research communications
2(HTeO3)(AsO4)
of ZnaInstitute for Chemical Technologies and Analytics, Division of Structural Chemistry, TU Wien, Getreidemarkt 9/164-SC, A-1060, Vienna, Austria
*Correspondence e-mail: felix.eder@tuwien.ac.at
Single crystals of Zn2(HTeO3)(AsO4), dizinc(II) hydroxidodioxidotellurate(IV) oxidoarsenate(V), were obtained as one of the by-products in a hydrothermal reaction between Zn(NO3)2·6H2O, TeO2, H3AsO4 and NH3 in molar ratios of 2:1:2:10 at 483 K for seven days. The of Zn2(HTeO3)(AsO4) contains one Te (site symmetry m), one As (m), one Zn (1), five O (three m, two 1) and one H (m) site. The ZnII atom exhibits a of 5 and is coordinated by four oxygen atoms and a hydroxide group, forming a distorted trigonal bipyramid. The hydroxide ion is positioned at a significantly larger distance on one of the axial positions of the bipyramid. The [ZnO4OH] polyhedra are connected to each other by corner-sharing to form ∞2[ZnO3/2(OH)1/2O1/1] layers extending parallel to (001). The TeIV atom is coordinated by three oxygen atoms and a hydroxide group in a one-sided manner in the shape of a bisphenoid, revealing stereochemical activity of its 5s2 electron lone pair. The AsV atom is coordinated by four oxygen atoms to form the tetrahedral oxidoarsenate(V) anion. By corner-sharing, [TeO3OH] and [AsO4] groups link adjacent ∞2[ZnO3/2(OH)1/2O1/1] layers along [001] into a three-dimensional framework structure.
Keywords: crystal structure; oxidotellurate(IV); oxidoarsenate(V); hydrogen bonding; lone pair electrons; stereochemical activity.
CCDC reference: 2079463
1. Chemical context
Only a few elements have such a diverse crystal chemistry as tellurium, especially in its +IV s2 electron pair of TeIV (Galy et al., 1975) that has a similar space requirement as coordinating ligands and therefore often results in one-sided and low-symmetry coordination spheres around TeIV atoms. An extensive review of the rich crystal chemistry of oxidotellurates(IV) was published recently by Christy et al. (2016).
This can be attributed to the stereochemically active non-bonding 5The peculiar crystal chemistry of TeIV makes it an interesting building block in the search for new compounds with crystal structures lacking inversion symmetry. As a prerequisite, a compound must be non-centrosymmetric in order to have ferro-, piezo- or pyroelectric properties or to possess non-linear optical properties (Ok et al., 2006). Another effect of the electron lone pair and its large space consumption is the frequent formation of open-framework structures in (transition) metal oxidotellurates(IV). Different structure units such as clusters, chains, layers or channels resulting from the presence of oxidotellurate(IV) anions are observed in various crystal structures (Stöger & Weil, 2013). Introducing secondary anions into transition-metal oxidotellurates(IV) can lead to even more structural diversification. Over the past few years, several anions have been incorporated into metal or transition-metal oxidotellurates, viz. sulfates [e.g. Cd4(SO4)(TeO3)3; Weil & Shirkhanlou, 2017a], selenates [e.g. Zn2(SeO4)(TeO3); Weil & Shirkhanlou, 2017b], carbonates [e.g. Pb5(SeO4)2(TeO4)(CO3); Weil & Shirkhanlou, 2017c], nitrates [e.g. Ca6Te5O15(NO3)2; Stöger & Weil, 2013], phosphates [e.g. Co3Te2O2(PO4)2(OH)4; Zimmermann et al., 2011] or, very recently, arsenates [Cu5(TeO3)2(AsO4)2; Missen et al., 2020]. Crystals of Cu5(TeO3)2(AsO4)2 have been grown by a chemical transport reaction (Binnewies et al., 2012), starting from CuO, TeO2 and As2O5 at temperatures of 1023 K (source) and 953 K (sink). The title compound, Zn2(HTeO3)(AsO4), however, was obtained at much milder temperatures (483 K) under hydrothermal conditions.
