Trivalent uranium anionic

A rather unique ligand system for the stabilization of the trivalent uranium center is the [Zr2(0-z-Pr)9](-> anion that reacts readily with Ul3(thf)4 to form the corresponding [Zr2(0-z -Pr)9]UI2(thf). The robustness of this... 

Crown ethers. Metal and crown ether complexes have to fulfill two requirements to form stable complexes. First, the coordination sphere of the metal must be stabilized by the crown ether and any complexing anions. A trivalent uranium coordination sphere is typically satisfied... 

Dissolution of the calcium fluoride in aluminum nitrate-nitric acid oxidizes the plutonium to the tetravalent hexanitrate complex (3), while the transplutonium nuclides remain in the trivalent state. The only actinides retained by a nitrate-form anion-exchange column are thorium, neptunium, and plutonium. The uranium distribution coeflBcient under these conditions is about ten, but uranium should not be present at this point since hexavalent uranium does not carry on calcium fluoride (4). 

Given the variety of important actinide oxidation states, what naturally occurring anion would best effect actinide mineralization The lanthanides, chemically analogous to the trivalent actinides, occur naturally in three commercially important forms monazite and xenotime, which are orthophosphate minerals, and bastnasite, which has the approximate composition LnFCOs. Uranium ores may be divided into... 

This is similar for mercury [15], caesium, technetium and uranium [16], as well as for molybdenum, which can be bound to iron oxides even in the form of the molybdate anion [17]. In some soils, hydrous oxides represent dominant substrates of copper [18] and cadmium [19]. The highly toxic, hexavalent chromium is by far more mobile than the trivalent, which makes its reduction in the environment especially important [20], although it also sorbs onto hydrous oxides [21]. 

Uranium, unlike thorium, has an accessible trivalent oxidation state. It has been shown that uranocene can be reduced by lithium naph-thalide to the bis([8]annulene)uranate(III) anion.23 The same complex can be synthesized by the reaction of two equivalents of [8]annulene dianion with one equivalent of uranium trichloride.23... 

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