Derivatives of 1,5-diamino-1H-tetrazole: a new family of energetic heterocyclic-based salts

1,5-Diamino-1H-tetrazole (2, DAT) can easily be protonated by reaction with strong mineral acids, yielding the poorly investigated 1,5-diaminotetrazolium nitrate (2a) and perchlorate (2b). A new synthesis for 2 is introduced that avoids lead azide as a hazardous byproduct. The reaction of 1,5-diamino-1H-tetrazole with iodomethane (7a) followed by the metathesis of the iodide (7a) with silver nitrate (7b), silver dinitramide (7c), or silver azide (7d) leads to a new family of heterocyclic-based salts. In all cases, stable salts were obtained and fully characterized by vibrational (IR, Raman) spectroscopy, multinuclear NMR spectroscopy, mass spectrometry, elemental analysis, X-ray structure determination, and initial safety testing (impact and friction sensitivity). Most of the salts exhibit good thermal stabilities, and both the perchlorate (2b) and the dinitramide (7c) have melting points well below 100 degrees C, yet high decomposition onsets, defining them as new (7c), highly energetic ionic liquids. Preliminary sensitivity testing of the crystalline compounds indicates rather low impact sensitivities for all compounds, the highest being that of the perchlorate (2b) and the dinitramide (7c) with a value of 7 J. In contrast, the friction sensitivities of the perchlorate (2b, 60 N) and the dinitramide (7c, 24 N) are relatively high. The enthalpies of combustion (Delta(c)H degrees ) of 7b-d were determined experimentally using oxygen bomb calorimetry: Delta(c)H degrees (7b) = -2456 cal g(-)(1), Delta(c)H degrees (7c) = -2135 cal g(-)(1), and Delta(c)H degrees (7d) = -3594 cal g(-)(1). The standard enthalpies of formation (Delta(f)H degrees ) of 7b-d were obtained on the basis of quantum chemical computations using the G2 (G3) method: Delta(f)H degrees (7b) = 41.7 (41.2) kcal mol(-)(1), Delta(f)H degrees (7c) = 92.1 (91.1) kcal mol(-)(1), and Delta(f)H degrees (7d) = 161.6 (161.5) kcal mol(-)(1). The detonation velocities (D) and detonation pressures (P) of 2b and 7b-d were calculated using the empirical equations of Kamlet and Jacobs: D(2b) = 8383 m s(-)(1), P(2b) = 32.2 GPa; D(7b) = 7682 m s(-)(1), P(7b) = 23.4 GPa; D(7c) = 8827 m s(-)(1), P(7c) = 33.6 GPa; and D(7d) = 7405 m s(-)(1), P(7d) = 20.8 GPa. For all compounds, a structure determination by single-crystal X-ray diffraction was performed. 2a and 2b crystallize in the monoclinic space groups C2/c and P2(1)/n, respectively. The salts of 7 crystallize in the orthorhombic space groups Pna2(1) (7a, 7d) and Fdd2 (7b). The hydrogen-bonded ring motifs are discussed in the formalism of graph-set analysis of hydrogen-bond patterns and compared in the case of 2a, 2b, and 7b.     

Salts of methylated 5-aminotetrazoles with energetic anions

1-methyl-5-aminotetrazole (4, MAT) can easily be protonated by strong acids, yielding known but largely uninvestigated 1-methyl-5-aminotetrazolium nitrate (4a) and perchlorate (4b). Methylation, rather than protonation, of 4 with iodomethane followed by the exchange of the iodide (5a) for nitrate (5b), perchlorate (5c), azide (5d), and dinitramide (5e) yields a new family of energetic methylated aminotetrazole salts. In all cases, stable salts were obtained and fully characterized by vibrational (IR, Raman) spectroscopy, multinuclear NMR spectroscopy, mass spectrometry, elemental analysis, and X-ray structure determination. Compounds 4a, 4b, and 5c crystallize in the monoclinic space group P2(1)/n, whereas compounds 5b and 5e crystallize in the orthorhombic space group P2(1)2(1)2(1) and 5d in the orthorhombic Fddd. Initial safety testing (impact, friction, and electrostatic sensitivity) and thermal stability measurements (DSC) were also carried out. The MAT salts all exhibit good thermal stabilities (decomposition above 150 degrees C). The constant volume energies of combustion (DeltacU) of 4a, 5b, 5d, and 5e were determined to be -2510(10) cal/g, -3190(30) cal/g, -4500(100) cal/g, and -2570(70) cal/g, respectively, experimentally using oxygen bomb calorimetry. From the experimentally determined density, chemical composition and energies of formation (back calculated from the heats of combustion), the detonation pressures and velocities of 4a (8100 m/s, 25.6 GPa), 5b (7500 m/s, 20.2 GPa), 5d (8200 m/s, 21.7 GPa), and 5e (7500 m/s, 21.2 GPa) were predicted using the EXPLO5 code.     

