Uranium aryloxides

Aryloxide ligands, thorium, 24 770 Aryloxides, uranium complexation with, 25 436-437... 

Oxygen-Gontaining Organics. Neutral and anionic oxygen-containing organic molecules form a wide variety of complexes with uranium. Much work has focused on alkoxides (222), aryloxides and carboxylates complexes with alcohols, ethers, esters, ketones, aldehydes, ketoenolates, and carbamates are also well known. 

Tripodal Carbene and Aryloxide Ligands for Small-Molecule Activation at Electron-Rich Uranium and Transition Metal Centers Karsten Meyer and Suzanne C. Bart... 

TRIPODAL CARBENE AND ARYLOXIDE LIGANDS FOR SMALL-MOLECULE ACTIVATION AT ELECTRON-RICH URANIUM AND TRANSITION METAL CENTERS... 

Fig. 5. Tris-aryloxide triazacyclononane ligand for uranium coordination chemistry.

As with the starting complex, 4 -U, the uranium ion is displaced below the plane formed by the aryloxide ligands by 0.66 A for... 

The uranium(III) complexes Cp2UI2(THF)3 and Cp UI2(py)3 have been structurally characterized [393b]. The similar tribromide complex Cp ThBr3(THF)3 [111] provides a convenient entry into the chemistry of mono(pentamethylcyclopentadienyl) derivatives of thorium. Aryloxide and alkyl derivatives may be readily prepared by treatment of Cp RhBr3(THF)3 with potassium aryloxide or alkyl Grignard reagents, respectively [373], for example (5.58)-(5.60) ... 

Both U(III) and U(IV) bis-Cp complexes have been isolated, with the former exhibiting slightly lower stabilities. Dimeric uranium(III) bis-ring complexes [CpJ2UX]2 (X = Cl [109144-35-6], Br [109192-52-1], I [109168-46-9], aryloxide) are readily cleaved in THF solution to give Cp 2UX(THF),... 

Since four of the same aryloxide ligands can bind to uranium in the uranium(iv) compound, a three coordinate U[0(2,6-Bu2C6H3)]3 is presumably coordinatively unsaturated, and so forms a uranium-ring bond coordinative saturation can also be achieved by forming an adduct with a Lewis base. 

Lewis base adducts of thorium(IV) and uranium(IV) aryloxides are readily prepared. Initial reports of phenoxide compounds of uranium(IV) describe NH3 derivatives from the reaction of UCI4 or UOCI2 with appropriate phenols in the presence of ammonia " (see Equations (15) to (17)) ... 

Actinide(IV) alkoxide complexes have been reported which are coordinated by a variety of other bulky ligand sets. Uranium(IV) amido compounds are reagents for the preparation of homoleptic uranium(IV) alkoxides as well as mixed alkoxide/amido species. A variety of mixed aryloxide-diethylamide derivatives have been pr ared including (U(NEt2)(0-2,6-Bu 2C6H3)3 and U(NEtp(0-2,6-R7CftH3)3. R = Pr . Bu ). The previously described metallacycle... 

The first example of a neutral homoleptic uranium (III) alkyl complex was prepared by reaction of bis(trimethylsilyl)methyllithium with a monomeric uranium aryloxide, U(0-2,6-f-Bu2C6H3)3, in hydrocarbon solution (equation 54). Attempts to prepare... 

None of the base-free uranium COT+/Cp compounds 4, 5 or 6 gave any changes in the H NMR or UV/vis. spectra when reacted with 1-2 bar N2, compared with those obtained under argon. The tris-aryloxide-tacn (tacn = triazacyclononane) U(III) systems described by Meyer et al., although highly reactive to many types of small molecule, similarly do not show any reactivity with N2, even with 80 psi overpressure [56]. 

The tris-aryloxide-tacn complex ( "ArO)3tacn U has been shown to react imder room temperature and pressure with CO to produce [ ( ArOjs tacn U]2(At -CO), bridged by a mono-anionic (CO)" imit - an unusual dimerisation in that only one of the two uranium centres has been oxidised [68]. The bridging unit resulting from one-electron reduction of CO gave the first evidence that U(lll) was capable of reducing carbon monoxide. 

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