Crystal structure and Hirshfeld surface analysis of bis[hydrazinium(1+)] hexafluoridosilicate: (N2H5)2SiF6
aLaboratoire de Physico-chimie des Matériaux Inorganiques, Université Ibn Tofail, Faculté des Sciences, BP 133, 14000 Kenitra, Morocco, bCentre Régional des Métiers de l'Education et de la Formation, Madinat Al Irfane, Souissi, BP 6210 Rabat, Morocco, and cLaboratoire de Chimie Appliquée des Matériaux, Centre des Sciences des Matériaux, Faculty of Sciences, Mohammed V University in Rabat, Avenue Ibn Batouta, BP 1014, Rabat, Morocco
*Correspondence e-mail: firstname.lastname@example.org
In the title inorganic molecular salt, (N2H5)2SiF6, the silicon atom at the centre of the slightly distorted SiF6 octahedron [range of Si—F distances = 1.6777 (4)–1.7101 (4) Å] lies on a crystallographic inversion centre. In the crystal, the ions are connected by N—H⋯N and N—H⋯F hydrogen bonds; the former link the cations into  chains and the latter (some of which are bifurcated or trifurcated) link the ions into a three-dimensional network. The two-dimensional fingerprint plots show that F⋯H/H⋯F interactions dominate the Hirshfeld surface (75.5%) followed by H⋯H (13.6%) and N⋯H/H⋯N (8.4%) whereas F⋯F (1.9%) and F⋯N/N⋯F (0.6%) have negligible percentages. The title compound is isostructural with its germanium-containing analogue.
Hydrazinium hexafluoridometalate compounds have been studied by X-ray diffraction, vibrational spectroscopy and thermal analyses: they have been found to exist with two different formulae: N2H6MF6 (Kojić-Prodić et al., 1971a,b; Frlec et al., 1980; Golič et al., 1980; Cameron et al., 1983; Knop et al., 1983; Ouasri et al., 2002) and (N2H5)2MF6 (Gantar & Rahten, 1988; Leban et al., 1994) where M = Ga, Si, Ti, Zr and Hf. The name `hydrazinium hexafluoridosilicate' has been applied to both compounds: N2H6SiF6 and (N2H5)2SiF6.
The crystal structure of N2H6SiF6 is well described by Frlec et al. (1980) and by Cameron et al. (1983), whereas that of (N2H5)2SiF6 has not previously been reported to our best knowledge. However, this compound was characterized by chemical analysis, vibrational spectroscopy and X-ray powder photography by Gantar & Rahten (1986), who determined the unit-cell parameters and the space group. We now describe the synthesis, single crystal structure and Hirshfeld surface analysis of the title compound, (I), at room temperature.
Compound (I) is an inorganic molecular salt built up from N2H5+ cations and SiF62− anions, as shown in Fig. 1. In this structure, all atoms are in general positions except for the silicon atom, which is located at the Wyckoff position 2d on the inversion centre of the space group P21/n. Thus, the silicon atom is connected to three unique fluorine atoms and their symmetry equivalents, forming a slightly elongated octahedron with Si—F distances in the range of 1.6777 (4) to 1.7101 (4) Å. The minimum and maximum cis F—S—F angles are 89.26 (2) and 90.74 (2)°, respectively. The N—N separation in the cation is 1.4416 (8) Å.
In the extended structure of (I), the hydrazinium cations are linked by strong N—H⋯N hydrogen bonds (Table 1), building an infinite zigzag chain propagating along the  direction as shown in Fig. 2. The [SiF6]2− anion interacts with the (N2H5)+ cations through electrostatic attraction and accepts no fewer than ten simple, bifurcated or trifurcated N—H⋯F hydrogen bonds (Fig. 3, Table 1). This results in a three-dimensional network in which the hydrazinium cations build zigzag chains parallel to the b-axis direction and the [SiF6]2− anions are stacked along the  direction (Fig. 4).
The packing of (I) was further investigated and quantified with a Hirshfeld surface analysis (McKinnon et al., 2004; Spackman & Jayatilaka, 2009) and two-dimensional fingerprint plots generated using the CrystalExplorer package (Turner et al., 2017).
