The Mg member of the isotypic series MTe₆O₁₃

MgTe₆O₁₃, magnesium hexa­tellurate(IV), is isotypic with the structures of divalent first-row transition metal analogues MTe₆O₁₃ (M = Mn, Fe, Co, Ni and Zn). The asymmetric unit contains one Mg, two Te and five O atoms of which the Mg and one O atom lie on a threefold rotation axis. The structure is made up from slightly distorted [MgO₆] octa­hedra (isolated from each other), distorted [TeO₄] bis­phenoids and [TeO_4 + 1] tetra­gonal pyramids sharing corners and edges. This arrangement leads to the formation of a dense three-dimensional structure.

Related literature

The title compound is isotypic with its Co, Mn, Ni (Irvine et al., 2003), Fe (van der Lee & Astier, 2007; van der Lee, 2013) and Zn (Nawash et al., 2007) analogues. For other phases in the system Mg–Te–O, see: Trömel & Ziethen-Reichnach (1970). For structure determinations of MgTe₂O₅ and Mg₂Te₃O₈, see: Weil (2005) and Lin et al. (2013), respectively. The crystal chemistry of oxotellurates(IV) has been reviewed by Zemann (1971).

Experimental

Crystal data

• MgTe₆O₁₃

• M_r = 997.91

• Trigonal,

• a = 10.1676 (2) Å

• c = 18.9701 (3) Å

• V = 1698.39 (5) ų

• Z = 6

• Mo Kα radiation

• μ = 15.38 mm⁻¹

• T = 295 K

• 0.22 × 0.14 × 0.09 mm

Data collection

• Bruker APEXII CCD diffractometer

• Absorption correction: multi-scan (SADABS; Bruker, 2012) T_min = 0.437, T_max = 0.749

• 50742 measured reflections

• 2875 independent reflections

• 2764 reflections with I > 2σ(I)

• R_int = 0.044

Refinement

• R[F² > 2σ(F²)] = 0.017

• wR(F²) = 0.034

• S = 1.36

• 2875 reflections

• 62 parameters

• Δρ_max = 1.17 e Å⁻³

• Δρ_min = −1.40 e Å⁻³

Table 1
Structural data of isotypic MTe₆O₁₃ compounds (Å, ų) in space group R

M^2+	a	c	V
Mg^a	10.1676 (2)	18.9701 (3)	1698.39 (5)
Mn^b	10.2505 (5)	19.2195 (9)	1748.89 (14)
Fe^c	10.16630 (10)	18.9330 (3)	1694.63 (4)
Co^b	10.1641 (5)	18.9814 (9)	1698.23 (14)
Ni^b	10.1522 (5)	18.8669 (9)	1684.30 (14)
Zn^d	10.1283 (9)	18.948 (3)	1683.3 (3)
Notes: (a) this work; (b) Irvine et al. (2003); (c) van der Lee & Astier (2007); (d) Nawash et al. (2007).

Table 2
Selected bond lengths (Å)

Mg1—O5	2.0676 (12)
Mg1—O2^i	2.1596 (12)
Te1—O3	1.8524 (12)
Te1—O2	1.9324 (11)
Te1—O1	2.1314 (2)
Te1—O2^ii	2.1842 (11)
Te2—O5	1.8489 (11)
Te2—O4	1.9186 (11)
Te2—O4^iii	2.0286 (12)
Te2—O3	2.2118 (12)
Te2—O5^iv	2.5908 (12)
Symmetry codes: (i) ; (ii) ; (iii) -y+1, x-y+1, z; (iv) -x+1, -y+1, -z.

Data collection: APEX2 (Bruker, 2012); cell refinement: SAINT (Bruker, 2012); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ATOMS for Windows (Dowty, 2008); software used to prepare material for publication: publCIF (Westrip, 2010).

