Indium tellurium trioxide chloride, InTeO₃Cl

The new oxy­chloride InTeO₃Cl was synthesized from a mixture of In₂O₃, InCl₃ and TeO₂. Its structure has been determined from single-crystal X-ray diffraction data. The structure is composed of layers separated by a van der Waals gap. The layers consist of edge-sharing chains of [InO₄Cl₂] octahedra linked through [TeO₃] trigonal pyramids. No free Cl atoms are located between the layers.

S1. Comment

One of the most common oxychlorides is FeOCl. This layered compound possesses various interesting chemical properties (Rouxel et al., 1987). Indeed, it is possible to intercalate alkali metals or molecules between the layers. It is also possible to substitute the chlorine layers by nucleophilic alkali metal salts, these grafting or pillaring reactions leading to new layered compounds. Some authors have developed the family of oxyhalide compounds with the synthesis of metal-tellurium oxyhalides (see, for instance, Jerez et al., 1987; Alonso, 1998; Nikiforov et al., 1999). All these compounds, as with FeOCl, exhibit lamellar organization. The structural differences observed depend on the nature of the metal and the oxidation state of the Te. The title compound is the first to be synthesized with a group 13 metal. The charge balance proposed for this compound is In³⁺Te⁴⁺O₃^2-Cl^-.

The structure is composed of puckered layers separated by a van der Waals gap, as shown in Fig. 1. The layers consist of edge-sharing chains of [InO₄Cl₂] octahedra running along the a direction and linked through [TeO₃] trigonal pyramids (Fig. 2). Such threefold coordination is usual for Te with a +4 oxidation state. The Te⁴⁺ lone electron pair points toward the van der Waals gap.

The In—O and In—Cl distances are comparable with the average distances encountered in InOCl (2.15 and 2.53 Å, respectively; Forsberg, 1956) and with the values reported by Shannon (1976) of 2.27 and 2.73 Å, respectively. The Te—O distances in the [TeO₃] trigonal pyramid [1.897 (5)–1.907 (4) Å] are close to the value of 1.87 Å expected from the Shannon table, and to the average distance found in SbTeO₃Cl (1.92 Å; Alonso, 1998). Concerning the two long Te—O distances of 2.586 Å between Te and O2 and O3, their bond valence contributions are equal to 0.19 (the values for the bond valence calculation are taken from Brown & Altermatt, 1985). Thus they can be considered as weak or secondary bonds. When these bonds are included in the bond valence sums, the sum around Te is 4.05 and that around O2 and O3 is 1.98, and these are in good agreement with the charge balance proposed.

Among the family of metal tellurium oxyhalides, InTeO₃Cl is a particular case because of the lack of free Cl atoms between the layers. Indeed, the Cl atoms belong to the In coordination polyhedra, while in SbTeO₃Cl and NdTe₂O₅Cl, for example, Sb and Nd are surrounded only by O atoms (Alonso, 1998; Nikiforov et al., 1999). Moreover, an orthorhombic symmetry is generally observed for this kind of compound, and the lowest symmetry observed for InTeO₃Cl (monoclinic) is certainly due to the asymmetry of the In environment, with four O and two Cl atoms. The InTeO₃Cl structure is closest to the layered structural type of FeOCl. Indeed, the iron(III) is also in octahedral coordination with four O and two Cl atoms, and the outer part of the slabs is built up with chlorine layers which belong to the metal coordination sphere. Thus, as in the case of FeOCl, some chemical reactions can be expected with InTeO₃Cl. If no intercalation chemistry seems to be possible, as the +2 oxidation state for the In is not stable, some grafting or pillaring reactions can be imagined.

S2. Experimental

The title compound was obtained during the synthesis of In₂Si₂O₇ single crystals by chemical vapour transport (CVT) using TeCl₄ as the transport agent. In addition to the silicate crystals, which are interesting for their scintillation properties (Garcia et al., 1995), very thin platelets were recovered in the cooler zone. Chemical analysis by electron probe microanalysis (EPMA) revealed a new compound containing In, Te, Cl and O in the ratio 1/1/1/3. Direct synthesis of InTeO₃Cl from a stoichiometric mixture of In₂O₃, InCl₃ and TeO₂ heated at 723 K in an evacuated silica tube for 15 h was successful. The experimental density of 5.34 kg m^-3 was measured by the hydrostatic pressure method (Rabardel et al., 1971). Because of the lamellar shape of the InTeO₃Cl crystals, it was very difficult to find a real single-crystal. Eventually, a well shaped crystal was cleaved, yielding a good single-crystal.

S3. Refinement

The In and Te positions were located from Patterson maps, and the O and Cl positions were determined afterwards from difference Fourier maps.

Computing details

Data collection: KappaCCD Software (Nonius, 1999); cell refinement: HKL DENZO (Otwinowski & Minor 1997); data reduction: HKL DENZO and SCALEPACK (Otwinowski & Minor 1997); program(s) used to solve structure: please provide details; program(s) used to refine structure: JANA2000 (Petricek & Dusek, 2000); software used to prepare material for publication: JANA2000.

Figures

	Fig. 1. A representation of the InTeO3Cl structure along the c axis showing its layered nature. The [InO4Cl2] octahedra are outlined. Grey, white and black circles represent Te, O and Cl, respectively.
	Fig. 2. A view of the [InO4Cl2] octahedra linked through [TeO3] trigonal pyramids. Displacement ellipsoids are shown at the 90% probability level.

