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Acta Chini. Slov. 1999, 46(3), pp. 339-354
THE SYNTHESIS, VIBRATIONAL SPECTRA, CRYSTAL STRUCTURE AND THERMAL DECOMPOSITION OF (N2H5)3AlF6+
A. Rahten, P. Benkič, A. Jesih
Jožef Stefan Institute, Jamova 39, 1111 Ljubljana, Slovenia
(Received 16.4.1999)
Abstract
(N2H5)3AlF6 has been synthesized by the reaction of AlF3.3H2O and N2H5F in a water solution. N-N stretching bands of the N2H5+ ions appear as medium band at 969 and as strong band at 955 cm-1 in infrared and at 965 and 955 cm-1 in Raman indicating different environments of the environment sensitive N2H5+ ions. The compound crystallizes in orthorhombic system, space group P212121 (No. 19), with a=9.015(2) A, b=9.191(2) A and c= 10.479(2) A. (N2H5)3AlF6 consists of separated AlF6-3 octahedra, arranged in a distorted fc.c. fashion. Octahedra are connected through hydrazinium ions and there are two types of strong hydrogen bonds regarding the orientation of NH2-NH3+ units. (N2H5)3AlF6 decomposes thermally by exothermic decomposition of hydrazinium(+1) ions to yield the mixture of (NH4)3AlF6 and NH4AlF4 at 243 oC. Further decomposition leads to NH4AlF4 at 301 oC and b-AlF3 at 460 oC. The final decomposition product is a-AlF3 at 700oC.
Introduction
Fluoroaluminates decompose on heating to yield AlF3 at temperatures higher than 460 oC. The course of thermal decomposition depends strongly also on cationic part of fluoroaluminates and on their structures. By the thermal decomposition of fluoroaluminates with different cations like pyridinH+ and (CH3)4N+, different new phases of AlF3 were prepared: h-AlF3[1], k-AlF3[1] and q-AlF3 [1, 2] besides already known and well characterized phases a-AlF3 and b-AlF3 as well as intermediates in new crystal modifications - b-NH4AlF4 [1]. AlF3 has found wide application as catalyst in Dedicated to the memory of Prof. Dr. Jože Šiftar
340
the production of fluorocarbons and its use is grown in the course of seek for CFC alternative materials. The activity of AlF3 to catalyse reactions depends upon its structure and specific surface area. Fluoroaluminates with hydrazinium(+1) and (+2) cations afford considerable volumes of gaseous products to be evolved during thermal decomposition which allow for large specific surface area of formed solid products. N2H6AlF5 [3], (N2H5)2AlF5×H2O [4] and (N2H5)2AlF5 [4] were isolated in the past and a very pure AlF3 was formed as final product of thermal decomposition of (N2H5)2AlF5.H2O [4]. The search for different hydrazinium(+1) fluoroaluminates resulted in the synthesis of (N2H5)3AlF6, which is a member of a (N2H5)3MF6 family of compounds, where M stands for V [5], Cr [5], Fe [6], and Ga [7].
Experimental
1.  Reagents. N2H4 was prepared by the fractional distillation of N2H4H2O (Merck, 80%), over solid NaOH in a nitrogen atmosphere [8]. N2H5F was prepared by the reaction of anhydrous N2H4 and solid N2H6F2 on a water bath. After cooling [9] the N2H5F was filtered and dried. AlF3×3H2O (Aldrich, 97 %), was used as received.
2.  Synthesis. AlF3.3H2O was dissolved in 4.3 % water solution of N2H5F (mole ratio AlF3×3H2O : N2H5F = 1 : 3.15). New compound (N2H5)3AlF6 was isolated by slow evaporation and crystallization at room temperature. The product was kept in a desiccator with silicagel.
3.   Analyses. Hydrazine content was determined by potentiometric titration with potassium iodate [10] and the content of ammonia by Kjeldahl method [11]. For the determination of aluminum and fluorine the new method was developed which utilises alkaline sample total decomposition and subsequent dissolution at pH < 3. Fluorine was determined by ionic selective electrode using reagent for masking aluminum ions [12], and aluminum by substitution titration at pH=10 [13].
