Uranium complexes with mono

A rare ytterbium(III) complex [Yb(HB(pz)3)3] has an eight-coordinate bicapped trigonal prismatic structure (48) with two tridentate ligands and one bidentate ligand. The complex is stereochemi-cally rigid in solution. 1 A number of thorium and uranium complexes have been reported. These include [U(HB(pz)3)4], [U(H2B(pz)2)4], [U(HB(pz)3)2Cl2], and mono- and di-Cp metal-halogen complexes.49... 

The H NMR spectra of the U" species show substantial isotropic shifts, and variable temperature experiments indicate restricted rotation around the U-N bond. The bis(dialkylamides) undergo stepwise migratory CO insertion to yield mono- and bis-carbamoyl derivatives. A large number of organouranium imido complexes with different uranium oxidation states IV and VI have been synthesized (Arney et al. 1992, Arney and Burns 1993, 1995) by both metathesis and direct protonation routes (scheme 16). 

Direct comparisons of the stability constants for formation of the dmpp complexes of molybdenum(VI) with those for uranium(VI) are not possible. The mono-ligand complexes have different stoichiometries, MoOaldmpp) versus U02(dmpp), while although log P2 is available for Mo02(dmpp)2 (175) the value of 40.2 refers to formation from Mo04 rather than from MoOg laq), and U02(dmpp)2 is too sparingly soluble for its formation constant to be determined (231). 

Mono(organo)nickel compounds, via oxidative addition, 8, 44 Monoorganotin hydroxides, preparation, 3, 850 Monoorganotin oxides, preparation, 3, 850 Mono(pentamethylcyclopentadienyl) actinide(IV) compounds, reactions, 4, 207 Mono(pentamethylcyclopentadienyl) lanthanide(III) compounds, synthesis and characteristics, 4, 66 Mono(pentamethylcyclopentadienyl) uranium(IV) sulfido complex, synthesis, 4, 207-208 Mono(phenoxy-aldehyde) trichlorides, with Zr(IV),... 

The uranium(III) complexes Cp2UI2(THF)3 and Cp UI2(py)3 have been structurally characterized [393b]. The similar tribromide complex Cp ThBr3(THF)3 [111] provides a convenient entry into the chemistry of mono(pentamethylcyclopentadienyl) derivatives of thorium. Aryloxide and alkyl derivatives may be readily prepared by treatment of Cp RhBr3(THF)3 with potassium aryloxide or alkyl Grignard reagents, respectively [373], for example (5.58)-(5.60) ... 

The mechanism of U02 " extraction by monoalkyl phosphoric acid reagents appears to be a more complex process than for their dialkyl counterparts. This results from the polymerization of the monoalkyl phosphate in the organic phase and the hydration of the extracted uranyl species so that variable stoichiometries arise for the extractant/water/UO complex. The extraction of from sulfuric acid by mono-2,6,8-trimethylnonyl phosphoric acid (H2DDP) and mono-n-butyl phosphoric acid (H2MBP) as 0.05 M solutions in benzene was shown to follow equations (61) and (62) when an excess of extractant was present. When an excess of uranium was present, equations (63) and (64) applied where n, x, y and z were variable numbers which depended upon the extent of extractant polymerization and hydration of the extracted species. Synergistic effects may also be found with the monoalkyl phosphoric acid extractants and in one recent example the use of tri-n-octylphosphine ocxide (TOPO) as a synergist with H2MEHP allowed the extraction of U02 from phosphoric acid solutions. The uranium may be returned to the aqueous phase by contact with concentrated acid, which reverses the extraction process by protonation of the phosphate. 

The synthesis and characterization of a series of mono(pentamethylcyclopentadienyl)uranium(m) complexes has been explored. The uranium(m) triiodide precursor UI3(THF)4 reacts at ambient temperature with 1 equiv. of sodium or potassium pentamethylcyclopentadienide in THF to form the monocyclopentadienyl complex(m) Cp UI2(THF)3 (Scheme 32).84... 

Bertsch PM, Seaman JC (1999) Characterization of complex mineral assemblages Implications for contaminant transport and environmental remediation. Proc Nat Acad Sci 96 3350-3357 Bertsch PM, Hunter DB, Sutton SR, Bajt S, Rivers ML (1994) In situ chemical speciation of uranium in soils and sediments by micro X-ray absorption spectroscopy. Envir Sci Techno 28 980-984 Bildeiback DH, Huang R (2001) X-ray tests of microfocusing mono-capillary optic for protein crystallography. Nucl Instrum Methods Phys Res A 467-468 954-967 Bilderback DH, Thiel DJ (1995) Microbeam generation with capillary optics. Rev Sci Instrum 66 2059-2063... 

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