Nitrogen-selenium systems

T. M. Klapotke, Binary Selenium-Nitrogen Species and Related Compounds, in R. Steudel (ed.) The Chemistry of Inorganic Ring Systems, Elsevier, pp. 409-427 (1992). 

About 100 gal of process wastewater is typically generated from 1 t of coke produced.15 These wastewaters from byproduct coke making contain high levels of oil and grease, ammonia nitrogen, sulfides, cyanides, thiocyanates, phenols, benzenes, toluene, xylene, other aromatic volatile components, and polynuclear aromatic compounds. They may also contain toxic metals such as antimony, arsenic, selenium, and zinc. Water-to-air transfer of pollutants may take place due to the escape of volatile pollutants from open equalization and storage tanks and other wastewater treatment systems in the plant. 

Bidentate ligand systems are also known with selenium and nitrogen donors. For example, Se/N bidentate phosphinochalcogenoic ligand and zinc amides react to form a distorted tetrahedral complex with two di-t-butylphosphinoselenoic isopropylamidate ligands.590... 

This review chapter focuses on the syntheses and reactions of these 5-membered heterocyclic ring systems containing nitrogen and sulfur (or selenium) (reported during 2006). The importance of these 71-rich heterocycles in medicinal chemistry and natural products is also covered. 

In Scheme 1, all the ring systems belonging to this chapter are depicted. The six-membered rings can be oxazine, thiazine, pyridazine, pyrazine, and pyrimidine, whereas the five-membered fused ring can contain oxygen, sulfur, selenium, phosphoms, and nitrogen atoms in various arrangements. 

Aspects of the chemistry of compounds belonging to more than 20 systems covered by this chapter have been reported, but the chemistry of only a few of these systems has been studied in detail. Chief among these are the 1,2,3-selenadiazoles, which have generated wide interest owing to their ready conversion into selenium heterocycles, reactive intermediates, and nitrogen- and selenium-free products, and the 1,2,5-selenadiazoles and 1,2,3,5-diselenadiazole systems in which interest stems from their use in the synthesis of potentially useful conducting materials. Compounds belonging to several new systems have been synthesized. 

The UV spectral data of various A,B-diheteropentalenes are presented in Table 2. The systems containing only sulfur and/or selenium show more absorption maxima in their UV spectra than those molecules possessing one or two nitrogen atoms. The UV spectrum of the quinonoid thieno[3,4-6]thiophene is in marked contrast to the UV spectra displayed by thieno-[2,3-6]- and -[3,2-6]-thiophenes (67TL761). The analogous, known... 

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