Energetic salts of the binary 5-cyanotetrazolate anion ([C2N5]-) with nitrogen-rich cations

The reaction of cyanogen (NC-CN) with MN(3) (M=Na, K) in liquid SO(2) leads to the formation of the 5-cyanotetrazolate anion as the monohemihydrate sodium (1·1.5 H(2)O) and potassium (2) salts, respectively. Both 1·1.5 H(2)O and 2 were used as starting materials for the synthesis of a new family of nitrogen-rich salts containing the 5-cyanotetrazolate anion and nitrogen-rich cations, namely ammonium (3), hydrazinium (4), semicarbazidium (5), guanidinium (6), aminoguanidinium (7), diaminoguanidinium (8), and triaminoguanidinium (9). Compounds 1-9 were synthesised in good yields and characterised by using analytical and spectroscopic methods. In addition, the crystal structures of 1·1.5 H(2)O, 2, 3, 5, 6, and 9·H(2)O were determined by using low-temperature single-crystal X-ray diffraction. An insight into the hydrogen bonding in the solid state is described in terms of graph-set analysis. Differential scanning calorimetry and sensitivity tests were used to assess the thermal stability and sensitivity against impact and friction of the materials, respectively. For the assessment of the energetic character of the nitrogen-rich salts 3-9, quantum chemical methods were used to determine the constant volume energies of combustion, and these values were used to calculate the detonation velocity and pressure of the salts using the EXPLO5 computer code. Additionally, the performances of formulations of the new compounds with ammonium nitrate and ammonium dinitramide were also predicted. Lastly, the ICT code was used to determine the gases and heats of explosion released upon decomposition of the 5-cyanotetrazolate salts.     

Energetic salts from N-aminoazoles

New energetic salts (2, 3, 5, 6, 13, 14, 21, 22) were synthesized via the quaternization of derivatives of N-aminoazoles with nitric or perchloric acid or with iodomethane followed by metathesis reaction with silver nitrate or silver perchlorate. The structure of 2-amino-4,5-dimethyltetrazolium nitrate (21) was confirmed by single-crystal X-ray analysis. Most of the salts exhibit good thermal stabilities and low melting points. By using experimentally determined constant volume combustion energies, the standard molar enthalpies of formation were derived on the basis of designed Hess thermochemical cycles.     

Triaminoguanidinium dinitramide-calculations, synthesis and characterization of a promising energetic compound

The highly energetic compound 1,3,5-triaminoguanidinium dinitramide (1) was prepared in high yield (82%) according to a new synthesis by the reaction of potassium dinitramide and triaminoguanidinium perchlorate. The heat of formation was calculated in an extensive computational study (CBS-4M). With this the detonation parameters of compound were computed using the EXPLO5 software: D = 8796 m s(-1), p = 299 kbar. In addition, a full characterization of the chemical properties (single X-ray diffraction, IR and Raman spectroscopy, multinuclear NMR spectroscopy, mass spectrometry and elemental analysis) as well as of the energetic characteristics (differential scanning calorimetry, thermal safety calorimetry, impact, friction and electrostatic tests) is given in this work. Due to the high impact (2 J) and friction sensitivity (24 N) several attempts to reduce these sensitivities were performed by the addition of wax. The performance of was tested applying a "Koenen" steel sleeve test resulting in a critical diameter of > or =10 mm.     

