Selenium-containing compounds

Selenazole is the selenium-containing compound in the series of heterocyclic 5-membered ring azoles with two different hetero atoms, of which the first two members are oxazole and thiazole. The numbering of the ring system is according to the scheme given (1). 

In the above-described displacement reactions (Sh2) of sulfur- and selenium-containing compounds, the mechanism could either be a synchronous or a stepwise process (Scheme 4.2). Thus, in the Sh2 stepwise mechanism an intermediate sulfuranyl or selenyl radical is formed, followed by a-cleavage [56]. Based on competitive studies, a stepwise process was suggested to occur in the reaction of (TMS)3Si radical with -decylphenylselenide [43]. On the other hand, ab initio calculations supported the synchronous process and the same observations were explained in terms of an overall reversible reaction [57]. 

An analytical technique has been developed for the determination of selenium species in urine to identify selenium containing compounds by combining electrospray MS/MS with ICP-MS after preparative solid phase extraction and final reversed phase HPLC separation.69... 

In our opinion the electrodeposition of selenium is quite promising for a variety of applications. For example, the possibility to deposit grey selenium, indium, and copper in one ionic liquid at variable temperatures might be regarded as the first step in making selenium-containing compound semiconductors like CIS by electrochemical means. 

The homolytic cleavage of the carbon-selenium bond provides an easy access to radicals, which can undergo various subsequent reactions. The plethora of radical chemistry is accessible using selenium-containing compounds and examples of free-radical reactions are described in Section 9.11.2.4. 

The ability of thienothiophenes and selenoloselenophenes to transmit substituent effects has been determined by H and l3C NMR, and also calculated by the CNDO/2 method [82CS(20)208 83CS(22)22]. As expected, resonance effects are better transmitted between the 2- and 5-positions in 8.185 than in 8.186, since only in the former is direct conjugation between these positions possible. Both resonance and inductive/field effects were greater in the sulfur- relative to the selenium-containing compounds, but in general, replacement of sulfur by selenium caused only minor perturbations of data, which follows from the fact that the main mode of transmission of substituent effects in five-membered heterocycles must be via the carbon chain (cf. Chapter 6, Section 9.C). 

An important method for the characterization of selenium-containing compounds is Se NMR spectroscopy. The Se isotope has a natural abundance of 7.5 % and its medium receptivity is about three times that of the nucleus. The... 

Ferrocene organomercurials were also used to prepare a number of other derivatives, namely, halogen-, sulfur-, or selenium-containing compounds, biferrocenyl, or triphenylmethylferrocene [Nesmeyanov, Perevalova, 0. A. Nesmeyanova 258,259)]. Lithiation or sodium metalation provided even more versatile reagents, the reactions being used by other investigators as well. 

Anodic Oxidation of Sulfur- and Selenium-Containing Compounds... 

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