Transuranium compounds

Magnetic susceptibility measurements are basic to the study of the magnetic properties of a compound samples under powder form are sufficient to start with and, what is very important in the case of actinides, small amounts of material are satisfactory (typically 100 mg). When working with transuranium compounds, safety requirements are fulfilled by working with sealed containers ... 

The chemistry of transition metals, lanthanides and actinides is significantly influenced by relativistic effects. Qualitatively, these effects become apparent in the comparison of certain structural properties or reactivity patterns for a group of metals, for example, trends in the chemistry of copper, silver and gold. Quantification of relativistic effects can, however, only be achieved by relating the experimental findings to the results of adequate ab initio studies. Reference to theory is required because nonrelativistic properties cannot be probed directly. Thus, elements behave relativis-tically in any kind of experiment, whether one deals with the spectrum of Hj or the properties of transuranium compounds. 

It has been more than fifty years since the discovery of the transuranium elements. The initial activities in this field established the fundamental solution and solid-state chemistry of the first two of these elements and their compounds under the auspices of the Manhattan Project. New separation methods including solvent extraction techniques and uranium isotope separation played a leading role in these programs. Tracer techniques were widely used to determine solubilities (or solubility liinits) of transuranium compounds as well as to obtain information about the coorination chemistry in aqueous solution. A little later, special solvent extraction and ion-exchange techniques were developed to isolate pure transplutonium elements on the milligram and smaller scale. The second edition of The Chemistry of the Actinide Elements, published in 1986 (i), covers most of these topics. A detailed overview of the history of transuranium chemistry is given in Transuranium Elements A Half Century (2). 

Since the review of 1984 a considerable amount of work has been done on single crystals of transuranium compounds (Burlet et al. 1988b, and references therein), and we will discuss a few of these results. The magnetic phase diagram of NpAs is... 

The magnetic critical scattering (sect. 5) continues to attract much theoretical interest. Since the earlier work (Rossat-Mignod et al. 1984) the experiments (and theory) have been extended to transuranium compounds. The early systematics (fig. 32) of Ce and U compounds with respect to the anisotropy ratio, R, do not appear to be followed by the Np and Pu compounds, particularly PuSb. Another point to make is the important challenge for theory to arrive at R-values as great as five, and to consider whether the fact that USb and NpSb have 3k structures has any connection with the large R-values. 

Special techniques for experimentation with the actinide elements other than Th and U have been devised because of the potential health ha2ard to the experimenter and the small amounts available (15). In addition, iavestigations are frequently carried out with the substance present ia very low coaceatratioa as a radioactive tracer. Such procedures coatiaue to be used to some exteat with the heaviest actinide elements, where only a few score atoms may be available they were used ia the earHest work for all the transuranium elements. Tracer studies offer a method for obtaining knowledge of oxidation states, formation of complex ions, and the solubiHty of various compounds. These techniques are not appHcable to crystallography, metallurgy, and spectroscopic studies. 

The effects of a rather distinct deformed shell at = 152 were clearly seen as early as 1954 in the alpha-decay energies of isotopes of californium, einsteinium, and fermium. In fact, a number of authors have suggested that the entire transuranium region is stabilized by shell effects with an influence that increases markedly with atomic number. Thus the effects of shell substmcture lead to an increase in spontaneous fission half-Hves of up to about 15 orders of magnitude for the heavy transuranium elements, the heaviest of which would otherwise have half-Hves of the order of those for a compound nucleus (lO " s or less) and not of milliseconds or longer, as found experimentally. This gives hope for the synthesis and identification of several elements beyond the present heaviest (element 109) and suggest that the peninsula of nuclei with measurable half-Hves may extend up to the island of stabiHty at Z = 114 andA = 184. 

A77. C. Keller, The Chemistry of the Transuranium Elements. Verlag Chemie, Weinheim, 1971. Chapter 8, Organometallic compounds of the actinides, pp. 187-193 (36). Not as comprehensive as reference 4.39. 

It was detected by Urey, Brickwedde and Murphy in 1932. It occurs in all natural compounds of hydrogen including water, as well as in free hydrogen molecules at the ratio of about one part per 6,000 parts hydrogen. The principal application of deuterium is in tracer studies for measuring rates and kinetics of chemical reactions. It also is used in thermonuclear reactions and as a projectile in cyclotrons for bombardment of atomic nuclei to synthesize isotopes of several transuranium elements. Deuterium oxide, D2O, or heavy water is used as a neutron moderator in nuclear reactors. 

