research communications
New 3)2Cl2 at 100 K
of the of Zn(NHaLaboratory of Physics of Complex Matter, Ecole Polytechnique Fédérale de Lausanne, Switzerland, and bCrystal Growth Facility, Ecole Polytechnique Fédérale de Lausanne, Switzerland
*Correspondence e-mail: wen.bi@epfl.ch
The 2(NH3)2], diamminedichloridozinc, was re-investigated at low temperature, revealing the positions of the hydrogen atoms and thus a deeper insight into the hydrogen-bonding scheme in the crystal packing. In comparison with previous determinations [MacGillavry & Bijvoet (1936). Z. Kristallogr. 94, 249–255; Yamaguchi & Lindqvist (1981). Acta Chem. Scand. 35, 727–728], an improved precision of the structural parameters was achieved. In the crystal, tetrahedral [Zn(NH3)2Cl2] units (point-group symmetry mm2) are linked through N—H⋯Cl hydrogen bonds into a three-dimensional network.
of [ZnClCCDC reference: 1949371
1. Chemical context
Zn(NH3)2Cl2 is found in discharged zinc–air batteries. It is formed by dissolution of the zinc electrode in an ZnCl2–NH4Cl electrolyte. At high Zn2+ concentrations, the cations subsequently undergo complex formation with NH3 and Cl− (Clark et al., 2017). Moreover, in the last century, Zn(NH3)nCl2 phases with n = 0.167–6 have been intensively investigated since these materials appear to be by-products of hydrocracking of heavy-oil fractions. The monoammine salt with n = 1 and the diammine salt with n = 2 are the most studied members in this family. Thermal stability, thermomechanical and thermogravimetric behaviour are well documented for these systems (Gardner et al., 1989).
The crystal-structure model of Zn(NH3)2Cl2 was to this day incomplete, lacking the positions of hydrogen atoms. The of Zn(NH3)2Cl2 was originally determined by MacGillavry & Bijvoet (1936) without of atomic positions [COD number ID 1010197; ICSD number 26136; PDF4 number 01-074-0506]. This incompleteness was rather normal considering the X-ray techniques and measurement conditions at that time. An improved structure model was obtained decades later from a room-temperature data set collected on a four-circle diffractometer by Yamaguchi & Lindqvist (1981), however without hydrogen-atom positions [PDF4 number 04-015-4717]. One more record of this phase in PDF4 [number 00-024-1435] can be found, however with a very limited X-ray powder diffraction pattern range from 5–63°/2θ, which is unsuitable for Rietveld refinement.
Large single crystals of Zn(NH3)2Cl2 were obtained as a side product of a chemical vapour transport (CVT) reaction, which allowed the reinvestigation of the at low temperature with a particular focus on determination of the H-atom positions.
2. Structural commentary
As shown in Fig. 1, the new structure of Zn(NH3)2Cl2 (100 K data) confirms the former model by Yamaguchi & Lindqvist (1981). The small shrinkage of the at low temperature is mainly due to lattice dynamics. However, the bond lengths within the Zn(NH3)2Cl2 tetrahedron refined from 100 K data are similar to the ones obtained from room-temperature data, but with higher precision. This confirms that the tetrahedron is a very rigid building block of the structure (Fig. 2). Two independent H atoms, one in a general position (H1A) and one on a mirror plane (H1B), bond to the nitrogen atom with refined bond lengths of N1—H1A = 0.825 (17) Å and N1—H1B = 0.74 (4) Å, respectively. Hydrogen-bonding interactions of weak-to-medium strengths (Table 1) between the NH3 group and the Cl ligands of adjacent tetrahedra lead to formation of a three-dimensional network, as shown in Fig. 3.
3. Synthesis and crystallization
Zn(NH3)2Cl2 was obtained during the course of a chemical vapour transport experiment. Prior to use, a silica tube sealed at one end (Ø = 15 mm, wall thickness = 2 mm) was heated under vacuum to 1073 K overnight. Zinc oxide (317 mg) and previously dried ammonium chloride (190 mg) were pressed into pellets and put into the pretreated silica tube. After evacuation to 10−6 mbar, the tube was sealed and placed into a horizontal tube furnace. The temperature at the source was slowly heated to 1173 K and maintained at this value for the whole duration of growth. At the low-temperature zone (873 K), a colourless powder mixed with high-quality single crystals of Zn(NH3)2Cl2 with an irregular morphology was collected after complete cooling to room temperature. Since the thermal stability of Zn(NH3)2Cl2 is limited as it already decomposes at 463 K (Gardner et al., 1989), it is very likely that Zn(NH3)2Cl2 crystallized at the very end of the cooling process.
