Anhydrous Photochemical Uranyl(VI) Reduction:  Unprecedented Retention of Equatorial Coordination Accompanying Reversible Axial Oxo/Alkoxide Exchange

Kannan, S.; Vaughn, Anthony E.; Weis, Eric; Barnes, Charles L.; Duval, Paul

doi:10.1021/ja065822w

Cited by 44 publications

(33 citation statements)

References 25 publications

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“…Reaction of U III [N(SiMe 3 ) 2 ] 3 with methyl benzoate gave immediate formation of U IV (OMe)[N(SiMe 3 ) 2 ] 3 ( 3 ) accompanied by formation of benzaldehyde (Scheme ). Previously, the installation of methoxy ligands to uranium ions has been accomplished by salt metathesis with sodium methoxide, reaction of uranium(III) iodide with methanol, and irradiation of uranyl in the presence of methanol . Compound 3 was isolated from the crude reaction mixture as a light brown powder in 41 % yield.…”

Section: Resultsmentioning

confidence: 99%

Reduction of Carbonyl Groups by Uranium(III) and Formation of a Stable Amide Radical Anion

Mullane

Cheisson

Nakamaru‐Ogiso

et al. 2017

Chemistry A European J

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Methyl benzoate, N,N-dimethylbenzamide, and benzophenone were reduced by U [N(SiMe ) ] resulting in uranium(IV) products. Reduction of benzophenone lead to U [OC⋅Ph )][N(SiMe ) ] , (1.1) which forms the dinuclear complex, [N(SiMe ) ] U (OCPhPh-CPh O)U [N(SiMe ) ] (1.2), through coupling of the ketyl radical species upon crystallization. Reaction of N,N-dimethylbenzamide with U [N(SiMe ) ] resulted in U [OC⋅(Ph)(NMe )][N(SiMe ) ] (2), a uranium(IV) compound and the first example of a charge-separated amide radical. In the case of methyl benzoate, the reduction resulted in U (OMe)[N(SiMe ) ] (3) and benzaldehyde as the reduced organic fragment. Compound 2 showed the ability to act as a uranium(III) synthon in its reactivity with trimethylsilyl azide, a reaction that yielded U (=NSiMe )[N(SiMe ) ] . Additionally, 2 was reduced with potassium graphite resulting in [U(μ-O)[O=C(NMe )(Ph)][N(SiMe ) ] ] (4), a dinuclear uranium compound bridged by oxo ligands. Reduction of 2 in the presence of 15-crown-5 afforded isolation of the mono-oxo compound, [(15-crown-5) K][UO[N(SiMe ) ] ] (5). The results expand the reduction capabilities of U complexes and demonstrate a strategy for isolating novel metal-stabilized radicals.

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Section: Resultsmentioning

confidence: 99%

Reduction of Carbonyl Groups by Uranium(III) and Formation of a Stable Amide Radical Anion

Mullane

Cheisson

Nakamaru‐Ogiso

et al. 2017

Chemistry A European J

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“…Studies of photochemical and electrolytic reduction of uranyl(VI) to uranyl(V) have been reported previously [20][21][22][23]29,16]. In this work, we have investigated thermal chemical reduction of uranyl(VI) (diamagnetic) to uranyl(V) (paramagnetic) with bromide, iodide, DMSO, and phenol by EPR spectroscopy.…”

Section: +mentioning

confidence: 95%

Investigation of charge-transfer absorptions in the uranyl UO22+(VI) ion and related chemical reduction of UO22+(VI) to UO2+(V) by UV–Vis and electron paramagnetic resonance spectroscopies

