Uranium cyclopentadienyls reactions

Uranium(IV) chalcogenolate compounds have been synthesizing with several stoichiometries as the homoleptic [U(SR)4] (R = Et, Pr, Ph) obtained by reaction of [U(BH4)4] or [U(NEt2)4] with thiols or by oxidation of uranium with the disulfide,571 or those bearing cyclopentadienyl rings as [UCp3(ER)]... 

A second example of a bis cyclopentadienyl uranium complex has resulted from the use of a bidentate, bridged bis(cyclopendadienyl) ligand to avoid further reaction to a tris species. It is prepared by the addition of the dianion of bis(cyclo-pentadienyl)methane to uranium tetrachloride in THE to give [CH2( — 5114)2]... 

The tris(cyclopentadienyl)thorium-, -uranium- and -plutonium chlorides are best prepared from TlCp in dimethoxyethane Np(Cp- )3Cl is formed in the Be(Cp)2 melt reaction . Analogous complexes containing bromide, iodide and/or indenyl ligands are prepared from K[Cp] or K[indenyl] and the appropriate MX4 compound (see Table 2). 

Tris(cyclopentadienyl)uranium is synthesized from UCI3 and K[Cp] in benzene solution , while the Pu and transplutonium analogs are obtained from the Be(Cp)2 melt reaction . A byproduct of the Bk reaction is the chloro-bridged dimer, [Bk(Cp- , )2Cl]2 . 

Scheme 1 Some reactions of tris (cyclopentadienyl) uranium (IV) chloride...

Uranium.— The thermolysis reactions of the alkyl complexes [UR( j-C6H6)3] are first order in uranium complex. Rate constants and free energies of activation are given in the Table. The order of stability of the alkyl compounds is primary > secondary > tertiary. In the thermolysis reaction intramolecular abstraction of hydrogen from a cyclopentadienyl occurs, giving RH with retention of configuration at carbon. ... 

Reaction of tris-cyclopentadienyluranium(iv) chloride with two moles of Li(CH2)2PPha at — 50 °C affords the first actinide phospho-ylide complex. The new compound forms red, air- and moisture-sensitive crystals whose structure (1) has been determined from an JT-ray study. Two bis(cyclopentadienyl)uranium groups are essentially bridged by the ylide ligand, which is unique in that it also... 

X-ray powder diffraction data reveal that CP3UCI and Cp3ThCl are isomor-phous. Tris(cyclopentadienyl)thorium derivatives of other halides, alkoxides, tetrahydroborates, etc., can be prepared in a manner analogous to the uranium reaction above [58]. Tris(cyclopentadienyl)neptunium chloride, Cp3NpCl, can be prepared either by a radiochemical synthesis [75] ... 

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