Energetic Silver Salts with 5-Aminotetrazole Ligands

Methylation of 5-amino-1H-tetrazole ( 1 ) gives 1-methyl-5-amino-1H-tetrazole ( 2 ) and 2-methyl-5-amino-1H-tetrazole ( 3 ). A new family of energetic silver complexes based on ligands 1 , 2 and 3 with perchlorate and nitrate anions ( 10 – 15 ) were synthesized and characterized by using IR, Raman, and NMR (¹H, ¹³C, ¹⁴N, and ³⁵Cl NMR) spectroscopy, elemental analysis, and mass spectrometry. The crystal structures of the compounds were determined where possible and reveal interesting structural details that are discussed herein. Additionally, differential scanning calorimetry was used to assess the thermal stability of the new salts, which showed excellent thermal stabilities at temperatures up to and above 225 °C. Standard tests were also used to assess the sensitivity of the materials towards impact and friction. All the silver complexes showed increased sensitivity values in comparison with analogous protonated 5-amino-1H-tetrazolium perchlorate and nitrate salts. Some of these materials have sensitivity values that are comparable to commonly used primary explosives and all of them either deflagrate ( 12 – 14 ) or detonate loudly ( 10 and 11 ) on contact with an open flame. Lastly, nitrate salt 11 is easily initiated by thermal shock. It shows reasonably low sensitivity in comparison with other silver salts (e.g., silver azide or silver fulminate), which makes handling it much less hazardous. Compound 11 also has good thermal stability, decomposing at ≈300 °C, and shows interesting properties as a more environmentally benign alternative to lead(II) diazide in initiation devices for civil and military applications.     

Synthesis,Characterization, and Energetic Properties of Salts of the 1-Cyanomethyl-1,1-dimethylhydrazinium Cation

1,1-Dimethylhydrazine can be readily alkylated with bromoacetonitrile to form 1-cyanomethyl-1,1-dimethylhydrazinium bromide ([(CH₃)₂N(CH₂CN)NH₂]Br, 1 ). The metathesis reaction of compound 1 led to the formation of a new family of energetic salts based on the [(CH₃)₂N(CH₂CN)NH₂]⁺ cation and nitrate ( 2 ), perchlorate ( 3 ), azide ( 4 ), 5-aminotetrazolate ([H₂N-CN₄]⁻, 5 ), 5,5′-azobistetrazolate ([N₄C-NN-CN₄]²⁻, 7 ), and picrate ( 8 ) anions. The new materials were characterized by elemental analysis, mass spectrometry, and (multinuclear) NMR and vibrational (infrared and Raman) spectroscopies. Additionally, the molecular structure of the [(CH₃)₂N(CH₂CN)NH₂]⁺ cation in compounds 1 , 3 , and 8 and that of sodium 5,5′-azobistetrazolate octahydrate (NaZT⋅8 H₂O) were solved by X-ray diffraction techniques. The hydrogen-bonding networks found in the structure of salts 1 , 3 , 8 , and NaZT⋅8 H₂O are described using graph-set analysis. The melting and decomposition points of the new compounds were determined by differential scanning calorimetry, and insight into their sensitivity towards impact, friction, and electrostatics was gained by submitting the materials to standard tests. Furthermore, we estimated some performance parameters of interest and predicted the decomposition gases formed upon decomposition of salts 2 , 3 , 4 , 5 , 6 , 7 , 8 and of mixtures with an oxidizer. The interesting thermal, sensitivity, and performance properties of some of the compounds described in this work make them attractive towards a prospective energetic application.     

Synthesis and Characterization of Various Photosensitive Copper(II) Complexes with 5‐(1‐Methylhydrazinyl)‐1H‐tetrazole as Ligand and Perchlorate,Nitrate, Dinitramide,and Chloride as Anions

The preparation of 5‐(1‐methylhydrazinyl)‐1H‐tetrazole monohydrate ( 1 ?H₂O) and various copper(II) complexes with perchlorate ( 2 and 3 ), nitrate ( 4 , 5 , and 6 ), dinitramide ( 7 ), and chloride ( 8 ) is described. The coordination compounds (monomers, dimers, and polymers) were characterized through infrared spectroscopy and elemental analysis. Further, the structures of 2 and 4 – 8 were determined by single‐crystal X‐ray diffraction. Compound 1 can act as a bidentate ligand in its neutral form (HMHT) and as a μ₂‐ or μ₃‐bridging ligand in its deprotonated form (MHT). The energetic properties of the synthesized complexes, such as their sensitivities toward impact and friction, were determined, and laser ignition tests were performed. New information about the laser initiation process and the role of the anion in the initiation criterion was obtained. The perchlorate complexes 2 (T_decomp=217 °C) and 3 (T_decomp=206 °C) are potential primary explosives.     