Supporting information

S1. Comment

Single crystals of Mg₂Te₃O₈ (Lin et al., 2013) and of the title compound, MgTe₆O₁₃, were obtained during hydrothermal phase formation studies in the system Mg–Se–Te–O. These two phases, along with MgTe₂O₅ have already been described as existing phases in the system Mg–Te–O and were characterized by their X-ray diffraction patterns at that time (Trömel & Ziethen-Reichnach, 1970). Whereas for MgTe₂O₅ (Weil, 2005) and Mg₂Te₃O₈ (Lin et al., 2013) structure determinations from single-crystal data were reported, detailed structure data for MgTe₆O₁₃ were missing up to now.

MgTe₆O₁₃ is a member of the isotypic series MTe₆O₁₃ crystallizing in space group R3. Structure determinations were reported for the Co, Mn, Ni (Irvine et al., 2003), Fe (van der Lee & Astier, 2007) and Zn (Nawash et al., 2007) members. It should be mentioned that the given space group R3m for FeTe₆O₁₃ (van der Lee & Astier, 2007) is incorrect. The correct space group in fact is R3 (van der Lee, 2013). Lattice parameters and volumes of the several MTe₆O₁₃ phases are in a narrow range (Table 1), as one expects from the similar ionic radii of Mg and the first row transition metals.

The magnesium cation is located on a threefold rotation axis and is surrounded by six oxygen atoms in a slightly distored octahedral environment. Because of the high tellurium content in the structure, the [MgO₆] octahedra are isolated from each other. The two distinct tellurium(IV) atoms exhibit different oxygen environments. Te1 is bonded to four oxygen atoms in form of a bisphenoid with distances ranging from 1.8524 (12) to 2.1842 (11) Å. Considering Te···O separations less than 3.1 Å, two remote O atoms (O3, O5) are also present, leading to a pentagonal pyramid [TeO_{4 + 2}] as the resulting coordination polyhedron. Atom Te2 is bonded to four O atoms with distances ranging from 1.8489 (11) to 2.2118 (12) Å, with an additional O atom 2.5908 (12) Å away. The resulting [TeO_{4 + 1}] polyhedron is a distorted tetragonal pyramid. It is augmented to a distorted octahedron if the remote O4 atom at a distance of 3.0387 (12) Å is also considered. For both [TeO_x] polyhedra (Fig. 1, Table 2) the rules derived by Zemann for the crystal chemistry of oxotellurates(IV) are valid (Zemann, 1971).

The [MgO₆], [Te1O₄] and [Te2O_{4 + 1}] building units share corners and edges, thereby forming a dense three-dimensional structure (Fig. 2). In a simpler view, the structure can be described as being built up from distorted hexagonal layers of the Mg and Te atoms extending parallel to (001) and stacked in an ABCA'B'C' sequence along [001]. The oxygen atoms are situated in the voids of this arrangement.

Related literature

The title compound is isotypic with its Co, Mn, Ni (Irvine et al., 2003), Fe (van der Lee & Astier, 20075: van der Lee, 2013) and Zn (Nawash et al., 2007) analogues. For other phases in the system Mg–Te–O, see: Trömel & Ziethen-Reichnach (1970). For structure determinations of MgTe₂O₅ and Mg₂Te₃O₈, see: Weil (2005) and Lin et al. (2013), respectively. The crystal chemistry of oxotellurates(IV) has been reviewed by Zemann (1971).

S2. Experimental

Magnesium oxide, tellurium dioxide and selenic acid (conc.; 96%_wt) were loaded in the stoichiometric ratio 3:2:1 in a Teflon lined stainless steel autoclave (overall volume 10 ml) that was filled up to two-thirds of its volume with water. The autoclave was then heated at 503 K for one week. Few colourless single crystals of Mg₂Te₃O₈ (Lin et al., 2013) and MgTe₆O₁₃, both with a platy habit, were isolated from the colourless solid reaction product. X-ray powder diffraction (XRPD) of the ground bulk material revealed Mg₂Te₃O₈ and TeO₂ as main products. Se-containing phases could not be identified by XRPD in the solid reaction product.