Chemical analyses for (N2H5)3AlF6: Observed: %N2H4 39.8; %Al 11.2; %F 46.8. Calc.: %N2H4 40.04; %Al 11.24; %F 47.47.
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4.  Thermal analyses. Thermal analyses were done on Mettler thermoanalyser TA-1 in argon atmosphere. 100 mg of sample was decomposing in a 0.9 ml platinum crucible, the reference material was a-Al 2O3. Measurements were made by measurement head TD-1 in the flow of argon at 5 L/min and heating rate 1 omin-1. In experiments where intermediates were isolated, 250 - 300 mg of sample was used. The temperatures at which thermal effects are recorded depend on the amount of a sample and the same thermal effects correspond to some 15 - 20 °C higher temperatures in case of analyses starting with 300 mg samples compared to analyses started with 100 mg samples.
5.  Vibrational spectroscopy. Infrared spectra were recorded on Perkin-Elmer FTIR 1710 spectrometer as Nujol and fluorolube mulls pressed between CsBr and NaCl and as powders pressed between CsBr windows in the range 220 - 4000 cm-1. Raman spectra were recorded on dispersion Raman instrument Renishaw Ramascope, System 1000. As excitation source the 632.8 nm He-Ne laser line or near-infrared semiconductor 782 laser diode line was used. Raman spectra were recorded in the range 100 - 4000 cm-1 using low power excitation line to prevent sample decomposition.
6.  Structure determination. Single crystall data were collected on a Rigaku AFC7S diffractometer with graphite monocromated Mo-K« radiation at a temperature of 23(1) °C using the co-26 scan technique to a maximum 26 value of 65.0 °. Scan of (1.42 + 0.35 tan 6)° were made at a speed of 8.0 7min (in co). The weak reflections (I < 10.0g(I)) were rescanned with maximum of 4 scans and the counts were accumulated to ensure good counting statistics. The computer-controlled slits were set to 3.0 mm (horizontal) and 3.0 mm (vertical). Only asymmetric set of data was collected with decay of standards 5.6 %. Further details are given in Table 1.
The structure was solved using direct methodes. After refinement of all non-hydrogen atoms including anisotropic displacement parameters, the positions of hydrogen atoms were located in a difference map and finally refined isotropic without any restrains being applied (Table 2). For better refinement of hydrogen atoms correction for secondary extinction was applied. An empirical psi-absorption correction based  on azimuthal  scans  of several  reflections was  applied which resulted  in
342
transmission factors ranging from 0.93 to 1.00. All calculations were performed using the teXsan [14] crystallographic software package of Molecular Structure Corporation.
Table 1 : Crystal data and structure refinement
Empirical Formula		N6H15AlF6
Formula Weight		240.13
Wavelength		0.71069 Â
Space Group		P212121 (No.19)
Lattice Parameters		a =   9.015(2) A b =   9.191(2) A c =  10.479(2) A V = 868.3(2) A3
