In the course of a general study of oxyfluorotellurates(IV), materials likely to exhibit interesting nonlinear optical properties, the crystal structures of the new phases scandium tellurium trioxide fluoride, ScTeO3F, and indium tellurium trioxide fluoride, InTeO3F, belonging to two different structural types and also differing from that of the recently published MTeO3F (M = Fe, Ga and Cr) series, have been determined. The ScTeO3F structure can be described as an intergrowth of two different layers of scandium octahedra connected via isolated TeO3 groups. The scandium ions occupy two different sites with ..2 and 2.. site symmetry. The Te, F and O atoms are on general positions of the Pnna space group. The InTeO3F structure consists of zigzag sheets of InO5F octahedra. The In, Te, O and F atoms are all located on general positions of the P21/a space group. TeO3F polyhedra are inserted between the zigzag sheets of InO5F octahedra and with them form double (InTeO3F)n layers. Therefore, InTeO3F is a true layer structure, unlike the previous types. In all these phases, the electronic lone pair of the TeIV atom is stereochemically active and a full O/F anionic ordering is observed.
Supporting information
ScTeO3F was prepared by a solid-state reaction. A mixture of Sc2O3
(Aldrich 99%), ScF3 (Aldrich 99%) and TeO2 (1:1:3) was heated in a
platinum sealed tube. The temperature was progressively increased to 1123 K,
held for 48 h and water-quenched to room temperature. TeO2 was prepared in
the laboratory by decomposition at 823 K under flowing oxygen of commercial
H6TeO6 (Aldrich, 99.9%). For the preparation of InTeO3F, a mixture of
InF3 (Aldrich 99.9%) and TeO2 (1.8:1) was heated in a sealed platinum
tube with the following thermal treatment: the temperature was increased from
298 to 943 K (5 K min-1), held for 106 h, and then decreased slowly to 673 K
(0.1 K min-1) and held for 164 h. The tube was then water-quenched.
Transparent tablet-shaped single crystals, air-stable and suitable for X-ray
diffraction study, were obtained in both cases.
The residues of electronic density are minimal for ScTeO3F, but for InTeO3F,
a residual density peak of 4.37 e Å-3 persists 0.6 Å from Te1. It
clearly cannot correspond to an extra atom but more likely to an imperfect
absorption correction, resulting from the much more irregular shape and poorer
quality of the single crystal of InTeO3F. However, the structural results do
not seem adversely affected, as attested by the reasonable R factors,
interatomic distances and bond valences.
For both compounds, data collection: KappaCCD Server Software (Nonius, 1998); cell refinement: DIRAX/LSQ (Duisenberg, 1992); data reduction: EVALCCD (Duisenberg et al., 2003); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).
(I) scandium tellurium trioxide fluoride
top
Crystal data top
ScTeO3F | F(000) = 848 |
Mr = 239.56 | Dx = 4.542 Mg m−3 |
Orthorhombic, Pnna | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P2a2bc | Cell parameters from 13064 reflections |
