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Acta Crystallogr Sect E Struct Rep Online. 2008 October 1; 64(Pt 10): i66.
Published online 2008 September 6. doi:  10.1107/S160053680802789X
PMCID: PMC2959450

Mg4Sb2O9 of the ilmenite structure type

Abstract

Single crystals of the title compound, tetra­magnesium dianti­monate(V), were obtained by the slow cooling method with K2CO3. The structure is isotypic with ilmenite, which is constructed by the alternate stacking of layers consisting of metal–oxygen coordination octa­hedra. In each layer, the octa­hedra are connected by sharing edges so as to make holes. One of the two non-equivalent metal sites is fully occupied by Mg (3 symmetry), while the second metal site (3 symmetry) is disordered and occupied by Mg and Sb with occupation factors of 1/3 and 2/3, respectively.

Related literature

For ilmenite structures, see: Wechsler & Prewitt (1984 [triangle]) for FeTiO3 and Wechsler & Von Dreele (1989 [triangle]) for MgTiO3. For further phases in the MgO–Sb2O5 system, see: Kasper (1969 [triangle]). For related literature, see: Becker & Coppens (1974 [triangle]); Blasse (1964 [triangle]); Michiue (2007 [triangle]).

Experimental

Crystal data

  • Mg4O9Sb2
  • M r = 484.7
  • Trigonal, An external file that holds a picture, illustration, etc.
Object name is e-64-00i66-efi1.jpg
  • a = 5.1722 (11) Å
  • c = 14.028 (2) Å
  • V = 324.99 (11) Å3
  • Z = 2
  • Mo Kα radiation
  • μ = 8.73 mm−1
  • T = 295 K
  • 0.22 × 0.22 × 0.04 mm

Data collection

  • Rigaku AFC-7R diffractometer
  • Absorption correction: analytical (Tompa Analytical, Rigaku 2004 [triangle]) T min = 0.210, T max = 0.671
  • 2359 measured reflections
  • 773 independent reflections
  • 715 reflections with I > 2σ(I)
  • R int = 0.046
  • 3 standard reflections every 200 reflections intensity decay: 4.6%

Refinement

  • R[F 2 > 2σ(F 2)] = 0.032
  • wR(F 2) = 0.074
  • S = 1.55
  • 773 reflections
  • 17 parameters
  • Δρmax = 3.78 e Å−3
  • Δρmin = −3.64 e Å−3

Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1994 [triangle]); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: CrystalStructure (Rigaku, 2004 [triangle]); method used to solve structure: structure of the present compound is isotypic with ilmenite; program(s) used to refine structure: JANA2000 (Petříček et al., 2000 [triangle]); molecular graphics: ATOMS (Dowty, 2005 [triangle]); software used to prepare material for publication: JANA2000.

Table 1
Selected bond lengths (Å), M = Mg, Sb

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S160053680802789X/si2101sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S160053680802789X/si2101Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Comment

A pronounced resemblance of X-ray diffraction patterns for Mg4Sb2O9 and the ilmenite MgTiO3 was pointed out by Blasse (1964). In general, ilmenite structure is represented by A2+B4+O3, that is including equal amounts of divalent and tetravalent cations such as FeTiO3 and MgTiO3. Although the chemical composition Mg4Sb2O9 is away from that of the typical ilmenite structure, the present analysis has confirmed that the structure of Mg4Sb2O9 is deduced from the ilmenite MgTiO3 by replacing the Ti4+ ions statistically by 1/3 Mg2+ and 2/3 Sb5+, as was supposed by Blasse (1964).

The structure is constructed by the alternate stacking of atomic layers along c as shown in Fig. 1. Each of the two nonequivalent metal sites is octahedrally coordinated by six oxygen ions. Two types of layers consisting of edge-shared octahedra are seen in the structure, both of which have holes as illustrated in Fig. 2.

Experimental

Single crystals of the title compound were obtained unintentionally as the product of a synthesis of K-hollandite by the slow cooling method with excess K2CO3 (Michiue, 2007).