Z value		4
pcalc		1.837 g/cm3
|j.(MoKa)		3.06 mm-1
F000		496.00
Crystal Dimensions		0.24 x 0.24 x 0.40 mm
Number of independent	data	1825
Number of observed (I > 2gi)		1484
Number of Variables		179
Refinement		Full-matrix least-squares on F2
Least Squares Weights		1/g2(Fo) = 4Fo2/g2(Fo2)
p-factor		0.091
Residuals (I > 2oI): R1;	wR2	0.076; 0.11
Residuals (all data): R1;	wR2	0.079; 0.12
Goodness of Fit Indicator		0.92
Max Shift/Error in Final	l Cycle	0.00
R1 = X||Fo| - |Fc|| /X|Fo
wR2 = [ X ( w (Fo2 - Fc2)2 )/ X w(Fo2)2]1/2
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Table 2: Final Positional and Displacement Parameters
Atom	X	y	z	isO'      GQ
Al	0.45623(7)	0.51210(7)	0.54802(7)	0.0123(1)
Fl	0.6407(2)	0.4369(2)	0.5317(2)	0.0250(3)
F2	0.4813(2)	0.5336(2)	0.7205(1)	0.0237(3)
F3	0.2719(2)	0.5830(2)	0.5614(2)	0.0246(3)
F4	0.4290(2)	0.4904(2)	0.3774(1)	0.0198(3)
F5	0.3859(2)	0.3301(2)	0.5738(2)	0.0276(3)
F6	0.5281(2)	0.6942(2)	0.5259(2)	0.0226(3)
NI	0.2624(3)	0.2885(3)	0.8026(2)	0.0199(4)
N2	0.1748(3)	0.1599(3)	0.7832(3)	0.0269(5)
N3	0.2422(3)	0.2670(3)	0.2996(2)	0.0214(4)
N4	0.3055(3)	0.1657(3)	0.2105(2)	0.0248(5)
N5	0.5766(3)	0.4822(3)	0.9687(2)	0.0214(4)
N6	0.4934(3)	0.5828(3)	1.0478(2)	0.0233(4)
Hl	0.187(8)	0.353(7)	0.826(6)	0.062(6)
H2	0.335(6)	0.261(5)	0.866(5)	0.047(7)
H3	0.298(5)	0.313(5)	0.727(4)	0.026(6)
H4	0.130(7)	0.171(7)	0.704(5)	0.054(6)
H5	0.251(9)	0.091(8)	0.763(6)	0.079(5)
H6	0.203(5)	0.212(4)	0.353(5)	0.029(7)
H7	0.310(8)	0.344(7)	0.328(6)	0.068(5)
H8	0.174(5)	0.305(4)	0.249(4)	0.023(6)
H9	0.329(6)	0.224(5)	0.146(6)	0.049(7)
HIO	0.385(4)	0.130(4)	0.252(3)	0.017(6)
Hll	0.665(8)	0.504(6)	0.960(6)	0.065(5)
H12	0.550(5)	0.389(4)	0.994(4)	0.027(7)
H13	0.548(4)	0.487(4)	0.890(4)	0.019(6)
H14	0.399(5)	0.550(5)	1.049(4)	0.030(6)
H15	0.489(5)	0.666(5)	1.004(4)	0.025(6)
22                  2                 2
Beq = 8/3 p (U11(aa*)   + U22(bb*)   + U33(cc*)   + 2U12(aa*bb*)cos g + 2U13(aa*cc*)cos b + 2U23(bb*cc*)cos a)
Table 3: Anisotropic Displacement Parameters
Atom	\J \ \	u 22	*-'33	u X2	*J 13	*-'23
Al	0.0160(3)	0.0160(3)	0.0148(3)	0.0003(2)	0.0007(2)	-0.0005(2)
Fl	0.0222(7)	0.0416(8)	0.0310(8)	0.0112(6)	0.0048(6)	0.0097(7)
F2	0.0348(8)	0.0404(9)	0.0147(6)	0.0030(7)	-0.0028(6)	-0.0010(5)
F3	0.0200(7)	0.0405(8)	0.0330(9)	0.0064(6)	-0.0003(6)	-0.0094(7)
F4	0.0287(6)	0.0291(7)	0.0174(6)	-0.0009(7)	-0.0011(5)	-0.0022(5)
F5	0.052(1)	0.0202(7)	0.0328(9)	-0.0086(7)	0.0169(8)	-0.0004(6)
F6	0.0363(9)	0.0205(6)	0.0290(8)	-0.0061(6)	-0.0007(6)	0.0008(5)
Nl	0.028(1)	0.0245(9)	0.023(1)	-0.0015(8)	0.0032(9)	0.0008(8)
N2	0.039(1)	0.029(1)	0.033(1)	-0.007(1)	0.005(1)	-0.004(1)
N3	0.031(1)	0.026(1)	0.025(1)	0.0017(9)	-0.0013(9)	0.0007(8)
N4	0.037(1)	0.028(1)	0.029(1)	-0.004(1)	0.009(1)	-0.0014(9)
N5	0.032(1)	0.030(1)	0.0190(9)	-0.0055(9)	-0.0034(7)	0.0042(8)
N6	0.029(1)	0.033(1)	0.027(1)	-0.0065(9)	0.0003(9)	0.0024(9)
Supplemental material is available from authors.
