes of copper(II) with carboxylic acids (320), complexes of copper(II) and the uranyl ion with thioglycolic acid and pyruvic acid (319), V-salicylideneglycinato complexes with manganese(II), nickel(II), copper(II), and zinc (246), ethyl xanthate complexes with cadmium, zinc, nickel(II), and cobalt(II) (284), a complex of maltol with the uranyl ion (66), the silver(I) perchlorate-pyridine complex (25), mercury(II)cyanide-iodide complexes (70), mixed chlorothiocyanato complexes of palladium(II) (37), the copper(II)-5-chloro-8-hydroxyquinoline-7-sulfonate complex (21), selenocyanato complexes of thorium in acetone and dimethylformamide (151), chromate in sulfuric acid (257), platinum(IV)-dinitroethylenediamine complexes (64), gallium(III) ethylenediaminetetraacetic acid (63), diethylenetriaminepentaacetic acid with gadolinium(III) and lutetium(III) (234), and triethylenetetraminehexaacetic acid with cerium(III) and (IV) (164).…”

Section: Complexesmentioning

confidence: 99%

Ultraviolet spectrometry

Crummett¹,

Hummel²

1970

Anal. Chem.

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mentioning

confidence: 99%

“…The spectrum of uranium (III) chloride has been measured in the molten eutectic mixture of MgC12-KC1-NaC1 [58-18-20 weight percent (w/o)] ( 14) in several mixtures of A1C13 and KC1 (or NaC1) of varying K(Na)C1/A1C13 ratios (15), and in the LiC1-KC1 eutectic (16). The effect of the activity of the chloride ions on the formation of complexes in ionic melts has been reported (14)(15)(16)). An examination of the compiled data suggests that the complex compounds, MUC14(UC14 in NaC1-KC1, at 700~ M2UCI~ (UC152-'in LiC1-KC1, 450~176 and M3UCl~ (UCI~ 3 in NaC1, 700 ~ 845~ may have a considerable stability in the alkali halide-rich region of the respective molten mixtures.…”

mentioning

confidence: 99%

Voltammetry of Uranium and Plutonium in Molten LiCl ‐ NaCl ‐ CaCl2 ‐ BaCl2 : I . Reduction of U(III) to Uranium Metal1

Poa

Tomczuk

Steunenberg

1988

J. Electrochem. Soc.

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The electrochemical reduction of U(III) to uranium metal in molten normalLiCl‐normalNaCl‐CaCl2‐BaCl2 electrolyte was investigated, using cyclic voltammetry. The reaction is reversible and controlled by diffusion mass transfer, both at low‐carbon steel and molybdenum electrodes. The rate increased with UCl3 concentration up to about 3.4 mole percent and with temperature over the range of 435°–528°C. Standard potentials ranged from −1.07 to −1.50V vs. normalAg/normalAgCl ; the U(III) diffusion coefficients were between 0.5 normaland 5.0×10−6 cm2/normals .

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Some remarks about 5f → 6d and charge transfer transitions in uranium(IV) and plutonium(IV) complexes

Cited by 6 publications

References 7 publications

Systematic Studies of Early Actinide Complexes: Uranium(IV) Fluoroketimides

Systematic Studies of Early Actinide Complexes: Uranium(IV) Fluoroketimides

Ultraviolet spectrometry

Voltammetry of Uranium and Plutonium in Molten LiCl ‐ NaCl ‐ CaCl2 ‐ BaCl2 : I . Reduction of U(III) to Uranium Metal1

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