S3. Refinement

The atomic coordinates of isotypic ZnTe₆O₁₃ (Nawash et al., 2007) were used as starting parameters for the refinement. Reflection 003 was affected from the beamstop and was omitted from the refinement. The highest positive and negative residual electron densities are located 0.68 and 0.48 Å, respectively, from atom Te1.

Computing details

Data collection: APEX2 (Bruker, 2012); cell refinement: SAINT (Bruker, 2012); data reduction: SAINT (Bruker, 2012); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ATOMS for Windows (Dowty, 2008); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures

	Fig. 1. The coordination spheres of the two tellurium(IV) atoms. Te—O bonds < 2.6 Å are given as solid lines, Te—O bonds between 2.6 and 3.1 Å as open lines; probability level of the displacement ellipsoids is 74%. [Symmetry codes: i) -y + 1, x-y+1, z; iii) -x + 2/3, -y + 1/3, -z + 1/3; iv) -x + 1, -y + 1, -z; vii) y, -x+y, -z; ix) x-y+2/3, x + 1/3, -z + 1/3.]
	Fig. 2. The crystal packing of the MgTe6O13 structure in a view along [100]. [MgO6] polyhedra are blue, [Te1O4] polyhedra are red and [Te2O4 + 1] polyhedra are orange. Probability level as in Fig. 1.

Magnesium hexatellurate(IV)

Crystal data

MgTe6O13	Dx = 5.854 Mg m^−3
Mr = 997.91	Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3	Cell parameters from 9908 reflections
Hall symbol: -R 3	θ = 3.2–43.5°
a = 10.1676 (2) Å	µ = 15.38 mm^−1
c = 18.9701 (3) Å	T = 295 K
V = 1698.39 (5) Å^3	Plate, colourless
Z = 6	0.22 × 0.14 × 0.09 mm
F(000) = 2568

Data collection

Bruker APEXII CCD diffractometer	2875 independent reflections
Radiation source: fine-focus sealed tube	2764 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.044
ω– and ϕ–scans	θmax = 43.6°, θmin = 2.6°
Absorption correction: multi-scan (SADABS; Bruker, 2012)	h = −19→19
Tmin = 0.437, Tmax = 0.749	k = −19→19
50742 measured reflections	l = −36→36

Refinement

Refinement on F^2	Primary atom site location: isomorphous structure methods
Least-squares matrix: full	w = 1/[σ^2(Fo^2) + 7.6037P] where P = (Fo^2 + 2Fc^2)/3
R[F^2 > 2σ(F^2)] = 0.017	(Δ/σ)max = 0.002
wR(F^2) = 0.034	Δρmax = 1.17 e Å^−3
S = 1.36	Δρmin = −1.40 e Å^−3
2875 reflections	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
62 parameters	Extinction coefficient: 0.000970 (18)
0 restraints

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
Mg1	0.3333	0.6667	−0.07728 (5)	0.00655 (14)
Te1	0.237607 (11)	0.082435 (11)	0.095241 (5)	0.00766 (2)
Te2	0.394752 (11)	0.496265 (11)	0.075896 (5)	0.00633 (2)
O1	0.0000	0.0000	0.08633 (11)	0.0085 (3)
O2	0.20309 (13)	0.11297 (14)	0.19252 (6)	0.01008 (18)
O3	0.25075 (15)	0.25178 (13)	0.05181 (7)	0.01187 (19)
O4	0.20451 (14)	0.48320 (14)	0.09819 (6)	0.00998 (17)
O5	0.38463 (14)	0.52546 (14)	−0.01971 (6)	0.00969 (17)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Mg1	0.0066 (2)	0.0066 (2)	0.0065 (3)	0.00329 (11)	0.000	0.000
Te1	0.01113 (4)	0.00635 (4)	0.00675 (4)	0.00530 (3)	0.00084 (2)	0.00065 (2)
Te2	0.00718 (4)	0.00727 (4)	0.00516 (3)	0.00408 (3)	−0.00023 (2)	0.00038 (2)
O1	0.0068 (4)	0.0068 (4)	0.0118 (7)	0.0034 (2)	0.000	0.000
O2	0.0065 (4)	0.0145 (5)	0.0060 (4)	0.0028 (4)	0.0005 (3)	−0.0017 (3)
O3	0.0137 (5)	0.0063 (4)	0.0146 (5)	0.0042 (4)	−0.0030 (4)	0.0017 (3)
O4	0.0090 (4)	0.0112 (4)	0.0123 (4)	0.0069 (4)	0.0017 (3)	0.0017 (3)
O5	0.0143 (5)	0.0116 (4)	0.0055 (4)	0.0083 (4)	−0.0002 (3)	0.0014 (3)

