Nitrogen Rich Salts Based on Energetic

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FULL PAPER, syntheses and energetic properties of salts that contain both zation had occurred for 2 due to a proton shift Scheme 2. nitroamino and azido groups in the cation or anion have not Isomers I and III are equivalent due to the fast proton. been well investigated movement in solution and display three distinct carbon sig. In this work we have investigated the energetic proper. ties of salts derived from an anion that contains both nitro. ACHTUNGREamino and azido groups 1 3 5 Triazine is an ideal backbone. for constructing energetic compounds due to its three readi. ly tunable ring positions through which 6 nitroamino 2 4. diazidoACHTUNGRE 1 3 5 triazine NADAT and 4 6 dinitroamino 2. azidoACHTUNGRE 1 3 5 triazine might be synthesized 4 6 Bis nitroimi. no 1 3 5 triazinan 2 one DNAM a high energetic s tria Scheme 2 Isomerization of 6 nitroamino 2 4 diazidoACHTUNGRE 1 3 5 triazine 2 in. solution through 1 3 H shift, zine derivative has been investigated in detail 4b 9 In a re. cently published patent Fronabarger et al reported the syn. theses of 6 nitroamino 2 4 diazidoACHTUNGRE 1 3 5 triazine and its po. tassium and rubidium salts 10 however the energetic prop nals at d 164 7 159 8 and 151 7 ppm because of the re. erties and reactivities of these compounds were little stricted rotation of the exocyclic C N bond that resulted in. studied Now we report the syntheses and characterization the inequivalence of C2 and C3 15 Isomer II displays two. of salts based on NADAT in combination with nitrogen rich carbon signals at d 171 7 and 164 8 ppm due to the free. cations Salts of 3 4 5 triamino 1 2 4 triazole guanazine rotation of the exocyclic C N bond No signal coalescence. with promising energetic anions were also prepared and but slow compound decomposition was observed when the. fully characterized here The detonation properties of these proton decoupled 13C NMR spectrum was attempted at. compounds have been calculated and the values suggest that 90 8C The proton decoupled 15N NMR spectrum of 2 was. they are insensitive energetic materials measured in D6 DMSO and seventeen signals ranged from. d 19 62 to 262 56 ppm with respect to CH3NO2 as an ex. ternal standard were found due to the isomerization the. Results and Discussion spectrum is shown in the Supporting Information. By taking advantage of the inherent high acidity of the ni. As shown in Scheme 1 6 amino 2 4 diazidoACHTUNGRE 1 3 5 triazine 1 troamino group 2 was treated directly with guanidinium car. was prepared by the selective monoamination of cyanuric bonate aminoguanidinium bicarbonate neutral 4 amino. chloride with aqueous ammonia at 0 8C followed by azido 1 2 4 triazole 3 5 diamino 1 2 4 triazole and 3 4 5 triamino. 1 2 4 triazole guanazine in water to form the correspond. ing salts 3 4 7 8 and 10 in excellent yields Scheme 3 By. using potassium carbonate as a base 2 could be convenient. ly deprotonated and then underwent metathesis reactions. with organic sulfate or halides to achieve the products 5 6. and 9 The barium or silver salt of 2 was not needed for. Scheme 1 Syntheses of 6 nitroamino 2 4 diazidoACHTUNGRE 1 3 5 triazine NADAT these metathesis reactions due to the relatively lower solu. 2 bility of the organic salts compared to that of the potassium. salt However only the potassium salt of 2 was recovered. substitution with sodium azide in acetone H2O 1 1 11 Sev from the water solution when diaminoguanidinium chloride. eral reagents for the nitration of the amino group in 1 to or triaminoguanidinium chloride were used as reactants. give the nitroamino group are available such as nitric acid under the same conditions Compound 2 was isolated when. in Ac2O or sulfuric acid 12 alkyl nitrate in alcohol 13 and ni 5 aminotetrazolium chloride was used as a cation source. tronium salt NO2BF4 in acetonitrile 14 Here 100 nitric which suggests that 5 aminotetrazole is the more acidic of. acid was used for the nitration of 1 to afford 6 nitroamino the two compounds The barium or silver salt of 2 may need. 2 4 diazidoACHTUNGRE 1 3 5 triazine NADAT 2 as a white powder in to be prepared in the future in order to obtain additional ni. 54 yield 10 Colorless flat crystals which were submitted trogen rich salts based on the NADAT anion. for single crystal X ray analysis can be obtained by recrys The three amino groups of guanazine should give rise to. tallization from hot water Strong absorption bands at n the formation of significantly hydrogen bonded networks. 