Uranium complexes cyclopentadienyls

Substituent effects, 9 510 Substituted alkylhydrazines, 13 572-573 Substituted amide waxes, 26 221 Substituted cyclopentadienyl uranium complexes, 25 440-441 Substituted cyclopentadienyl (Cp)... 

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]... 

An unusual electron-poor cyclopentadienyl complex (C5H4PPh2, BH3)2U(BH4)2 was reported [424]. It was shown that 31P NMR spectra of borane adducts of diphenylphosphidocyclopentadienyl-uranium complexes and corresponding molybdenum heterobimetallics are very similar. This strongly suggests that such boranes... 

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... 

Scheme 20 Synthesis of 0-bridged chelating bis(cyclopentadienyl) uranium complex [260]...

Abstract The coordination chemistry of uranium has become an increasingly popular topic in the last 15 years. Much of the reason for this interest has come from the development of easy to synthesize, stable starting materials. These materials allowed an entry point for the exploration of uranium with any ligand imaginable. This chapter covers the most significant developments in the coordination chemistry of non-cyclopentadienyl uranium complexes and their reactivity with small molecules. 

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. ... 

Cyclopentadienyl uranium complexes react with TiW-0,q anions to... 

Allyl Complexes. Allyl complexes of uranium are known and are usually stabilized by cyclopentadienyl ligands. AEyl complexes can be accessed via the interaction of a uranium halide and an allyl grignard reagent. This synthetic method was utilized to obtain a rare example of a "naked" homoleptic allyl complex, U(T -C2H )4 [12701 -96-17, which decomposes at 0°C. Other examples, which are more stable than the homoleptic allyl complex have been synthesized, ie, U(allyl)2(OR)2 (R = alkyl), U(allyl)2X (X = halide), and U(allyl)(bipy)2. 

The question of the mode of bonding of the cyclopentadienyl rings in complexes of the type U(C5Hs)sX was settled by the structural determination of tris(ben-zylcyclopentadienide)uranium(IV) chloride (69). The structure as viewed down... 

The ground state geometries in these complexes are often determined by a subtle balance of the energy released by an increase in coordination number and the energy lost by intramolecular repulsion. The question of versus bonding in the tris(cyclopentadienyl)uranium aUyls is one molecular example. The structures of the lanthanide tiicyclopentadienides represent another example in extended crystalline arrays. 

The polymerization of ethylene was also qualitahvely inveshgated by pulse injec-hons of ethylene into helium flowing over thorium (67) and uranium (86) metallocene hydrocarbyl complexes supported on 7-AI2O3.950 at 25 °C, both revealing similar achvihes [171, 173]. Supported thorium half-sandwich complexes 65 exhibited higher achvity than surface species, resulhng from coordinatively more saturated tris(cyclopentadienyl) and metallocene U/Th-alkyl/hydride complexes, that is, 77, 79, 82, 90 and 91 [171]. C CP MAS NMR spectra revealed no clear evidence of ethylene insertion into [Th-CHs] or [AL5-CH3] moiehes of material... 

Bis(2,4-pentanedionato)chromium, 3320 Bis(benzene)chromium dichromate, 3845 Bis(benzeneiron)—fulvalenediyl complex, 3828 Bis(cycloctatetraene)uranium(0), 3701 Bis(cyclopentadienyl)bis(pentafluorophenyl)zirconium, 3824 Bis(cyclopentadienyldinitrosylchromium), 3269 Bis(cyclopentadienyl)hexafluoro-2-butynechromium, 3629 Bis(cyclopentadienyl)lead, 3288 Bis(cyclopentadienyl)magnesium, 3271 Bis(cyclopentadienyl)manganese, 3272 Bis(cyclopentadienyl)niobium tetrahydroborate, 3318... 

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