Geometric parameters (Å, º)

Mg1—O5^i	2.0676 (12)	Te1—O2^vi	2.1842 (11)
Mg1—O5^ii	2.0676 (12)	Te1—O3^vii	2.9337 (13)
Mg1—O5	2.0676 (12)	Te1—O5^vii	3.0387 (12)
Mg1—O2^iii	2.1596 (12)	Te2—O5	1.8489 (11)
Mg1—O2^iv	2.1596 (12)	Te2—O4	1.9186 (11)
Mg1—O2^v	2.1596 (12)	Te2—O4^i	2.0286 (12)
Te1—O3	1.8524 (12)	Te2—O3	2.2118 (12)
Te1—O2	1.9324 (11)	Te2—O5^viii	2.5908 (12)
Te1—O1	2.1314 (2)	Te2—O4^ix	3.0560 (12)
O5^i—Mg1—O5^ii	94.67 (5)	Te1^x—O1—Te1^xi	119.377 (15)
O5^i—Mg1—O5	94.67 (5)	Te1—O2—Mg1^xii	130.51 (6)
O5^ii—Mg1—O5	94.67 (5)	Te1—O2—Te1^vi	105.30 (5)
O5^i—Mg1—O2^iii	99.09 (5)	Mg1^xii—O2—Te1^vi	122.67 (6)
O5^ii—Mg1—O2^iii	76.38 (5)	Te1—O2—Te2^vi	94.79 (5)
O5—Mg1—O2^iii	164.10 (5)	Mg1^xii—O2—Te2^vi	84.08 (4)
O5^i—Mg1—O2^iv	76.38 (5)	Te1^vi—O2—Te2^vi	78.72 (4)
O5^ii—Mg1—O2^iv	164.10 (5)	Te1—O2—Te1^xi	75.79 (4)
O5—Mg1—O2^iv	99.09 (5)	Mg1^xii—O2—Te1^xi	74.86 (4)
O2^iii—Mg1—O2^iv	91.88 (5)	Te1^vi—O2—Te1^xi	140.31 (5)
O5^i—Mg1—O2^v	164.10 (5)	Te2^vi—O2—Te1^xi	140.94 (4)
O5^ii—Mg1—O2^v	99.09 (5)	Te1—O2—Te2^xiii	124.64 (5)
O5—Mg1—O2^v	76.38 (5)	Mg1^xii—O2—Te2^xiii	77.64 (3)
O2^iii—Mg1—O2^v	91.88 (5)	Te1^vi—O2—Te2^xiii	81.17 (4)
O2^iv—Mg1—O2^v	91.88 (5)	Te2^vi—O2—Te2^xiii	139.31 (3)
O3—Te1—O2	102.12 (6)	Te1^xi—O2—Te2^xiii	67.54 (2)
O3—Te1—O1	82.59 (5)	Te1—O3—Te2	130.72 (6)
O2—Te1—O1	82.98 (6)	Te1—O3—Te1^xiv	120.60 (6)
O3—Te1—O2^vi	90.88 (5)	Te2—O3—Te1^xiv	105.58 (4)
O2—Te1—O2^vi	74.70 (5)	Te1—O3—Te1^xi	91.57 (5)
O1—Te1—O2^vi	154.89 (5)	Te2—O3—Te1^xi	107.62 (5)
O3—Te1—O3^vii	81.28 (3)	Te1^xiv—O3—Te1^xi	87.42 (3)
O2—Te1—O3^vii	172.70 (4)	Te2—O4—Te2^ii	136.27 (7)