a = 5.7740 (5) Å | θ = 5.1–30.0° |
b = 22.062 (5) Å | µ = 10.13 mm−1 |
c = 5.5000 (12) Å | T = 293 K |
V = 700.6 (2) Å3 | Tablet shape, colourless |
Z = 8 | 0.1 × 0.08 × 0.04 mm |
Data collection top
Nonius KappaCCD diffractometer | 1019 independent reflections |
Radiation source: fine-focus sealed tube | 895 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.046 |
Detector resolution: 9 pixels mm-1 | θmax = 30.0°, θmin = 5.1° |
CCD scans | h = −7→8 |
Absorption correction: multi-scan (SADABS; Bruker 2001) | k = −30→30 |
Tmin = 0.363, Tmax = 0.667 | l = −7→7 |
17528 measured reflections | |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.018 | w = 1/[σ2(Fo2) + (0.0112P)2 + 1.5494P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.035 | (Δ/σ)max = 0.001 |
S = 1.18 | Δρmax = 0.98 e Å−3 |
1019 reflections | Δρmin = −1.00 e Å−3 |
57 parameters | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
0 restraints | Extinction coefficient: 0.0091 (2) |
Crystal data top
ScTeO3F | V = 700.6 (2) Å3 |
Mr = 239.56 | Z = 8 |
Orthorhombic, Pnna | Mo Kα radiation |
a = 5.7740 (5) Å | µ = 10.13 mm−1 |
b = 22.062 (5) Å | T = 293 K |
c = 5.5000 (12) Å | 0.1 × 0.08 × 0.04 mm |
Data collection top
Nonius KappaCCD diffractometer | 1019 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker 2001) | 895 reflections with I > 2σ(I) |
Tmin = 0.363, Tmax = 0.667 | Rint = 0.046 |
17528 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.018 | 57 parameters |
wR(F2) = 0.035 | 0 restraints |
S = 1.18 | Δρmax = 0.98 e Å−3 |
1019 reflections | Δρmin = −1.00 e Å−3 |
Special details top
Experimental. The integrated intensities were corrected for absorption effects by using a
multi-scan method (SADABS, Bruker 2001). Structure solution by direct
methods in the Pnna space group for ScTeO3F and in the
P21/a space group for InTeO3F followed by refinement of
atomic coordinates and anisotropic thermal parameters were performed using
successively the SHELXS97 and the SHELXL97 programs (Sheldrick,
2008). |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell e.s.d.'s are taken
into account individually in the estimation of e.s.d.'s in distances, angles
and torsion angles; correlations between e.s.d.'s in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s.
planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor
wR and goodness of fit S are based on F2, conventional
R-factors R are based on F, with F set to zero for
negative F2. The threshold expression of F2 >
σ(F2) is used only for calculating R-factors(gt) etc.
and is not relevant to the choice of reflections for refinement.
R-factors based on F2 are statistically about twice as large
as those based on F, and R- factors based on ALL data will be
even larger. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
Te1 | 0.20456 (3) | 0.392628 (7) | 0.19594 (3) | 0.00529 (7) | |
Sc1 | 0.2500 | 0.5000 | 0.67882 (14) | 0.00527 (16) | |
