2,5,8-Trihydrazino-s-heptazine: a precursor for heptazine-based iminophosphoranes Edwin Kroke, Tatyana Saplinova, Vadym Bakumov, Tobias Gmeiner, Jörg Wagler, Marcus Schwarz To cite this version: Edwin Kroke, Tatyana Saplinova, Vadym Bakumov, Tobias Gmeiner, Jörg Wagler, et al.. 2,5,8- Trihydrazino-s-heptazine: a precursor for heptazine-based iminophosphoranes. Journal of Inorganic and General Chemistry / Zeitschrift für anorganische und allgemeine Chemie, Wiley-VCH Verlag, 2009, 10.1002/zaac.200900311. hal-00518304 HAL Id: hal-00518304 https://hal.archives-ouvertes.fr/hal-00518304 Submitted on 17 Sep 2010 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. 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ZAAC 2,5,8-Trihydrazino-s-heptazine: a precursor for heptazine- based iminophosphoranes Journal: Zeitschrift für Anorganische und Allgemeine Chemie Manuscript ID: zaac.200900311.R1 Wiley - Manuscript type: Article Date Submitted by the 17-Jul-2009 Author: Complete List of Authors: Kroke, Edwin; TU Bergakademie Freiberg, Institut fuer Anorganische Chemie Saplinova, Tatyana; TU Bergakademie Freiberg, Institut fuer Anorganische Chemie Bakumov, Vadym; Swiss Federal Laboratories for Materials Testing and Research, Laboratory for High Performance Ceramics Gmeiner, Tobias; Universität Konstanz, FB Chemie Wagler, Jörg; TU Bergakademie Freiberg, Institut fuer Anorganische Chemie Schwarz, Marcus; TU Bergakademie Freiberg, Institut fuer Anorganische Chemie Keywords: Heterocycle, Tri-s-triazine , Hydrazine, Azide, Phosphazene Wiley-VCH Page 1 of 21 ZAAC 1 2 3 4 2,5,8-Trihydrazino-s-heptazine: a precursor for heptazine-based 5 6 iminophosphoranes 7 8 9 10 11 Tatyana Saplinova, [a] Vadym Bakumov,[b] Tobias Gmeiner,[c] Jörg Wagler,[a] Marcus 12 [a] [a] 13 Schwarz, Edwin Kroke* 14 15 16 17 Keywords : Heterocycle; s-Heptazine; Hydrazine; Azide; Phosphazenes; Crystal structure 18 19 20 21 Abstract: The title compound 1 C 6N7(NHNH 2)3 was obtained from melem C 6N7(NH 2)3 or 22 melon [C 6N7(NH 2)NH] n and hydrazine via an autoclave synthesis. Upon treatment with a 23 24 10 % HCl solution it is transformed into the trihydrochloride 2, [C6N7(NHNH 3)3]Cl 3. 25 Compounds 1 and 2 were analysed with 13 C NMR, 15 N NMR, FTIR- and Raman- 26 27 spectroscopy. Furthermore, the single crystal X-ray structure of the pentahydrate of 2 is 28 reported ( P-1, a = 674.96(3), b = 1214.17(6), c = 1272.15(6) pm, α = 66.288(2)°, 29 6 3 30 β = 75.153(2)°, γ = 80.420(2)°, V = 920.30(8) · 10 pm , Z = 2, T = 90(2) K). The thermal 31 decomposition of 1 and 2 was investigated with TG/DTA. Reaction of 1 with NaNO /HCl 32 2 n 33 yields triazido-s-heptazine, C 6N7(N 3)3 3. Tris(tri butylphosphinimino)-s-heptazine 4 was 34 13 31 1 35 synthesized from 3 and characterised by means of C, P, H NMR, FTIR and MALDI-TOF 36 spectroscopy. Similar to s-heptazine derivative 3, compounds 1 and 4 are precursors for 37 38 graphitic carbon nitrides, which have attracted considerable attention recently, and to various 39 potential applications, such as flame retardants and (photo)catalysis. 40 41 42 43 44 45 [a] T. Saplinova, Dr. J. Wagler, Dr. M. Schwarz, Prof. Dr. E. Kroke 46 Institut für Anorganische Chemie, TU Bergakademie Freiberg 47 Leipziger Strasse 29, D-09596 Freiberg (Germany) 48 Fax: (+49)3731-39-4058 49 E-mail: [email protected] 50 51 [b] V. Bakumov 52 Now with: EMPA Swiss Federal Laboratories for Materials Testing and Research 53 Laboratory for High Performance Ceramics 54 Ueberlandstrasse 129 55 CH-8600 Duebendorf (Switzerland) 56 57 [c] T. Gmeiner 58 FB Chemie, Universität Konstanz 59 D-78457 Konstanz (Germany) 60 1 Wiley-VCH ZAAC Page 2 of 21 1 2 3 Introduction 4 5 6 Within the last decade numerous publications addressed the preparation of carbon 7 nitride materials.[1] Binary compounds with C N stoichiometry and 3D structure are 8 3 4 9 postulated to exhibit very specific physicochemical properties, in particular their hardness is 10 11 expected to exceed that of diamond. [2] 12 [3] 13 Among potential precursors for graphitic CN x materials, s-heptazine based 14 [4,5] [6] [7] [1g,8] 15 compounds, such as trichloro-s-heptazine, triazido-s-heptazine, melem and melon 16 attracted considerable interest in recent years. Here we report on the melem-related nitrogen- 17 18 rich substance 2,5,8-trihydrazino-s-heptazine 1 (Scheme 1). Although the synthesis of 1 has 19 [9] 20 been described in a patent in 1965, its further characterization was missing yet. 21 22 23 24 25 NH NH2 26 27 N N 28 29 30 H2N NH N NH NH2 31 32 2,4,6-trihydrazino-s-triazine 33 34 35 NH NH2 3+ 36 NH NH3 37 N N 38 N N 39 - 40 N N N 3Cl 41 N N N 42 H2N NHN N NH NH2 43 H3N NHN N NH NH3 44 45 2,5,8-trihydrazino-s-heptazine, 1 2,5,8-trihydrazino-s-heptazine trihydrochloride, 2 46 47 48 Scheme 1. 