2. Structural commentary
The 2(HTeO3)(AsO4) contains one Te, one As, one Zn, one H and five O atoms located either on a special position with m (Wyckoff position 2 a; Te1, As1, O3, O4, O5, H1) or on general positions (Wyckoff position 4 b; Zn1, O1, O2). Selected bond lengths are collated in Table 1.
of ZnThe zinc cation (Zn1) is coordinated by five oxygen atoms with one (O3, as part of the hydroxy group) being at a significantly longer distance [2.3259 (18) Å] than the other four [1.979 (3)–2.0486 (16) Å]. The resulting polyhedron has the shape of a distorted trigonal bipyramid, with the remote O3 site occupying one of the axial positions and the equatorial positions being slightly tilted towards it (Fig. 1). The geometry index τ5 (Addison et al., 1984), which is 0 for an ideal square pyramid and 1 for an ideal trigonal bipyramid, amounts to 0.665 for the [ZnO4OH] polyhedron. The [ZnO4OH] polyhedra are connected to each other by sharing four corners with neighbouring polyhedra to form ∞2[ZnO3/2(OH)1/2O1/1] layers extending parallel to (001). The bond-valence sum (BVS; Brown, 2002) of Zn1 was calculated to be 1.98 valence units (v.u.) using the values of Brese & O'Keeffe (1991).
The tellurium(IV) atom (Te1) is coordinated by four oxygen atoms with bond lengths in the range 1.880 (2)–2.131 (4) Å. The BVS of Te1 is 4.02 v.u. using the values of Brese & O'Keeffe (1991) for calculation. With the revised bond-valence values by Mills & Christy (2013), a lower BVS of 3.86 v.u. was calculated under consideration of the four nearest oxygen atoms. However, the BVS increases to 4.03 v.u. if all oxygen atoms within a distance of up to 3.5 Å are accounted for, as is suggested by Mills & Christy (2013). The resulting [TeO3OH] is a bisphenoid. Under consideration of the space requirement of the 5s2 electron lone pair, the corresponding [ΨTeO3OH] polyhedron has the shape of a distorted trigonal bipyramid with the non-bonding electron pair occupying an equatorial position (Fig. 2). The geometry index τ5 of the [ΨTeO3OH] polyhedron is 0.413. The LPLoc software (Hamani et al., 2020) revealed the position of the electron lone pair with resulting fractional coordinates of x = 0.7781, y = 0, z = 0.5519. The radius of the electron lone pair was calculated to be 1.32 Å with a distance of 1.680 Å from the Te1 position. The oxygen atom (O3) of the hydroxy group is located on an axial position of the [ΨTeO3OH] polyhedron. Its hydrogen atom is directed to the O5 site, forming a weak linear hydrogen bond towards the O5 site with a O3⋯O5 distance of 3.213 (5) Å (Table 2). It is remarkable that the hydrogen atom is located on the oxidotellurate(IV) unit instead of the oxidoarsenate(V) anion given that for 0.1–0.01 N solutions, the pKb value of the [AsO4]3– anion is much smaller (2.40 at 291 K) than that of the [TeO3]2– anion (6.30 at 298 K) (Weast & Astle, 1982). Even though the conditions during the hydrothermal experiment are far from the tabulated values, it is surprising that a difference in the equilibrium constants of almost four orders of magnitude was overridden in the resulting crystal. Nevertheless, as evidenced from a difference-Fourier map and BVS calculations (BVS without contribution of the H atom amounts to 1.15 v.u. for O3), the hydroxide group is located on the oxidotellurate(IV) unit.
The arsenic(V) atom (As1) is coordinated tetrahedrally by four oxygen atoms with distances in the range 1.673 (2)–1.716 (3) Å. The mean As—O bond length of 1.693 (23) Å is slightly longer than those reported for AsO43– groups [1.667 (18) Å; Schwendtner & Kolitsch, 2019] or for oxidoarsenate groups in general (also including As—OH bonds, with an overall mean of 1.687 (27) Å; Gagné & Hawthorne, 2018). The BVS is 4.91 v.u. using the values of Brese & O'Keeffe (1991) for calculation.
The 2(HTeO3)(AsO4) is built up from ∞2[ZnO3/2(OH)1/2O1/1] layers extending parallel to (001) (Fig. 3). The [TeO3OH] units are situated below a ∞2[ZnO3/2(OH)1/2O1/1] layer and are isolated from each other. An individual [TeO3OH] unit shares three corners with two [ZnO4OH] polyhedra each, and one corner with an [AsO4] tetrahedron. Likewise, the oxidoarsenate anions, situated above a ∞2[ZnO3/2(OH)1/2O1/1] layer, are isolated from each other, but share corners with other building units: two corners with one [ZnO4OH] polyhedron each, one corner with two [ZnO4OH] polyhedra and one corner with a [TeO3OH] unit. This way, a three-dimensional framework structure is established (Fig. 4).
of ZnIn the s2 electron lone pairs at the TeIV atoms lead to the formation of channels parallel to [110] (Fig. 4). The weak O—H⋯O hydrogen bond is directed across these channels. There are also smaller channels oriented parallel to [100] that, however, remain empty (Fig. 5).