Sc2 | −0.06902 (14) | 0.2500 | 0.2500 | 0.00481 (16) | |
F1 | 0.1863 (3) | 0.26783 (8) | 0.4982 (4) | 0.0165 (4) | |
O1 | 0.0563 (4) | 0.44955 (8) | 0.4069 (4) | 0.0086 (4) | |
O2 | 0.1338 (4) | 0.43931 (9) | −0.0742 (4) | 0.0093 (4) | |
O3 | −0.0468 (4) | 0.33984 (9) | 0.1528 (4) | 0.0094 (4) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Te1 | 0.00610 (12) | 0.00480 (9) | 0.00497 (11) | 0.00010 (6) | −0.00010 (8) | 0.00012 (6) |
Sc1 | 0.0066 (4) | 0.0051 (3) | 0.0041 (4) | −0.0006 (3) | 0.000 | 0.000 |
Sc2 | 0.0057 (4) | 0.0044 (3) | 0.0044 (4) | 0.000 | 0.000 | 0.0007 (2) |
F1 | 0.0160 (10) | 0.0167 (8) | 0.0170 (9) | −0.0007 (8) | −0.0111 (8) | 0.0012 (8) |
O1 | 0.0091 (10) | 0.0084 (9) | 0.0082 (10) | 0.0021 (7) | −0.0003 (9) | −0.0045 (8) |
O2 | 0.0086 (11) | 0.0099 (9) | 0.0094 (11) | −0.0016 (8) | 0.0003 (9) | 0.0035 (8) |
O3 | 0.0103 (11) | 0.0061 (8) | 0.0119 (11) | −0.0027 (7) | −0.0021 (8) | 0.0012 (8) |
Geometric parameters (Å, º) top
Te1—O2 | 1.854 (2) | Sc1—Sc1iv | 3.4934 (14) |
Te1—O3 | 1.876 (2) | Sc1—Sc1vii | 3.4934 (14) |
Te1—O1 | 1.912 (2) | Sc2—F1viii | 2.017 (2) |
Te1—O3i | 2.664 (2) | Sc2—F1ix | 2.017 (2) |
Te1—O2i | 2.766 (2) | Sc2—F1 | 2.047 (2) |
Sc1—O2ii | 2.022 (2) | Sc2—F1x | 2.047 (2) |
Sc1—O2iii | 2.022 (2) | Sc2—O3x | 2.057 (2) |
Sc1—O1iv | 2.142 (2) | Sc2—O3 | 2.057 (2) |
Sc1—O1v | 2.142 (2) | F1—Sc2v | 2.017 (2) |
Sc1—O1 | 2.174 (2) | O1—Sc1iv | 2.142 (2) |
Sc1—O1vi | 2.174 (2) | O2—Sc1xi | 2.022 (2) |
| | | |
O2—Te1—O3 | 94.20 (9) | O1vi—Sc1—Sc1iv | 92.17 (8) |
O2—Te1—O1 | 91.31 (10) | O2ii—Sc1—Sc1vii | 95.97 (7) |
O3—Te1—O1 | 97.93 (9) | O2iii—Sc1—Sc1vii | 130.73 (6) |
O2—Te1—O3i | 77.55 (9) | O1iv—Sc1—Sc1vii | 123.95 (7) |
O3—Te1—O3i | 93.12 (7) | O1v—Sc1—Sc1vii | 36.28 (5) |
O1—Te1—O3i | 164.87 (7) | O1—Sc1—Sc1vii | 92.17 (7) |
O2—Te1—O2i | 78.26 (6) | O1vi—Sc1—Sc1vii | 35.66 (5) |
O3—Te1—O2i | 153.36 (8) | Sc1iv—Sc1—Sc1vii | 111.47 (6) |
O1—Te1—O2i | 107.67 (7) | F1viii—Sc2—F1ix | 91.07 (13) |
O3i—Te1—O2i | 60.38 (6) | F1viii—Sc2—F1 | 178.40 (12) |
O2ii—Sc1—O2iii | 95.59 (13) | F1ix—Sc2—F1 | 90.52 (5) |
O2ii—Sc1—O1iv | 94.45 (8) | F1viii—Sc2—F1x | 90.52 (5) |
O2iii—Sc1—O1iv | 102.59 (8) | F1ix—Sc2—F1x | 178.40 (12) |
O2ii—Sc1—O1v | 102.59 (8) | F1—Sc2—F1x | 87.89 (13) |
O2iii—Sc1—O1v | 94.45 (8) | F1viii—Sc2—O3x | 91.95 (8) |
O1iv—Sc1—O1v | 154.58 (12) | F1ix—Sc2—O3x | 93.05 (8) |
O2ii—Sc1—O1 | 166.38 (8) | F1—Sc2—O3x | 88.11 (8) |
O2iii—Sc1—O1 | 87.27 (9) | F1x—Sc2—O3x | 86.75 (8) |
O1iv—Sc1—O1 | 71.93 (8) | F1viii—Sc2—O3 | 93.05 (8) |
O1v—Sc1—O1 | 90.42 (7) | F1ix—Sc2—O3 | 91.95 (8) |
O2ii—Sc1—O1vi | 87.27 (9) | F1—Sc2—O3 | 86.75 (8) |
O2iii—Sc1—O1vi | 166.38 (8) | F1x—Sc2—O3 | 88.11 (8) |
O1iv—Sc1—O1vi | 90.42 (7) | O3x—Sc2—O3 | 172.86 (13) |
O1v—Sc1—O1vi | 71.93 (8) | Sc2v—F1—Sc2 | 157.62 (10) |
O1—Sc1—O1vi | 93.07 (12) | Te1—O1—Sc1iv | 125.27 (11) |
O2ii—Sc1—Sc1iv | 130.73 (6) | Te1—O1—Sc1 | 121.55 (11) |
O2iii—Sc1—Sc1iv | 95.97 (7) | Sc1iv—O1—Sc1 | 108.07 (8) |