Energetic Salts Based on an Oxygen‐Containing Cation: 2,4‐Diamino‐1,3,5‐triazine‐6‐one

A family of energetic salts with high thermal stability and low impact sensitivity based on an oxygen‐containing cation, 2,4‐diamino‐1,3,5‐triazine‐6‐one, were synthesized and fully characterized by IR and multinuclear (¹H, ¹³C) NMR spectroscopy, elemental analysis, and differential scanning calorimetry. Insights into their sensitivities towards impact, friction, and electrostatics were gained by submitting the materials to standard tests. The structures of 2,4‐diamino‐1,3,5‐triazine‐6‐one nitrate, 2,4‐diamino‐1,3,5‐triazine‐6‐one sulfate, 2,4‐diamino‐1,3,5‐triazine‐6‐one perchlorate, 2,4‐diamino‐1,3,5‐triazine‐6‐one 5‐nitrotetrazolate were determined by single‐crystal X‐ray diffraction; their densities are 1.691, 1.776, 1.854, and 1.636 g cm^?3, respectively. Most of the salts decompose at temperatures over 180 °C; in particular, the salts 2,4‐diamino‐1,3,5‐triazine‐6‐one nitrate and 2,4‐diamino‐1,3,5‐triazine‐6‐one perchlorate, which decompose at 303.3 and 336.4 °C, respectively, are fairly stable. Furthermore, most of the salts exhibit excellent impact sensitivities (>40 J), friction sensitivities (>360 N), and are insensitive to electrostatics. The measured densities of these energetic salts range from 1.64 to 2.01 g cm^?3. The detonation pressure values calculated for these salts range from 14.6 to 29.2 GPa, and the detonation velocities range from 6536 to 8275 m s^?1; these values make the salts potential candidates for thermally stable and insensitive energetic materials.     

Low melting inorganic salts of alkyl-, fluoroalkyl-, alkyl ether-, and fluoroalkyl ether-substituted oxazolidine and morpholine

N-Alkyl- and N-fluoroalkyl-substituted oxazolidinium- and morpholinium-based quaternary salts and ionic liquids have been synthesized and characterized. Reactions of N-methyloxazolidine (1) or N-methylmorpholine (2) with 3-fluoropropyl bromide or iodopropane in THF at 25 degrees C gave the quaternary salts (3a,b, 4a,b). These salts were metathesized with various metal salts to yield the corresponding ionic liquids (5a-h, 6a-i). N-Alkoxyethyl- and N-(fluoroalkoxy)ethyl-substituted morpholines (8-11) were prepared and quaternized with methyl iodide (8a-11a). Their corresponding ionic liquids (12-18) were obtained by anion exchange and characterized. For both series of compounds, nitrate, hexafluorophosphate, perchlorate, triflate, and bis(trifluoromethanesulfonyl)amide were utilized. Most of the final products are liquids at 25 degrees C and are thermally stable with long liquid ranges as determined by thermal gravimetric analyses. For compounds 12, 16, and 18, thermal stabilities of > or =400 degrees C were observed. All the new compounds were characterized by spectroscopic and elemental analyses. Their densities and viscosities were also determined.     

Heterocyclic-based nitrodicyanomethanide and dinitrocyanomethanide salts: a family of new energetic ionic liquids

Twelve novel energetic salts 1a-f and 2a-f with nitrodicyanomethanide and dinitrocyanomethanide anions paired with 1,5-diamino-4-methyltetrazolium, 1,4-dimethyl-5-aminotetrazolium 1,4,5-trimethyltetrazolium, 1-methyl-4-amino-1,2,4-triazolium, 1,4-dimethyltriazolium, and 1,3-dimethylimidazolium have been prepared through metathesis reactions of equivalent silver(I) salts with corresponding iodide salts in acetonitrile. Key physical properties, such as melting point, thermal stability and density, were measured. The relationship between their structures and these properties was determined. The structures of 1,5-diamino-4-methyltetrazolium-based salts 1a and 2a were further confirmed by single-crystal X-ray analysis. The densities and standard enthalpies of formation for these energetic salts were calculated. All of the salts possess higher enthalpies of formation than the nitrate analogues.     

