Next Article in Journal
Acknowledgement to Reviewers of Crystals in 2015
Next Article in Special Issue
5-Azido-4-dimethylamino-1-methyl-1,2,4-triazolium Hexafluoridophosphate and Derivatives
Previous Article in Journal
Formation Mechanism of Porous Cu3Sn Intermetallic Compounds by High Current Stressing at High Temperatures in Low-Bump-Height Solder Joints
Previous Article in Special Issue
Electrostatic Potentials, Intralattice Attractive Forces and Crystal Densities of Nitrogen-Rich C,H,N,O Salts
Open AccessArticle

Crystal Structures of Two 1,4-Diamino-1,2,4-triazolium Salts

1
Faculty of Chemistry and Pharmacy, University of Innsbruck, 6020 Innsbruck, Austria
2
Institute of Mineralogy and Petrography, University of Innsbruck, 6020 Innsbruck, Austria
*
Author to whom correspondence should be addressed.
Academic Editor: Helmut Cölfen
Crystals 2016, 6(1), 13; https://doi.org/10.3390/cryst6010013
Received: 30 December 2015 / Revised: 13 January 2016 / Accepted: 18 January 2016 / Published: 20 January 2016
(This article belongs to the Special Issue Nitrogen-Rich Salts)

Abstract

Bis(1,4-diamino-1,2,4-triazolium) sulfate (1) was obtained from the corresponding chloride by ion metathesis using Ag2SO4. Further metathesis with barium 5,5′-azotetrazolate yielded bis(1,4-diamino-1,2,4-triazolium) 5,5′-azotetrazolate (2). Numerous NH···N and NH···O interactions were identified in the crystal structures of 1 and 2. Both compounds undergo exothermal decomposition upon heating.
Keywords: azotetrazolate; hydrogen bond; sulfate; thermoanalysis; triazolium azotetrazolate; hydrogen bond; sulfate; thermoanalysis; triazolium

1. Introduction

N-Aminoazoles are pillars of heterocyclic chemistry, and interest in N-aminoazoles and their salts ranges from agrichemistry to medicinal chemistry. In particular, N,N′-diaminoazolium salts exhibited attractive biological activities [1]. Thus far, the crystal structure of only one 1,4-diamino-1,2,4-triazolium salt, the chloride, has been published [2]. One of the most exciting developments are nitrogen-rich salts. The synthesis of sodium 5,5′-azotetrazolate was first reported by Thiele [3]. A lot has happened since then in terms of compound synthesis and developments, and a number of salts containing 5,5′-azotetrazolate ions and their crystal structures have been described [4,5,6]. One can still find small and simple molecules that are neglected in the literature. The 1,4-diamino-1,2,4-triazolium cation is one of those missing links. Bis(1,4-diamino-1,2,4-triazolium) 5,5′-azotetrazolate was reported to spontaneously evolve nitrogen gas and to undergo violent decomposition at 134 °C [7], but no crystal structure was disclosed. Recently, the structure of the closely related bis(1,3-diaminoimidazolium) 5,5′-azotetrazolate was determined [8]. Here, we report the crystal structures of bis(1,4-diamino-1,2,4-triazolium) 5,5′-azotetrazolate and its precursor, bis(1,4-diamino-1,2,4-triazolium) sulfate.