4. Refinement
Crystal data, data collection and structure . Unlike the two previous refinements in Imam, the was chosen to be in the standard setting (Imma) for No. 74. Three reflections (020, 002, 004) affected by the incident beam-stop were omitted. The two H atoms were refined freely.
details are summarized in Table 2Supporting information
CCDC reference: 1949371
https://doi.org/10.1107/S2056989019011757/wm5517sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989019011757/wm5517Isup2.hkl
Data collection: CrysAlis PRO (Rigaku OD, 2019); cell
CrysAlis PRO (Rigaku OD, 2019); data reduction: CrysAlis PRO (Rigaku OD, 2019); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015b); molecular graphics: DIAMOND (Brandenburg, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).[ZnCl2(NH3)2] | Dx = 2.165 Mg m−3 |
Mr = 170.34 | Mo Kα radiation, λ = 0.71073 Å |
Orthorhombic, Imma | Cell parameters from 1597 reflections |
a = 7.7077 (2) Å | θ = 3.6–37.4° |
b = 8.0226 (2) Å | µ = 5.56 mm−1 |
c = 8.4526 (3) Å | T = 100 K |
V = 522.67 (3) Å3 | Irregular, colourless |
Z = 4 | 0.26 × 0.18 × 0.16 mm |
F(000) = 336 |
Rigaku SuperNOVA diffractometer | 678 reflections with I > 2σ(I) |
Radiation source: micro-focus sealed X-ray tube | Rint = 0.017 |
ω scans | θmax = 36.3°, θmin = 3.5° |
Absorption correction: analytical (CrysAlis PRO; Rigaku OD, 2019) | h = −12→8 |
Tmin = 0.277, Tmax = 0.454 | k = −13→12 |
2303 measured reflections | l = −12→14 |
708 independent reflections |
Refinement on F2 | Hydrogen site location: difference Fourier map |
Least-squares matrix: full | All H-atom parameters refined |
R[F2 > 2σ(F2)] = 0.015 | w = 1/[σ2(Fo2) + (0.0188P)2] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.036 | (Δ/σ)max = 0.001 |
S = 1.04 | Δρmax = 0.50 e Å−3 |
708 reflections | Δρmin = −0.55 e Å−3 |
25 parameters | Extinction correction: SHELXL2018 (Sheldrick, 2015b), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
0 restraints | Extinction coefficient: 0.0043 (6) |
Primary atom site location: structure-invariant direct methods |
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. |
x | y | z | Uiso*/Ueq | ||
Zn1 | 0.500000 | 0.250000 | 0.61168 (2) | 0.01163 (6) | |
Cl1 | 0.500000 | 0.47954 (3) | 0.76915 (3) | 0.01375 (6) | |
N1 | 0.28237 (15) | 0.250000 | 0.47949 (13) | 0.01603 (17) | |
H1A | 0.274 (3) | 0.3281 (19) | 0.416 (2) | 0.045 (4)* | |
H1B | 0.206 (5) | 0.250000 | 0.533 (4) | 0.090 (11)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Zn1 | 0.01002 (9) | 0.01352 (9) | 0.01134 (9) | 0.000 | 0.000 | 0.000 |
Cl1 | 0.01288 (11) | 0.01346 (11) | 0.01490 (11) | 0.000 | 0.000 | −0.00253 (7) |
N1 | 0.0136 (4) | 0.0211 (4) | 0.0134 (4) | 0.000 | −0.0016 (3) | 0.000 |
Zn1—Cl1i | 2.2722 (3) | N1—H1Aii | 0.825 (17) |
Zn1—Cl1 | 2.2722 (3) | N1—H1A | 0.825 (17) |
Zn1—N1i | 2.0155 (11) | N1—H1B | 0.74 (4) |
Zn1—N1 | 2.0155 (11) | ||
Cl1i—Zn1—Cl1 | 108.282 (14) | Zn1—N1—H1Aii | 115.0 (13) |
N1—Zn1—Cl1 | 108.951 (17) | Zn1—N1—H1A | 115.0 (13) |
N1i—Zn1—Cl1i | 108.951 (17) | Zn1—N1—H1B | 109 (3) |
N1—Zn1—Cl1i | 108.951 (17) | H1A—N1—H1Aii | 99 (2) |
N1i—Zn1—Cl1 | 108.950 (17) | H1A—N1—H1B | 109 (2) |
N1i—Zn1—N1 | 112.66 (7) | H1B—N1—H1Aii | 109 (2) |
Symmetry codes: (i) −x+1, −y+1/2, z; (ii) x, −y+1/2, z. |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···Cl1iii | 0.825 (17) | 2.806 (18) | 3.4552 (9) | 137.0 (17) |
N1—H1A···Cl1iv | 0.825 (17) | 2.897 (18) | 3.5505 (9) | 137.6 (16) |
N1—H1B···Cl1v | 0.74 (4) | 2.95 (3) | 3.5556 (10) | 141 (1) |
N1—H1B···Cl1vi | 0.74 (4) | 2.95 (3) | 3.5556 (10) | 141 (1) |
Symmetry codes: (iii) −x+1, −y+1, −z+1; (iv) −x+1/2, −y+1, z−1/2; (v) −x+1/2, −y+1/2, −z+3/2; (vi) x−1/2, y, −z+3/2. |
Acknowledgements
DWB is grateful to the help of Dr Rosario Scopelliti in ISIC of EPFL. We would like to express our great appreciation to Professor László Forró in LPMC of EPFL for the fruitful discussions and support.
Funding information
Funding for this research was provided by: Swiss National Science Foundation (SNF) Sinergia network "NanoSkyrmionics" (grant No. CRSII5-171003).
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