The acceptor atoms in the interactions are shown with negative electrostatic potentials (red regions), and donor atoms are shown with positive electrostatic potentials (blue regions). The N—H⋯F interactions in the structure are apparent from the relatively bright red-spots on the Hirshfeld surface of (I) mapped over dnorm (Fig. S1 in the supporting information). In order to provide quantitative information on the contribution of the intermolecular interactions to the crystal packing, the three-dimensional dnorm surface is resolved into two-dimensional fingerprint plots, generated based on de and di distance scales and illustrated in Fig. 5(a)–(f) The F⋯H/H⋯F interactions appear as distinct spikes in the fingerprint plot, and occupy the majority of the total Hirshfeld surface (75.5%) as illustrated in Fig. 5(a); the characteristic `wingtip' features indicate the N—H⋯F hydrogen bonds. The H⋯F interaction are represented by a spike (di = 0.8, de = 1.1 Å) at the bottom left (donor), whereas the F⋯H interactions are represented by a spike (di = 1.1, de = 0.8 Å) at the bottom right (acceptor) of the fingerprint plot. The H⋯H contacts appear in the middle of the scattered points; these contacts comprise 13.6% of the total Hirshfeld surface [Fig. 5(c)]. The N⋯H contacts cover 8.4% of the total surface, as the third important contributor in the crystal packing, Fig. 5(d) while the F⋯F and F⋯N/N⋯F contacts make negligible contributions of 1.9% [Fig. 5(e)] and 0.6% [Fig. 5(f)], respectively.
Hydrazinium (2+) hexafluoridosilicate, N2H6SiF6, at room temperature, crystallizes in a pseudo-tetragonal orthorhombic space group (Pbca, Z = 4), with a = 7.605 (1) Å, b = 7.586 (2) Å and c = 8.543 (1) Å (Frlec et al., 1980; Cameron et al., 1983). Its structure consists of centrosymmetric N2H62+ and SiF62− ions arranged in a NaC1-type packing and connected by N—H⋯F hydrogen bonds, forming layers of cations and anions lying parallel to (001) plane.
Hydrazinium (1+) hexahalogenometallates were studied by Gantar and co-workers (Gantar et al., 1985; Gantar & Rahten, 1986) who showed that (N2H5)2GeF6 crystallizes in the monoclinic system, space group P21/n (Z = 2), with cell parameters a = 6.015 (2) Å, b = 5.249 (1) Å, c = 11.181 (2)Å and β = 100.15 (2)° and is clearly isostructural with (I).
Fluoride complexes of titanium (IV) with ammonium cation derivatives include two hydrazinium hexafluoridotitanates (IV), (N2H5)2TiF6 (Leban et al., 1994) and N2H6TiF6 (Kojić-Prodić et al.,1971a,b). The monoclinic crystals of (N2H5)2TiF6 [P21; Z = 4; a = 7.815 (1) Å, b = 10.019 (1) Å, c = 9.338 (1) Å; β = 93.58 (1)°] exhibit racemic twinning but are not isostructural with (I). The crystal structure of (N2H5)2TiF6 consists of N2H5+ cations and two types of slightly distorted octahedral (TiF6)2− anions. The N2H5+ cations and (TiF6)2− anions are linked via N—H⋯F and N—H⋯N hydrogen bonds, building a three-dimensional network. Two other isostructural hydrazinium (l+) hexafluorido complexes, (N2H5)2ZrF6 and (N2H5)2HfF6, were prepared and characterized by chemical analysis, vibrational spectroscopy and X-ray powder diffraction (Gantar & Rahten, 1988). The infrared spectrum analysis of the title compound at room temperature confirms the obtained results by Gantar & Rahten with the exception of the assignments of two infrared bands (see supporting information).
Hydrazinium (1+) hexafluoridosilicate (N2H5)2SiF6 crystals in the form of colourless blocks were obtained by slow evaporation, at room temperature, of an aqueous solution containing stoichiometric amounts of hydrazine NH2NH2 and H2SiF6. The infrared spectrum was recorded in the range 450–4000 cm−1 with a Vertex 70 FTIR spectrometer.
Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms were located in a difference-Fourier map and refined using a riding model with N—H = 0.86 Å and Uiso(H) = 1.2Ueq(N). The highest peak and the deepest hole in the final Fourier map are at 0.67 Å from F3 and 0.0 Å from Si1.
