Single-crystal structure determination of NO2SbF6, XeF5SbF6 and XeF5Sb2F11

Journal of Fluorine Chemistry 175 (2015) 47–50

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Single-crystal structure determination of NO2SbF6, XeF5SbF6 and XeF5Sb2F11 Zoran Mazej *, Evgeny A. Goreshnik Jozˇef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia

A R T I C L E I N F O

A B S T R A C T

Article history: Received 25 February 2015 Received in revised form 11 March 2015 Accepted 16 March 2015 Available online 24 March 2015

NO2SbF6 crystalizes at 150 K in the orthorhombic Cmmm space group (No. 65) with a = 6.8119(7) A˚, b = 7.3517(7) A˚, c = 5.5665(5) A˚, V = 278.77(5) A˚3, and Z = 2. Its crystal structure exhibits a different packing of the [NO2]+ and [SbF6] ions than in the known crystal structure of NO2AsF6. The XeF5SbF6 compound is orthorhombic at 150 K, space group Pnma (No. 62), with a = 16.7159(6) A˚, b = 8.1093(3) A˚, c = 5.7576(2) A˚, V = 780.47(5) A˚3, Z = 4, and it is isotypic with the known XeF5MF6 crystal structures of M = Nb, Ru, and Pt. The unit cell of XeF5Sb2F11 is triclinic at 200 K, P 1¯ space group (No. 2), with a = 8.5223(8) A˚, b = 8.5582(8) A˚, c = 9.2012(8) A˚, a = 68.799(8)8, b = 74.897(8)8, g = 76.252(8)8, V = 596.35(10) A˚3 and Z = 2. Each [XeF5]+ cation has four interactions with the three [Sb2F11] anions. ß 2015 Elsevier B.V. All rights reserved.

Keywords: Xenon Antimony pentafluoride Nytril Crystal structure

1. Introduction In 1964, Gard and Cady reported on the preparation and some of the properties of Xe2F11SbF6, XeF5SbF6 and XeF5Sb2F11 [1]. XeF5SbF6 was also investigated by 19F NMR spectroscopy in an anhydrous hydrogen solution [2]. According to the available literature there are twelve known compounds of the type XeF5MF6 (M = V [3], Nb [4], Ta [5], Ru [6], Ir [7], Os [8], Pt [9], Au [8], As [10], Sb [1], Bi [11] and U [12]). In some reviews [XeF5]+[PdF6] with Pd(V) is mentioned [13–15]. However, this must be a typographical error, since an inspection of the original literature shows that in reality [XeF5]2+[PdF6]2 with Pd(IV) was reported [16,17]. In contrast to the XeF5MF6 phases (XeF6:MF5 = 1:1) there are only two compounds known with a 1:2 ratio (i.e., XeF5M2F11). XeF5V2F11 is only stable under its own vapor pressure, without decomposition at least to its melting point (39  1 8C) [3]. XeF5Sb2F11 has a melting point of 108  1 8C [1]. A saturated solution of XeF5Sb2F11 in BrF5 was investigated using 19F NMR spectroscopy [2], while the solid compound was studied by Mo¨ssbauer spectroscopy [18]. The synthesis and vibrational data are available for NO2SbF6 [19,20] but there is no information about its crystal structure.

* Corresponding author. Tel.: +386 1 477 3301. E-mail address: [email protected] (Z. Mazej). http://dx.doi.org/10.1016/j.jfluchem.2015.03.004 0022-1139/ß 2015 Elsevier B.V. All rights reserved.

Single crystals of XeF5SbF6, XeF5Sb2F11 and NO2SbF6 were grown during attempts to prepare analog mixed-cation compounds such as NO2XeF5(SbF6)2 [21] with other cations. Their crystal structures were determined and are described in the present paper. 2. Experimental 2.1. Apparatus, techniques and reagents The volatile materials (anhydrous HF, F2, SbF5, NO2F) were handled in a nickel vacuum line and an all-PTFE vacuum system equipped with PTFE valves, as previously described [22]. The nonvolatile materials were manipulated in a dry-box (M. Braun, Germany) in which the residual water in the atmosphere never exceeded 1 ppm. The reactions were carried out in FEP (tetrafluoroethylene-hexafluoropropylene; Polytetra GmbH, Germany) reaction vessels (height 250–300 mm with an inner diameter of 15.5 mm and an outer diameter of 18.75 mm) equipped with PTFE valves [23] and PTFE-coated stirring bars. Prior to their use, all the reaction vessels were passivated with elemental fluorine (Solvay). The SbF5, NO2SbF6 and XeF5SbF6 were prepared as described previously [21]. Anhydrous HF (Linde, Fluorwasserstoff 3.5) was treated with K2NiF6 (Ozark-Mahoning, 99%) for several hours prior to its use. The xenon difluoride was prepared by a photochemical reaction between Xe and F2 at ambient temperature [24]. The H3OSbF6 and XeFSbF6 were synthesized in a reaction between H2O and XeF2, respectively, and an equimolar amount of SbF5 in aHF.