1553 1334 and 1279 cm 1 in the IR spectrum of 2 support which could result in salts with high densities This property. the successful introduction of the nitro group makes guanazine a reasonable candidate for achieving ionic. One broad singlet in the 1H NMR spectrum of 2 appeared energetic compounds Recently guanazinium 16 and methyl. at d 11 57 ppm Unusual behavior of 2 in solution was ob guanazinium 17 salts with anions such as perchlorate nitrate. served in the 13C NMR spectrum acquired in D6 DMSO 10 5 nitrotetrazolate dinitramide and bistetrazolate were syn. Five signals at d 171 7 164 8 164 7 159 8 and 151 7 ppm thesized and fully characterized In our current work guana. in the proton decoupled 13C NMR spectrum of 2 recorded at zinium salts with such energetic anion counterparts as 4 ni. room temperature were found which indicated that isomeri troamino 1 2 4 triazole 11 18 N N bis 1H tetrazol 5 yl. Chem Eur J 2011 17 1538 1546 2011 Wiley VCH Verlag GmbH Co KGaA Weinheim www chemeurj org 1539. J M Shreeve et al, ACHTUNGREimino group which has restricted free rotation of the C N. bond and resulted in the inequivalence of C2 and C3 The. proton decoupled 15N NMR spectrum of salt 6 was also re. corded in D6 DMSO and eleven signals were found in addi. tion to the three signals for the guanylurea cation at d. 270 26 291 75 and 296 83 ppm 22 which clearly indi. cated the unsymmetric character of the NADAT anion due. to the formation of a nitroimino structure see the spectrum. in the Supporting Information, The melting points Tm and the decomposition tempera. tures Td of compounds 3 15 were obtained by using differ. ential scanning calorimetry DSC from the first heating. cycle at a heating rate of 5 8C min 1 As shown in Table 1. for salts 3 10 in which the NADAT anion was present only. 5 and 6 appear sufficiently thermally stable melting at 136. and 152 8C respectively For compounds 3 10 thermal deg. radation temperatures Td are in the range of 130 8C 4. amino 1 2 4 triazolium 7 to 196 8C aminocarbonylguanidi. nium 6 For salts 10 15 which contain the same guanizini. um cation better thermal stability were exhibited with Td in. the range of 191 257 8C As one of the important physical. properties of energetic salts densities of 3 15 were mea. sured by using a gas pycnometer Table 1 and found to fall. in the range of 1 60 1 78 g cm 3 The densities were also esti. mated by employing our tabulated volume parameters 23. which agree reasonably well with the experimental values. Scheme 3 Syntheses of the 6 nitroamino 2 4 diazidoACHTUNGRE 1 3 5 triazine salts Oxygen balance W is used to indicate the degree to which. 3 10 a compound can be oxidized Compounds 3 15 possess neg. ative oxygen balances that are in the range of 24 8 to. 62 0 which are comparable to TNT 24 7 For, amine 12 19 5 nitroiminotetrazole 13 4 trinitroimidazole compounds 10 15 which contain the same guanazinium.
14 20 and 3 amino 6 nitroamino tetrazine 15 21 were syn cation trinitroimidazolate 14 shows the best oxygen balance. thesized and their thermal properties were studied 12 6 due to three nitro groups in the anion Impact. sensitivities of the salts 3 13 and 15 were determined by. using a BAM Fall hammer apparatus with a 10 kg drop. weight with approximately 15 mg samples 24 and found to. be in the range of 20 to 40 J which places them in the less. sensitive class It is worthwhile to point out that all of the. salts are stable upon storing for two years at room tempera. ture without significant change in the 1H and 13C NMR spec. Heat of formation DfH is another important parameter. in evaluating the performance of energetic salts This prop. erty can be calculated with good accuracy from the lattice. energy of the salts The heat of formation of the cations and. anions 25 were calculated by using Gaussian 03 26 The calcu. lated DfH values of nitrogen rich cations vary between. 350 59 aminocarbonylguanidinium 6 and 1903 56 kJ mol 1. diguanidinotetrazinium 9 The DfH value of the 6 nitro. All ionic compounds 3 15 were characterized by IR ACHTUNGREamino 2 4 diazidoACHTUNGRE 1 3 5 triazine anion is 651 80 kJ mol 1. H NMR and 13C NMR spectroscopy and elemental analy which is higher than the values of the other energetic anions. ses Three signals at d 151 7 159 8 and 164 8 ppm as selected for making salts 11 15 The positive heats of forma. signed to the NADAT anion were observed in the 13C NMR tion DfH of salts 3 15 are calculated by using the Born. spectra of compounds 3 10 This result further confirmed Haber energy cycles see the Experimental Section and. the explanation for the five signals in the 13C NMR spec fall in the range of 0 72 14 to 3 68 kJ g 1 7. trum of 2 because the electron delocalization of the anion The performance of a high explosive is characterized by. causes the exocyclic nitroamino group to resemble a nitro its detonation velocity vD m s 1 and detonation pressure. 