The performance of a high explosive is measured by its detonation velocity (v D (km sec À1 )) and detonation pressure (P CJ (kbar)). These parameters are determined by the oxygen balance (OB CO ), [1a] density (1), and heat of formation (DH f ), [1b] the higher the oxygen balance, density, and heat of formation, the better the performance. The energy of traditional polynitro compounds (Scheme 1) is primarily derived from the combustion of the carbon backbone using the oxygen carried by the nitro group. [2] For modern polynitro compounds (Scheme 2), the performance is enhanced not only by an excellent oxygen balance but also by a ring/cage strain which improves both the heat of formation and density. [4] Recently, a new class of energetic compounds containing a large fraction of nitrogen has been investigated. [5][6][7][8] These "high-nitrogen" compounds form a unique class of energetic materials [5a, 9] whose energy is derived from their very high positive heat of formation rather than from the combustion of the carbon backbone or the ring/cage strain (Scheme 3). The high heat of formation is directly attributable to the large number of inherently energetic NÀN and CÀN bonds.High-nitrogen compounds containing polyazides possess even higher heats of formation because their energy content rapidly increases with the number of energetic azido groups in the molecule. However, they are notorious for their extreme sensitivity [10a] to spark, friction, and impact (H 50 ) [10b] as well as poor thermal stability, [10a, 11, 12] so their applications are very limited. Examples include 3,6-diazido-1,2,4,5-tetrazine [13] and cyanuric azide (2,4,6-triazido-1,3,5-triazine; [14] Scheme 4).

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