the spatial requirements of the 53. Synthesis and crystallization
Crystals of Zn2(HTeO3)(AsO4) were obtained by hydrothermal synthesis. The reactants, 0.1949 g of Zn(NO3)2·6H2O (0.670 mmol), 0.0512 g of TeO2 (0.321 mmol), 0.1365 g 80%wt of H3AsO4 (aq) (0.713 mmol) and 0.22 g of 25%wt NH3 (aq) (3.23 mmol) were weighed into a small Teflon vessel with an inner volume of ca 3 ml. The vessel was filled with deionized water to three-quarters of its volume and the reactants were mixed by manual stirring. The Teflon vessel was then put into a steel autoclave and heated to 483 K for 7 d at autogenous pressure. Afterwards, the autoclave was cooled to room temperature within about 4 h. The resulting product was a colourless multi-phase solid. In the X-ray powder pattern of the bulk, Zn2(HTeO3)(AsO4) was found as a by-product, in addition to (NH4)Zn(AsO4) (Feng et al., 2001) and the educt TeO2 (α-TeO2; Stehlik & Balak, 1948). Under a polarizing microscope, small colourless block-shaped crystals of Zn2(HTeO3)(AsO4) were visible that were manually separated for the single-crystal X-ray diffraction study.
4. Refinement
Crystal data, data collection and structure . Atom labels and coordinates were standardized with Structure Tidy (Gelato & Parthé, 1987) implemented in PLATON (Spek, 2020). The H atom of the hydroxy group was located in a difference-Fourier map and was refined freely. The was refined under consideration of revealing a minor contribution of 3.2 (12)% for the inversion-related twin component.
details are summarized in Table 3
|
Supporting information
CCDC reference: 2079463
https://doi.org/10.1107/S2056989021004333/pk2657sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989021004333/pk2657Isup2.hkl
Data collection: APEX3 (Bruker, 2016); cell
SAINT (Bruker, 2016); data reduction: SAINT (Bruker, 2016); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL (Sheldrick, 2015b); molecular graphics: ATOMS for Windows (Dowty, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).Zn2(HTeO3)(AsO4) | F(000) = 404 |
Mr = 446.27 | Dx = 4.950 Mg m−3 |
Monoclinic, Cm | Mo Kα radiation, λ = 0.71073 Å |
a = 6.9040 (12) Å | Cell parameters from 5391 reflections |
b = 7.7212 (13) Å | θ = 3.6–40.6° |
c = 5.726 (1) Å | µ = 18.25 mm−1 |
β = 101.196 (5)° | T = 100 K |
V = 299.43 (9) Å3 | Block, colourless |
Z = 2 | 0.06 × 0.04 × 0.03 mm |
Bruker APEXII CCD diffractometer | 1918 reflections with I > 2σ(I) |
ω– and φ–scans | Rint = 0.044 |
Absorption correction: multi-scan (SADABS; Krause et al., 2015) | θmax = 40.6°, θmin = 3.6° |
Tmin = 0.538, Tmax = 0.748 | h = −12→12 |
8261 measured reflections | k = −14→14 |
1986 independent reflections | l = −10→10 |
Refinement on F2 | All H-atom parameters refined |
Least-squares matrix: full | w = 1/[σ2(Fo2)] where P = (Fo2 + 2Fc2)/3 |
R[F2 > 2σ(F2)] = 0.019 | (Δ/σ)max < 0.001 |
wR(F2) = 0.040 | Δρmax = 1.79 e Å−3 |
S = 0.92 | Δρmin = −1.16 e Å−3 |
1986 reflections | Extinction correction: SHELXL (Sheldrick, 2015b), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
63 parameters | Extinction coefficient: 0.0043 (5) |
2 restraints | Absolute structure: Refined as an inversion twin |
Hydrogen site location: difference Fourier map | Absolute structure parameter: 0.032 (12) |