1540 www chemeurj org 2011 Wiley VCH Verlag GmbH Co KGaA Weinheim Chem Eur J 2011 17 1538 1546. Nitrogen Rich Energetic Salts,FULL PAPER,Table 1 Thermal properties of energetic salts. Salt 1 a Tm b Td c W d fHcation e fHanion f fHlat g fHsalt h P i vD j IS k. ACHTUNGRE g cm 3 8C 8C ACHTUNGRE kJ mol 1 ACHTUNGRE kJ mol 1 ACHTUNGRE kJ mol 1 ACHTUNGRE kJ mol 1 ACHTUNGRE kJ g 1 ACHTUNGRE GPa ACHTUNGRE m s 1 J. 3 1 60ACHTUNGRE 1 63 190 28 4 575 85 651 80 462 04 765 61 2 71 22 2 7859 20. 4 1 68ACHTUNGRE 1 64 168 29 6 667 41 651 80 461 68 857 53 2 89 26 3 8431 20. 5 1 63ACHTUNGRE 1 65 136 151 24 8 1618 16 651 80 1346 03 1575 73 2 88 22 7 7866 28. 6 1 63ACHTUNGRE 1 69 152 196 27 1 350 59 651 80 447 81 554 58 1 71 21 0 7675 40. 7 1 68ACHTUNGRE 1 67 130 28 6 936 28 651 80 457 81 1130 27 3 68 25 3 8178 25. 8 1 67ACHTUNGRE 1 66 158 29 8 763 99 651 80 451 62 964 17 3 00 23 9 8073 40. 9 1 63ACHTUNGRE 1 63 193 27 4 1903 56 651 80 1295 44 1911 72 2 98 22 0 7768 40. 10 1 68ACHTUNGRE 1 68 191 30 8 841 98 651 80 447 13 1046 65 3 10 25 2 8280 25. 11 1 71ACHTUNGRE 1 63 219 42 8 841 98 141 50 488 31 495 16 2 04 27 0 8646 40. 12 1 63ACHTUNGRE 1 63 170 257 50 9 841 98 500 1 470 75 871 33 3 26 24 3 8399 40. 13 1 78ACHTUNGRE 1 69 231 32 8 841 98 9 8 492 91 358 87 1 47 30 3 9048 40. 14 1 71ACHTUNGRE 1 76 196 l 242 l 12 6 841 98 156 68 456 15 229 15 0 72 25 8 8055 m. 15 1 64ACHTUNGRE 1 65 103 209 62 0 841 98 260 71 496 24 632 98 2 33 24 8 8323 40. a Measured density calculated density b Melting point c Decomposition temperature d CO oxygen balance W is an index of the deficiency or. excess of oxygen in a compound required to convert all C into CO and all H into H2O For a compound with the molecular formula of CaHbNcOd with. out crystal water W 1600 d a b 2 Mw e Calculated molar enthalpy for the formation of the cation f Calculated molar enthalpy for the. formation of the anion g Calculated molar lattice energy h Calculated molar enthalpy for the formation of the salt i Detonation pressure j Deto. nation velocity k Impact sensitivity l Measured at a heating rate of 10 8C min 1 m Not determined. P GPa 27 These parameters are directly related to the. oxygen balance OB density and heat of formation and. were calculated based on the traditional Chapman Jouget. thermodynamic detonation theory suggested by Kamlet and. Jacobs 28 with the program Cheetah 5 0 29 The calculated. detonation pressures P for the new salts fall in the range. of 21 0 6 to 30 3 GPa 13 and the detonation velocities. nD are distributed from 7675 6 to 9048 m s 1 13 Al. though the denotation data are lower than the correspond. ing values for RDX P 33 8 GPa vD 8750 m s 1 most,of them are superior to TNT P 20 6 GPa nD. 6850 m s 1 and thus the investigated compound may be of. interest as potential energetic materials For salts 3 10 with. the same anion the aminoguanidinium salt 4 P, 26 3 GPa nD 8431 m s 1 exhibits the best performance. and for salts 10 15 which contain the guanazinium cation Figure 1 a Thermal ellipsoid plot 30 and labeling scheme for 6 ni. the nitroiminotetrazolate 13 P 30 3 GPa nD troamino 2 4 diazidoACHTUNGRE 1 3 5 triazine NADAT 2 Hydrogen atoms are in. 9048 m s 1 and 4 nitroamino 1 2 4 triazolate 11 P cluded but are unlabelled for clarity b Packing diagram of 2 viewed. 27 0 GPa nD 8646 m s 1 exhibit excellent performance down the a axis. X ray crystallography Crystals of 2 and its biguanidinium the N C N angles from 126 97 10 to 127 49 10 8 The angles. salt 5 that were suitable for X ray diffraction were obtained for the two azido groups are 171 63 12 N11 N10 N9 and. by slow recrystallization from water at room temperature 171 92 13 N14 N13 N12 respectively which differ not vir. The structures are shown in Figures 1 and 2 Crystallograph tually from analogous parameters for the molecules of. ic and structural refinement data are listed in Table 2 Com azido substituted 1 3 5 triazines 32 The planar molecules. pound 2 crystallized in the orthorhombic space group Pnma are assembled through hydrogen bonds and strictly parallel. with a calculated density of 1 836 g cm 3 based on four mole to the 001 plane Figure 1 b Intermolecular hydrogen. Nitrogen Rich Salts Based on Energetic NitroaminodiazidoACHTUNGRE 1 3 5 triazine and Guanazine Yangen Huang a Yanqiang Zhang b and Jeanne M Shreeve b Introduction Energetic materials as controllable storage systems for rela tively large amounts of chemical energy are widely applied in military and industrial venues In the last decade a unique class of high energetic compounds

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