Refinement

Partial substitution of Sb for Mg at the Mg2 site was checked by refining the occupation factors of Mg and Sb at the site. In the refinement the full occupation at all the metal and oxygen sites was assumed and the charge neutrality of the whole crystal was kept by imposing constraint conditions. The possibility of the existence of Sb ions at the Mg2 site was excluded because the occupation factor of Sb at the site was slightly negative, -0.001, and that of Mg was 1.001 after the refinement. Thus, it was concluded that Sb ions are only at the Mg1/Sb1 site.

Figures

Fig. 1.
The projection of Mg4Sb2O9 along [110].
Fig. 2.
Layers with holes consisting of (a) Mg2O6 octahedra extending around z = 0 and (b) (Mg1/Sb1)O6 octahedra around z = 1/6 in Mg4Sb2O9.

Crystal data

Mg4O9Sb2Dx = 4.952 Mg m3
Mr = 484.7Mo Kα radiation, λ = 0.71069 Å
Trigonal, R3Cell parameters from 20 reflections
Hall symbol: -R 3θ = 9.3–13.5°
a = 5.1722 (11) ŵ = 8.73 mm1
c = 14.028 (2) ÅT = 295 K
V = 324.99 (11) Å3Plate, colorless
Z = 20.22 × 0.22 × 0.04 mm
F(000) = 444

Data collection

Rigaku AFC-7R diffractometer715 reflections with I > 2σ(I)
Radiation source: rotating-anode X-ray tubeRint = 0.047
graphiteθmax = 50.1°, θmin = 4.4°
ω/2θ scansh = −11→11
Absorption correction: analytical (Tompa Analytical, Rigaku 2004)k = −11→11
Tmin = 0.210, Tmax = 0.671l = 0→30
2359 measured reflections3 standard reflections every 200 reflections
773 independent reflections intensity decay: 4.6%

Refinement

Refinement on F2Primary atom site location: isomorphous structure methods
Least-squares matrix: fullWeighting scheme based on measured s.u.'s w = 1/(σ2(I) + 0.0009I2)
R[F2 > 2σ(F2)] = 0.032(Δ/σ)max = 0.0004
wR(F2) = 0.075Δρmax = 3.78 e Å3
S = 1.55Δρmin = −3.64 e Å3
773 reflectionsExtinction correction: B-C type 1 Lorentzian isotropic (Becker & Coppens, 1974)
17 parametersExtinction coefficient: 0.071 (3)
0 restraints

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)

xyzUiso*/UeqOcc. (<1)
Mg1000.152618 (14)0.00628 (7)0.3333
M1000.152618 (14)0.00628 (7)0.6667
Mg2000.35806 (10)0.0098 (2)
O10.3091 (3)0.0125 (3)0.24710 (7)0.0078 (3)

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
Mg10.00711 (10)0.00711 (10)0.00461 (10)0.00356 (5)00
M10.00711 (10)0.00711 (10)0.00461 (10)0.00356 (5)00
Mg20.0080 (3)0.0080 (3)0.0133 (4)0.00401 (13)00
O10.0097 (4)0.0073 (4)0.0069 (3)0.0047 (3)−0.0010 (3)0.0011 (2)

Geometric parameters (Å, °)