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Results and Discussion 1. Vibrational spectra. Partial assignment of (N2H5)3AlF6 vibrational spectra was done by comparison to the spectra of (N2H5)3VF6 [15], (N2H5)3CrF6 [16] and to the spectra of fluoroaluminates [17, 18, 19]. According to primarily the position of the N-N vibration and then the frequencies of the N-H deformation and rockings, N2H5+ compounds have been divided into three groups [15]: where the stretching frequency is between 950 and 980 cm-1, where the N-N vibration is likewise at ca 980 cm-1 and where the N-N vibration is between 1000 and 1020 cm-1.
The bands in vibrational spectra of (N2H5)3AlF6 correspond to the spectra of the first group, N-N stretching appears at 955 cm-1 with strong band and with medium band at 969 cm-1 (Figure 1, Table 4) Two distinct stretching frequencies indicate different environments of the environment sensitive N2H5+ ions in the solid (N2H5)3AlF6. In related compounds corresponding bands appear at 975 and 950 cm-1 in the spectra of (N2H5)3CrF6 [16] and at 960 and 949 cm-1 in the spectra of (N2H5)3VF6 [15].
Bands which correspond to the N-N stretching appear strong both in Raman and infrared spectra of (N2H5)3AlF6 which is again characteristic of N2H5+ ion [15].
A
i
n'v' "»»"«r
> "<¦'  i.fi'»»'^»^'
__JV_jJ
_JUaAJ
3600         3100
2600
* Nujol
2100 cm-1
1600
1100
600
100
Figure 1: Infrared and Raman spectra of (N2H5)3AlF6.
345
Table 4: Infrared and Raman spectra of (N2H5)3AlF6 from 4000 to 950 cm-1
IR
n/ cm-1
Raman n/cm-1
Assignment*
3363 vs	3360 (2.5)
3350 vs	3348 (2)
3313 vs	3304(4)
3265 vw	3272 (4)
	3199 (3)
3093 vs	3111 (2)
3009 vs	3008 (4)
2755 s	2754 (1)
2667 s	2662 (1)
2047 w	2047 (1)
	1667 sho
1641 m	1639 (3)
(NH2)s
(NH3+)s
comb. band (NH2)d
}
IR
n/ cm-1
1595 s 1559 s 1537 s
1414 w 1306 vw 1261 vw 1128 s 1098 s 969 sho 955 s
Raman n/cm-1
1590 (1)
1538 (2) 1453 (1) 1410 (1)
1256 (1) 1136 (2) 1102 (3.5) 965 (8) 955 (10)
Assignment
*
(NH3)d
(NH2)r
(NH3)r
>     (N-N) s
Legend: s – strong, m – medium, w – weak, v Raman intensities are given in parentheses. * s – stretching, d – deformation, r – rocking.
very, sho - shoulder.
AlF63- ion of octahedral symmetry has six fundamental frequencies, two of them are infrared active - n3 and n4, three are Raman active, n1, n2 and n5, while the n6 is inactive.
The bands in vibrational spectra of octahedral AlF63- ion (Table 5) are very close to the calculated values [19]. Infrared active frequencies n3 and n4 which are usually both observed in infrared spectra of fluorometallates appear as strong band at 564 cm-1 and as medium band at 383 cm-1. Three Raman active vibrations n1, n2 and n5 appear at 531, 404 and 315 cm-1. n1 also appears in Raman, and the n6 frequency was observed in both Raman and infrared due to the departure of AlF63- ion from the ideal octahedral symmetry.