Energetic 2,2‐Dimethyltriazanium Salts: A New Family of Nitrogen‐Rich Hydrazine Derivatives

Amination of 1,1‐dimethylhydrazine with NH₂Cl or hydroxylamine‐O‐sulfonic acid yields 2,2‐dimethyltriazanium (DMTZ) chloride ( 3 ) and sulphate ( 4 ), respectively. The DMTZ cation was paired with the nitrogen‐rich anions 5‐aminotetrazolate ( 5 ), 5‐nitrotetrazolate ( 6 ), 5,5′‐azobistetrazolate ( 7 ), and azide ( 8 ), yielding a new family of energetic salts. The synthesis was carried out by metathesis reactions of salts 3 or 4 and a suitable silver or barium salt. To minimize the risks involved when using heavy metal salts, we used electrodialysis for the synthesis of azide 8 , which avoids the use of highly sensitive species. The DMTZ derivatives were characterized by IR and multinuclear NMR spectroscopy, elemental analysis, and X‐ray diffraction. Thermal stabilities were measured using DSC analysis and their sensitivities towards classical stimuli were determined using standard tests. Lastly, the relationship between hydrogen bonding in the solid state and sensitivity is discussed.     

The first 1-alkyl-3-perfluoroalkyl-4,5- dimethyl-1,2,4-triazolium salts

Syntheses of quaternary 1-alkyl-3-perfluoroalkyl-4,5-dimethyl-1,2,4-triazolium iodides have led to a variety of new quaternary salts via metathesis reactions. 1,4,5-Trimethyl-3-trifluoro-methyl-1,2,4-triazolium iodide (6) with LiN(SO(2)CF(3))(2), KSO(3)CF(3), AgClO(4), AgBF(4); 1-(3-fluoropropyl)-3-trifluoromethyl-4,5-dimethyl-1,2,4-triazolium iodide (7) with LiN(SO(2)CF(3))(2); and 1,4,5-trimethyl-3-perfluorooctyl-1,2,4-triazolium iodide (8) with LiN(SO(2)CF(3))(2), AgClO(4), AgBF(4) gave excellent yields of new thermally stable and relatively low melting quaternary salts. The structure of 1,4,5-trimethyl-3-perfluorooctyl-1,2,4-triazolium tetrafluoroborate (11c) was confirmed by single-crystal X-ray analysis. Although the molecular weight of 11c (cation) is 3-fold greater than that of the 3-trifluoromethyl derivative 9d, its melting point is 32 degrees C lower.     

Energetic bicyclic azolium salts

Bicyclic azoles, 2-methyl-5-(imidazol-1-yl)-2H-tetrazole (1), 2-methyl-5-(1,2,4-triazol-1-yl)-2H-tetrazole (4), 1-methyl-5-(imidazol-1-yl)-1H-tetrazole (7), 1-methyl-5-(1,2,4-triazol-1-yl)-1H-tetrazole (10), 1-methyl-4-nitro-2-(imidazol-1-yl)-1H-imidazole (13), and 1-methyl-4-nitro-2-(1,2,4-triazol-1-yl)-1H-imidazole (16) were prepared. Their thermally stable azolium salts, 3, 6, 9, 12, 15, and 18-21, with densities ranging between 1.519-1.674 g cm-3, were synthesized by quaternization with nitric or perchloric acid or with iodomethane followed by metathesis reactions with silver nitrate and silver perchlorate. The structures of 12 b and 21 b were confirmed by single-crystal X-ray analysis. The standard enthalpies of formation for some of the new salts were calculated by using the computationally feasible DFT(B3LYP) and MP2 methods in conjunction with an empirical approach based on densities of salts. The calculated values range from DeltaHdegreef=209.9 (21 a) to 412.3 (12 b) kJ mol-1 in which the experimental densities are >1.515 g cm-3.     

Decomposition of aminotetrazole based energetic materials under high heating rate conditions

A T-jump/time-of-flight mass spectrometer (T-Jump/TOFMS) is used to probe the decomposition of several aminotetrazole containing energetic materials under very high heating rates of 10(5)-10(6) K/s. The materials investigated are 5-amino-1-methyl-1H-tetrazolium dinitramide (MeHAT_DN), 1,5-diamino-4-methyl-1H-tetrazolium dinitramide (MeDAT_DN), 1,5-diamino-1H-tetrazolium nitrate (DAT_N), 1,5-diamino-4-methyl-1H-tetrazolium azide (MeDAT_N3), and 5-aminotetrazolium dinitramide (HAT_DN). Subtle differences between materials in functional group placement and anion composition allow for further understanding of the decomposition pathway of the tetrazole structure and various anions. Two decomposition pathways for the tetrazole ring are observed, which result in the primary formation of HN(3) or N(2). The N(2) formation pathway occurs when functional groups are placed symmetrically around the tetrazole ring, whereas asymmetric placement results in HN(3) production. The differing anion compositions also show effects on thermal stability of the salts, as is demonstrated by a lower decomposition temperature for the azide containing salt compared to the similar dinitramide containing material. For the decomposition of the dinitramide molecule, high temperature (N(2)O forming) and low temperature (NO(2) forming) decomposition pathways are observed, as has been previously suggested.     

