Actinide 1:1 compounds

Lanthanide and actinide compounds are difficult to model due to the very large number of electrons. However, they are somewhat easier to model than transition metals because the unpaired / electrons are closer to the nucleus than the outermost d shell. Thus, all possible spin combinations do not always have a significant effect on chemical bonding. 

J. M. Haschke, ia G. Meyer and L. R. Morss, eds.. Synthesis ofEanthanide and Actinide Compounds, Kluwer Academic PubUshers, Dordrecht, the... 

J. D. Corbett in Synthesis of Lanthanide and Actinide Compounds, pp. 159-73, Kluwer Acad. Publ., Dordrecht, (1991),... 

The electronic spectra of actinide compounds arise from three types of electronic transition ... 

Equilibrium vapor pressures were measured in this study by means of a mass spectrometer/target collection apparatus. Analysis of the temperature dependence of the pressure of each intermetallic yielded heats and entropies of sublimation. Combination of these measured values with corresponding parameters for sublimation of elemental Pu enabled calculation of thermodynamic properties of formation of each condensed phase. Previ ly reported results on the subornation of the PuRu phase and the Pu-Pt and Pu-Ru systems are correlated with current research on the PuOs and Pulr compounds. Thermodynamic properties determined for these Pu-intermetallics are compared to analogous parameters of other actinide compounds in order to establish bonding trends and to test theoretical predictions. 

The free energies of formation for the actinide compounds above are given by the following table ... 

Antimonide-actinide compounds, lattice parameter for rock-salt... 

Hay, P. J., Martin, R. L., 1998, Theoretical Studies of the Structures and Vibrational Frequencies of Actinide Compounds Using Relativistic Effective Core Potentials With Hartree-Fock and Density Functional Methods ... 

Muller HL, Taya A, Drosselmeyer E, et al. 1989. Cellular aspects of retention and transport of inhaled soluble and insoluble actinide compounds in the rat lung. Sci Total Environ 83 239-251. 

Figure 4. Dependence of the ratio u u on the number of 5f electrons for light actinide compounds x free ion values, ° experimental values, form band calculations. The hybridisation between 5f and 3d electrons leads to the reduction of the 5f orbital moments (metallic covalency).

Lebech, B., Wulff, M. and Lander G.H. (1991) Spin and orbital moments in actinide compounds (invited), J. Appl. Phys., 69, 5891-5896. 

The general magnetic properties of ionic and molecular actinide compounds have been reviewed recently [15], and only the briefest of overviews is given here. The 5f3 ions U5+ and Np6+ have 2F5/2 ground multiplets in the Russell-Saunders... 

Reports on studies of solvent exchange reactions on actinide compounds are very scarce. The most studied cation is U02+. The commonly observed solvated species have five (H20, DMSO, DMF, TMP) (262,263)... 

Ab initio quantum chemistry has advanced so far in the last 40 years that it now allows the study of molecular systems containing any atom in the Periodic Table. Transition metal and actinide compounds can be treated routinely, provided that electron correlation1 and relativistic effects2 are properly taken into account. Computational quantum chemical methods can be employed in combination with experiment, to predict a priori, to confirm, or eventually, to refine experimental results. These methods can also predict the existence of new species, which may eventually be made by experimentalists. This latter use of computational quantum chemistry is especially important when one considers experiments that are not easy to handle in a laboratory, as, for example, explosive or radioactive species. It is clear that a good understanding of the chemistry of such species can be useful in several areas of scientific and technological exploration. Quantum chemistry can model molecular properties and transformations, and in... 

The methods used to describe the electronic structure of actinide compounds must, therefore, be relativistic and must also have the capability to describe complex electronic structures. Such methods will be described in the next section. The main characteristic of successful quantum calculations for such systems is the use of multiconfigurational wave functions that include relativistic effects. These methods have been applied for a large number of molecular systems containing transition metals or actinides, and we shall give several examples from recent studies of such systems. 

Nonrelativistic quantum chemistry has been discussed so far. But transition metal (starting already from the first row) and actinide compounds cannot be studied theoretically without a detailed account of relativity. Thus, the multiconfigurational method needs to be extended to the relativistic regime. Can this be done with enough accuracy for chemical applications without using the four-component Dirac theory Much work has also been done in recent years to develop a reliable and computationally efficient four-component quantum chemistry.25,26 Nowadays it can be combined, for example, with the CC approach for electron correlation. The problem is that an extension to multiconfigurational... 

The chemistry of uranium interacting with atmospheric components, like carbon, nitrogen, and oxygen, poses a formidable challenge to both experimentalists and theoreticians. Few spectroscopic observations for actinide compounds are suitable for direct comparison with properties calculated for isolated molecules (ideally, gas phase data are required for such comparisons). It has been found that even data for molecules isolated in cryogenic rare gas matrixes, a medium that is usually considered to be minimally perturbing, can... 

The distribution of componentsof binary solid solutions over the solid phase and the aqueous phase has been studied for a number of systems. Table I contains a summary of some of these systems with references. This literature review is not complete more data are available especially for rare earth and actinide compounds, which primarily obey type I Equations to a good approximation. In the following sections, the theory above will be applied to some special systems which are relevant to the fields of analytical chemistry, inorganic chemistry, mineralogy, oceanography and biominerals. 

For successful use of the van Arkel-De Boer process starting with an actinide compound, it is necessary that the original actinide compound react readily with Ij to yield a volatile actinide iodide. Both ThC and PaC, easily prepared from the corresponding metal oxides by car-boreduction (Section II,C), react with I2 at 625 K to yield volatile iodides and carbon. Above 1475 K these iodides are unstable and decompose into the respective metals and iodine. 

Many substituted uranocenes have been made and there is a substantial body of organometallic chemistry of uranocene derivatives now known 16, 17). Some of this chemistry will be mentioned in passing but wiU not be covered in a systematic way since other reviews of the organic chemistry are available 18). The only other actinide cyclooctatetraene complex structurally characterized to date is bis[(l,3,5,7-tetramethylcyclooctatetraenyl]uranium(IV) 19), which was of interest because the presence of methyl groups allowed the planarity and relative orientation of the dianion rings to be determined. Crystal and molecular parameters for these three actinide compounds are summarized in Table 1. 

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