- Redox-switchable carboranes for uranium capture and release
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The uranyl ion (UO2 2+; U(vi) oxidation state) is the most common form of uranium found in terrestrial and aquatic environments and is a central component in nuclear fuel processing and waste remediation efforts. Uranyl capture from either seawater or nuclear waste has been well studied and typically relies on extremely strong chelating/binding affinities to UO2 2+ using chelating polymers1,2, porous inorganic3–5 or carbon-based6,7 materials, as well as homogeneous8 compounds. By contrast, the controlled release of uranyl after capture is less established and can be difficult, expensive or destructive to the initial material2,9. Here we show how harnessing the redox-switchable chelating and donating properties of an ortho-substituted closo-carborane (1,2-(Ph2PO)2-1,2-C2B10H10) cluster molecule can lead to the controlled chemical or electrochemical capture and release of UO2 2+ in monophasic (organic) or biphasic (organic/aqueous) model solvent systems. This is achieved by taking advantage of the increase in the ligand bite angle when the closo-carborane is reduced to the nido-carborane, resulting in C–C bond rupture and cage opening. The use of electrochemical methods for uranyl capture and release may complement existing sorbent and processing systems.
- Keener, Megan,Hunt, Camden,Carroll, Timothy G.,Kampel, Vladimir,Dobrovetsky, Roman,Hayton, Trevor W.,Ménard, Gabriel
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p. 652 - 655
(2020/01/29)
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- Cationic Ti(IV) and neutral Ti(III) titanocene-phosphinoaryloxide frustrated Lewis pairs: Hydrogen activation and catalytic amine-borane dehydrogenation
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Titanium-phosphorus frustrated Lewis pairs (FLPs) based on titanocene-phosphinoaryloxide complexes have been synthesised. The cationic titanium(iv) complex [Cp2TiOC6H4P( tBu)2][B(C6F5
- Chapman, Andy M.,Wass, Duncan F.
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p. 9067 - 9072
(2012/09/08)
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- Redox chemistry, acid reactivity, and hydrogenation reactions of two-electron mixed valence diiridium and dirhodium complexes
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The syntheses and reaction chemistry of two electron mixed-valence diphosphazane- bridged dirhodium and diiridium complexes M2 0,II(tfepma)2(CNtBu)2Cl2 [M = Rh (1), Ir (2); tfepma = MeN[P(OCH2CF3) 2]2, CNtBu = tert-butyl isocyanide] are described. 1 and 2 undergo addition and two-electron oxidation and reduction chemistries. In the presence of CNtBu, the addition product with the stoichiometry M20,II(tfepma)2- (CN tBu)3Cl2 [M = Rh (3), Ir (3)] is generated; in the presence of 1 equiv of CNtBu and 2 equiv of bis(pentamethyl- cyclopentadienyl)cobalt(II), 1 and 2 are reduced to furnish M2 0,0(tfepma)2(CNtBu)3 [M=Rh (5), Ir (6)], which feature both four- and five-coordinate M0 centers. Complexes 1, 2, 5, and 6 all possess coordinatively unsaturated square planarM0 centers that are reactive: (1) 2 reacts with PhICl 2 to produce Ir2II,II(tfepma) 2(CNtBu)2Cl4 (7); (2) protonation of 2 with HX yields Ir2II,II(tfepma) 2(CNtBu)2Cl2HX [X = Cl- (8), OTs- (9)]; (3) protonation of 5 with HOTs produces [Rh 2 I,I(tfepma)2(CNtBu) 3(μ- H)](OTs); and (4) the reversible hydrogenation of 2 proceeds smoothly, furnishing the cisdihydride complex Ir2II, II(tfepma)2(CNtBu)2(H) 2Cl2 (11). Substitution of tfepma in 2 with bis(diphenylphsophino)methane (dppm) yields the orthometalated complex Ir 2II,II(dppm)(PPh(o-C6H 4)CH2PPh2)(CNtBu)2Cl 2H (12). The X-ray crystal structures of 11 compounds are presented and discussed, and spectroscopic characterization by multinuclear and variable temperature NMR provides details about solution structures and in some cases the formation of isomeric products. The electronic spectra of the new complexes are also described briefly, with absorption and emission features derived from the bimetallic core.
- Teets, Thomas S.,Cook, Timothy R.,McCarthy, Brian D.,Nocera, Daniel G.
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p. 5223 - 5233
(2011/07/09)
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- Synthesis and Crystal Structure of a Self-Assembled, Octanuclear Oxo-Tantalum(V) Derivative Containing the First Example of a Transition Metal M8(μ-O)12 Cage
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By reduction with CoCp*2 in THF or toluene, the tantalum(V) chlorocarbamato complex TaCl2(O2CNEt2)3, 1, gives high yields of the tantalum(III) N,N-diethylcarbamate. Ta(O2CNEt2)3, 2. On the other hand, good yields of the octanuclear μ-oxo-N,N-diethylcarbamato cage compound Ta8(μ-O)12(O2CNEt2)16, 3, were secured by reaction of 1 with sodium in THF. Compound 3 has been characterized by analytical and spectroscopic methods and by X-ray diffractometry. Crystal data for C80H160N16O44Ta8: M = 3497.84, triclinic, space group = P1 (no. 2), 1a = 15.440(3) A, b = 15.710(1) A, c = 16.090(2) A, α = 101.53(4)°, β= 107.51(5)°, γ = 118.79(3)°, V = 2971.4(3) A3, Z = 1, Dc = 1.955 Mg/m3, μ = 7.416 mm-1, F(000) = 1688, R1 = 0.0350, wR2 = 0.0798, T = 213 K. The eight tantalum atoms are located at the vertexes of a cube whose edges are occupied by 12 bridging oxo groups. Hexacoordination at tantalum is completed by bridging and terminal N,N-diethylcarbamato ligands. Both THF and the carbon dioxide fragments of the carbamato groups are involved in the formation of the μ-oxo cage oxides.
- Arimondo, Paola B.,Calderazzo, Fausto,Hiemeyer, Ralph,Maichle-Moessmer, Caecilia,Marchetti, Fabio,Pampaloni, Guide,Straehle, Joachim
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p. 5507 - 5511
(2008/10/08)
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