Synthesis of 5‐Aminotetrazole‐1 N‐oxide and Its Azo Derivative: A Key Step in the Development of New Energetic Materials

1‐Hydroxy‐5‐aminotetrazole ( 1 ), which is a long‐desired starting material for the synthesis of hundreds of new energetic materials, was synthesized for the first time by the reaction of aqueous hydroxylamine with cyanogen azide. The use of this unique precursor was demonstrated by the preparation of several energetic compounds with equal or higher performance than that of commonly used explosives, such as hexogen (RDX). The prepared compounds, including energetic salts of 1‐hydroxy‐5‐aminotetrazole (hydroxylammonium ( 2 , two polymorphs) and ammonium ( 3 )), azo‐coupled derivatives (potassium ( 5 ), hydroxylammonium ( 6 ), ammonium ( 7 ), and hydrazinium 5,5′‐azo‐bis(1‐N‐oxidotetrazolate ( 8 , two polymorphs)), as well as neutral compounds 5,5′‐azo‐bis(1‐oxidotetrazole) ( 4 ) and 5,5′‐bis(1‐oxidotetrazole)hydrazine ( 9 ), were intensively characterized by low‐temperature X‐ray diffraction, IR, Raman, and multinuclear NMR spectroscopy, elemental analysis, and DSC. The calculated energetic performance, by using the EXPLO5 code, based on the calculated (CBS‐4M) heats of formation and X‐ray densities confirm the high energetic performance of tetrazole‐N‐oxides as energetic materials. Last but not least, their sensitivity towards impact, friction, and electrostatic discharge were explored. 5,5′‐Azo‐bis(1‐N‐oxidotetrazole) deflagrates close to the DDT (deflagration‐to‐detonation transition) faster than all compounds that have been investigated in our research group to date.     

High‐Oxygen‐Balance Furazan Anions: A Good Choice for High‐Performance Energetic Salts

3,4‐Diaminofurazan was conveniently converted into energetic salts of 3,4‐dinitraminofurazan that were paired with nitrogen‐rich cations in fewer than three steps. Seven energetic salts were prepared and fully characterized by multinuclear (¹H, ¹³C) NMR and IR spectroscopy, differential scanning calorimetry (DSC), and elemental analysis. In addition, the structures of the ammonium salt ( 2 ), hydrazinium salt ( 4 ), hydroxylammonium salt ( 5 ), aminoguanidinium salt ( 7 ), diaminoguanidinium salt ( 8 ) and triaminoguanidinium salt of 3,4‐dinitraminofurazan ( 9 ) were further confirmed by single‐crystal X‐ray diffraction. The densities of these salts were between 1.673 ( 8 ) and 1.791 g cm^?3 ( 5 ), whilst their oxygen balances were between ?48.20 % ( 9 ) and ?6.25 % ( 5 ). These salts showed high thermal stabilities, with decomposition temperatures between 179 ( 5 ) and 283 °C ( 6 ). Their sensitivities towards impact and friction were measured by BAM equipment to be between <1 J ( 9 ) and >40 J ( 6 – 8 ) and 64 N ( 9 ) and >360 N ( 6 ), respectively. The detonation performance of these compounds, which was calculated by using the EXPLO5 program, revealed detonation pressures of between 28.0 ( 6 ) and 40.5 GPa ( 5 ) and detonation velocities of between 8404 ( 6 ) and 9407 m s^?1 ( 5 ).     

Hydroxylammonium 5‐Nitriminotetrazolates

The hydroxylammonium salts of monodeprotonated 5‐nitriminotetrazole ( 4 ), double deprotonated 5‐nitriminotetrazole ( 5 ), 1‐methyl‐5‐nitriminotetrazole ( 6 ), and 2‐methyl‐5‐nitraminotetrazole ( 7 ) have been prepared in high yield from the corresponding 5‐nitriminotetrazoles as free acids and an aqueous solution of hydroxylamine or the metathesis reactions of hydroxylammonium hydrochloride with the silver salt of the corresponding nitriminotetrazole, respectively. The energetic salts 4 – 7 were fully characterized by single‐crystal X‐ray diffraction ( 4 – 6 ), NMR spectroscopy, IR‐ and Raman spectroscopy as well as DSC measurements. The sensitivities towards impact, friction and electrical discharge were determined. In addition, several detonation parameters (e.g. heat of explosion, detonation velocity) were computed by the EXPLO5.04 computer code based on calculated (CBS‐4M) heats of formation and X‐ray densities.     