49 50 51 52 53 This fact becomes especially intriguing, when compared to the s-triazine derivative the 2,4,6- 54 55 trihydrazino-s-triazine (Scheme 1). The latter is a well known substance (its crystal structure 56 [10] 57 has been determined already in 1976) which found broad application in synthetic and 58 59 coordination chemistry. For instance, a variety of compounds combining the triazine core and 60 [11] different functional groups, such as CN, COOR, CH 2OH, CONH 2, N=N–R (R = alkyl, aryl)[12,13] can be obtained from 2,4,6-trihydrazino-s-triazine. Furthermore, it can act as a 2 Wiley-VCH Page 3 of 21 ZAAC 1 2 3 poly-dentate ligand, giving complexes with transition metals, such as Co(II), Ni(II), Cu(I), 4 [14] 5 and Zn(II). Zn(II) complexes of C 3N3(NHN=C(CH 3)2)3 were investigated for their non- 6 [15] 7 linear optic (NLO) properties. The industrial application of 2,4,6-trihydrazino-s-triazine as 8 9 a blowing agent in polymer industry for producing plastic foams is a consequence of its 10 ability to produce gaseous products by thermal decomposition. [16] 11 12 Contrary to 2,4,6-trihydrazino-s-triazine, compound 1 exhibits poor solubility in water and 13 14 organic solvents (dmf, dmso). In addition, chemical inactivity of its hydrazine groups (see 15 16 Results and Discussion) and relatively low yield of the reported procedure (27 %) are the 17 18 possible reasons for scant knowledge about 1. 19 During our investigation we improved the synthesis procedure of 1 (yield 47 %). The 20 21 crystal structure of 2,5,8-trihydrazino-s-heptazine trihydrochloride pentahydrate 2 was 22 23 determined by X-ray single crystal diffraction. Furthermore, the 2,5,8-triazido-s-heptazine 3, 24 25 an important intermediate to CN x-compounds and chemically-interesting substance, was 26 obtained by reaction of 1 with sodium nitrite in HCl-solution. One of the applications of 3 is a 27 28 synthesis of heptazine-based iminophosphoranes via the Staudinger reaction; [17] the latter 29 [18,20] 30 were suggested as halogen-free flame retardants for plastics. In this context, compound 4, 31 n 32 tris(tri butylphosphinimino)-s-heptazine, was synthesized by the Staudinger reaction of 3 with 33 n 34 tri butylphosphine. 35 36 37 38 Results and Discussion 39 40 The 2,5,8-trihydrazino-s-heptazine 1 was synthesized analogously to the reported 41 procedure,[9] while the reaction conditions were slightly modified (see Experimental Section). 42 43 The reaction was carried out according to Scheme 2. Two types of heptazine-containing 44 45 starting materials, i. e. melem and melon, can be engaged. This variation of starting materials 46 47 does not have any influence on the purity and yield of product 1. 48 2,5,8-trihydrazino-s-heptazine is a yellowish solid, which decomposes (changes its 49 50 colour to dark-brown) without melting at about 300°C and proved soluble in diluted mineral 51 52 acids, such as HCl, H 3PO 4, H 2SO 4, HNO 3. Contrary to our expectations, the nucleophilicity of 53 54 the terminal amino groups of hydrazine substituents in 1 is somewhat lower than in melem. 55 56 Besides Uhl et al. have performed several attempts to investigate reactivity of 1 towards 57 aluminium alkyls, aiming for alkylaluminium hydrazides.[19] Unfortunately, all reactions to 58 59 yield the expected product failed. Furthermore, our attempt to perform the Kirsanov reaction 60 [18,20] between 1 and PCl 5 failed, whereas this reaction route proceeds perfectly with melem. 3 Wiley-VCH ZAAC Page 4 of 21 1 2 3 One possible explanation is an involvement of the amino groups of 1 into strong hydrogen 4 5 bonding. 6 7 8 NH2 9 10 N N 11 12 N N N 13 NH NH 14 2 15 H2N N N NH2 16 N N 17 3 N2H4 H2O 18 N N N autoclave 19 NH2 20 H2N NHN N NH NH2 21 N N 22 1 23 24 N N N 25 26 HN N N NH 27 28 29 30 Scheme 2.