Redetermination of SrTe₃O₈ from a hydro­thermally grown single crystal

The crystal structure of the mixed-valence tellurium compound strontium ditellurate(IV) tellurate(VI) was redetermined from single-crystal data. The previous structural model, determined ab initio from powder X-ray diffraction data [Barrier et al. (2006). J. Solid State Chem. 179, 3484–3488], was confirmed, but with all atoms refined with anisotropic displacement parameters and with differences in individual Te—O bond lengths up to 0.05 Å. The structure is composed of [Te₃O₈]_∞²⁻ chains that extend parallel to [001] and [110] to form a channel structure. Whereas one half of the channel is occupied by the Sr atoms in an eightfold coordination, the other half remains unoccupied, with the electron lone pairs of Te^IV protruding into the empty space. Except for one O atom, all other atoms are on special positions: Sr (.. symmetry), Te1 (m..), Te2 (2/m..), O1 (m..) and O2 (m..).

Key indicators

• Single-crystal X-ray study
• T = 295 K
• Mean [sigma](e-Te) = 0.001 Å
• R factor = 0.023
• wR factor = 0.058
• Data-to-parameter ratio = 15.1

checkCIF/PLATON results

No syntax errors found



Alert level C
CRYSR01_ALERT_1_C  _exptl_crystal_size_rad not in the CIF when expected.
PLAT031_ALERT_4_C Refined Extinction Parameter within Range ......       3.00 Sigma
PLAT062_ALERT_4_C Rescale T(min) & T(max) by .....................       0.76

Alert level G
ABSTM02_ALERT_3_G  When printed, the submitted absorption T values will be
            replaced by the scaled T values. Since the ratio of scaled T's
            is identical to the ratio of reported T values, the scaling
            does not imply a change to the absorption corrections used in
            the study.
            Ratio of Tmax expected/reported      0.757
            Tmax scaled      0.265 Tmin scaled      0.232

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

   1 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
   2 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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Computing details

Data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ATOMS (Dowty, 2006); software used to prepare material for publication: SHELXL97.

tellurium compound strontium ditellurate(IV) tellurate(VI)

Crystal data

SrTe3O8	Dx = 6.298 Mg m^−3
Mr = 598.42	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P42/m	Cell parameters from 2677 reflections
Hall symbol: -P 4c	θ = 3.0–31.0°
a = 6.8321 (3) Å	µ = 22.14 mm^−1
c = 6.7605 (5) Å	T = 295 K
V = 315.56 (3) Å^3	Spheroid, colourless
Z = 2	0.07 × 0.06 × 0.06 mm
F(000) = 516

Data collection

Bruker SMART APEX CCD diffractometer	530 independent reflections
Radiation source: fine-focus sealed tube	525 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.023
ω scans	θmax = 31.0°, θmin = 3.0°
Absorption correction: multi-scan (SADABS; Sheldrick, 2002)	h = −9→9
Tmin = 0.306, Tmax = 0.350	k = −9→9
3678 measured reflections	l = −9→9

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.023	w = 1/[σ^2(Fo^2) + (0.0267P)^2 + 2.521P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.058	(Δ/σ)max < 0.001
S = 1.20	Δρmax = 1.04 e Å^−3
530 reflections	Δρmin = −2.08 e Å^−3
35 parameters	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.0018 (6)

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
Sr	0.0000	0.0000	0.2500	0.0184 (2)
Te1	0.43571 (6)	0.21739 (6)	0.0000	0.00859 (14)
Te2	0.0000	0.5000	0.0000	0.00639 (15)
O1	0.4098 (5)	0.1876 (5)	0.3060 (5)	0.0119 (6)
O2	0.1178 (6)	0.2446 (6)	0.0000	0.0099 (8)
O3	0.6767 (7)	0.0450 (7)	0.0000	0.0108 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Sr	0.0202 (3)	0.0202 (3)	0.0149 (4)	0.000	0.000	0.000
Te1	0.0087 (2)	0.0068 (2)	0.0103 (2)	0.00086 (12)	0.000	0.000
Te2	0.0072 (2)	0.0058 (2)	0.0062 (2)	0.00125 (16)	0.000	0.000
O1	0.0163 (15)	0.0128 (14)	0.0068 (13)	0.0032 (12)	0.0006 (11)	0.0008 (11)
O2	0.0074 (18)	0.0064 (18)	0.016 (2)	0.0018 (14)	0.000	0.000
O3	0.0095 (19)	0.0092 (19)	0.014 (2)	0.0040 (15)	0.000	0.000