O1iv—Sc1—Sc1iv | 36.28 (5) | Te1—O2—Sc1xi | 146.46 (12) |
O1v—Sc1—Sc1iv | 123.95 (7) | Te1—O3—Sc2 | 127.85 (11) |
O1—Sc1—Sc1iv | 35.66 (5) | | |
Symmetry codes: (i) x+1/2, y, −z; (ii) −x+1/2, −y+1, z+1; (iii) x, y, z+1; (iv) −x, −y+1, −z+1; (v) x+1/2, y, −z+1; (vi) −x+1/2, −y+1, z; (vii) −x+1, −y+1, −z+1; (viii) x−1/2, −y+1/2, z−1/2; (ix) x−1/2, y, −z+1; (x) x, −y+1/2, −z+1/2; (xi) x, y, z−1. |
(II) indium tellurium trioxide fluoride
top
Crystal data top
InTeO3F | F(000) = 536 |
Mr = 309.42 | Dx = 5.968 Mg m−3 |
Monoclinic, P21/a | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P2yab | Cell parameters from 6421 reflections |
a = 7.9395 (11) Å | θ = 5.1–32.0° |
b = 5.3867 (8) Å | µ = 15.03 mm−1 |
c = 8.0529 (12) Å | T = 293 K |
β = 91.058 (13)° | Tablet shape, colourless |
V = 344.35 (9) Å3 | 0.06 × 0.04 × 0.02 mm |
Z = 4 | |
Data collection top
Nonius KappaCCD diffractometer | 1187 independent reflections |
Radiation source: fine-focus sealed tube | 1044 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.045 |
Detector resolution: 9 pixels mm-1 | θmax = 32.0°, θmin = 5.1° |
CCD scans | h = −11→11 |
Absorption correction: multi-scan (SADABS; Bruker 2001) | k = −8→7 |
Tmin = 0.406, Tmax = 0.740 | l = −12→12 |
7758 measured reflections | |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.029 | w = 1/[σ2(Fo2) + (0.0509P)2 + 2.4678P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.086 | (Δ/σ)max = 0.001 |
S = 1.06 | Δρmax = 4.37 e Å−3 |
1187 reflections | Δρmin = −2.73 e Å−3 |
56 parameters | Extinction correction: SHELXL97, Fc^*^=kFc[1+0.001xFc^2^λ^3^/sin(2θ)]^-1/4^ |
0 restraints | Extinction coefficient: 0.0027 (6) |
Crystal data top
InTeO3F | V = 344.35 (9) Å3 |
Mr = 309.42 | Z = 4 |
Monoclinic, P21/a | Mo Kα radiation |
a = 7.9395 (11) Å | µ = 15.03 mm−1 |
b = 5.3867 (8) Å | T = 293 K |
c = 8.0529 (12) Å | 0.06 × 0.04 × 0.02 mm |
β = 91.058 (13)° | |
Data collection top
Nonius KappaCCD diffractometer | 1187 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker 2001) | 1044 reflections with I > 2σ(I) |
Tmin = 0.406, Tmax = 0.740 | Rint = 0.045 |
7758 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.029 | 56 parameters |
wR(F2) = 0.086 | 0 restraints |
S = 1.06 | Δρmax = 4.37 e Å−3 |
1187 reflections | Δρmin = −2.73 e Å−3 |
Special details top
Experimental. The integrated intensities were corrected for absorption effects by using a
multi-scan method (SADABS, Bruker 2001). Structure solution by direct
methods in the Pnna space group for ScTeO3F and in the
P21/a space group for InTeO3F followed by refinement of
atomic coordinates and anisotropic thermal parameters were performed using
successively the SHELXS97 and the SHELXL97 programs (Sheldrick,
2008). |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell e.s.d.'s are taken
into account individually in the estimation of e.s.d.'s in distances, angles
and torsion angles; correlations between e.s.d.'s in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s.
