Uranium cyclopentadienyls derivatives

It was soon noted that iron was by no means unique in forming tt-cyclopentadienyl derivatives, and research groups in several countries set out to determine the nature and scope of cyclopentadienyl-metal chemistry. At the present time, practically all the metals of the short transition series, as well as nearly all the metals and metalloids of the main group series, form one or more cyclopentadienyl compounds. In addition, cyclo-pentadienyl derivatives of over one-half the lanthanides have now been described, and even cyclopentadienyl derivatives of U, Th, and several mns-uranium elements are known. The present status of cyclopentadienyl-metal chemistry is illustrated in part in Figure 1. Elements designated by shaded areas are known to form one or more cyclopentadienyl derivatives. 

In view of these general considerations, the observation of only one band for the ionization of the f2 configuration in the uranium(IV) cyclopentadienyl derivatives is reasonable the band is assigned to the 2F5),2 ion state with any ligand field splitting unresolved. 

Figure 5.8 Tra-cyclopentadienyl uranium derivative chemistry. (From Ref. 263, with permission.)...

The complexes [ N[CH2CH2NSiMc3]3 AnCl]2 (An = Th, U) were first reported the molecular structure of the uranium complex demonstrated it was dimeric in the solid state. The chloride ligand may be substituted, and derivatives incorporating cyclopentadienyl, borohydride, alkoxide, amide, and diazabutadiene derivatives have been characterized. Attempts to alkylate the... 

The reactivity of U-H and U-C bonds in electron-poor tris(cyclopentadienyl)uranium complexes has been investigated. The compounds (C5H4PPh2-BH3)3UX (X = C1, Me) have been synthesized.81 The series of new tris(cylopentadienyl)uranium complexes also includes the borohydride derivatives Cp 3U(BH4) (Cp = Gp, C5H4PPh2, C5Me4PPh2-BH3, G5H4PPh2 BH3, C5Me4H, C5Me4PPh2).57 81... 

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] ... 

The compounds (r/-CsHs)3UCl and (r/-CsHs)3ThCl are useful precursors for the synthesis of a large number of organoactinides, such as tris(cyclopentadienyl)metal alkoxides, tetrahydroborates, alkyls and aryls, halides, amides, and other derivatives,The chlorouranium compound was first synthesized by Reynolds and Wilkinson in 1956 from uranium tetrachloride and sodium cyclopentadienide in tetrahydrofuran. Vacuum sublimation, in our hands, invariably gives the pure product in low yield. The thorium analog was originally prepared in a similar manner,... 

I.2.2. Actinides. The s5oithesis of trivalent uranium Cp3U can be carried out by different methods (Marks and Ernst 1982), for example by reduction of several derivatives or by photo-induced 3-hydride elimination of tris-cyclopentadienyl uranium(IV)isopropyl... 

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