- ZUR KENNTNIS DES DIAQUA-TRIS(η5-CYCLOPENTADIENYL)URAN(IV)KATIONS: ISOLIERUNG UND EIGENSCHAFTEN DES SALZES NO3
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In contrast to the re-examined system which appears to contain weakly hydrogen-bonded H2O rather than a genuine + cation, the salt-like precipitate NO3 is shown to be the first well-defined +-derivative of adequate stability, the anion of which is not coordinated to the central metal.Ample evidence for the existense of similar, but mostly metastable precipitation products X and , respectively, (X = e.g.Cl, Br, I, ClO4, HCO2 including the replacement of H2O by NH3) is presented.Some interesting, common features of organo-uranium- and -tin-systems, R3MIVX, are elucidated.
- Fischer, R.D.,Klaehne, E.,Sienel, G.R.
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- Oxidative addition of organic halides to (ν-C5H5)3U(THF) (THF = tetrahydrofuran). A convenient new synthesis of triscyclopentadienyl uranium(IV) hydrocarbyl complexes
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Cp3U(THF) (Cp = η-C5H5; THF = tetrahydrofuran) react with organic halides RX to give the equimolecular mixture of the Cp3UX and Cp3UR compounds.The features of the reaction are characteristic of an atom abstraction oxidative addition mechanism.Treatment o
- Villiers, Claude,Ephritikhine, Michel
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- Molecular structure and charge distribution in organometallics of the 4f and 5f elements. I. Dipole moment and charge distribution of the actinoid(IV) tetracyclopentadienides, An(C5H5)4
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The dipole moments of the tetracyclopentadienides, An(C5H5)4, of the lighter actinoids thorium, uranium and neptunium were measured in benzene solution. Although the compounds in the solid state have a quasi-Td molecular symmetry their dipole moments are not zero, owing to lowering of the molecular symmetry. The origin of the nonzero dipole moments is discussed.
- Kanellakopulos,Maier,Heuser
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- Reactions of uranium cyclopentadienyl compounds with some alkyl and arylchlorides
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Uranium cyclopentadienyl compounds Cp4U, Cp3U-n-Bu, and Cp3U-i-Bu (Cp = η5-C5H5, Bu = C4H9) react with alkyl and aryl chlorides n-BuCl, t-BuCl, and BzCl (Bz = CH2C6H5) at an appreciable rate in the temperature range 25-80°C depending on the structure of the reactants. When thehalide is taken in a six- to tenfold excess, the reaction time decrease s by an order of magnitude. The major products of reactions of Cp4U withn-BuCl and t-BuCl are, respectively, Cp3U-n-Bu and Cp3UCH2C(CH3)2Cl, an d with BzCl, Cp3UBz (at a threefold excess of BzCl, CpUBz3). With a 30-fold excess of t-BuCl and BzCl, Cp4U gives, respectively, CpU[CH2C(CH3)2Cl]3 and CpUBz3. These compounds are characterized by a high extent of coordination unsaturation of the uranium atom and probably catalyze the concomitant polycondensation of the alkyl and aryl chlorides taken into the reaction. Reactions of Cp3U-n-Bu and Cp3U-i-Bu with BzCl gave Cp3UCl and the corresponding amylbenzenes.
- Leonov, M. R.,Gramoteeva, N. I.,Il'yushenkov, V. A.,Pogodina, L. A.
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p. 228 - 230
(2008/10/08)
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- Bi- and triheteronuclear complexes of uranium and group VI transition metals
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The new heterobimetallic compounds Cp3U[OCM(CO)2Cp′] containing uranium and group VI transition metals are synthesized from Cp3UCl and Na[M(CO)3Cp′] or from Cp3UCH3 and H[M(CO)3Cp′] (M = Mo, W; Cp = C5H5; Cp′ = C5H5 or C5Me5). In a same manner, the trimetallic Cp2U[OCMo(CO) 2Cp]2 is obtained starting from Cp2U(NEt2)2 and H[Mo(CO)3Cp]. All these complexes exhibit low CO stretching frequencies characteristic of isocarbonyl linkages between uranium and Mo or W atoms.
- Dormond, Alain,Moise, Claude
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p. 595 - 598
(2008/10/08)
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- Crystal and molecular structure of (η-C5H5)3U=CHP(CH3) 2(C6H5). A compound with a uranium-carbon multiple bond
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The structure of the complex (η5-C5H5)3U=CHP(CH 3)2(C6H5) has been determined by single-crystal X-ray methods. The compound crystallizes with four molecles in space group P21/c of the monoclinic system in a cell with dimensions of a = 10.835 (2) A?, b = 8.481 (2) A?, c = 25.57 (1) A?, β = 111.77 (3)°, V = 2182 A?3, and ρcalcd = 1-78 g/cm3. The structure has been refined by least-squares methods to a final R index on F of 0.071 for the 91 variables and 1985 data. The uranium is bound in a tetrahedral fashion to three cyclopentadienyl ligands and a CHP(CH3)2(C6H5) ligand. The bond to the carbon atom of the phosphoylide ligand, 2.29 (3) A?, is the shortest U-C bond yet observed, and this is interpreted as indicating mutliple bonding in the U-C bond.
- Cramer, Roger E.,Maynard, Richard B.,Paw, Josephine C.,Gilje, John W.
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p. 1336 - 1340
(2008/10/08)
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- COMPLEXES BISCYCLOPENTADIENYLES DISSYMETRIQUES ET TRISCYCLOPENTADIENYLES MIXTES DE L'URANIUM(IV). U COMME CENTRE DE PSEUDOASYMETRIE
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Starting from the monocyclopentadienyls U(C5Me4R)X3 (X = Cl or NEt2, R = CH3 or C2H5), the bis-cyclopentadienyl dissymetric complexes U(C5Me4R)CpX2 (Cp = substituted or unsubstituted cyclopentadienyl ligand) and the tris-cyclopentadienyl complexes U(C5Me4R)Cp2Cl are obtained.If the two Cp ligands have a chiral center, a mixture of one racemic and two meso isomers is obtained.In the meso isomers, the uranium atom is a pseudoasymmetric center.
- Dormond, A.
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- COMPLEXES CYCLOPENTADIENYLES DE L'URANIUM(IV). II. COMPLEXES TRICYCLOPENTADIENYLES D'URANIUM(IV) A CHIRALITE CENTRO-METALLEE. DIASTEREOTOPIE ET DIASTEREOISOMERIE
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The synthesis of η5-Cp'3UCl, η5-Cp-η5-Cp'2UCl, η5-Cp2-η5-Cp'UCl (Cp = C5H5; Cp' = substituted cyclopentadienyl) complexes and of similar complexes bridged between the two cyclopentadienyl ligands is described.Several complexes of this type have a prochiral uranium atom.The bridged complexes obtained from the bidentate dianion 2- bear a chiral carbon and a chiral uranium atom in the same structure.The two diastereoisomeric forms have not been separated but are easily identified by NMR analysis.
- Dormond, A.,Duval-Huet, C.,Tirouflet, J.
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p. 341 - 354
(2007/10/02)
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