O1—Te1—O3^vii	91.12 (6)	Te2—O4—Te2^xiii	106.42 (5)
O2^vi—Te1—O3^vii	111.91 (4)	Te2^ii—O4—Te2^xiii	103.43 (4)
O3—Te1—O5^vii	89.65 (5)	Te2—O4—Te1^xi	115.96 (5)
O2—Te1—O5^vii	130.80 (4)	Te2^ii—O4—Te1^xi	98.97 (4)
O1—Te1—O5^vii	146.21 (6)	Te2^xiii—O4—Te1^xi	82.34 (3)
O2^vi—Te1—O5^vii	57.32 (4)	Te2—O4—Te2^i	71.27 (4)
O3^vii—Te1—O5^vii	55.14 (3)	Te2^ii—O4—Te2^i	70.62 (3)
O5—Te2—O4	95.29 (5)	Te2^xiii—O4—Te2^i	104.98 (3)
O5—Te2—O4^i	94.31 (5)	Te1^xi—O4—Te2^i	168.27 (4)
O4—Te2—O4^i	93.39 (7)	Te2—O5—Mg1	133.10 (7)
O5—Te2—O3	85.36 (5)	Te2—O5—Te2^viii	105.65 (5)
O4—Te2—O3	83.67 (5)	Mg1—O5—Te2^viii	111.82 (5)
O4^i—Te2—O3	177.00 (5)	Te2—O5—Te1^xiv	112.67 (5)
O5—Te2—O5^viii	74.35 (5)	Mg1—O5—Te1^xiv	94.65 (4)
O4—Te2—O5^viii	166.09 (5)	Te2^viii—O5—Te1^xiv	90.25 (3)
O4^i—Te2—O5^viii	96.57 (5)	Te2—O5—Te2^i	71.20 (4)
O3—Te2—O5^viii	86.22 (5)	Mg1—O5—Te2^i	68.01 (4)
O5—Te2—O4^ix	160.15 (4)	Te2^viii—O5—Te2^i	114.99 (4)
O4—Te2—O4^ix	72.54 (5)	Te1^xiv—O5—Te2^i	153.01 (4)
O4^i—Te2—O4^ix	71.41 (4)	Te2—O5—Te2^ii	71.12 (4)
O3—Te2—O4^ix	108.16 (4)	Mg1—O5—Te2^ii	67.95 (4)
O5^viii—Te2—O4^ix	119.92 (3)	Te2^viii—O5—Te2^ii	172.20 (5)
Te1—O1—Te1^x	119.377 (15)	Te1^xiv—O5—Te2^ii	97.55 (3)
Te1—O1—Te1^xi	119.377 (15)	Te2^i—O5—Te2^ii	57.381 (17)

Symmetry codes: (i) −y+1, x−y+1, z; (ii) −x+y, −x+1, z; (iii) −y+1/3, x−y+2/3, z−1/3; (iv) x+1/3, y+2/3, z−1/3; (v) −x+y+1/3, −x+2/3, z−1/3; (vi) −x+2/3, −y+1/3, −z+1/3; (vii) y, −x+y, −z; (viii) −x+1, −y+1, −z; (ix) x−y+2/3, x+1/3, −z+1/3; (x) −x+y, −x, z; (xi) −y, x−y, z; (xii) x−1/3, y−2/3, z+1/3; (xiii) y−1/3, −x+y+1/3, −z+1/3; (xiv) x−y, x, −z.