Tris complexes uranium

Triscarbonato uranium(VI) solids, 25 432 Tris-Cp uranium complexes, 25 440 2,4,6-Tris(dimethylaminomethyl)phenol (TDMAMP), 10 412... 

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 tris(cyclopentadienyl)uranium(m) complexes Cp"3U and (GsMe4H)3U were prepared by synthetic routes that involve the reduction of the appropriate tetravalent uranium metallocene precursors with potassium metal and NaCioHg, respectively (Scheme 14). The molecular structure of (CsMe4H)3U shows a perfectly trigonal structure with a threefold axis (all Cp (centroid)-U-Cp (centroid) angles equal to 120°).46... 

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... 

Apart from the cyclopentadienyl Hgand, complexes with other hgands have also been reported. The tris(indenyl)uranium and tris(indenyl)thorium... 

TABLE 21. Different examples of so far investigated [101,102,111] bis- and tris-cyclopentadienyl uranium(IV) complexes (C5H R )UL( w) involving atoms... 

Ring-substituted tris(cyclopentadienyl)uranium(iv) complexes can be straightforwardly prepared from ring-substituted cyclopentadienylating reagents. Some examples are illustrated below [71, 72] ... 

Ion Excha.nge, The recovery of uranium from leach solutions using ion exchange is a very important process (42). The uranium(VI) is selectively adsorbed to an anion-exchange resin as either the anionic sulfato or carbonato complexes. In carbonate solutions, the uranyl species is thought to be the tris carbonato complex, U02(C03) 3 [24646-13-7] and from sulfate solutions the anion is likely to be U02(S0 , where nis ) [56959-61-6] or 2 [27190-85-8], The uranium is eluted from the resin with a salt or acid solution of 1 AfMCl or MNO (M = H", Na", The sulfate solution is... 

Tri-n-butyl phosphate, ( -C4H9)3P04. This solvent is useful for the extraction of metal thiocyanate complexes, of nitrates from nitric acid solution (e.g. cerium, thallium, and uranium), of chloride complexes, and of acetic acid from aqueous solution. In the analysis of steel, iron(III) may be removed as the soluble iron(III) thiocyanate . The solvent is non-volatile, non-flammable, and rapid in its action. 

Uranium. tetrathiocyanatotetrakis[tris-(dimethylamino)phosphine oxide]-structure, 1.87 Uranium carbide nuclear fuels dissolution, 6, 928 Uranium complexes, 3,1131-1215 carbamic acid... 

Reactions of UCI4 with [Li RC(NCy)2 (THF)]2 (R = Me, Bu ) in THF gave the tris(amidinate) compounds [RC(NCy)2]3UCl that could be reduced with lithium powder in THF to the dark-green homoleptic uranium(lll) complexes [RC(NCy)2]3U. Comparison of the crystal structure of [MeC(NCy)2]3U with those of the lanthanide analog showed that the average U-N distance is shorter than expected from a purely ionic bonding model. ... 

Fernandez-Gonzales et al. [16] described a method for determination of OTC in medicated premixes and feeds by second-derivative synchronous spectrofluorome-try. The assay based on the reaction of oxytetracycline with divalent metal ion (Ca2+) at pH 6-10 to form a yellow complex that can be analyzed by synchronous spectrofluorometry (AX = 115 nm). Rao et al. [17] described a spectrophotometric method for the determination of OTC in pharmaceutical formulations based on the color reaction with uranium, which was detected at 413 nm. 

The first successful isolation of a mononuclear uranium-tacn complex was achieved by treatment of the free l, 7-tris(3,5-di-fert-butyl-2-hydroxybenzyl)-1,4,7-triazacyclononane (( ArOH)3tacn) (4 - ) (25) with one equivalent of [U(N(SiMe3)2)3] (35) in cold pentane... 

The tris cyclopentadienide complex of uranium was first prepared by the direct reaction of uranium trichloride with a benzene suspension of potassium cyclopentadienide. More recently it has been prepared by the reduction of tetra-... 

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 pyrrolyl ligand is interesting in that it can function as both a u-bonded amido group or a yr-bonded multihapto ligand. The pyrrolyl group appears to be a weaker electron donor than the cyclopentadienide anion 90). In the tetrakis-(2,5-dimethylp3u rolyl)uranium(IV) complex a preliminary structure has been revised with a tris(monohapto) (pentahapto) structure now assigned from variable temperature PMR spectra 90). 

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 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... 

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