2. Results and Discussion

The synthesis of bis(1,4-diamino-1,2,4-triazolium) sulfate (1) was accomplished by metathesis of the corresponding chloride with silver sulfate (Figure 1). In a second metathetical step of the sulfate 1 and barium 5,5′-azotetrazolate, bis(1,4-diamino-1,2,4-triazolium) 5,5′-azotetrazolate (2) was obtained. Both steps gave high yields (90% and 98%, respectively). It should be noted that N-aminoazoles and N-aminoazolium salts which are not derived from hydrazine have to be prepared by electrophilic amination. They are therefore expensive and only of academic interest.
N,N-Diaminoazolium cations are potent hydrogen bond donors [2,8,9,10], and it seemed to be of interest to examine the interactions of the 1,4-diamino-1,2,4-triazolium cation with acceptor anions such as sulfate or 5,5′-azotetrazolate in the solid state. The crystal data and refinement details are summarized in Table 1.
Figure 1. Syntheses of 1,4-diamino-1,2,4-triazolium sulfate (1) and 5,5′-azotetrazolate (2).
Figure 1. Syntheses of 1,4-diamino-1,2,4-triazolium sulfate (1) and 5,5′-azotetrazolate (2).
Crystals 06 00013 g001
Table 1. Crystal data and structure refinement for 1 and 2.
Table 1. Crystal data and structure refinement for 1 and 2.
Compound12
CCDC No.14415221441523
Empirical formula2(C2H6N5)·O4S2(C2H6N5)·C2N10
Formula weight296.30364.36
Crystal systemMonoclinicMonoclinic
Space groupPcP21/c
a11.0114(3)3.5735(3)
b8.4671(2)14.8270(12)
c12.8156(5)13.4559(11)
β/°92.356(3)95.664(3)
Volume/Å31193.85(6)709.47(10)
Z42
Dx/g·cm−31.6481.706
μ/mm−10.310.13
F(000)616376
T/K173183
Crystal size/mm30.54 × 0.20 × 0.160.18 × 0.04 × 0.03
θmax25.425.0
Index ranges–13 ≤ h ≤ 11, –10 ≤ k ≤ 10, –14 ≤ l ≤ 15–4 ≤ h≤ 3, –17 ≤ k ≤ 17, –15 ≤ l ≤ 15
Reflections collected70809515
Independent reflections (Rint)3571 (0.028)1250 (0.060)
Observed reflections [I > 2σ(I)]34281001
Absorption correctionmulti-scanmulti-scan
Restraints/parameters18/3924/135
Goodness-of-fit on F21.091.06
R1/wR2 [I > 2σ(I)]0.026/0.0770.037/0.092
R1/wR2 (all data)0.029/0.0790.052/0.098
Δρmax/Δρmin/e.Å−30.23/–0.250.54/–0.22

2.1. Bis(1,4-diamino-1,2,4-triazolium) Sulfate (1)

Hydrogen atoms at N3 and N5 were found and refined isotropically. The geometry of the N-amino groups was pyramidal, indicating sp3 hybridization. The N-amino group conformations relative to the azolium ring planes were eclipsed (lone pair closely aligned with the ring plane, N–H bonds out of the ring plane), as observed in the structure of the corresponding chloride (Cambridge Structural Database reference code MEBPOZ).
The crystal structure of this simple salt was found to be unexpectedly complicated. There are four independent cations and two anions in the asymmetric unit. Numerous NH···O hydrogen bonds (Table 2) create a three-dimensional framework. These interactions are depicted separately, for the sake of clarity, for each of the four independent cations AD in Figure 2.
Table 2. Hydrogen bond geometry for 1 and 2 (Å, °).
Table 2. Hydrogen bond geometry for 1 and 2 (Å, °).
CompoundInteractionH···AD···AD–H···ASymmetry Operation A
1N5A–H51A···O52.04(2)2.913(3)160(3)x, y, z
N5A–H52A···O32.04(2)2.946(3)173(3)x, y, z
N3C–H31C···O12.11(3)3.008(3)169(3)x, y, z
N3C–H31C···O32.48(3)3.115(3)128(3)x, y, z
N3C–H32C···O52.19(3)2.962(4)144(3)x, −y, −1/2 + z
N3B–H31B···O22.15(2)2.932(3)145(3)x, 1 + y, z
N3B–H32B···O72.07(2)2.951(3)172(3)1 + x, y, z
N5D–H51D···O82.06(3)2.871(3)151(3)x, y, z
N5D–H52D···O22.16(2)2.996(3)155(3)−1 + x, y, z
N3D–H31D···O12.00(2)2.889(3)163(3)x, y, z
N3D–H32D···O52.16(2)3.042(4)170(3)x, −1 + y, z
N5B–H51B···O42.14(2)2.989(4)162(3)x, −y, −1/2 + z
N5B–H52B···N3A2.26(2)3.108(4)159(3)x, −y, −1/2 + z
N5C–H52C···O52.11(3)2.922(4)152(3)x, 1 − y, −1/2 + z
N3A–H31A···O62.03(2)2.874(3)157(3)1 + x, y, z
N3A–H32A···O21.98(2)2.856(3)166(3)x, −y, 1/2 + z
N3B–H32B···O82.54(3)3.123(3)124(2)1 + x, y, z
N5C–H51C···O12.56(3)3.353(3)150(3)x, 1 + y, z
N5C–H51C···N3D2.68(3)3.301(4)129(2)x, 1 + y, z
2N10–HA···N32.12(2)3.018(2)169(2)x, y, z
N10–HB···N12.16(2)3.048(2)167(2)x, 3/2 – y, –1/2 + z
N8–HA···N22.38(2)3.152(2)146(2)1 – x, 1 – y, 1 – z
N8–HB···N42.64(3)3.221(2)125(2)x, –1/2 + y, 1/2 – z

