Properties of Halides

By virtue of the fact that the actinide elements constitute a family of elements whose electronic configurations are related to each other in a quite unique way, a comparison of the physical and chemical properties of a series of related compounds has more than the usual interest. In this section some of the more important properties of the actinide element halides are summarized in tabular form, and a number of topics of current interest are described. 

Crystal structure data obtained by X-ray diffraction methods for the actinide element halides are collected in Table IV. Crystal structure determinations have been most important in identifying new compounds of the actinide elements the data are sufficiently extensive now for use in drawing conclusions regarding systematic trends and relations among the actinide elements. The tetrafluorides, for instance, supply one of the best illustrations of an actinide contraction that is entirely similar to the well-known lanthanide contraction (Table V). 

The vibrational spectra of all of the known actinide element hexafluorides can be interpreted on the basis of the structure of a regular octahedron. Malm et al. (56) have measured the infrared spectra of NpF and PuFe and have deduced the fundamental vibration frequencies (Table VI). 

Only v3 is directly observed in the infrared. All of the frequencies for NpF6 lie intermediate between UF6 and PuFa. The infrared data make it possible to deduce the value of the Raman active frequencies in the case of uranium hexafluoride, a discrepancy was revealed between the value for the Raman spectrum as deduced by the method of Gaunt (88) from infrared measurements and the experimentally determined Raman spectrum of Bigeleisen et al. (10). Consequently, Claassen et al. (17) have measured 

Designation Symmetry species Spectral activity Frequencies (cm -1) 

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Pankratz LB (1984) Thermodynamic properties of halides. US Dept, of Interior Bureau of Mines, Washington DC Lin JS, Catlow CRA (1993) J Mater Chem 3 1217 Guo XC, Hoffman A, Yates JT (1989) J Chem Phys 90 5787... 

Brown G, Bailey SR, Novotny M, Carter R, Flahaut E, Coleman KS, Hutchison JL, Green MLH, Sloan J (2003) High yield incorporation and washing properties of halides incorporated into single walled carbon nanotubes. Appl. Phys. A 76 457 162. 

These uncertainties are increased when the existence of compounds of CO with metals, the carbonyls such as Fe(CO)5, for which no electrostatic model is conceivably possible are considered. The iron obviously is not present in the compound as an ion how then can the attraction for the CO molecules be explained Even in the straight ammoniates there is some doubt regarding the validity of the simple electrostatic representation of the structure for it is found experimentally that the magnetic properties of halides are radically altered by the taking up of molecules of ammonia. This shows that - some of the electrons of the positive ions are influenced by the ammonia molecules in a way which an electrostatic picture cannot explain. 

The radius thus calculated from the theory of Smith and Symons does not correspond to any known property of halide ions. However, when the acceptable physical model of Franck and Platzman is combined with the concept of a variable radius, as proposed by Smith and Symons, both absolute value and environmental effects can be accounted for. This was done in the theory of Stein and Treinin (18, 19, 47), using an improved energetic cycle to obtain absolute values of r, the spectroscopically effective radius of the cavity containing the X ion. These values were then found to correspond to the known partial ionic radii in solution, as did values of dr/dT to values obtained from other experiments. The specific effects of temperature, solvents, and added salts could be used to differentiate between internal and such CTTS transitions where the electron interacts in the excited state strongly with the medium. These spectroscopic aspects of the theory were examined later in detail and compared with experiment by Treinin and his co-workers (3, 4, 32, 33, 42,48). 

The addition of a-deprotonated alkyl halides to alkenes or carbonyl compounds can, because of the good leaving-group properties of halides, also lead to formation of cyclopropanes [292] or epoxides [187, 304, 306, 310], respectively. Because of the inherent instability of a-halo organometallic compounds, these intermediates should be handled carefully and on a small scale only. The ketone produced by the last reaction in Scheme 5.34 is probably formed by Oppenauer oxidation of the intermediate alcohol by the excess benzaldehyde [310],... 

L. B. Pankratz, Thermodynamic Properties of Halides, Bulletin 674, Bureau of Mines, U.S. Department of the interior, Washington, D.C. 1984. 

In addition to the development of very large IR optics, often difficult to accomplish with crystalline materials, an important property of halide glasses is the potential for the development of very transparent IR optical fibers. With its... 

Rahlfs, O., and Fischer, W. Thermal properties of halides. VI. Vapor pressures and vapor densities of beryllium and zirconium halides. Z. Anorg. AUgem. Chem. 211, 349-367 (1933). 

The preparation and properties of halides of the actinides have been described fully. As most of these complexes are solid state, rather than molecular in nature, only overview information on classes of compounds will be provided. Adducts of the halide complexes will be discussed in the context of compounds of the respective Lewis bases vide infra). 

Needs of the industrial technologies called for extensive studies and measurement of the physicochemical properties of halides and oxohalides their thermodynamic characteristics, phase diagrams, reactions, complexing in gases and so forth. After two decades of growth, the intensity of these works waned today, such studies are scarce, though the properties of a number of compounds are still known with low accuracy. 

The last three chapters summarize unique structural and chemical features of a variety of glasses. They also provide an overview of the important aspects of the glass systems. Chapters 12 and 13 discuss respectively oxide and chalcogenide glasses particularly in view of their chemistry, structure and a number of special phenomena associated with them. In chapter 14, synthesis, structure and properties of halide, oxyhalide, oxynitride and metallic glasses are discussed. Some aspects of glass-like carbon have also been presented. 

Pogliani, L. (2005b) Model of the physical properties of halides with complete graph-based indices. Int, J, Quant, Chem, 102, 38-52. 

L.B. Pankratz et ah Thermodynamic Properties of Elements and Oxides, Thermodynamic Properties of Halides, Thermodynamic Data for Mineral Technology, US Bur. of Mines, Buii. 672 (Elements and Oxides), 1982, Bull. 674 (Halides), 1984, Bull. 677 (Data for Mineral Tfechnology), 1984, Supt. of Docs. US. Government of Printing Office, Washington, D.C., USA, 1982-1984. 

The preparations, structures, and properties of halides have been reviewed. 

J. B. Pankratz, Thermodynamic properties of halides. Bureau of Mines Bulletin 674, Washington, DC, US Government Printing Office, 1984. 

The adsorption mechanism and the influence of complexing properties of halides include the chemical aspects for the mechanism, which is ignored in most papers. Besides, for the nucleation of pits, halides are also important for their further growth, which will be discussed in the next section. 

Table 4.1. Steric properties of halides and halide ligands.

Ionova GV (2002) Thermodynamic properties of halide compounds of tetravtilent transactinides. Russ Chem Rev 71 401-416... 

The thermal properties of halides are characterized by melting and dehydration of the water present at a particular stage during heating. 

Because of the fundamental and applied interest in the many actinide halides, their thermodynamic properties have received much attention. The recent authoritative assessment by Fuger et al. [20] is dted throughout Table 17.14 for most actinide halides. The discussion that follows will be limited to systematic properties of halide families and areas needing further study. Thermodynamic properties of many gaseous actinide halides and their ions have been assessed by Hildenbrand et al. [354] and by Kleinschmidt and Ward [362] only properties of halide species are included in Table 17.14. 

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