Geometric parameters (Å, º)

Sr—O2^i	2.509 (3)	Te1—Te1^vi	3.0976 (8)
Sr—O2^ii	2.509 (3)	Te1—Sr^i	3.7315 (4)
Sr—O2	2.509 (3)	Te2—O2	1.922 (4)
Sr—O2^iii	2.509 (3)	Te2—O2^xi	1.922 (4)
Sr—O3^iv	2.798 (4)	Te2—O1^xii	1.934 (3)
Sr—O3^v	2.798 (4)	Te2—O1^iv	1.934 (3)
Sr—O3^vi	2.798 (4)	Te2—O1^xiii	1.934 (3)
Sr—O3^vii	2.798 (4)	Te2—O1^ix	1.934 (3)
Sr—O1	3.102 (4)	Te2—Sr^xiv	3.8113 (2)
Sr—O1^viii	3.102 (4)	Te2—Sr^i	3.8113 (2)
Sr—O1^ii	3.102 (4)	Te2—Sr^xi	3.8113 (2)
Sr—O1^ix	3.102 (4)	O1—Te2^xv	1.934 (3)
Te1—O3^vi	1.951 (5)	O2—Sr^i	2.509 (3)
Te1—O3	2.024 (4)	O3—Te1^vi	1.951 (5)
Te1—O1	2.086 (3)	O3—Sr^xvi	2.798 (4)
Te1—O1^x	2.086 (3)	O3—Sr^vi	2.798 (4)
Te1—O2	2.180 (4)
O2^i—Sr—O2^ii	116.98 (7)	O1—Sr—O1^ii	90.853 (15)
O2^i—Sr—O2	95.32 (13)	O1^viii—Sr—O1^ii	90.853 (15)
O2^ii—Sr—O2	116.98 (7)	O2^i—Sr—O1^ix	112.72 (11)
O2^i—Sr—O2^iii	116.98 (7)	O2^ii—Sr—O1^ix	130.30 (11)
O2^ii—Sr—O2^iii	95.32 (13)	O2—Sr—O1^ix	56.59 (11)
O2—Sr—O2^iii	116.98 (7)	O2^iii—Sr—O1^ix	61.15 (10)
O2^i—Sr—O3^iv	165.40 (14)	O3^iv—Sr—O1^ix	53.61 (10)
O2^ii—Sr—O3^iv	76.89 (12)	O3^v—Sr—O1^ix	60.07 (11)
O2—Sr—O3^iv	81.14 (9)	O3^vi—Sr—O1^ix	110.59 (10)
O2^iii—Sr—O3^iv	54.07 (13)	O3^vii—Sr—O1^ix	137.79 (10)
O2^i—Sr—O3^v	54.07 (13)	O1—Sr—O1^ix	90.853 (15)
O2^ii—Sr—O3^v	165.40 (14)	O1^viii—Sr—O1^ix	90.853 (15)
O2—Sr—O3^v	76.89 (12)	O1^ii—Sr—O1^ix	165.99 (12)
O2^iii—Sr—O3^v	81.14 (9)	O3^vi—Te1—O3	77.6 (2)
O3^iv—Sr—O3^v	111.40 (6)	O3^vi—Te1—O1	82.93 (10)
O2^i—Sr—O3^vi	76.89 (12)	O3—Te1—O1	90.69 (9)
O2^ii—Sr—O3^vi	81.14 (9)	O3^vi—Te1—O1^x	82.93 (10)
O2—Sr—O3^vi	54.07 (13)	O3—Te1—O1^x	90.69 (9)
O2^iii—Sr—O3^vi	165.40 (14)	O1—Te1—O1^x	165.14 (19)
O3^iv—Sr—O3^vi	111.40 (6)	O3^vi—Te1—O2	71.70 (18)
O3^v—Sr—O3^vi	105.68 (11)	O3—Te1—O2	149.32 (18)