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Table 1 Summary of the crystal-data and refinement results for NO2SbF6, XeF5SbF6 and XeF5Sb2F11. Formula T (K) Crystal system Space group a (A˚) b (A˚) c (A˚) a (8) b (8) g (8) V (A˚3) Z Dcalcd (g/cm3) l (A˚) m (mm1) GOF indicatora R1 b wR2 c

NO2SbF6 150 Orthorhombic Cmmm 6.8119(7) 7.3517(7) 5.5665(5) / / / 278.77(5) 2 3.3563 0.71073 5.031 0.984 0.034 0.088

XeF5SbF6 150 Orthorhombic Pnma 16.7159(6) 8.1093(3) 5.7576(2) / / / 780.47(5) 4 3.9317 0.71073 7.957 1.046 0.022 0.055

XeF5Sb2F11 200 Triclinic P 1¯ 8.5223(8) 8.5582(8) 9.2012(8) 68.799(8) 74.897(8) 76.252(8) 596.35(10) 2 3.7798 0.71073 7.513 1.033 0.029 0.067

a GOF = [Sw(F02  Fc2 )2/(No  Np)]1/2, where No = no. of reflns and Np = no. of refined parameters. b R1 = SjjFoj  jFcjj/SjFoj. c wR2 = [Sw(F02  Fc2 )2/S(w(F02 )2]1/2.

The O2SbF6 was synthesized by a reaction between SbF5, F2 and O2 in aHF as a solvent in the presence of a UV-source (450 W, immersion-type photochemical lamp, Ace Glass Inc., USA). 2.2. Crystal growth of XeF5SbF6, XeF5Sb2F11 and NO2SbF6 A T-shaped apparatus consisting of two FEP tubes (6 mm and 19 mm outer diameters) was used for the single-crystal growth. The solids were loaded (approximately 150 mg) into the wider arm of the crystallization vessel in a dry-box. The aHF (4 ml) was then condensed onto the starting material at 77 K. The crystallization mixture was brought up to ambient temperature and the clear solution that had developed, was decanted into the narrower arm. The evaporation of the solvent from this solution was carried out by maintaining a temperature gradient corresponding to about 10 K between both tubes for two months. The effect of this treatment was to enable the aHF to be slowly evaporated from the narrower into the wider tube, leaving behind the crystals. Single crystals of NO2SbF6 were grown during the attempt to prepare the (NO2)(XeF)(SbF6)2 compound as in the case of Xe(VI) where NO2XeF5(SbF6)2 [21] was synthesized. In a similar attempt to prepare unknown (H3O)XeF5(SbF6)2 by a reaction between H3OSbF6 and XeF5SbF6 only single crystals of the latter were found between the powdered material. The crystallization of the O2SbF6/XeF5SbF6 mixture yields only single crystals of XeF5Sb2F11 instead of the desired unknown O2XeF5(SbF6)2. The crystallization products were immersed in perfluorinated oil (Fluorchem, melting point 263 K) in a dry-box. The single crystals were then selected from the crystallization products under the microscope outside the dry-box and then transferred into the cold nitrogen stream of the diffractometer.

DIAMOND 3.1 [30] and Balls & Sticks (freely available) software [31]. More details about the crystal-structure investigations may be obtained from Fachinformationszentrum Karlsruhe, 76344 Eggenstein-Leopoldshafen, Germany (fax: +49 7247 808 666; e-mail: crysdata@fiz-karlsruhe.de, http://www.fiz-karlsruhe.de) by quoting the deposition numbers CSD-429243 (NO2SbF6), CSD-429244 (XeF5SbF6) and CSD-429245 (XeF5Sb2F11).