planes. |
Refinement. Refinement of F^2^ against ALL reflections. The weighted
R-factor wR and goodness of fit S are based on
F^2^, conventional R-factors R are based on F,
with F set to zero for negative F^2^. The threshold expression
of F^2^ > σ(F^2^) is used only for calculating
R-factors(gt) etc. and is not relevant to the choice of
reflections for refinement. R-factors based on F^2^ are
statistically about twice as large as those based on F, and R-
factors based on ALL data will be even larger. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
In1 | 0.67668 (4) | 0.78326 (7) | 0.85804 (4) | 0.00767 (13) | |
Te1 | 0.84905 (4) | 0.30493 (6) | 0.70479 (4) | 0.00916 (13) | |
O1 | 0.8228 (4) | 0.1146 (7) | 0.9037 (4) | 0.0097 (7) | |
F1 | 0.7013 (4) | −0.0355 (7) | 0.6209 (4) | 0.0165 (7) | |
O2 | 0.6371 (5) | 0.4518 (7) | 0.7228 (5) | 0.0126 (7) | |
O3 | 0.9277 (5) | 0.5886 (7) | 0.8392 (5) | 0.0127 (7) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
In1 | 0.00724 (19) | 0.0062 (2) | 0.0095 (2) | 0.00016 (11) | −0.00046 (13) | 0.00065 (11) |
Te1 | 0.00793 (18) | 0.0098 (2) | 0.00979 (19) | 0.00137 (10) | 0.00186 (12) | 0.00217 (11) |
O1 | 0.0126 (16) | 0.0072 (17) | 0.0093 (16) | −0.0031 (13) | 0.0010 (13) | 0.0011 (13) |
F1 | 0.0209 (16) | 0.0140 (16) | 0.0147 (15) | −0.0056 (13) | 0.0024 (13) | −0.0016 (13) |
O2 | 0.0057 (15) | 0.0111 (17) | 0.0208 (19) | 0.0005 (13) | −0.0018 (13) | −0.0040 (16) |
O3 | 0.0079 (15) | 0.0097 (18) | 0.0205 (19) | −0.0019 (13) | −0.0003 (14) | −0.0011 (15) |
Geometric parameters (Å, º) top
In1—O3i | 2.097 (4) | Te1—O3 | 1.968 (4) |
In1—O2 | 2.112 (4) | Te1—F1 | 2.273 (4) |
In1—O1ii | 2.122 (4) | Te1—O2iv | 2.674 (4) |
In1—O1iii | 2.157 (4) | Te1—F1v | 2.782 (3) |
In1—F1iii | 2.157 (4) | O1—In1vi | 2.122 (4) |
In1—O3 | 2.260 (4) | O1—In1vii | 2.157 (4) |
In1—Te1 | 3.1776 (6) | F1—In1vii | 2.157 (4) |
Te1—O2 | 1.868 (4) | O3—In1viii | 2.097 (4) |
Te1—O1 | 1.917 (4) | | |
| | | |
O3i—In1—O2 | 96.31 (15) | F1iii—In1—Te1 | 88.66 (10) |
O3i—In1—O1ii | 101.10 (15) | O2—Te1—O1 | 92.83 (17) |
O2—In1—O1ii | 95.86 (16) | O2—Te1—O3 | 84.58 (17) |
O3i—In1—O1iii | 104.07 (15) | O1—Te1—O3 | 89.64 (17) |
O2—In1—O1iii | 149.57 (15) | O2—Te1—F1 | 84.49 (15) |
O1ii—In1—O1iii | 102.00 (9) | O1—Te1—F1 | 75.72 (14) |
O3i—In1—F1iii | 83.55 (15) | O3—Te1—F1 | 161.23 (15) |
O2—In1—F1iii | 86.63 (15) | O1—Te1—In1 | 93.14 (12) |
O1ii—In1—F1iii | 174.42 (14) | F1—Te1—In1 | 123.09 (9) |
O1iii—In1—F1iii | 73.69 (13) | Te1—O1—In1vi | 121.9 (2) |
O3i—In1—O3 | 168.39 (16) | Te1—O1—In1vii | 111.51 (17) |
O2—In1—O3 | 72.32 (14) | In1vi—O1—In1vii | 120.04 (16) |
O1ii—In1—O3 | 82.81 (14) | In1vii—F1—Te1 | 99.02 (14) |
O1iii—In1—O3 | 85.60 (14) | Te1—O2—In1 | 105.81 (17) |
F1iii—In1—O3 | 93.24 (15) | Te1—O3—In1viii | 125.8 (2) |
O3i—In1—Te1 | 130.63 (11) | Te1—O3—In1 | 97.23 (15) |
O1ii—In1—Te1 | 90.59 (10) | In1viii—O3—In1 | 132.37 (19) |
O1iii—In1—Te1 | 120.22 (10) | | |