Table 5:   Infrared and Raman spectrum of (N2H5)3AlF6 below 600 cm-1
IR	R	Assignment
n/cm	n/cm	
564 vs		n3 (F1u) AlF63-
535 m	531 (1)	n1 (A1g) AlF63-
	404 (1)	n2 (Eg) AlF63-
383 m		n4 (F1u) AlF63-
309 sho	315 (1)	n5 (F2g) AlF63-
	215 (2)	n6 (F2u) AlF63-
	180 (1)	Lattice vibrations
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2. Description of the structure. (N2H5)3AlF6 is isostructural with already known compounds (N2H5)3CrF6 [20] and (N2H5)3GaF6 [7]. Some differences arise because of different properties of anions. The structure consists of separated quite regular AlF63-octahedra, which are arranged in a distorted f.c.c. fashion (Figure 2). The octahedra are connected through hydrazinium ions, where extensive hydrogen bonding of N-H×××F type is present (Figure 3).
There are two types of strong hydrogen bonds in sense of orientation of NH2-NH3+ units. So each hydrogen atom on –NH3 part of hydrazinium ion (atoms N1, N3 and N5) interacts with different AlF63- octahedra in hydrogen bond of –NH23H××××F type. Hydrogen atoms on N6 atom additionally participate in strong hydrogen bonds of –NH3H××××F type with atoms F5 and F3 respectively (Figure 3, Table 6A). In distance limit [21] 3.00 A two fluorine atoms around the N4 atom are also found, but in respect with orientation of hydrogen atoms this contact can be more likely considered as weaker bifurcated hydrogen bond between F3 and F6 atoms arising from different AlF63-octahedra (Table 6B). In mentioned distance limit no fluorine atoms can be found around N2 atom.
On AlF63- unit all fluorine atoms are involved in hydrogen bonding, where each of five fluorine atoms strongly interact with two hydrogen atoms arising from two different N2H5+ units. All strong hydrogen bonds are of –NH23H××××F type with exception of F5 atom, where one hydrogen bond is of –NH3H××××F type. F3 atom participates only in the one strong hydrogen bond of –NH3H××××F type (Figure 3, Table 6). In 3.00 A distance limit F3 atom is also surrounded with three other nitrogen atoms but positions of hydrogen atoms could only justify weak bifurcated hydrogen bond to N3 and N4 atom arising from same hydrazinium ion and even weaker interactions with N1 (Table 7B). Consequence of considerable weaker hydrogen bonding on F3 atom is probably shorter distance Al-F3 in comparison with other distances in octahedral AlF63-(Table 7).
347
Figure 2: ORTEP [22] steroview of unit cell packing.
Figure 3: ORTEP view of asymmetric unit (labelled atoms) with NH2NH3
environment of AlF63- anion.
348
Table 6: Hydrogen Bonds
A) The strongest hydrogen bonds of N-H—F type:
Distances (A)                  Angles (Deg)                                Type
F1-N3’	2.734(7)	N3'-	—H6’-	•Fl	170(4)	-NHj-	-H-	•F
F1-N5’	2.736(5)	N5'-	—Hll’•	•Fl	151(6)	-NHr	-H	•F
F2-N3’	2.846(7)	N3'-	—H8’-	•F2	147(3)	-NHr	-H-	•F
F2-N5	2.780(4)	N5-	—H13-	•F2	170(3)	-NHr	-H-	•F
F3-N6’	2.839(6)	N6'-	—H14’-	•F3	161(4)	-NH-	-a-	F
F4-N1’	2.778(7)	Nl'-	—HI’-	•F4	167(6)	-NHr	-H-	•F
F4-N3	2.777(7)	N3-	—H7—	•F4	177(6)	-NHr	-H	•F
F5-N1	2.671(5)	Nl-	—H3—	•F5	170(4)	-NHr	-H-	•F
F5-N6’	2.824(7)	N6'-	—H15’-	•F5	144(4)	-NH-	-H-	•F
F6-N1’	2.748(7)	Nl'-	—H2’-	•F6	175(4)	-NHr	-H-	•F
F6-N5’	2.812(4)	N5'-	—H12’-	•F6	156(4)	-NHr	-H-	•F
B) Some weaker interactions:
Distances (A)		Angles (Deg)		Type	
F3-N1’	2.974(5)	Nl—Hl’-F3	107(4)	-NH^-H	...p
F3-N3’	2.854(6)	N3'—H8’-F3	123(3)	-NH^-H	...p
F3-N4’	2.874(7)	N4'—H9’-F3	134(5)	-NH—H	•F
F6-N4’	2.907(6)	N4—H9’--F6	133(4)	-NH—H	•F
N2 -N4’	3.093(5)	N2—H5.....N4’	122(6)	-NH—H	•N
N4-N2	3.093(5)	N4—H10’--N2	105(2)	-NH—H	•N
N2 -N5’	3.041(7)	N5'—H12’-N2	108(3)	-NH—H	•N
’ denotes atoms generated with symmetry codes.					