M1—O12.0527 (15)Mg2—O12.2091 (17)
M1—O1i1.9928 (11)Mg2—O1vi2.0455 (17)
M1—O1ii2.0527 (19)Mg2—O1ii2.209 (2)
M1—O1iii1.9928 (18)Mg2—O1vii2.0455 (14)
M1—O1iv2.0527 (12)Mg2—O1iv2.2091 (15)
M1—O1v1.9928 (17)Mg2—O1viii2.046 (2)
O1—M1—O1i83.77 (5)O1—Mg2—O1vi87.88 (6)
O1—M1—O1ii82.80 (6)O1—Mg2—O1ii75.84 (7)
O1—M1—O1iii166.22 (6)O1—Mg2—O1vii89.32 (5)
O1—M1—O1iv82.80 (6)O1—Mg2—O1iv75.84 (7)
O1—M1—O1v92.43 (7)O1—Mg2—O1viii160.12 (8)
O1i—M1—O183.77 (5)O1vi—Mg2—O187.88 (6)
O1i—M1—O1ii92.43 (5)O1vi—Mg2—O1ii160.12 (8)
O1i—M1—O1iii99.93 (6)O1vi—Mg2—O1vii103.48 (8)
O1i—M1—O1iv166.22 (6)O1vi—Mg2—O1iv89.32 (6)
O1i—M1—O1v99.93 (6)O1vi—Mg2—O1viii103.48 (7)
O1ii—M1—O182.80 (6)O1ii—Mg2—O175.84 (7)
O1ii—M1—O1i92.43 (5)O1ii—Mg2—O1vi160.12 (8)
O1ii—M1—O1iii83.77 (7)O1ii—Mg2—O1vii87.88 (6)
O1ii—M1—O1iv82.80 (6)O1ii—Mg2—O1iv75.84 (7)
O1ii—M1—O1v166.22 (5)O1ii—Mg2—O1viii89.32 (6)
O1iii—M1—O1166.22 (6)O1vii—Mg2—O189.32 (5)
O1iii—M1—O1i99.93 (6)O1vii—Mg2—O1vi103.48 (8)
O1iii—M1—O1ii83.77 (7)O1vii—Mg2—O1ii87.88 (6)
O1iii—M1—O1iv92.43 (7)O1vii—Mg2—O1iv160.12 (8)
O1iii—M1—O1v99.93 (8)O1vii—Mg2—O1viii103.48 (7)
O1iv—M1—O182.80 (6)O1iv—Mg2—O175.84 (7)
O1iv—M1—O1i166.22 (6)O1iv—Mg2—O1vi89.32 (6)
O1iv—M1—O1ii82.80 (6)O1iv—Mg2—O1ii75.84 (7)
O1iv—M1—O1iii92.43 (7)O1iv—Mg2—O1vii160.12 (8)
O1iv—M1—O1v83.77 (6)O1iv—Mg2—O1viii87.88 (6)
O1v—M1—O192.43 (7)O1viii—Mg2—O1160.12 (8)
O1v—M1—O1i99.93 (6)O1viii—Mg2—O1vi103.48 (7)
O1v—M1—O1ii166.22 (5)O1viii—Mg2—O1ii89.32 (6)
O1v—M1—O1iii99.93 (8)O1viii—Mg2—O1vii103.48 (7)
O1v—M1—O1iv83.77 (6)O1viii—Mg2—O1iv87.88 (6)

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

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: SI2101).

References

  • Becker, P. J. & Coppens, P. (1974). Acta Cryst. A30, 129–147.
  • Blasse, G. (1964). Z. Anorg. Allg. Chem.331, 44–50.
  • Dowty, E. (2005). ATOMS Shape Software, Kingsport, Tennessee, USA.
  • Kasper, H. (1969). Z. Kristallogr.128, 72–84.
  • Michiue, Y. (2007). J. Solid State Chem.180, 1840–1845.
  • Molecular Structure Corporation (1994). MSC/AFC Diffractometer Control Software MSC, The Woodlands, Texas, USA.
  • Petříček, V., Dušek, M. & Palatinus, L. (2000). JANA2000 Institute of Physics, Prague, Czech Republic.
  • Rigaku (2004). CrystalStructure and Tompa Analytical Rigaku Corporation, Tokyo, Japan.
  • Wechsler, B. A. & Von Dreele, R. B. (1989). Acta Cryst. B45, 542–549.
  • Wechsler, B. A. & Prewitt, C. T. (1984). Am. Mineral.69, 176–185.

Articles from Acta Crystallographica Section E: Structure Reports Online are provided here courtesy of International Union of Crystallography