3. Results and discussion Details of the data-collection parameters and other crystallographic information about NO2SbF6, XeF5SbF6 and XeF5Sb2F11 are provided in Table 1. 3.1. Crystal structure of NO2SbF6 It was surprising to find that the crystal structures of NO2AsF6 and NO2SbF6 are not isotypic. The former crystallizes in the monoclinic C2/m space group (No. 12) at 291 K [32] and the latter in the orthorhombic Cmmm space group (No. 65) at 150 K. The crystal structures differ in terms of the packing of the XF6 (X = As, Sb) octahedra and the positions of the [NO2]+ cations (Fig. 1). However, in both structures the nitrogen atoms of the [NO2]+ cations have four equal contacts to the fluorine atoms of the four [XF6] anions (Fig. 2). All the atoms in NO2SbF6 occupy special positions. The oxygen atoms of the cation lie at the 4j Wyckoff position with m2m site symmetry, and the nitrogen atoms occupy the 2d position with mmm symmetry. The NO bond lengths in the NO2SbF6 are shorter (1.111(8) A˚ at 150 K) than those in the NO2AsF6 (1.159(3) A˚ at 291 K) [32] and are comparable to those observed in NO2Xe2F13 (1.10–1.12 A˚ at 130 K) [33], (NO2)2ReF8 (1.1164 A˚ at 125 K) [34] and NO2ReOF6 (1.085–1.14 A˚ at 132 K) [35]. The [SbF6] anion geometry is also restricted by symmetry: each SbF6 moiety contains only two crystallographically independent fluorine atoms located at the 8o (m symmetry) and 4j (m2m) positions, respectively, resulting together with the 2b (mmm) Wyckoff position of the Sb atom in a pair of equal Sb1–F2 and four identical Sb1–F1 bonds.

2.3. Crystal structure determination of XeF5SbF6, XeF5Sb2F11 and NO2SbF6 Single-crystal data for all three compounds were collected on a Gemini A diffractometer equipped with an Atlas CCD detector, using graphite monochromated MoKa radiation. The data were treated using the CrysAlis software suite program package [25]. The structures were solved with the charge-flipping method using the Superflip [26] program (Olex crystallographic software [27]) and refined with the SHELXL-2013 [28] software, implemented in program package WinGX. [29]. The figures were prepared using the

Fig. 1. Part of the crystal structure of NO2SbF6 (a, c) showing packing of the [NO2]+ and [SbF6] ions. For comparison, the packing of the [NO2]+ and [AsF6] in NO2AsF6 (b, d) is also given. [32].

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Fig. 2. Perpendicular view of part of the layer (in the bc plane) in the crystal structure of the NO2SbF6 showing the interactions of the [NO2]+ cations with the [SbF6] anions; thermal ellipsoids are drawn at the 50% probability level. Fig. 4. Packing of [XeF5]+ cations and [Sb2F11] anions in the crystal structure of XeF5Sb2F11.

Fig. 3. Part of the crystal structure of the XeF5SbF6 showing the interactions between the [XeF5]+ cation and the [SbF6] anions; thermal ellipsoids are drawn at the 50% probability level.

Four secondary N  F contacts in the NO2SbF6 are equal to 2.540(4) A˚ and comparable to the N  F contacts in the other [NO2]+ fluorides [32–35]. The four equatorial SbF1 bonds involved in the secondary bonding with the N are slightly elongated (1.879(4) A˚) in comparison to the remaining SbF2 bonds (1.865(7) A˚).

Fig. 5. Part of the crystal structure of XeF5Sb2F11 showing the interactions between the [XeF5]+ cation and the three [Sb2F11] anions; thermal ellipsoids are drawn at the 50% probability level.

compound has been well described in previous X-ray crystallographic studies and requires no further discussion. The interactions between the [XeF5]+ and [SbF6] ions are shown in Fig. 3 and the selected bond distances are given in Table 2. The XeF bond lengths of the [XeF5]+ cation are similar to those determined in [XeF5][SbF6]XeOF4 at 151 K [36].

3.2. Crystal structure of XeF5SbF6 The XeF5SbF6 single-crystal determination revealed that the compound is isotypic to the known XeF5MF6 (M = Ru [6], Pt [9]) as previously suggested on the basis of the X-ray powder diffraction data [11]. Both, the cation and the anion are located at mirror planes. In each XeF5 unit the Xe1 and F1 atoms reside on special 4c positions resulting in one Xe1–F1, two Xe1–F2 and two Xe1–F3 distances. Four fluorine atoms (F4, F5, F6, F8) together with the Sb atom are located at the mirror plane and the remaining F7 occupies a general position (Fig. 3). This structural type of XeF5MF6 Table 2 Selected distances, Xe  F contacts (A˚) and angles (8) in the crystal structure of XeF5SbF6. Sb1–F4 Sb1–F5 Sb1–F6 Sb1–F7 Sb1–F8