It can be concluded, that despite of three crystallographicaly distinct N2H5 units, with respect to the strength of hydrogen bonds, there are only two distinct kinds of hydrazinium ions (Table 7).
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Table 7: Interatomic Distances and Angles
Distances (A):
Anion AlF6
3-
Al-Fl A1-F3 A1-F5
1.809(3) 1.791(3) 1.809(3)
A1-F2	1.832(2)
A1-F4	1.816(2)
A1-F6	1.809(3)
Cations N2H5+
N1-N2 N3-N4 N5-N6
1.436(4) 1.437(5) 1.451(5)
3-
Angles (deg) in anion AlF63-:
Cis
F1-A1-F2	91.2(2)	F1-A1-F4	89.4(2)
F1-A1-F5	89.0(2)	F1-A1-F6	90.7(2)
F2-A1-F3	89.9(2)	F2-A1-F5	89.7(2)
F2-A1-F6	89.0(2)	F3-A1-F4	89.5(2)
F3-A1-F5	90.0(2)	F3-A1-F6	90.3(2)
F4-A1-F5	89.9(2)	F4-A1-F6	91.4(2)
Trans
F1-A1-F3 F2-A1-F4 F5-A1-F6
178.51(9) 179.28(8) 178.72(9)
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2. Thermal decomposition. The thermal decomposition of sample starts at 128 oC with endothermic effect which is not accompanied by loss of weight (Figure 4). Similar effect, explained by the melting of sample, was observed at 125 oC during the thermal decomposition of (N2H5)3CrF6 [16] and during the thermal decomposition of (N2H5)3VF6 [23].
The DTA peak at 198 oC corresponds to the strongly exothermic decomposition of hydrazinium(+1) ions. The decomposition is accompanied by weight loss which at 230 oC amounts 30.3 % (Table 8). The analysis of intermediate isolated at 243 oC is: %NH4 24.0; %Al 14.9; %F 58.3; Calc. for (NH4)3AlF6: %NH4 27.74; %Al 13.83; %F 58.43; Calc. for NH4AlF4: %NH4 14.91; %Al 22.30; %F 62.80. The analysis, x-ray powder data (Table 9) as well as infrared spectra of the intermediate (Figure 5) confirm intermediate isolated at 243 oC being a mixture of (NH4)3AlF6 and NH4AlF4. Similar thermal behaviour was observed during the thermal decomposition of (N2H5)3CrF6 [16], where at the same experimental conditions (N 2H5)3CrF6 decomposed to (NH4)3CrF6. After the endothermic DTA peak at 257 oC intermediate was isolated at 301 oC. The analysis of intermediate gave: %NH4 14.7; %Al 21.3; %F 61.3. The thermal effect is connected to the further decomposition of (NH4)3AlF6 into NH4AlF4 which is the main product at this temperature. The composition has been confirmed also by infrared spectra (Figure 4) [24] which correspond to the infrared spectra of NH4AlF4. NH4F formed at this stage may cause some hydrolyses to occur on further decomposition, due to its reaction with a quartz wall and H2O production [25].
NH4AlF4 decompose further on and the intermediate isolated at 356o C has the composition: %NH4 10.0; %Al 24.0; %F 61.7 which indicates NH4AlF4 decomposed partly. According to the powder diffraction data it may be concluded that hydrolysis products have formed in small quantities too [26, 27].
Intermediate isolated at 460 o C contains mainly b-AlF3, with small quantities of NH4. Analysis: %NH4 0.5-1.3. The final product of the thermal decomposition of (N2H5)3AlF6 isolated at 700 o C is a-AlF3. Analyses: 65.9% F, Calc. for AlF3: 67.87 %. The powder diffraction pattern of the product corresponds to the a-AlF3.
