Triazoles, tetrazoles and pentazoles

Part II. Transition metal derivatives of ric-triazoles, tetrazoles, and pentazoles. Adv. Inorg. Chem. Radiochem. 31, in preparation. 

The triazoles are numbered to indicate the relative positions of the nitrogen atoms, tetrazole and pentazole are unambiguous names. 1,2,3-Triazoles are surprisingly stable, when one considers that they contain three directly-linked nitrogen atoms, but on flash vacuum pyrolysis at 500 °C they do lose nitrogen to give 2. f-azirines,... 

S.2.2.2 Al and Al Oxides Benzotriazole, imidazole, tetrazole, and pentazole were adsorbed on Al(lll) in the same spirit as the study on Cu(lll) [71]. The bonding of adsorbates on Al(lll) is not very different from that on Cu(lll), with the trend imidazole > triazole > tetrazole > pentazole. 

CATENATED NITROGEN LIGANDS PART II.1 TRANSITION METAL DERIVATIVES OF TRIAZOLES, TETRAZOLES, PENTAZOLES, AND HEXAZINE... 

Catenated Nitrogen Ligands Part II. Transition Metal Derivatives of Triazoles, Tetrazoles, Pentazoles, and Hexazine... 

Systematic replacement of CH in pyrrole 1 (Chapter 2.3) by N leads to nine additional monocyclic heteroaromatic nitrogen systems 2-10 (Figure 1), which are known collectively as azoles. Annular tautomerism is an important feature of all azoles having an NH function. For example, the triazoles 4 and 6, the triazoles 5 and 7, and the tetrazoles 8 and 9 can equilibrate by proton transfer (see Section 2.4.5). N-Substituted derivatives cannot equilibrate. Tautomers of the parent ring systems of all the azoles except pentazole 10 are known TV-aryl derivatives of pentazole have been characterized . 

While triazole compounds are not often energetic enough and pentazole species are kinetically too labile, the tetrazole derivatives often combine the desired endo-thermicity with kinetic stability (Fig. 9.7). Aminotetrazole (AT) and diaminotetraz-... 

Fig. 9.7 The basic structures of 1,2,4-triazole (a), tetrazole (b) and pentazole compounds (c).

In order to stabilize nitrogen-rich molecules, n aromatic delocahzation may be used. In this context five-membered heterocycles with three N atoms - triazoles -, four N atoms - tetrazoles -, and five N atoms - pentazoles - play an important role (Fig. 7). While triazoles often do not possess enough intrinsic energy to be suitable candidates for high explosives, pentazole derivatives are usually either far too sensitive and unstable for any application or need to be kinetically stabilized by bulky groups, which reduce the nitrogen con-... 

The classical age of preparative organic chemistry saw the exploration of the extensive field of five-membered heterocyclic aromatic systems. The stability of these systems, in contrast to saturated systems, is not necessarily affected by the accumulation of neighboring heteroatoms. In the series pyrrole, pyrazole, triazole, and tetrazole an increasing stability is observed in the presence of electrophiles and oxidants, and a natural next step was to attempt the synthesis of pentazole (1). However, pentazole has eluded the manifold and continual efforts to synthesize and isolate it. 

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