Actinide derivatives

As yet (but see section 3.4.3) no actinide derivatives of the B isomer of [PW9034] illustrated in Figure 4 have been reported. However there are structural analogs, [XWgOss]" with X = As , Sb , Bi , Se " and Te in which the unshared electron pair of the heteroatom X occupies the position of the... 

An actinide derivative is prepared by means of a salt elimination in concert with alkane elimination. The product is isolated as black crystals in 62% yield. 

Sufficient data are now available to discuss two important structural aspects involved in the activation of CO by bis(penta-methylcyclopentadienyl) actinide derivatives. First, the structural features accompanying various degrees of coordinative un saturation in the organoactinide reactants are discussed. Second, the nature of the nonelassically bound CO in organoactinide migratory insertion products is considered and compared with d-element analogues. 

The first structurally characterized isocyanate actinide derivative, [(U02)2(NC0)50]2[(Et4N)6]-2MeCN-H20 and isocyanato uranate (Et4N)6 [(U02)2(NC0)50]2 2MeCN H2O were reported (Fig. 12) [65].Structural... 

The /-block consists of the 4/ metals, La-Lu, and the 5/ metals, Ac-Lr. The common terms lanthanide and actinide derive from the names of the first elements of each series, and the symbol Ln, not assigned to any particular element, is a useful way to designate the lanthanides as a class. The older term for lanthanides, rare earths, is sometimes encountered. The actinides are radioactive, and only Th and U are sufficiently stable to be readily handled outside high-level radiochemical facilities t /2 = 4.5 x 10 years Th, ti/2 = 1.4 x 10 years). Even though they have no / electrons, scandium (Sc) and yttrium (Y) in group 3 are also typically considered with the /-block elements because of their rather similar chemistry. 

The chemical differences between lanthanide and actinide derivatives are mainly due to some differences in their electronic structures. The 5f orbitals of early actinides are incompletely shielded from external influences by the 6s and 6p electrons, thus they have sufficient radial expansion for some overlap with ligand orbitals. As a consequence, organoactinides show a consistent covalent contribution to bonding, even though the prevalent ionic character remains. In the later actinides the increased nuclear charge causes contraction of 5f orbitals so that the metal-ligand overlap decreases and the trivalent oxidation state dominates in the more ionic derivatives. 

Lanthanide(IV) derivatives with modified Cp are as yet unknown so this section reports only on actinide derivatives... 

While CP2MCI2 (M = Ti, Zr, Hf) compounds are stable and extremely interesting in organometallic chemistry, the corresponding actinide derivatives are notably unstable towards intermolecular ligand redistribution processes. Thus CP2UCI2 obtained by the following reaction ... 

Carbon monoxide [630-08-0] (qv), CO, the most important 7T-acceptor ligand, forms a host of neutral, anionic, and cationic transition-metal complexes. There is at least one known type of carbonyl derivative for every transition metal, as well as evidence supporting the existence of the carbonyls of some lanthanides (qv) and actinides (1) (see AcTINIDES AND THANSACTINIDES COORDINATION COMPOUNDS). 

A further group of elements, the transuranium elements, has been synthesized by artificial nuclear reactions in the period from 1940 onwards their relation to the periodic table is discussed fully in Chapter 31 and need not be repeated here. Perhaps even more striking today are the predictions, as yet unverified, for the properties of the currently non-existent superheavy elements.Elements up to lawrencium (Z = 103) are actinides (5f) and the 6d transition series starts with element 104. So far only elements 104-112 have been synthesized, ) and, because there is as yet no agreement on trivial names for some of these elements (see pp. 1280-1), they are here referred to by their atomic numbers. A systematic naming scheme was approved by lUPAC in 1977 but is not widely used by researchers in the field. It involves the use of three-letter symbols derived directly from the atomic number by using the... 

Brdnsted-Lowry theory, 194 contrast definitions, 194 indicators, 190 reactions, 188 titrations, 188 Acids, 183 aqueous, 179 carboxylic, 334 derivatives of organic, 337 equilibrium calculations, 192 experimental introduction, 183 names of common, 183 naming of organic, 339 properties of, 183 relative strengths, 192, 451 strength of, 190 summary, 185 weak, 190, 193 Actinides, 414 Actinium... 