Protactinium dipnictides (X = As, Sb) have been synthesized by reaction of As or Sb vapour with metal hydride at 400-700 Pa3As4 was obtained by thermal dissociation of PaAs2 at 840 °C, Pa3Sb4 from the corresponding dipnictide at 1200 °C. Monopnictides of protactinium were not obtained by thermal dissociation of higher compounds. The diantimonides of the transuranium elements Np, Pu, Am dissociate between 700-800 °C into the monocompounds. Monopnictides of the higher transuranium elements have been obtained at the pg scale with and 0 by thermal dissociation. 

The XPS valence band spectra for the dioxides of the transuranium elements (from Np to Bk) have been presented in an extensive and pioneering work that also includes core level spectra and has been for a long time the only photoemission study on highly radioactive compounds. High resolution XPS spectra (AE = 0.55 eV) were recorded on oxidized thin metal films (30 A) deposited on platinum substrates with an isotope separator. (The oxide films for Pu and the heavier actinides may contain some oxides with lower stoichiometry, since starting with Pu, the sesquioxides of the heavier actinides begin to form in high vacuum conditions.)... 

Exhaustive accounts of the chemistry of thorium, protactinium, uranium and the transuranium elements appear in the most recent supplementary volumes of the Gmelin series.12 Unless otherwise indicated by the inclusion of references to specific papers, further information on the compounds discussed in this chapter will be found in the Gmelin volumes and in the work cited in reference 2. 

The M(OR) derivatives are known now for almost all the elements of the Periodic Table (including the transuranium elements and Xenon). They are formal analogs of hydroxides but possess much higher thermal stability. Their properties are determined not only by the electronegativity of the metal atom but also by the nature of the radical — its ramification and the acidity of the corresponding alcohol, which provides their various properties. From this point of view they can be subdivided into the following groups of compounds ... 

The information presented in this chapter will be included in the material property database for f-elements and compounds (/-MPD) of the Institute of Transuranium Elements, which is accessible through internet.3 Complete thermodynamic tables can be retrieved at that site, which will be updated regularly with new information. 

Among the elements known before transuranium elements started to be synthesized in 1940, uranium has a unique characteristic, the extreme stability of the triatomic uranyl ion OUO+z. Not only are the numbers of uranium(VI) compounds larger than of U(IV), and far larger than of the two other oxidation states U(V) and U(III) known from non-metallic compounds, but until the preparation of UOFj discussed below, the only two U(VI) compounds known to contain less than two oxygen atoms per uranium atom were the octahedral molecules UFe and UQ6. 

LaChapette, T. J., L. B. Magnusson, and J. C. Hindman The Chemistry of Neptunium. First Preparation and Solubilities of some Neptunium Compounds in Aqueous Solution. In G. T. Seaborg, J. J. Katz, and W. M. Manning (Eds.), The Transuranium Elements, National Nuclear Energy Series, Div. IV, Vol. 14B, p. 1097. New York McGraw-Hill 1949. 

Solubility data for Np, Pu, and Am hydroxo compounds in the III to VI oxidation states in alkaline media were first published in 1949 by the researchers of the Manhattan Project. Later, these data were confirmed and refined by other researchers Irom different countries. In the following, we consider some data on hydroxides and peroxides of transuranium elements. 

A.D. Gelman, A.I. Moskvin, L.M. Zaitseva, M.P. Mefod eva, Kompleksnye Soedineniya Transuranovykh elementov (Complex Compounds of Transuranium Elements), USSR Academy of Sciences Publ., 1961, p. 223. 

The actinide iodate system is one of considerable interest that has attracted chemists for more than 150 years (vide supra). In fact one of the first forms that was isolated in was as the iodate salt, presumably as 1 0(103)4 [63], The precipitation of iodate compounds of the actinides has been used for decades as a method of separated them from lanthanides and other fission products. The precipitation of thorium iodate is perhaps best known in this regard [64-66], but several patents exist describing selective precipitation of transuranium elements [67-72], Despite the key importance of iodate in actinide chemistry the structures of actinide iodates were not described in detail until approximately 2000. 

This book is a series of reviews of recent results on the state-of-art of structural and crystal chemistry of uranium and transuranium element compounds. 

Intermetallic compounds, even those of the transuranium elements, can be prepared by vapor transport and deposition of thin films. The compound AUCm was recently formed in this way on the submilligram scale. ... 

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