Symmetry codes: (i) x−1/2, −y+3/2, z; (ii) −x+3/2, y+1/2, −z+2; (iii) x, y+1, z; (iv) x+1/2, −y+1/2, z; (v) −x+3/2, y+1/2, −z+1; (vi) −x+3/2, y−1/2, −z+2; (vii) x, y−1, z; (viii) x+1/2, −y+3/2, z. |
Experimental details
| (I) | (II) |
Crystal data |
Chemical formula | ScTeO3F | InTeO3F |
Mr | 239.56 | 309.42 |
Crystal system, space group | Orthorhombic, Pnna | Monoclinic, P21/a |
Temperature (K) | 293 | 293 |
a, b, c (Å) | 5.7740 (5), 22.062 (5), 5.5000 (12) | 7.9395 (11), 5.3867 (8), 8.0529 (12) |
α, β, γ (°) | 90, 90, 90 | 90, 91.058 (13), 90 |
V (Å3) | 700.6 (2) | 344.35 (9) |
Z | 8 | 4 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 10.13 | 15.03 |
Crystal size (mm) | 0.1 × 0.08 × 0.04 | 0.06 × 0.04 × 0.02 |
|
Data collection |
Diffractometer | Nonius KappaCCD diffractometer | Nonius KappaCCD diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker 2001) | Multi-scan (SADABS; Bruker 2001) |
Tmin, Tmax | 0.363, 0.667 | 0.406, 0.740 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 17528, 1019, 895 | 7758, 1187, 1044 |
Rint | 0.046 | 0.045 |
(sin θ/λ)max (Å−1) | 0.703 | 0.746 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.018, 0.035, 1.18 | 0.029, 0.086, 1.06 |
No. of reflections | 1019 | 1187 |
No. of parameters | 57 | 56 |
Δρmax, Δρmin (e Å−3) | 0.98, −1.00 | 4.37, −2.73 |
Selected bond lengths (Å) for (I) topTe1—O2 | 1.854 (2) | Sc1—O1iii | 2.142 (2) |
Te1—O3 | 1.876 (2) | Sc1—O1 | 2.174 (2) |
Te1—O1 | 1.912 (2) | Sc2—F1iv | 2.017 (2) |
Te1—O3i | 2.664 (2) | Sc2—F1 | 2.047 (2) |
Te1—O2i | 2.766 (2) | Sc2—O3 | 2.057 (2) |
Sc1—O2ii | 2.022 (2) | | |
Symmetry codes: (i) x+1/2, y, −z; (ii) −x+1/2, −y+1, z+1; (iii) −x, −y+1, −z+1; (iv) x−1/2, y, −z+1. |
Selected bond lengths (Å) for (II) topIn1—O3i | 2.097 (4) | Te1—O2 | 1.868 (4) |
In1—O2 | 2.112 (4) | Te1—O1 | 1.917 (4) |
In1—O1ii | 2.122 (4) | Te1—O3 | 1.968 (4) |
In1—O1iii | 2.157 (4) | Te1—F1 | 2.273 (4) |
In1—F1iii | 2.157 (4) | Te1—O2iv | 2.674 (4) |
In1—O3 | 2.260 (4) | Te1—F1v | 2.782 (3) |
Symmetry codes: (i) x−1/2, −y+3/2, z; (ii) −x+3/2, y+1/2, −z+2; (iii) x, y+1, z; (iv) x+1/2, −y+1/2, z; (v) −x+3/2, y+1/2, −z+1. |
Table 3 topBond valences for ScTeO3F |
Atoms | Sc1 | Sc2 | Te1 | Vij |
O1 | 2×0.453/2×0.415 | – | 1.192 | 2.06 |
O2 | 2×0.627 | – | 1.396/0.119 | 2.14 |
O3 | – | 2×0.570 | 1.314/0.156 | 2.04 |
F1 | – | 2×0.498/2×0.459 | – | 0.96 |
Vij | 2.99 | 3.05 | 4.18 | – |
Table 4 topBond valences for InTeO3F |
Atoms | Te1 | In1 | Vij |
O1 | 1.176 | 0.552/0.502 | 2.23 |
O2 | 1.343/0.152 | 0.567 | 2.06 |
O3 | 1.025 | 0.59/0.38 | 2.00 |
F1 | 0.336/0.110 | 0.373 | 0.82 |
Vij | 4.14 | 2.96 | |
