Tetrazole Ring-Containing Complexes

Heterocycles with high nitrogen content (triazoles and tetrazoles) have been studied by researchers of energetic materials for a very long time. The triazole derivatives were found to be useful in the area of secondary explosives and propellants, while tetrazole compounds were found to have some potential in priming. Heavy metal salts of a variety of tetrazole derivatives were examined in early studies and some even found practical applications. 

One of the reasons stimulating the search for new primary explosives today is the need to replace toxic lead azide with some environmentally benign alternative (other reasons are described in Chap. 1). A suitable replacement needs to have many of lead azide s properties within relatively narrow ranges. It would therefore be desirable to have the ability to influence the properties of the resulting substance by slightly modifying its structure. This goal is not achievable with metal salts alone but seems to be realistic with metal complexes or coordination compounds or, as recommended by lUPAC, coordination entities [1]. 

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Esters of tetrazole-5-carboxylic acids are attractive substrates for aminolysis with various amines. These reactions are frequently involved in the synthesis of complex biologically active substances containing a tetrazole ring (cf. Section 6.07.12.1). Reactions of ethyl tetrazole-5-carboxylate 369 with anilines may be cited as an example that results in products of type 370 (Equation 68) <2003BML369>. 

A review of the complexes of 1,5-disubstituted tetrazoles, which covers the earlier literature and contains tables of comparative physical constants for the various complexes, has been published.10 Recent studies have been concerned mainly with determining the nature of the bonding and the structure in tetrazole complexes and with assessing the rr-donor ability of the tetrazole ring. 

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