Uranium , direct bonding

The IR spectra again indicate a direct interaction of the uranium with the oxygens of the ligand. The NMR data indicate a C2V environment for the uranium and bonding to the cryptate oxygens (84). 

The use of VD polyhedra allows one to characterize specific properties of the coordination spheres of cations by means of the (r, (p) distributions [24]. In Figure 9, each point corresponds to the VD polyhedron with a given r(U=0), r(U-O), or r(U/0) bond length and the (p angle between the Da vector and the direction of the corresponding uranium-oxygen bond (we remind the reader that... 

The linewidths for protons on carbons directly bonded to uranium are less than 50 Hz and rapidly decrease for protons on carbons not directly bonded to the metal atom, so that J-J coupling is often observed. A review of early work on the H NMR spectra of U(IV) compounds apepared in 1971 (7). 

Prior to and during the Manhattan Project, considerable eflFort was directed toward the synthesis of volatile uranium alkyl compounds such as U( 2115)4 for use in isotope separation. These attempts were unsuccessful (8, 9) and it was assumed that the uranium alkyl bond was intrinsically unstable. Thus, for several decades the nature of the uranium-to-carbon linkage remained unexplored, and there was even some question as to whether such bonding could take place. 

EXAFS is a nondestructive, element-specific spectroscopic technique with application to all elements from lithium to uranium. It is employed as a direct probe of the atomic environment of an X-ray absorbing element and provides chemical bonding information. Although EXAFS is primarily used to determine the local structure of bulk solids (e.g., crystalline and amorphous materials), solid surfaces, and interfaces, its use is not limited to the solid state. As a structural tool, EXAFS complements the familiar X-ray diffraction technique, which is applicable only to crystalline solids. EXAFS provides an atomic-scale perspective about the X-ray absorbing element in terms of the numbers, types, and interatomic distances of neighboring atoms. 

Uranyl is formed due to o and n bonds of 5/, 6d, 7s electrons of the uranium atom and 2p electrons of two oxygen atoms. Molecular orbitals of uranyl are formed by the interaction of atomic orbitals of uraniiun and oxygen with the same type ofsymmetry and close energy levels. Bonding orbitals la , lag, l7r , iTTg are filled with electrons with antiparallel spin directions. Nonbonding orbitals la, la. In, In and so on are empty and form excitation levels. The... 

It is generally agreed that the extracted uranium species is U02(N03)2(TBP)2 in which, in contrast to the species extracted into ether, the extractant molecules are directly coordinated to the metal ion. The extraction of uranium(VI) by neutral organophosphorus compounds increases with the number of C—P bonds (as opposed to C—0—P bonds) and with the increased branching of the substituent alkyl groups, as would be expected from the effect of these changes on the electron-donor properties of the phosphoryl group. The extracted thorium(IV) complex has been formulated as Th(N03)4-2S and as Th(N03)4-3S,2 2 and its composition may depend to some extent on the conditions of extraction. The extraction of thorium (like that of... 

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