Redetermination of MgTe₂O₅

The crystal structure of the title compound, magnesium penta­oxoditellurate(IV), has been redetermined from a crystal grown from the melt and confirms the previous study [Trömel (1975). Z. Anorg. Allg. Chem. 418, 141–144], but with improved precision. It is isotypic with β-MnTe₂O₅ and contains MgO₆ octa­hedra and TeO₃₊₁ units, with the latter forming an extended sheet structure. Mg and one O atom occupy special positions with site symmetry 2.

Key indicators

• Single-crystal X-ray study
• T = 295 K
• Mean [sigma](g-O) = 0.001 Å
• R factor = 0.018
• wR factor = 0.041
• Data-to-parameter ratio = 31.0

checkCIF/PLATON results

No syntax errors found



Alert level G
ABSTM02_ALERT_3_G  The ratio of expected to reported Tmax/Tmin(RR') is < 0.90
            Tmin and Tmax reported:      0.126     0.242
            Tmin(prime) and Tmax expected:      0.046     0.074
            RR(prime) =      0.839
            Please check that your absorption correction is appropriate.

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   0 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion

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Computing details

Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: CAD-4 Software; data reduction: HELENA implemented in PLATON (Spek, 2003); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ATOMS (Dowty, 2000); software used to prepare material for publication: SHELXL97.

magnesium pentaoxoditellurate(IV)

Crystal data

MgTe2O5	F(000) = 624
Mr = 359.51	Dx = 5.169 Mg m^−3
Orthorhombic, Pbcn	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2n 2ab	Cell parameters from 25 reflections
a = 7.2391 (9) Å	θ = 11.3–16.1°
b = 10.658 (1) Å	µ = 12.68 mm^−1
c = 5.9880 (6) Å	T = 295 K
V = 462.00 (9) Å^3	Fragment, colourless
Z = 4	0.22 × 0.22 × 0.21 mm

Data collection

Enraf–Nonius CAD-4 diffractometer	1112 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.038
Graphite monochromator	θmax = 37.4°, θmin = 3.4°
ω/2θ scans	h = −12→12
Absorption correction: numerical (HABITUS; Herrendorf, 1997)	k = −18→18
Tmin = 0.126, Tmax = 0.242	l = −10→10
8781 measured reflections	3 standard reflections every 300 min
1210 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Primary atom site location: isomorphous structure methods
Least-squares matrix: full	w = 1/[σ^2(Fo^2) + (0.0172P)^2 + 0.3586P] where P = (Fo^2 + 2Fc^2)/3
R[F^2 > 2σ(F^2)] = 0.018	(Δ/σ)max = 0.001
wR(F^2) = 0.041	Δρmax = 1.54 e Å^−3
S = 1.25	Δρmin = −1.62 e Å^−3
1210 reflections	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
39 parameters	Extinction coefficient: 0.0928 (16)
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
Mg	0.0000	0.44331 (7)	0.2500	0.00966 (14)
Te	0.133353 (13)	0.154562 (9)	0.010001 (18)	0.00856 (5)
O1	0.19064 (18)	0.29457 (11)	0.1816 (2)	0.0145 (2)
O2	0.35061 (16)	0.06582 (12)	0.0487 (2)	0.0120 (2)
O3	0.0000	0.06250 (16)	0.2500	0.0156 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Mg	0.0094 (3)	0.0092 (3)	0.0104 (3)	0.000	−0.0014 (2)	0.000
Te	0.00683 (7)	0.00788 (7)	0.01098 (8)	0.00041 (2)	−0.00014 (2)	−0.00088 (2)
O1	0.0138 (5)	0.0109 (5)	0.0189 (6)	0.0010 (4)	−0.0022 (4)	−0.0049 (4)
O2	0.0098 (5)	0.0123 (5)	0.0138 (5)	0.0051 (4)	0.0015 (4)	0.0016 (4)
O3	0.0175 (7)	0.0106 (6)	0.0186 (8)	0.000	0.0092 (6)	0.000

Geometric parameters (Å, º)

Mg—O2^i	2.0801 (13)	Te—O2	1.8498 (11)
Mg—O2^ii	2.0801 (13)	Te—O1	1.8588 (12)
Mg—O2^iii	2.0926 (14)	Te—O3	1.9900 (9)
Mg—O2^iv	2.0926 (14)	Te—O1^viii	2.4048 (13)
Mg—O1^v	2.1413 (14)	Te—Mg^viii	3.2491 (4)
Mg—O1	2.1413 (14)	O1—Te^iii	2.4048 (13)
Mg—Mg^vi	3.2287 (6)	O2—Mg^ix	2.0801 (13)
Mg—Mg^vii	3.2287 (6)	O2—Mg^viii	2.0926 (14)
Mg—Te^iv	3.2491 (4)	O3—Te^v	1.9900 (9)
Mg—Te^iii	3.2491 (4)
O2^i—Mg—O2^ii	102.24 (8)	O1^v—Mg—O1	84.48 (7)
O2^i—Mg—O2^iii	78.62 (5)	O2—Te—O1	98.71 (6)
O2^ii—Mg—O2^iii	104.82 (5)	O2—Te—O3	94.00 (5)
O2^i—Mg—O2^iv	104.82 (5)	O1—Te—O3	96.01 (6)
O2^ii—Mg—O2^iv	78.62 (5)	O2—Te—O1^viii	76.55 (5)
O2^iii—Mg—O2^iv	174.67 (8)	O1—Te—O1^viii	98.80 (2)
O2^i—Mg—O1^v	91.08 (5)	O3—Te—O1^viii	163.46 (5)
O2^ii—Mg—O1^v	155.58 (6)	Te—O1—Mg	123.79 (7)
O2^iii—Mg—O1^v	97.77 (5)	Te—O1—Te^iii	138.70 (7)
O2^iv—Mg—O1^v	78.22 (5)	Mg—O1—Te^iii	91.05 (4)
O2^i—Mg—O1	155.58 (6)	Te—O2—Mg^ix	146.68 (8)
O2^ii—Mg—O1	91.08 (5)	Te—O2—Mg^viii	110.85 (7)
O2^iii—Mg—O1	78.22 (5)	Mg^ix—O2—Mg^viii	101.38 (5)
O2^iv—Mg—O1	97.77 (5)	Te—O3—Te^v	120.91 (9)

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