Metal salts of the 4,5-dicyano-2H-1,2,3-triazole anion ([C4N5])Electronic supplementary information (ESI) available: General method, calculated IR/Raman frequencies, X-ray tables for compounds 4, 6 and 8b and graph-set analysis of compounds 6 and 8b. CCDC reference numbers 852499852501. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2dt12100j

Diaminomaleodinitrile was reacted at low temperatures with in situ generated nitrous acid to form 4,5-dicyano-2 H -1,2,3-triazole ( 1 ) in yields above 90%. Crystalline 1 was then reacted with one equivalent of a suitable alkali or alkaline earth metal base (typically a hydroxide or a carbonate) in a polar solvent to form the corresponding alkali and alkaline earth metal salts of 4,5-dicyano-2 H -1,2,3-triazole (compounds 29 ). The thermal stability of the metal salts 29 was assessed by differential scanning calorimetry, which showed excellent thermal stabilities up to above 350 C. Due to the energetic character of triazole-based salts, initial safety testing was used to assess the sensitivity of compounds 29 towards impact, friction, electrostatic discharge and fast heating. These results revealed very low sensitivities towards all four stimuli. Additionally, compounds 29 were characterized by mass spectrometry, elemental analysis, infrared and Raman spectroscopy and ( 1 H, 13 C and 14 N) NMR spectroscopy. We also determined the solid state structure of the 4,5-dicyano-2 H -1,2,3-triazole anion of one of the alkali metal salts ( 4 : Monoclinic, P 2 1 / c , a = 9.389(1) , b = 10.603(1) , c = 6.924(1) , = 102.75(1) and V = 1036.58(3) 3 ) and one of the alkaline earth metal salts ( 6 : Monoclinic, P 2 1 / c , a = 9.243(1) , b = 15.828(2) , c = 6.463(1) , = 90.23(1) and V = 945.5(2) 3 ). Furthermore, we noted the hydrolysis of one of the cyano groups of the 4,5-dicyano-2 H -1,2,3-triazole anion in the strontium salt 8 to form the 5-cyano-2 H -1,2,3-triazole-4-carboxylic acid derivative 8b , as confirmed by X-ray studies ( 8b : Monoclinic, P 2 1 / n , a = 6.950(1) , b = 17.769(1) , c = 13.858(1) , = 92.98(1) and V = 1709.1(1) 3 ). Lastly, we computed the NBO and Mlliken charges for the anion of compounds 29 and those of the anion of compound 8b . Metal salts of the 4,5-dicyano-2 H -1,2,3-triazole anion exhibit promising energetic properties, which suggest their potential for use as pyrotechnics.