Compounds of Thorium and Uranium in Low (&lt;IV) Oxidation States

Santos, Isabel; Matos, António Pires de; Maddock, A. G.

doi:10.1016/s0898-8838(08)60015-x

Cited by 14 publications

(11 citation statements)

References 269 publications

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“…For fundamental reasons as well as industrial and environmental challenges, it is crucial to better understand the properties of the 5f elements (some of which are too radioactive or unstable to be easily handled). Thus, comparison of the chemical behavior of similar complexes of the actinides and/or the lanthanides gives information on the influence of the f orbitals in the metal–ligand bonding and on the effects of the 5f/4f contraction on the chemical reactivity of these ions, as they become progressively harder and more ionic along the series. , For such studies, organometallic species of the actinides are particularly attractive because of the large variety of available ligands, which enables solubility in organic solvents and facile 1 H NMR detection.…”

Section: Introductionmentioning

confidence: 99%

Structural Diversity in Cyanido Thorocene Complexes

et al. 2014

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International audience(Cot)2Th (1) was found to react with Na*CN (Cot = η8-C8H8; Na* = Na(18-crown-6)) or the ammonium salts NR4CN (R = Et, nBu) in pyridine to give a variety of anionic products, depending on the (Cot)2Th:MCN ratio and the nature of M+ (Na*+ or NR4+). When it was treated with 1 mol equiv of NR4CN (R = Et, nBu) or Na*CN, (Cot)2Th (1) was transformed into the anionic monocyanide derivative [Th(Cot)2(CN)]− (2−) with a bent geometry and crystallized either as a binuclear complex with a Th−CN−Na ligation mode in [(Cot)2Th(μ-CN)][Na*] (2[Na*]) or as a 1D coordination polymer in [(Cot)2Th(μ-CN)][NEt4]∞ (2[NEt4]) due to the presence of Th−CN−Th bridges. The structure of 2[NEt4] is remarkable because it is different from that of [(Cot)2U(CN)][NEt4], where the cyanide is terminal, and because it evidences two available coordination sites on the bent-thorocene fragment, suggesting that the anionic species [(Cot)2Th(μ-CN)Th(Cot)2]− (4) and [(Cot)2Th(CN)2]2− (5) could be obtained. In the presence of 0.5 mol equiv of NnBu4CN in pyridine, 1 was indeed transformed into the binuclear complex [(Cot)2Th2(CN)][NnBu4] (4[NnBu4]), which was characterized by X-ray diffraction, as well as its analogue [(Cot)2Th2(μ-CN)][Na*(py)2]·2py (4[Na*(py)2]·2py) obtained under similar conditions. Crystallization of [(Cot)2Th(CN)][NnBu4] (2[NnBu4]) did not afford a polymeric compound analogous to 2[NEt4] but gave crystals of 4[NnBu4] and of the trinuclear compound [(Cot)2Th(μ-CN)2Th(Cot)2][NnBu4]2·py (3[NnBu4]2·py). Thorocene 1 rapidly reacted with 2 mol equiv of NnBu4CN to give the dianionic complex [(Cot)2Th(CN)2][NnBu4]2 (5[NnBu4]2). However, with an excess of NEt4CN, only the monocyanide compound 2[NEt4] could be obtained from 1, likely as the result of distinct solubilities. The reactions reported here illustrate the chemical potential of thorocene which, in contrast to (Cot)2U, can easily trap strongly coordinating anions and evidence that [Th(CN)]q− species such as 2− may be useful building blocks for the formation of polymetallic derivatives and clusters. Crystal structures show that compounds 2−5 exhibit an unusual bent-thorocene moiety, a long-sought and rare geometry for bis(cyclooctatetraenyl) complexes

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Section: Introductionmentioning

confidence: 99%

Structural Diversity in Cyanido Thorocene Complexes

et al. 2014

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“…The metallocene chemistry of trivalent uranium is based largely upon tris(cyclopentadienyl) complexes of the type Cp‘ 3 U or Cp‘ 3 U(L), where Cp‘ is C 5 H 5 or a substituted cyclopentadienyl ligand and L is a Lewis base. , Complexes with only two cyclopentadienyl rings on the uranium, Cp‘ 2 UX, cannot be isolated in pure form unless the cyclopentadienyl group contains sterically demanding substituents. The bulky rings prevent ligand redistribution by stabilizing Cp‘ 2 UX relative to Cp‘ 3 U.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, their high solubility in hydrocarbon solvents offers the opportunity for studying ligand exchange reactions and fluxional processes, provided that ring redistribution reactions are slow. In this paper we describe our synthetic and 1 H NMR solution studies on the dimers (1,3-R 2 C 5 H 3 ) 4 U 2 -(µ-X) 2 , where X is a halide and R is SiMe 3 (Cp′′) or CMe 3 (Cp q ).…”

Section: Introductionmentioning

confidence: 99%

Solution Structure and Behavior of Dimeric Uranium(III) Metallocene Halides

et al. 1999

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The variable-temperature 1H NMR behavior of the uranium(III) dimers [Cp‘ ‘2UX]2 and [Cp⧧ 2UX]2, where X is F, Cl, Br, or I, Cp‘ ‘ is 1,3-(Me3Si)2C5H3, and Cp⧧ is 1,3-(Me3C)2C5H3, has been examined. At low temperature, the number of inequivalent CMe3 or SiMe3 groups implies that the solution structure is the same as the solid-state structure in all of these complexes. The barriers to ring rotation in the Cp‘ ‘ series are strongly dependent upon the U−X distance, but all of the barriers to ring rotation in the Cp⧧ series are the same. The trends in ring rotation barriers are explained by the different conformations of the Cp ligands in the dimers. In addition to the homo-halide dimers, the variable-temperature NMR behavior of the hetero-halide dimers Cp‘4U2(μ-X)(μ-Y), where Cp‘ is Cp‘ ‘ or Cp⧧ and X and Y are halides where X ≠ Y, was examined. Above room temperature, the halide atoms exchange sites rapidly on the NMR time scale.

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“…5 While an increasing number of lanthanide complexes of aromatic amines have been reported in the last few years, very little is known about the coordination chemistry of actinides() with these ligands. 2 The preparation of U() complexes of 1,10-phenanthroline and 2,2Ј-bipyridine was reported several years ago by Hart and Tajik, who were unable to characterize the complexes due to their extreme reactivity with traces of oxygen or moisture. 6 In order to gain more insight into the chemistry of f elements with nitrogen donor ligands, we have started to study the coordination chemistry of Ln() and An() with the tripodal aromatic amines.…”

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confidence: 99%