Explosive Werner-type cobalt(iii) complexes

Abstract

A series of potentially explosive Werner-type cobalt(iii) complexes comprising the anions azotetrazolate, nitrotetrazolate, picrate and dipicrylamide were prepared via simple metathetical routes. Treatment of [Co(NH3)5NO2]Cl2, trans-[Co(NH3)4(py)NO2]Cl2 (py = pyridine), trans-[Co(NH3)4(NO2)2]Cl, and [Co(NH3)5N3]Cl2 with equimolar amounts of disodium azotetrazolate, (Na2C2N10·5H2O, 1), in aqueous solutions afforded new cobalt(iii) azotetrazolate salts [Co(NH3)5NO2](C2N10)·2H2O (2), trans-[Co(NH3)4(py)NO2](C2N10)·2H2O (3), trans-[Co(NH3)4(NO2)2]2(C2N10) (4), and [Co(NH3)5N3](C2N10)·H2O (5) in moderate to excellent yields (46-88%). Similar treatment of trans-[Co(NH3)4(NO2)2]Cl with 1 equiv. of sodium 5-nitrotetrazolate dihydrate (= NaNT, 6) afforded the novel cobalt(iii) 5-nitrotetrazolate derivative trans-[Co(NH3)4(NO2)2](NT)·H2O (7) as orange, rectangular prismatic crystals in 64% yield. Two complex cobalt(iii) picrates, trans-[Co(NH3)4(NO2)2](picrate)·H2O (9) and [Co(NH3)5N3](picrate)2 (10), were prepared in a similar manner from the corresponding chloride precursors and equimolar amounts of sodium picrate. The reaction of trans-[Co(NH3)4(NO2)2]Cl with sodium dipicrylamide (= NaDPA) in a 1 : 1 molar ratio gave the first cobalt(iii) dipicrylamide, trans-[Co(NH3)4(NO2)2](DPA)·H2O (12). Finally, the highly explosive, dark blue-green dichroitic non-electrolyte complex mer-[Co(en)(py)(N3)3] (13) was formed upon treatment of [Co(en)(py)2(NH3)Cl]Cl2·H2O with excess NaN3 in hot water (93% yield). The molecular and crystal structures of 2, 3, 4, 5, 7, 9, 10, 12, and 13 were determined by single-crystal X-ray diffraction. In the solid state, all compounds comprised extensive hydrogen-bonded supramolecular networks. Representative studies of the energetic properties (impact and friction sensitivity, combustion) revealed that some of the new compounds can be classified as primary explosives.