In recent years, many tellurates(IV) of transition metals or heavy metals have generated interest for their excellent nonlinear optical properties. Therefore, a general study of the structural and physical properties of some homologous oxyfluorotellurates(IV) and oxyfluoroiodates(V) has been undertaken. Indeed, few fluorides and oxyfluorides of tellurium(IV) and iodine(V) were known because of the highly hygroscopic character of most of these phases. In the present series of studies, the compounds are generally more thermally stable and moisture resistant. Following on our characterization of the new series MTeO3F (M = Fe, Ga and Cr; Laval et al., 2008) and NaIO2F2 (Laval & Jennene Boukharrata, 2008), the present paper describes the synthesis and crystal structure of two phases, ScTeO3F and InTeO3F, belonging to two new structure types that differ from that of the first MTeO3F (M = Fe, Ga and Cr) series.
In ScTeO3F, the TeIV atom is bonded to three O atoms, O1, O2 and O3, and occupies the center of a tetrahedron whose fourth corner corresponds to the direction of the stereochemically active lone pair E (Fig. 1 and Table 1). If weak bonds are considered, Te1 is connected to two additional O atoms at more remote distances.
Atoms Sc1 and Sc2 occupy two different sixfold-coordinated sites. Atom Sc1 occupies the center of an ScO6 irregular octahedron with two shorter and four slightly longer Sc1—O bonds (Fig. 2a and Table 1). Atom Sc2 is located at the center of an almost regular ScF4O2 octahedron in which the F atoms occupy the square base and the O atoms the two apices (Fig. 2b). The ScIII cations are generally six-coordinated by O atoms in oxides and can be sevenfold coordinated in mixed oxyfluorides, for example in ScOF belonging to the ZrO2 baddeleyite type (Vlasse et al., 1979). The ScO6 octahedra are often irregular with a low point symmetry and Sc—O distances generally ranging from 2.0 to 2.25 Å or more. The octahedra evidenced in ScTeO3F are in agreement with those described in most Sc oxide phases.
The ScTeO3F structure results from the stacking of two types of scandium layers interconnected via layers of isolated TeO3 polyhedra.
The first type of layer consists of Sc1O6 octahedra sharing O1···O1) edges in the [100] direction, so forming `zigzag' chains (Fig. 3a). These chains are similar to those observed in the MoOCl3 structure (Hyde & Andersson, 1989) and to the zigzag chains of MO4F2 octahedra, alternately sharing O···O and F···F edges, in the MTeO3F (M = Fe, Ga and Cr) series (Laval et al., 2008). Along the [001] direction, successive parallel chains are interconnected via O1 and O2 corners of TeO3 polyhedra, so forming layers perpendicular to the [010] direction. In the MTeO3F (M = Fe, Ga and Cr) type, zigzag chains of octahedra are also interconnected via TeO3 polyhedra, giving a structure related to the α-PbO2 classical type of hcp framework (Hyde & Andersson, 1989). However, this last interconnection occurs on one side via one O3 corner and on the other side via O1 and O2 corners belonging to three different chains of the same type. In ScTeO3F, the O3 atoms of the TeO3 polyhedra are shared with Sc2 atoms belonging to a second completely different type of layer.
