Astatine chemistry

Normal physicoorganic methods used for the formal identification of organic compounds are not applicable to organic astatine chemistry. The mass quantities required for the characterization of compounds by UV, NMR, and IR spectroscopy are in the region 10 -10" g molar concentrations of 10 preclude the application of such techniques. Mass spectrometry has not yet been developed to operate at such a concentration, except under special laboratory conditions (4). 

Radiochim. Acta (Special Issue on Astatine Chemistry), 47, Nos. 2/3 (1989). 

Since (he mo.si. stable isotope of astatine has a half-life of only 8.3 hours, the chemistry of this halogen ha.s not been studied extensively. In the following discussion generalities made about the halogens may or may not include astatine. In the present in.siance AlBr and AtCI have been prepared. See the discussion of astatine chemistry later in this chapter. 

A quick word about astatine may be of interest here. All isotopes of astatine are intensely radioactive even the most stable, At, has a half-life of only 8.1 h. Astatine chemistry is therefore understandably relatively little explored. It is utterly fascinating, however. Thus, condensed, bulk astatine (which is yet to be prepared) has been predicted to be metallic. Experimentally, there is significant evidence for At+ cations in aqueous solution. Two possible closed-shell structures for such species are the following ... 

Champion J, Seydou M, Sabatie-Gogova A, Renault E, Montavon G et al (2011) Assessment of an effective quasirelativistic methodology designed to study astatine chemistry in aqueous solution. Phys Chem Chem Phys 13(33) 14984—14992... 

All isotopes of element 85, astatine, are intensely radioactive with very short half-lives (p. 795). As a consequence weighable amounts of the element or its compounds cannot be prepared and no bulk properties are known. The chemistry of the element must, of necessity, be studied by tracer techniques on extremely dilute solutions, and this introduces the risk of experimental errors and the consequent possibility of erroneous... 

E. H. Appelman, Astatine, Chap. 6 in MTP International Review of Science, Inorganic Chemistry, Series 1. Vol. 3, Main Group Elements Group VII and Noble Gases. pp. 181-98, Butterworths, London, 1972 see also ref. 23, pp. 1573-94, Astatine. 

A rudimentary chemistry of organic derivatives of astatine is emerging, but the problems of radiation damage, product separation and tracer... 

K. Berei and L. Vasaros, The Organic Chemistry of Astatine, in S. PataI and Z. Rappaport (eds.). The Chemistry of Organic Functional Groups, Wiley, New York, 1983. 

Adli S. Kana an and John L. Margrave The Chemistry of Astatine A. H. W. Aten. Jr. 

Lavrukhina, A. K., Pozdnyakov, A. A. Analytical Chemistry of Technetium, Promethium, Astatine, and Francium. Ann Arbor Humphrey Science Publishers 1970... 

Many aspects of the nuclear physics, and inorganic and organic chemistry, of the astatine radionuclides have been the subject of a number of excellent reviews (5, 6,17, 18, 49, 79, 80, 90,110). 

Astatine has properties very similar to those of iodine, but has a more metallic character. The oxidation of astatide to astatine occurs at a potential ca. 0.4 V less positive compared to that for the oxidation of iodine. Fundamental information about the redox chemistry of astatine is available in an earlier review [158] and standard data collections [14]. A summary of the approximate standard potentials and known redox states is given in Scheme 8. 

The halogens will be restricted to chlorine, bromine and iodine since fluorine, as the most electronegative element, does not function as the central atom in a complex and astatine has only short-lived, radioactive isotopes, so that very little of its coordination chemistry has been investigated.2 ... 

It was noted above that discussion of astatine together with the other halogens is inconvenient. Although it is, as expected, the most metallic of the halogens, there arc few values or experimental data to cite in support of this. (Note for example that such fundamental quantities as experimental ionization energies are unavailable.) Various isotopes ok astatine arc produced only in trace amounts, with half-lives of a few hours or less, and therefore the chemistry of astatine is essentially the descriptive chemistry obtained by tracer methods macroscopic amounts arc not available. The best known oxidation state of astatine is — I. Astatine may be readily reduced to as ta tide ... 

This review will attempt to deal with the chemistry of the halogens appropriate to those compounds considered as coordination compounds. It will not include reference to astatine, which is covered by the general reviews listed above and for which little chemistry is known at all, and almost none as a coordinated ligand. Since the chemistry of the halides of individual elements is treated in the chapters for those elements, this section will be concerned with an overview of the general properties of the group. 

Astatine Astatine, like francium in group 1 A, is a radioactive element that occurs only in minute amounts in nature. No more than about 5 X 10-8 g has ever been prepared at one time, and little is known about its chemistry. 

Little is known about the chemistry of astatine (At) from direct observation, but reasonable predictions can be made. 

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