The dianion of 5-cyanoiminotetrazoline: C2N62-

Several salts (alkali, Pd(NH(3))(3), and (i)PrNH(2)) of 5-cyanoiminotetrazoline (C(2)N(6)(2-), 5-cyanoiminotetrazolinediide, CIT) were investigated. A full characterization by means of X-ray, Raman, NMR techniques, mass spectrometry, and elemental analysis is presented for the (i)()PrNH(2) (4), Cs (5), and Pd(NH(3))(3) (6) salts. The CIT dianion represents a nitrogen-rich binary CN dianion, and 5 forms monoclinic crystals (a = 7.345(2) Angstroms, b = 9.505(2) Angstroms, c = 10.198(2) Angstroms, beta = 92.12(3) degrees, space group P2(1)/n, Z = 4). DSC and in situ temperature-dependent X-ray diffraction measurements of the cesium salt 5 revealed an astonishing thermal stability accompanied by a reversible phase transition from the low-temperature alpha modification to the metastable beta modification at 253 degrees C. Above the melting point (334 degrees C), the cesium salt decomposes yielding cesium azide and cesium dicyanamide, which decomposes under further heating under release of nitrogen. The reaction of Cs(2)CIT with SO(2) resulted in the surprising formation of a new cesium salt with the 5-cyaniminotetrazoline-1-sulfonate dianion (Cs(2)CITSO(3).SO(2) (7)). 7 crystallizes in the monoclinic space group P2(1) with one SO(2) solvent molecule (a = 8.0080(2) Angstroms, b = 8.0183(2) Angstroms, c = 9.8986(3) Angstroms, beta = 108.619(1) degrees, Z = 2). The structure and bonding of the 10pi dianion are discussed on the basis B3LYP/aug-cc-pvTZ computations (MO, NBO), and the three-dimensional array of the cesium salts with respect to the Cs(delta) (+)-N(delta)(-) in 5 compared to the Cs(delta)(+)-N(delta)(-) and Cs(delta)(+)-O(delta)(-) in 7 is discussed. Due to the expected rich bonding modes of the CIT anions, the coordination chemistry with palladium was also studied, yielding monoclinic crystals of [Pd(CIT)(NH(3))(3)].H(2)O (6, a = 7.988(2) Angstroms, b = 8.375(2) Angstroms, c = 13.541(3) Angstroms, beta = 104.56 degrees, space group P2(1)/n, Z = 4). In the solid state, the complex is composed of dimers, showing two agostic interactions and an unusual close interplanar pi-pi stacking of the tetrazole moiety of the CIT ligand.     

Selective Synthesis and Characterization of the Highly Energetic Materials 1-Hydroxy-5H-tetrazole (CHN4O), its Anion 1-Oxido-5H-tetrazolate (CN4O−) and Bis(1-hydroxytetrazol-5-yl)triazene

For the first time, an adequate selective synthesis, circumventing the formation of 2-hydroxy-5H-tetrazole, of 1-hydroxy-5H-tetrazole (HTO), as well as the synthesis of bis(1-hydroxytetrazol-5-yl)triazene (H₃T) are reported. Several salts thereof were synthesized and characterized which resulted in the formation of new primary and secondary explosives containing the 1-oxidotetrazolate unit. Molecular structures are characterized by single-crystal X-ray diffraction, ¹H and ¹³C NMR, IR, and elemental analysis. Calculation of the detonation performance using the Explo5 code confirmed the energetic properties of 1-hydroxy-5H-tetrazole. The detonation properties can be adjusted to the requirements for those of a secondary explosive by forming the hydroxylammonium ( 6 ) or hydrazinium ( 7 ) salts, or to meet the requirements of a primary explosive by forming the silver salt 4 , which shows a fast DDT on contact with a flame. The sensitivities of all compounds towards external stimuli such as impact, friction, and electrostatic discharge were measured.