O2^i—Sr—O3^vii	81.14 (9)	O1—Te1—O2	85.63 (9)
O2^ii—Sr—O3^vii	54.07 (13)	O1^x—Te1—O2	85.63 (9)
O2—Sr—O3^vii	165.40 (14)	O2—Te2—O2^xi	180.0
O2^iii—Sr—O3^vii	76.89 (12)	O2—Te2—O1^xii	89.33 (14)
O3^iv—Sr—O3^vii	105.68 (11)	O2^xi—Te2—O1^xii	90.67 (14)
O3^v—Sr—O3^vii	111.40 (6)	O2—Te2—O1^iv	90.67 (14)
O3^vi—Sr—O3^vii	111.40 (6)	O2^xi—Te2—O1^iv	89.33 (14)
O2^i—Sr—O1	130.30 (11)	O1^xii—Te2—O1^iv	180.00 (15)
O2^ii—Sr—O1	56.59 (11)	O2—Te2—O1^xiii	90.67 (14)
O2—Sr—O1	61.15 (10)	O2^xi—Te2—O1^xiii	89.33 (14)
O2^iii—Sr—O1	112.72 (11)	O1^xii—Te2—O1^xiii	94.62 (19)
O3^iv—Sr—O1	60.07 (11)	O1^iv—Te2—O1^xiii	85.38 (19)
O3^v—Sr—O1	137.79 (10)	O2—Te2—O1^ix	89.33 (14)
O3^vi—Sr—O1	53.61 (10)	O2^xi—Te2—O1^ix	90.67 (14)
O3^vii—Sr—O1	110.59 (10)	O1^xii—Te2—O1^ix	85.38 (19)
O2^i—Sr—O1^viii	61.15 (10)	O1^iv—Te2—O1^ix	94.62 (19)
O2^ii—Sr—O1^viii	112.72 (11)	O1^xiii—Te2—O1^ix	180.00 (19)
O2—Sr—O1^viii	130.30 (11)	Te2^xv—O1—Te1	135.24 (17)
O2^iii—Sr—O1^viii	56.59 (11)	Te2^xv—O1—Sr	95.54 (13)
O3^iv—Sr—O1^viii	110.59 (10)	Te1—O1—Sr	89.76 (12)
O3^v—Sr—O1^viii	53.61 (10)	Te2—O2—Te1	119.7 (2)
O3^vi—Sr—O1^viii	137.79 (10)	Te2—O2—Sr^i	118.05 (15)
O3^vii—Sr—O1^viii	60.07 (11)	Te1—O2—Sr^i	105.25 (14)
O1—Sr—O1^viii	165.99 (12)	Te2—O2—Sr	118.05 (15)
O2^i—Sr—O1^ii	56.59 (11)	Te1—O2—Sr	105.25 (14)
O2^ii—Sr—O1^ii	61.15 (10)	Sr^i—O2—Sr	84.68 (13)
O2—Sr—O1^ii	112.72 (11)	Te1^vi—O3—Te1	102.4 (2)
O2^iii—Sr—O1^ii	130.30 (11)	Te1^vi—O3—Sr^xvi	102.11 (14)
O3^iv—Sr—O1^ii	137.79 (10)	Te1—O3—Sr^xvi	134.91 (12)
O3^v—Sr—O1^ii	110.59 (10)	Te1^vi—O3—Sr^vi	102.11 (14)
O3^vi—Sr—O1^ii	60.07 (11)	Te1—O3—Sr^vi	134.91 (12)
O3^vii—Sr—O1^ii	53.61 (10)	Sr^xvi—O3—Sr^vi	74.32 (11)

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