Sun

Kolling

Mazagri

et al. 2015

Inorganica Chimica Acta

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a b s t r a c tThe uranyl UO 2 2+ (VI) cation (hydrated) exhibited strong charge-transfer absorptions at 350-400 nm in aqueous solutions containing bromide and iodide. The charge-transfer absorptions originate from a single-electron transfer from a halide anion to the uranium(VI) valence shell. Their intensities (represented by absorbance at 375 nm) were found to be directly proportional to molar concentrations of the halide (bromide or iodide) and UO 2 2+ in solution, respectively, showing the nature of a bimolecular interaction in the charge-transfer absorption transition. The absorptions were also greatly enhanced by sulfuric acid, and their intensity (absorbance at 375 nm) increased linearly as a function of the acid molarity. An electron paramagnetic resonance (EPR) study has indicated that the charge-transfer also took place slowly in the dark, resulting in appreciable thermal chemical reduction of diamagnetic UO 2 2+ (VI) (hydrated) to paramagnetic UO 2 + (V) (hydrated) (g = 2.08) by bromide and iodide. In the presence of sulfuric acid, CH 3 SOCH 3 (DMSO) was shown by EPR to undergo a charge-transfer oxidation by UO 2 2+(VI) to a stable CH 3 SOCH 2 Å (DMSO Å ) radical (singlet, g = 2.01), and UO 2 2+ (VI) was reduced to UO 2 + (V). A possible mechanism for this oxidation-reduction has been proposed. The charge-transfer absorption transition (350-400 nm) between UO 2 2+ (VI) and phenol (PhOH) in acetone was observed and characterized. A chemical oxidation-reduction of UO 2 2+ (VI) [in the form of U VI O 2 (acetone) 5 2+] and PhOH in acetone was found by EPR to give UO 2 + (V) [in the form of U V O 2 (acetone) 5 + ] and a stable phenoxyl (PhO Å ) radical (singlet, g = 2.00) via a simultaneous charge-transfer and deprotonation pathway.

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“…10−12 Uranyl reduction is generally thought to proceed through the pentavalent uranyl ion, [UO 2 ] + . 13 However, these complexes can be difficult to isolate due to the propensity for uranium (V) complexes to disproportionate to uranium(IV) and uranium-(VI) products. 14 While pentavalent uranyl complexes have been successfully isolated, 15 they are relatively rare as compared to their higher valent counterparts.…”

Section: ■ Introductionmentioning

confidence: 99%

Synthesis, Characterization, and Stoichiometric U–O Bond Scission in Uranyl Species Supported by Pyridine(diimine) Ligand Radicals

et al. 2015

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Two uranium(VI) uranyl compounds, Cp*UO2((Mes)PDI(Me)) (3) and Cp*UO2((t)Bu-(Mes)PDI(Me)) (3-(t)Bu) (Cp* = 1,2,3,4,5-pentamethylcyclopentadienide; (Mes)PDI(Me) = 2,6-((Mes)N=CMe)2C5H3N; (t)Bu-(Mes)PDI(Me) = 2,6-((Mes)N=CMe)2-p-C(CH3)3C5H2N; Mes = 2,4,6-trimethylphenyl), have been synthesized by addition of N-methylmorpholine N-oxide to trianionic pyridine(diimine) uranium(IV) precursors, Cp*U((Mes)PDI(Me))(THF) (1), Cp*U((Mes)PDI(Me))(HMPA) (1-HMPA), and Cp*U((t)Bu-(Mes)PDI(Me))(THF) (1-(t)Bu). These uranyl complexes contain singly reduced pyridine(diimine) ligands suggesting formation occurs via cooperative ligand/metal oxidation. Treating 3 or 3-(t)Bu with stoichiometric equivalents of Me3SiI results in stepwise oxo silylation to form (Me3SiO)2UI2((Mes)PDI(Me)) (5) or (Me3SiO)UI2((t)Bu-(Mes)PDI(Me)) (5-(t)Bu), respectively. Additional equivalents result in full uranium-oxo bond scission and formation of UI4(1,4-dioxane)2 with extrusion of hexamethyldisiloxane. The uranium complexes have been characterized via multinuclear NMR, vibrational, and electronic absorption spectroscopies and, in some cases, X-ray crystallography.

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Anhydrous Photochemical Uranyl(VI) Reduction: Unprecedented Retention of Equatorial Coordination Accompanying Reversible Axial Oxo/Alkoxide Exchange

Cited by 44 publications

References 25 publications

Reduction of Carbonyl Groups by Uranium(III) and Formation of a Stable Amide Radical Anion

Reduction of Carbonyl Groups by Uranium(III) and Formation of a Stable Amide Radical Anion

Investigation of charge-transfer absorptions in the uranyl UO22+(VI) ion and related chemical reduction of UO22+(VI) to UO2+(V) by UV–Vis and electron paramagnetic resonance spectroscopies

Synthesis, Characterization, and Stoichiometric U–O Bond Scission in Uranyl Species Supported by Pyridine(diimine) Ligand Radicals

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