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. |
Refinement. Refined as a two-component inversion twin. |
x | y | z | Uiso*/Ueq | ||
Te1 | 0.70945 (3) | 0.000000 | 0.81776 (3) | 0.00418 (6) | |
As1 | 0.24451 (6) | 0.000000 | 0.51174 (7) | 0.00440 (9) | |
Zn1 | 0.46889 (7) | 0.23359 (4) | 0.17917 (8) | 0.00521 (7) | |
O1 | 0.1089 (4) | 0.1808 (3) | 0.4941 (4) | 0.0081 (4) | |
O2 | 0.1998 (4) | 0.3177 (3) | 0.0329 (4) | 0.0062 (4) | |
O3 | −0.0007 (6) | 0.000000 | 0.0002 (6) | 0.0087 (6) | |
O4 | 0.3941 (5) | 0.000000 | 0.3064 (6) | 0.0063 (5) | |
O5 | 0.3968 (5) | 0.000000 | 0.7868 (6) | 0.0065 (5) | |
H1 | 0.114 (13) | 0.000000 | −0.064 (14) | 0.015 (19)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Te1 | 0.00465 (12) | 0.00392 (11) | 0.00381 (11) | 0.000 | 0.00040 (8) | 0.000 |
As1 | 0.0040 (2) | 0.0047 (2) | 0.00427 (18) | 0.000 | 0.00031 (16) | 0.000 |
Zn1 | 0.00389 (15) | 0.00549 (13) | 0.00595 (15) | 0.00021 (15) | 0.00023 (11) | 0.00043 (13) |
O1 | 0.0090 (10) | 0.0078 (10) | 0.0068 (9) | 0.0039 (8) | −0.0006 (8) | −0.0004 (7) |
O2 | 0.0061 (9) | 0.0058 (9) | 0.0068 (9) | 0.0000 (8) | 0.0015 (7) | 0.0021 (7) |
O3 | 0.0055 (14) | 0.0116 (14) | 0.0085 (13) | 0.000 | 0.0001 (11) | 0.000 |
O4 | 0.0067 (14) | 0.0064 (13) | 0.0062 (12) | 0.000 | 0.0025 (11) | 0.000 |
O5 | 0.0049 (13) | 0.0103 (14) | 0.0041 (11) | 0.000 | 0.0001 (10) | 0.000 |
Te1—O2i | 1.880 (2) | As1—O5 | 1.716 (3) |
Te1—O2ii | 1.880 (2) | Zn1—O2v | 1.979 (3) |
Te1—O3iii | 2.070 (4) | Zn1—O1v | 1.987 (3) |
Te1—O5 | 2.131 (4) | Zn1—O2 | 1.993 (3) |
As1—O1iv | 1.673 (2) | Zn1—O4 | 2.0486 (16) |
As1—O1 | 1.673 (2) | Zn1—O3vi | 2.3259 (18) |
As1—O4 | 1.709 (3) | O3—H1 | 0.94 (9) |
O2i—Te1—O2ii | 96.96 (14) | O2v—Zn1—O3vi | 80.87 (12) |
O2i—Te1—O3iii | 79.82 (10) | O1v—Zn1—O3vi | 92.08 (11) |
O2ii—Te1—O3iii | 79.82 (10) | O2—Zn1—O3vi | 71.53 (12) |
O2i—Te1—O5 | 83.70 (10) | O4—Zn1—O3vi | 170.38 (14) |
O2ii—Te1—O5 | 83.70 (10) | As1—O1—Zn1vii | 120.01 (13) |
O3iii—Te1—O5 | 155.01 (13) | Te1viii—O2—Zn1vii | 124.12 (13) |
O1iv—As1—O1 | 113.14 (19) | Te1viii—O2—Zn1 | 111.74 (13) |
O1iv—As1—O4 | 111.36 (10) | Zn1vii—O2—Zn1 | 121.25 (11) |
O1—As1—O4 | 111.36 (10) | Te1ix—O3—Zn1vii | 93.51 (11) |
O1iv—As1—O5 | 106.93 (11) | Te1ix—O3—Zn1x | 93.51 (11) |
O1—As1—O5 | 106.93 (11) | Zn1vii—O3—Zn1x | 124.36 (16) |
O4—As1—O5 | 106.69 (17) | Te1ix—O3—H1 | 128 (5) |
O2v—Zn1—O1v | 99.25 (11) | Zn1vii—O3—H1 | 109.1 (18) |
O2v—Zn1—O2 | 130.47 (12) | Zn1x—O3—H1 | 109.1 (18) |
O1v—Zn1—O2 | 121.53 (11) | As1—O4—Zn1 | 118.20 (8) |
O2v—Zn1—O4 | 104.71 (11) | As1—O4—Zn1iv | 118.20 (8) |
O1v—Zn1—O4 | 94.69 (11) | Zn1—O4—Zn1iv | 123.38 (16) |
O2—Zn1—O4 | 99.06 (12) | As1—O5—Te1 | 120.43 (18) |
Symmetry codes: (i) x+1/2, −y+1/2, z+1; (ii) x+1/2, y−1/2, z+1; (iii) x+1, y, z+1; (iv) x, −y, z; (v) x+1/2, −y+1/2, z; (vi) x+1/2, y+1/2, z; (vii) x−1/2, −y+1/2, z; (viii) x−1/2, y+1/2, z−1; (ix) x−1, y, z−1; (x) x−1/2, y−1/2, z. |
D—H···A | D—H | H···A | D···A | D—H···A |
O3—H1···O5xi | 0.94 (9) | 2.28 (9) | 3.213 (5) | 179 (7) |
Symmetry code: (xi) x, y, z−1. |
Acknowledgements
The X-ray centre of the TU Wien is acknowledged for financial support and for providing access to the single-crystal and powder X-ray diffractometers.
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