2.2. Bis(1,4-diamino-1,2,4-triazolium) 5,5′-Azotetrazolate (2)

The salt (C2H6N5)2(C2N10) consists of 76.9 percent nitrogen and thus can be rightly considered to be “nitrogen-rich.” The hydrogen atoms at N8 and N10 were found and refined isotropically with bond restraints, and the N-amino groups again are pyramidal. The ions form cyclic hydrogen-bonded assemblies (Figure 3), which can be described by a R 2 2 ( 13 ) graph set [11], meaning a 13-membered ring with 2 hydrogen bond donors and 2 acceptors. In contrast, in the structure of the related 1,3-diaminoimidazolium 5,5′-azotetrazolate (CSD reference code YEHTAI) [8] hydrogen bonds between two cations and two anions create centrosymmetric ring-shaped aggregates, graph set R 4 4 ( 20 ) . In 2, a wave-like arrangement of the ions is observed (Figure 3), whereas the very similar salt, 4-amino-1-methyl-1,2,4-triazolium 5,5′-azotetrazolate (CSD reference code PAPMOJ), packed in flat layers and crystallized in an orthorhombic space group [7]. Obviously, the structure of 2 is controlled by the additional hydrogen bonding of the second amino group.
Figure 2. Bis(1,4-diamino-1,2,4-triazolium) sulfate (1). (ad) The four independent cations as hydrogen-bond donors. Symmetry codes: (i) 1+x, y, z; (ii) x, –y, ½ + z; (iii) x, 1 + y, z; (iv) x, –y, –1/2 + z; (v) x, 1 – y, –1/2 + z; (vi) x, –1 + y, z; (vii) –1 + x, y, z; (e) Asymmetric unit.
Figure 2. Bis(1,4-diamino-1,2,4-triazolium) sulfate (1). (ad) The four independent cations as hydrogen-bond donors. Symmetry codes: (i) 1+x, y, z; (ii) x, –y, ½ + z; (iii) x, 1 + y, z; (iv) x, –y, –1/2 + z; (v) x, 1 – y, –1/2 + z; (vi) x, –1 + y, z; (vii) –1 + x, y, z; (e) Asymmetric unit.
Crystals 06 00013 g002
Figure 3. Bis(1,4-diamino-1,2,4-triazolium)5,5′-azotetrazolate (2). (a) The cation as hydrogen-bond donor; (b) The anion as hydrogen-bond acceptor; (c) Wave-like arrangement of the ions in the unit cell. Symmetry codes: (i) –x, –1/2 + y, 1/2 – z; (ii) 1 – x, 1 – y, 1 – z; (iii) x, 3/2 – y, –1/2 + z; (iv) –x, 1/2 + y, 1/2 – z; (v) x, 3/2 – y, 1/2 + z.
Figure 3. Bis(1,4-diamino-1,2,4-triazolium)5,5′-azotetrazolate (2). (a) The cation as hydrogen-bond donor; (b) The anion as hydrogen-bond acceptor; (c) Wave-like arrangement of the ions in the unit cell. Symmetry codes: (i) –x, –1/2 + y, 1/2 – z; (ii) 1 – x, 1 – y, 1 – z; (iii) x, 3/2 – y, –1/2 + z; (iv) –x, 1/2 + y, 1/2 – z; (v) x, 3/2 – y, 1/2 + z.
Crystals 06 00013 g003

2.3. Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA)

Thermoanalysis of the triazolium salts 1 and 2 showed initial melting followed by exothermal decomposition (maxima at 164 and 165 °C) with approximately 60% loss of mass. Decomposition gases are not limited to N2, but also include NH3, CH4 and HCN [6], which are formed in varying amounts. Thermograms are depicted in Figure 4.
Figure 4. DSC and TGA of (a) bis(1,4-diamino-1,2,4-triazolium) sulfate (1) and (b) 5,5′-azotetrazolate (2). Heating rate 10 °C·min−1.
Figure 4. DSC and TGA of (a) bis(1,4-diamino-1,2,4-triazolium) sulfate (1) and (b) 5,5′-azotetrazolate (2). Heating rate 10 °C·min−1.
Crystals 06 00013 g004