351
Figure 4: TG, DTG and DTA curves for (N2H5)3AlF6.
Figure 5: Infrared spectra of (N2H5)3AlF6 and of thermal decomposition products in
order of isolation.
352
Table 8: Thermal behaviour of (N2H5)3AlF6
Temp.	Intermediate	Weight loss (%)	DTA efects
(oC)	(NH4)3AlF6, NH4AlF4	Calc.          Found 30.3	(oC)
230			198 exo
268	NH4AlF4	49.61          48.9	257 endo
338	Mostly NH4AlF4	54.3	
470	Impure b - AlF3	63.1	312 endo, 368 endo
690	a - AlF3	65.03          65.5	
Weight of the sample – 100mg.
Table 9: Powder diffraction data for the intermediates isolated at the thermal
decomposition of (N2H5)3AlF6
Intermediate at 243oC
d (D)
6.42 5.17 4.47 3.60
3.15
2.580
2.232
1.414
1.252 1.192
I
w
vs
s
vw
m
2.053	w
1.996	w
1.826	m-w
1.718	m
1.580	m-w
1.514	w
1.491	w
m
vw
vw
(NH4)3AlF6a		Intermediate at	
		301°C	
d (D)	I	d (D)	I
		6.34	s
5.15	100		
4.46	55		
		3.59	s
		3.19	w
3.157	45		
		3.13	s
2.579	20		
		2.54	m
		2.37	m-w
2.233	30	2.24	w
		2.12	w
2.049	4		
1.998	3	1.991	vw
1.824	6	1.830	m
		1.797	s-m
1.720	11	1.731	m-w
		1.608	m
1.579	5	1.591	m-w
		1.560	m
1.510	4		
1.489	2		
		1.453	vw
1.412	4		
1.363	2	1.372	vw
1.347	1		
1.290	2		
		1.281	vw
1.2514	2		
1.2389	1		
1.1941	3		
NH4A1F4
d(D)
6.346
3.585 3.175
3.128
2.534 2.364 2.234 2.114
1.984 1.823 1.790 1.724 1.603 1.585 1.557
1.456
1.368
1.347
1.279
100
80 10
80
30 40 10 15
10
25 50 15 15 7 20
10
3
15
a JCPDS 22-1036, b JCPDS     22-0077 Intensities: s strong; m medium; w weak; v very.
s
s
7
353
Acknowledgement
Authors are acknowledged to the Ministry of Science and Technology of Slovenia for providing funding. Thanks to Ms. B. Sedej for chemical analyses.
References
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354
Povzetek
Z reakcijo med AlF3.3H2O in N2H5F v vodni raztopini je bil sintetiziran (N2H5)3AlF6. V infrardečem spektru (N2H5)3AlF6 se pojavi N-N valenčno nihanje N 2H5+ iona kot srednje močan trak pri 969 in močan trak pri 955 cm -1, v ramanskem spektru pa pri 965 in 955 cm-1, kar kaže na različno okolje na okolico občutljivega iona N             2H5+.  Spojina
kristalizira v ortorombski prostorski skupini P212121 (št. 19) z dimenzijami osnovne celice a=9.015(2) A, b=9.191(2) A in c=10.479(2) A. Struktura (N2H5)3AlF6 sestoji iz samostojnih oktaedrov AlF6-3, ki se zlagajo v popačeni ploskovno centrirani kubični sklad in so med sabo povezani preko hidrazinijevih(1+) ionov.   Glede na orientacijo NH2-NH3+ enot obstajata d va tipa močnih vodikovih vezi. Termični razkroj (N           2H5)3AlF6 poteče z
eksotermnim razkrojem hidrazinijevega iona preko mešanice (NH4)3AlF6 in NH4AlF4 pri 243oC. Pri nadalnjem razkroju pri 301oC nastane NH4AlF4 in pri 460oC b-AlF3 Končni produkt termičnega razkroja pri 700oC je a-AlF3.