BTA Copper Complexes

Cupric oxide is one of the most important additives used (a) to catalyze decomposition reactions in gas generators
to obtain cooler reaction gases, (b) as burning enhancer for ammonium perchlorate-based composite propellants,
and (c) as coloring agent in pyrotechnics. In this context, the reaction of Cu2+ ions in aqueous ammonia solution
with bis(tetrazolyl)amine (H2bta) was investigated. Depending on the reaction conditions three complexes were
obtained:  Cu(bta)(NH3)2 (1), Cu(bta)(NH3)2·H2O (2), and (NH4)2Cu(bta)2·2.5H2O (3). The crystal structures of 1
and 2 are discussed with respect to the coordination mode of the dianion of N,N-bis(1(2)H-tetrazol-5-yl)-amine
(bta), which mediates in the case of 1 and 2 weak superexchange interactions between the adjacent magnetic
transition-metal CuII cations. These antiferromagnetic interactions result from 1D copper chains over an hidden
azide end-to-end bridge. Interestingly, the structural arrangement of 1 completely changes in the presence of
crystal-bound water. Moreover, some physicochemical properties (e.g., heat of formation, friction, and impact sensitivity,
DSC) of these complexes with respect to high-energetic materials are discussed.