(I)

Crystal data

InTeO3Cl	F(000) = 568
Mr = 325.87	Dx = 5.48 Mg m^−3 Dm = 5.34 Mg m^−3 Dm measured by hydrostatic
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 8.2596 (4) Å	Cell parameters from 12538 reflections
b = 6.8752 (3) Å	θ = 2.5–35.0°
c = 7.1394 (3) Å	µ = 13.74 mm^−1
β = 103.121 (2)°	T = 293 K
V = 394.84 (3) Å^3	Plate, pale yellow
Z = 4	0.40 × 0.16 × 0.04 mm

Data collection

Enraf-Nonius KappaCCD area-detector diffractometer	944 reflections with I > 2σ(I)
CCD scans	Rint = 0.100
Absorption correction: gaussian (Templeton & Templeton, 1978)	θmax = 29.8°, θmin = 3.9°
Tmin = 0.064, Tmax = 0.610	h = −11→11
6506 measured reflections	k = −9→9
1128 independent reflections	l = −9→9

Refinement

Refinement on F^2	Weighting scheme based on measured s.u.'s w = 1/(σ^2(I) + 0.0004I^2)
R[F^2 > 2σ(F^2)] = 0.037	(Δ/σ)max < 0.001
wR(F^2) = 0.093	Δρmax = 2.18 e Å^−3
S = 1.30	Δρmin = −2.38 e Å^−3
1128 reflections	Extinction correction: Becker & Coppens (1974), type II
56 parameters	Extinction coefficient: 0.07 (2)

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
In	0.32477 (7)	0.24979 (5)	0.20399 (6)	0.0071 (2)
Te	0.29289 (6)	0.72638 (6)	0.94533 (6)	0.00698 (15)
Cl	0.0950 (2)	0.2093 (2)	0.8921 (2)	0.0156 (5)
O1	0.5235 (6)	0.7838 (5)	0.0060 (6)	0.0099 (14)
O2	0.3158 (7)	0.5536 (5)	0.7441 (6)	0.0113 (15)
O3	0.3128 (7)	0.5533 (5)	0.1578 (6)	0.013 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
In	0.0110 (3)	0.0041 (2)	0.0070 (2)	0.0002 (2)	0.0035 (2)	0.00025 (15)
Te	0.0071 (2)	0.0079 (2)	0.0066 (2)	0.0010 (2)	0.0028 (2)	0.00084 (15)
Cl	0.0121 (9)	0.0246 (9)	0.0110 (7)	−0.0029 (7)	0.0044 (6)	0.0006 (6)
O1	0.013 (2)	0.015 (2)	0.002 (2)	−0.003 (2)	0.002 (2)	0.001 (2)
O2	0.018 (3)	0.004 (2)	0.013 (2)	−0.001 (2)	0.005 (2)	−0.002 (2)
O3	0.019 (3)	0.004 (2)	0.017 (2)	−0.002 (2)	0.008 (2)	0.002 (2)

Geometric parameters (Å, º)

In—Cl^i	2.592 (2)	Te—O1^v	1.897 (5)
In—Cl^ii	2.577 (2)	Te—O2	1.907 (4)
In—O1^iii	2.174 (5)	Te—O2^vi	2.586 (4)
In—O1^iv	2.176 (4)	Te—O3^v	1.905 (4)
In—O2^ii	2.109 (4)	Te—O3^vi	2.586 (4)
In—O3	2.111 (4)
Cl^i—In—Cl^ii	88.69 (7)	O1^iv—In—O3	92.23 (16)
Cl^i—In—O1^iii	79.65 (14)	O2^ii—In—O3	175.4 (2)
Cl^i—In—O1^iv	168.59 (17)	O1^v—Te—O2	92.0 (2)
Cl^i—In—O2^ii	88.23 (13)	O1^v—Te—O2^vi	78.9 (2)
Cl^i—In—O3	88.44 (13)	O1^v—Te—O3^v	92.7 (2)
Cl^ii—In—Cl^i	88.69 (7)	O1^v—Te—O3^vi	79.50 (18)
Cl^ii—In—O1^iii	168.27 (13)	O2—Te—O2^vi	169.9 (2)
Cl^ii—In—O1^iv	79.96 (16)	O2—Te—O3^v	101.9 (2)
Cl^ii—In—O2^ii	89.13 (17)	O2—Te—O3^vi	74.43 (17)
Cl^ii—In—O3	87.69 (17)	O2^vi—Te—O2	169.9 (2)
O1^iii—In—O1^iv	111.7 (2)	O2^vi—Te—O3^v	74.45 (16)
O1^iii—In—O2^ii	91.82 (19)	O2^vi—Te—O3^vi	107.82 (14)
O1^iii—In—O3	90.6 (2)	O3^v—Te—O3^vi	171.1 (2)
O1^iv—In—O1^iii	111.7 (2)	O3^vi—Te—O3^v	171.1 (2)
O1^iv—In—O2^ii	90.42 (16)

Symmetry codes: (i) x, y, z−1; (ii) x, −y+1/2, z−1/2; (iii) −x+1, −y+1, −z; (iv) −x+1, y−1/2, −z+1/2; (v) x, y, z+1; (vi) x, −y+3/2, z+1/2.