That magnetic measurements often raise more problems than they solve, is demonstrated for the indicated compound. We prepared a series of [ (C2H5N] i,An(NSC) e compounds (An = Th, U, Np, Pu) with cubic coordination of the actinide ion. We derived a consistent interpretation of the magnetic and optical properties of the uranium and the neptunium compounds (6 ). In the case of Pu we expect an isolated T1 ground state and a first excited state at about 728 cm-1. To our surprise we found a magnetic ground state much more pronounced than in the case of the hexachloro-complex, Fig. 4. 

In contrast to the situation observed in the trivalent lanthanide and actinide sulfates, the enthalpies and entropies of complexation for the 1 1 complexes are not constant across this series of tetravalent actinide sulfates. In order to compare these results, the thermodynamic parameters for the reaction between the tetravalent actinide ions and HSOIJ were corrected for the ionization of HSOi as was done above in the discussion of the trivalent complexes. The corrected results are tabulated in Table V. The enthalpies are found to vary from +9.8 to+41.7 kj/m and the entropies from +101 to +213 J/m°K. Both the enthalpy and entropy increase from ll1 "1" to Pu1 with the ThSOfj parameters being similar to those of NpS0 +. Complex stability is derived from a very favorable entropy contribution implying (not surprisingly) that these complexes are inner sphere in nature. 

Extractants derived from the carbamoylmethylphosphoryl moiety (CMP) were studied in the phosphonate, phosphinate, and phosphine oxide classes. Our studies focused on dihexyl-N,N-diethylcarba-moylmethylphosphonate, DHDECMP, hexyl hexyl-N,N-diethylcarbamoyl-methylphosphinate, HHDECMP, and octyl(phenyl)-N,N-diisobutylcarba-moylmethylphosphine oxide, 0D[ IB]CMP0. The three types of CMP extractants were compared on the basis of nitric acid and extractant dependencies for Am(III), solubility of complexes on loading with Nd(III) and U(VI), and selectivity over fission products. On the basis of the above data two conceptual flowsheets were developed. The first flowsheet involves the extraction of all of the actinides from HLLW using 0.4 M 0D[IB]CMP0 in DEB. The second flowsheet involves the extraction of all of the actinides from dissolved spent LWR fuel using 0.8 M DHDECMP in DEB. 

Calculations—See Data analysis Carbamoylmethylphosphoryl derivatives as actinide... 

Among the CeCo3B2-derivative structures the actinide metal combinations " ManMj3B2 (Man = U, Pu M - = Ru, Os) adopt a simple superstructure (a = 2a ,... 

Compounds containing group-lIB-transition-metal bonds arc characterized for almost every transition metal. Although there are more derivatives containing Hg than Zn or Cd, there is no difficulty in producing analogous compounds of each of these metals. No compound is known in which Zn, Cd or Hg is bonded to either lanthanide or actinide elements. 

Experimental clinopyroxene-melt (Brooker et al. 2003) and wollastonite-melt (Law et al. 2000) partitioning data can be fitted to the electrostatic model (see Fig. 9). Only species entering the large cation site (e.g., M2 in clinopyroxene) are considered. For each isovalent group (actinides, lanthanides etc.) derived as shown in Figure 4, is... 

Information on the transplacental transfer of americium in humans is not available directly, but the information from experiments with americium and other actinides has been used to derive biokinetic models and perform dosimetric models for the human (NCRP 1998 NRC 1996 Sikov and Kelman 1989). Studies in animals that received parenteral injections of americium have shown that absorbed americium is transferred to the fetus (Hisamatsu and Takizawa 1983 Paquet et al. 1998 Sasser at al. 1986 Schoeters et al. 1990 Weiss et al. 1980) (see Section 3.4.2.1). Limited reports indicate that241 Am may induce fetal death and teratogenic effects in rodents (Moskalev et al. 1969 Rommerein and Sikov 1986). 

The redox salt which decomposes at 100°C, evolving nitrogen and oxygen [1] is overall an oxidant but has been used as a reducant in actinide processing [2], It has been used recently as a missile monopropellant [3], and also as an oxidant, with its isopropyl derivative as the fuel [4],... 

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