Data collection: APEX3 (Bruker, 2016); cell refinement: SAINT-Plus (Bruker, 2016); data reduction: SAINT-Plus (Bruker, 2016); program(s) used to solve structure: SHELXT2014/7 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2015b); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: Mercury (Macrae et al., 2008)and publCIF (Westrip, 2010).
|F6H10N4Si||F(000) = 212|
|Mr = 208.21||Dx = 2.045 Mg m−3|
|Monoclinic, P21/n||Mo Kα radiation, λ = 0.71073 Å|
|a = 5.9496 (3) Å||Cell parameters from 1488 reflections|
|b = 5.2484 (2) Å||θ = 3.7–35.0°|
|c = 11.0029 (5) Å||µ = 0.42 mm−1|
|β = 100.245 (1)°||T = 296 K|
|V = 338.10 (3) Å3||Block, colourless|
|Z = 2||0.31 × 0.24 × 0.16 mm|
|Bruker D8 VENTURE Super DUO |
|1488 independent reflections|
|Radiation source: INCOATEC IµS micro-focus source||1379 reflections with I > 2σ(I)|
|HELIOS mirror optics monochromator||Rint = 0.027|
|Detector resolution: 10.4167 pixels mm-1||θmax = 35.0°, θmin = 3.7°|
|φ and ω scans||h = −9→9|
|Absorption correction: multi-scan |
(SADABS; Krause et al., 2015)
|k = −8→8|
|Tmin = 0.638, Tmax = 0.746||l = −17→17|
|19683 measured reflections|
|Refinement on F2||Hydrogen site location: mixed|
|Least-squares matrix: full||H-atom parameters constrained|
|R[F2 > 2σ(F2)] = 0.021|| w = 1/[σ2(Fo2) + (0.0348P)2 + 0.036P] |
where P = (Fo2 + 2Fc2)/3
|wR(F2) = 0.059||(Δ/σ)max = 0.001|
|S = 1.06||Δρmax = 0.27 e Å−3|
|1488 reflections||Δρmin = −0.22 e Å−3|
|54 parameters||Extinction correction: SHELXL-2018/3 (Sheldrick 2015b), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4|
|0 restraints||Extinction coefficient: 0.093 (10)|
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
|F1||0.28419 (6)||−0.13785 (8)||0.55514 (4)||0.02516 (10)|
|F3||0.31234 (7)||0.21784 (8)||0.42375 (4)||0.02473 (10)|
|F2||0.55101 (7)||0.18926 (8)||0.62475 (4)||0.02576 (10)|
|N1||0.46840 (9)||0.60149 (11)||0.77712 (5)||0.02307 (11)|
|N2||0.43562 (9)||0.83227 (11)||0.84285 (5)||0.02447 (11)|
|Si1||0.01429 (10)||0.01983 (11)||0.01242 (10)||0.00065 (6)||0.00149 (6)||−0.00092 (6)|
|F1||0.02032 (17)||0.0332 (2)||0.02288 (17)||−0.00450 (14)||0.00636 (13)||0.00188 (14)|
|F3||0.02217 (17)||0.02512 (18)||0.02510 (18)||0.00506 (13)||−0.00071 (13)||0.00348 (13)|
|F2||0.02585 (18)||0.0309 (2)||0.01981 (17)||0.00025 (14)||0.00210 (13)||−0.01005 (14)|
|N1||0.0199 (2)||0.0245 (2)||0.0237 (2)||−0.00006 (16)||0.00101 (16)||0.00587 (18)|
|N2||0.0222 (2)||0.0289 (2)||0.0220 (2)||−0.00171 (18)||0.00320 (17)||0.00167 (18)|
|Si1—F2i||1.6777 (4)||N1—N2||1.4416 (8)|
|F2i—Si1—F1i||89.90 (2)||F1—Si1—F3||89.48 (2)|
|Symmetry code: (i) −x+1, −y, −z+1.|
|Symmetry codes: (ii) x, y+1, z; (iii) −x+1, −y+1, −z+1; (iv) −x+1/2, y−1/2, −z+3/2; (v) x+1/2, −y+1/2, z+1/2; (vi) −x+3/2, y+1/2, −z+3/2; (vii) −x+1/2, y+1/2, −z+3/2; (viii) x+1/2, −y+3/2, z+1/2.|
The authors thank the Faculty of Science, Mohammed V University in Rabat, Morocco, for the X-ray measurements.
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