1.895(3) 1.857(3) 1.859(3) 2  1.882(2) 1.898(3)

Xe1–F1 Xe1–F2 Xe1–F3 Xe1  F4 Xe1  F7 Xe1  F8

1.804(3) 2  1.841(2) 2  1.844(2) 2.617(3) 2  2.860(2) 2.638(3)

Fig. 6. Part of the crystal structure of XeF5Sb2F11 showing the interactions between the [Sb2F11] anion and the three [XeF5]+ cations; thermal ellipsoids are drawn at the 50% probability level.

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Table 3 Selected distances (A˚) and angles (8) in the crystal structure of XeF5Sb2F11. Xe–F1 Xe–F2 Xe–F3 Xe–F4 Xe–F5 Xe  F9 Xe  F10 Xe  F15 Xe  F16 Sb1–F6 Sb1–F7 Sb1–F8 Sb1–F9

1.803(3) 1.830(3) 1.832(3) 1.834(3 1.835(3) 2.915(3) 2.848(3) 2.775(3) 2.814(3) 1.838(3) 1.846(3) 1.853(3) 1.866(3)

Sb1–F10 Sb1–F11 Sb2–F11 Sb2–F12 Sb2–F13 Sb2–F14 Sb2–F15 Sb2–F16

1.883(3) 2.019(3) 2.029(3) 1.837(3) 1.838(3) 1.843(3) 1.870(3) 1.878(3)

Sb2F11 angles Sb1–Fb–Sb2a Torsion angleb

145.09(16) 37.5

The crystal structure of XeF5Sb2F11 represents the only known example of XeF6:MF5 = 1:2 compound. Acknowledgement The authors gratefully acknowledge the financial support from the Slovenian Research Agency (ARRS) within the research program: P1-0045 Inorganic Chemistry and Technology. Appendix A. Supplementary data

a

Bending of two SbF5 groups about Fb (bridging fluorine) which is expressed in terms of the bridge angle a. b Torsion of two planar SbF4,eq groups from eclipsed to staggered conformation expressed as the torsion angle (c) [37,38].

3.3. Crystal structure of XeF5Sb2F11 The crystal structure of XeF5Sb2F11 is composed of discrete [XeF5]+ cations and [Sb2F11] anions (Fig. 4) that interact by means of a secondary fluorine-bridge contact (Figs. 5 and 6). The geometry of [XeF5]+ is similar to that of XeF5SbF6, i.e. the Xe–Fax is shorter than the rest of the Xe–Feq bonds (Table 3). The xenon atom of each [XeF5]+ cation of XeF5Sb2F11 has four secondary fluorine bridges (Xe  F) to three different [Sb2F11] anions (Fig. 5) and each [Sb2F11] is involved in secondary contacts with three [XeF5]+ groups (Fig. 6). These contacts avoid the lonepair domain of xenon. With the torsion angle (37.58, Table 2, Fig. 6) the four Feq atoms of the Sb(1)F6 and Sb(2)F6 groups are in a staggered position. The Sb–F distances with F involved in the Xe  F contacts are elongated in comparison to the rest of the Sb–F bonds (Table 3, Figs. 5 and 6). 4. Conclusions The crystal structures of twelve known XeF5MF6 (M = V, Nb, Ta, Ru, Ir, Os, Pt, Au, As, Sb, Bi and U) compounds, where for M = Nb [4], Ru [6], Pt [9], As [10], Sb, Au [8] and U [12] the crystal structures were determined on single-crystal data, can be divided into three groups. In the first group there are the As and Au compounds. In the second are the Nb, Ru, Pt, Sb and according to X-ray powder diffraction data also the Ta [5,39], Ir [7,8] and Os [8] compounds. The uranium compound is the only example of the third group; meanwhile no structural information is available for the V [3] or the Bi compound [11]. The crystal structures of the NO2AsF6 (determined at 291 K) [32] and NO2SbF6 (determined at 150 K) are not isotypic. They differ in terms of packing of the XF6 (X = As, Sb) octahedra and locations of the [NO2]+ cations. In the future it would be interesting to check whether there is a possible phase transition and what is the situation with the NO2MF6 crystal structures consisting of [MF6] anions of similar size, i.e. M = Nb, Ta, Au, etc.

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[24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39]

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