3. Experimental Section

1,4-Diamino-1,2,4-triazolium chloride [CASRN 122583-43-1] was prepared as previously described [12]. Barium 5,5′-azotetrazolate pentahydrate [CASRN 441747-65-5] was prepared according to a published procedure [13]. All other chemicals were purchased from Sigma-Aldrich (Steinheim, Germany). NMR spectra were recorded with a Bruker Avance DPX 300 spectrometer (Billerica, MA, USA). IR spectra were obtained with a Bruker Alpha FT (Billerica, MA, USA) instrument. DSC was performed with a DSC 7 (Perkin-Elmer, Norwalk, CT, USA) applying a heating rate of 10 °C·min−1. TGA was carried out with a TGA 7 system (Perkin-Elmer) at a heating rate of 10 °C·min−1.
Single crystal diffraction intensity data were recorded by ω scans with an Oxford Diffraction Gemini-R Ultra (Oxford Diffraction Ltd., Abingdon, Oxfordshire, UK) or by φ and ω scans with a Bruker D8 Quest Photon 100 (Billerica, MA, USA) diffractometer using MoKα radiation. CCDC reference numbers: 1441522 and 1441523. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre (Cambridge, UK).

3.1. Bis(1,4-diamino-1,2,4-triazolium) Sulfate (1)

A solution of 1,4-diamino-1,2,4-triazolium chloride (0.65 g, 4.8 mmol) in hot H2O (30 mL) was added to a solution of Ag2SO4 (0.75 g, 2.4 mmol) in hot H2O (60 mL). The mixture was sonicated for 10 minutes, and the precipitate was removed by centrifugation. The supernatant was taken to dryness under reduced pressure, and the residue was crystallized from hot MeOH. Single crystals were obtained by slow diffusion of MeOH into a H2O/2-PrOH solution. Yield: 0.64 g (90%). M.p. 151–154 °C (decomposition). 1H NMR (DMSO-d6, 300 MHz): δ 6.9 (br s, 2H), 7.4 (br s, 2H), 9.06 (s, 1H), 10.20 (s, 1H) ppm. IR (neat): ν ˜ 3216 (m), 3119 (m), 2991 (m), 1646 (w), 1409 (w), 1053 (s), 985 (m), 974 (m), 901 (m), 751 (w), 652 (w), 605 (s), 488 (m) cm−1.

3.2. Bis(1,4-diamino-1,2,4-triazolium) 5,5′-Azotetrazolate (2)

A solution of bis(1,4-diamino-1,2,4-triazolium) sulfate (50 mg, 0.17 mmol) in H2O (2 mL) was added to a suspension of barium 5,5′-azotetrazolate pentahydrate (66 mg, 0.17 mmol) in H2O (4 mL). The mixture was stirred at 20 °C for 72 h, and the precipitate was removed by filtration through a 0.45 μm filter. The clear filtrate was taken to dryness at 20 °C under reduced pressure (0.1 mbar) to yield a yellow powder (60 mg, 98%). Single crystals were obtained by slow diffusion of Et2O into a MeOH solution. M.p. 135 °C (decomposition). 1H NMR (DMSO-d6, 300 MHz): δ 7.05 (s, 2H), 7.46 (s, 2H), 9.10 (s, 1H), 10.28 (s, 1H) ppm. 13C NMR (DMSO-d6, 75 MHz): δ 140.9, 143.5, 173.3 ppm. IR (neat): ν ˜ 3313 (w), 3213 (w), 3171 (w), 3085 (m), 2998 (m), 2919 (m), 1627 (m), 1442 (m), 1390 (s), 1171 (m), 1159 (m), 1081 (m), 1047 (m), 1019 (s), 953 (s), 897 (m), 732 (s), 650 (s), 625 (s), 608 (s) cm−1.

4. Conclusions

One can still find small and simple molecules which are neglected in the literature—in other words, hidden treasures. The 1,4-diamino-1,2,4-triazolium cation is one of those. Intricate networks of hydrogen bonds are observed in the crystal structures of two nitrogen-rich salts.