This second type of layer (Fig. 3b), perpendicular to the [010] axis, consists of F1 corner-connected Sc2O2F4 tilted octahedra forming a square 44 plane net similar to the plane net of SnF6 octahedra described in the SnF4 type (Wells, 1975). Two TeO3 isolated units are connected to each Sc2 atom above and below the empty square holes of the 44 plane net through O3 corners. However, the Te1 atoms are not located above and below the center of these square holes, which would give overly long Te1—O3 bonds, like, for example, the Ca—O bonds in CaTiO3 perovskite (Hyde & Anderson, 1989), but rather are shifted along the [100] direction towards the Sc2 atoms, sitting above and below an F1···F1 edge of each Sc2O2F4 octahedron. This shift allows a stronger connection between the Sc2 and Te1 polyhedra via O3 corners and releases the volume necessary for the active lone pair of TeIV to be directed towards the center of the empty square holes.
Therefore, the Te atoms, located between the scandium layers, provide the connection between the [(Sc1)nO4n+2] chains through O1—Te1—O2 bridges, so forming mixed [(Sc1)n(Te1)nO4n+2] layers, and also provide the linking of both types of layers through Te1—O3 bonds (Fig. 4). This constitutes the main difference from the MTeO3F (M = Fe, Ga and Cr) type: the chains of MO4F2 octahedra, interconnected by TeO3 polyhedra, are replaced by alternate chains of ScO6 and layers of ScO2F4 octahedra, these chains and layers being also interconnected by TeO3 polyhedra.
In the InTeO3F structure, the Te atom is surrounded by four O and two F atoms (Fig. 5). Three O atoms are strongly bonded at distances less than 2 Å, while the first Te—F bond is somewhat longer, and the fourth O (O2iv) and the second F (F1v) atoms are weakly bonded at much longer distances (Table 2). The corresponding complete polyhedron can be described as a distorted TeO4F2 octahedron. The stereochemically active lone pair E is located between the two longest bonds. Taking into account only the four shortest bonds, TeO3F is a square pyramid whose vertex is occupied by the lone pair E, but in a first approximation, it can also be described as a TeO3 trigonal bipyramid, like those in the other MTeO3F structures. The In atom is sixfold coordinated. It is slightly shifted from the center of a distorted InO5F octahedron (Fig. 6).
The InTeO3F structure consists of zigzag sheets of InO5F octahedra separated by spaces into which the stereochemically active lone pair E of the Te atom is directed (Fig. 7a). Each sheet is formed by isolated chains of tilted InO5F octahedra sharing O corners and connected by TeO3F polyhedra (Fig.7b). Contrary to the two other MTeO3F types in which TeO3 polyhedra connect single sheets of M octahedra, in InTeO3F, the TeO3F polyhedra form with the zigzag sheets of InO5F octahedra independent double (InTeO3F)n sheets, with the lone pairs pointing to the space between successive sheets. Therefore, InTeO3F is a true layer structure, different from the two other MTeO3F types, with only weak Te—O and Te—F bonds connecting the double sheets (Fig. 8).
Bond valence calculations (Brown, 1981) show O valences varying from 2.04 to 2.14 and from 2.00 to 2.23, and F valences as 0.96 and 0.82 in ScTeO3F (Table 3) and InTeO3F (Table 4), respectively. It must be noted that, in most oxyfluorides, the calculated anionic valences are sometimes imprecise. The discrepancies can be attributed to imperfect electrostatic equilibrium in some cases, to the empirical character of the constants used in Brown's equation and to a poor knowledge of the ionic radii of rare elements (e.g. scandium), based on a limited number of solved structures. In spite of these limitations, the calculated valences of atoms Sc1, Sc2, In1 and Te1 are very close to their ideal values, which are consistent with a full O/F ordering in both ScTeO3F and InTeO3F.
In conclusion, these three structure types differ in the manner of connection of the M(O,F)6 octahedra and in the respective O/F distribution in these octahedra, but they have an interesting common feature: in the MTeO3F (M = Fe, Cr and Ga) type, in ScTeO3F and to a first approximation in InTeO3F, the fluoride anions are not directly bonded to the tellurium cations, which are threefold coordinated by O cations only. This feature draws these compounds closer to Te oxides than to the Te fluorides or oxyfluorides previously described, the latter phases being characterized by four- or fivefold coordination (Guillet et al., 1999, 2001; Ider et al., 1996, 1999). This may also explain the unusually high thermal and chemical stability of these phases compared with the main oxyfluorotellurates(IV) already known.