Author Contributions

Gerhard Laus conceived and designed this study, carried out experimental work (synthesis, crystallization and characterization) and wrote the manuscript. Klaus Wurst and Volker Kahlenberg determined the crystal structures. Herwig Schottenberger contributed conceptual details and supported this study.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Link, H.; Klötzer, W.; Karpitschka, E.M.; Montavon, M.; Müssner, R.; Singewald, N. 1-Amino-and 1,3-Diaminoimidazolium Salts. Angew. Chem. Int. Ed. Engl. 1990, 29, 556–557. [Google Scholar] [CrossRef]
  2. Laus, G.; Kahlenberg, V.; Többens, D.M.; Jetti, R.K.R.; Griesser, U.J.; Schütz, J.; Kristeva, E.; Wurst, K.; Schottenberger, H. Lattice architecture and hydrogen-bonding networks of N-aminoazolium and N,N′-diaminoazolium chlorides. Cryst. Growth Des. 2006, 6, 404–410. [Google Scholar] [CrossRef]
  3. Thiele, J. Ueber Azo- und Hydrazoverbindungen des Tetrazols. Ann. Chem. 1898, 303, 57–75. (In German) [Google Scholar] [CrossRef]
  4. Laus, G.; Kahlenberg, V.; Wurst, K.; Schottenberger, H.; Fischer, N.; Stierstorfer, J.; Klapötke, T.M. Synthesis and crystal structures of new 5,5′-azotetrazolates. Crystals 2012, 2, 127–136. [Google Scholar] [CrossRef]
  5. Lampl, M.; Laus, G.; Braun, D.E.; Kahlenberg, V.; Wurst, K.; Fuhrmann, G.; Schottenberger, H.; Huppertz, H. New crystal structures in the realm of 5,5′-azotetrazolates. Z. Naturforsch. 2015, 70, 125–134. [Google Scholar] [CrossRef]
  6. Klapötke, T.M.; Sabaté, C.M. New energetic compounds based on the nitrogen-rich 5,5′-azotetrazolate anion ([C2N10]2−). New J. Chem. 2009, 33, 1605–1617. [Google Scholar] [CrossRef]
  7. Ye, C.; Xiao, J.-C.; Twamley, B.; Shreeve, J.M. Energetic salts of azotetrazolate, iminobis(5-tetrazolate) and 5,5′-bis(tetrazolate). Chem. Commun. 2005, 21, 2750–2752. [Google Scholar] [CrossRef] [PubMed]
  8. Laus, G.; Wurst, K.; Schottenberger, H. Crystal structure of bis(1,3-diaminoimidazolium) 5,5′-azotetrazolate, (C3H7N4)2 (C2N10), C8H14N18. Z. Kristallogr. New Cryst. Struct. 2012, 227, 293–294. [Google Scholar] [CrossRef]
  9. Laus, G.; Kahlenberg, V.; Schottenberger, H. Crystal structure of 1,3-diaminoimidazolium hexafluorophosphate, [C3H7N4]PF6. Z. Kristallogr. New Cryst. Struct. 2010, 225, 463–464. [Google Scholar] [CrossRef]
  10. Bentivoglio, G.; Schwärzler, A.; Wurst, K.; Kahlenberg, V.; Nauer, G.; Bonn, G.; Schottenberger, H.; Laus, G. Hydrogen Bonding in the Crystal Structures of New Imidazolium Triflimide Protic Ionic Liquids. J. Chem. Cryst. 2009, 39, 662–668. [Google Scholar] [CrossRef]
  11. Bernstein, J.; Davis, R.E.; Shimoni, L.; Chang, N.-L. Patterns in Hydrogen Bonding: Functionality and Graph Set Analysis in Crystals. Angew. Chem. Int. Ed. Engl. 1995, 34, 1555–1573. [Google Scholar] [CrossRef]
  12. Laus, G.; Klötzer, W. Synthesis of 1-amino-1H-1,2,4-triazoles. Synthesis 1989, 4, 269–272. [Google Scholar] [CrossRef]
  13. Hammerl, A.; Holl, G.; Klapötke, T.M.; Mayer, P.; Nöth, H.; Piotrowski, H.; Warchhold, M. Salts of 5,5′-azotetrazolate. Eur. J. Inorg. Chem. 2002, 4, 834–845. [Google Scholar] [CrossRef]
Back to TopTop