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Dipotassium dialuminium diantimonate, K2[Al2Sb2O7], crystallizes in the trigonal space group P\overline 3m1. The structure is isotypic with K2Pb2Ge2O7 and consists of [Al2Sb2O7]2− layers containing Al3+ in a nearly regular tetrahedral and Sb3+ in a Ψ-tetrahedral environment of O ligands.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270199012184/br1259sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270199012184/br1259Isup2.hkl
Contains datablock I

Comment top

The title compound (Fig. 1) is isotypic with the thallium vanadate Tl4V2O7 (= Tl2I[Tl2IV2VO7]; Jouanneaux et al., 1992), the structure of which was determined from powder diffraction data. K2Pb2Ge2O7 (Bassi & Lajzerowicz, 1965) is probably isotypic, but was first described as crystallizing in the subgroup P3. A symmetry check (Le Page, 1987) and transformation to the standard setting with the help of the program STRUCTURE TIDY (Gelato & Parthé, 1987) shows the isotypic nature of K2Pb2Ge2O7 and the title compound.

The Al atoms in K2Al2Sb2O7 are located on the edges of the unit cell (Fig. 2) and are coordinated by four O atoms in an approximately regular tetrahedral environment, with Al—O distances of 1.702 (1) (Al—O2, × 1) and 1.762 (2) Å (Al—O1, × 3) and O—Al—O angles ranging from 108.1 (1) to 110.9 (1)° (shown as tetrahedra in Fig. 2). Two AlO4 tetrahedra are connected by a common O2 atom to form linear [Al2O7] dimers with a staggered conformation of the six O1 ligands (Fig. 1). These dimers are connected by Sb3+ ions to form layers perpendicular to the threefold axis. The Sb atoms are coordinated by three O ligands in a Ψ-tetrahedral coordination, with an Sb—O distance of 1.936 (2) Å and an O—Sb—O angle of 91.8 (1)°. The corresponding distances and angles in CsSbO2 (Hirschle & Röhr, 1998), Cs4Sb2O5 (Hirschle & Röhr, 1999) and Na3SbO3 (Stöver & Hoppe, 1980) are comparable to these values. They clearly indicate the stereochemical activity of the antimony(III) lone pair, which in K2Al2Sb2O7 points towards the centre of the layered [Al2Sb2O7]2− anions running perpendicular to the (001) direction. The anions are bounded by oxygen kagome (3.6.3.6) nets stacked in the sequence A—B. The K+ cations are intercalated between the [Al2Sb2O7]2− layers, with a resulting coordination number of nine and K—O distances ranging from 2.900 (2) to 2.979 (1) Å.

Experimental top

Potassium (156 mg; 4.0 mmol; Merck, 99%) was reacted with a powdered mixture of Al2O3 (204 mg, 2.0 mmol; Merck, p.a.??), Sb2O3 (292 mg, 1.0 mmol; Merck, p.a.) and Sb2O5 (323 mg, 1.0 mmol; ABCR, 99%) in a corundum crucible under an argon (99.99%) atmosphere. The mixture was heated up to 1050 K at a rate of 100 K h−1 and then cooled to 590 K at 5 K h−1 and from 590 K to room temperature at 15 K h−1. The title compound crystallizes in clear thin plates of hexagonal shape. The X-ray powder patterns of the samples can be indexed with the single-crystal data of the title compound and show only weak reflections of corundum, Sb2O3 and additional unknown compounds.

Computing details top

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: HELENA (Spek, 1993); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP (Johnson, 1968) and DRAWxtl (Finger & Kroeker, 1997); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. ORTEP (Johnson, 1968) view of the layered [Al2Sb2O7]2− anions in the title compound. Displacement ellipsoids are shown at the 50% probability level.
[Figure 2] Fig. 2. View of the unit cell of the crystal structure of the title compound.
Potassium oxoaluminate antimonate(III) top
Crystal data top
K2[Al2Sb2O7]Dx = 3.664 Mg m3
Mr = 487.66Mo Kα radiation, λ = 0.71070 Å
Trigonal, P3m1Cell parameters from 25 reflections
a = 5.6325 (8) Åθ = 6.3–23.8°
c = 8.045 (2) ŵ = 7.25 mm1
V = 221.04 (7) Å3T = 293 K
Z = 1Hexagonal plate, colourless
F(000) = 2220.10 × 0.07 × 0.03 mm
Data collection top
Enraf-Nonius CAD-4
diffractometer
319 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.085
Graphite monochromatorθmax = 32.4°, θmin = 4.2°
ω/2θ scansh = 88
Absorption correction: ψ-scans
(North et al., 1968)
k = 88
Tmin = 0.589, Tmax = 0.805l = 120
1691 measured reflections3 standard reflections every 7200 min
342 independent reflections intensity decay: none
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.018 w = 1/[σ2(Fo2) + (0.0191P)2]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.044(Δ/σ)max < 0.001
S = 1.14Δρmax = 1.28 e Å3
342 reflectionsΔρmin = 0.81 e Å3
19 parametersExtinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.014 (3)
Crystal data top
K2[Al2Sb2O7]Z = 1
Mr = 487.66Mo Kα radiation
Trigonal, P3m1µ = 7.25 mm1
a = 5.6325 (8) ÅT = 293 K
c = 8.045 (2) Å0.10 × 0.07 × 0.03 mm
V = 221.04 (7) Å3
Data collection top
Enraf-Nonius CAD-4
diffractometer
319 reflections with I > 2σ(I)
Absorption correction: ψ-scans
(North et al., 1968)
Rint = 0.085
Tmin = 0.589, Tmax = 0.8053 standard reflections every 7200 min
1691 measured reflections intensity decay: none
342 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.01819 parameters
wR(F2) = 0.0440 restraints
S = 1.14Δρmax = 1.28 e Å3
342 reflectionsΔρmin = 0.81 e Å3
Special details top

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 (Å2) top
xyzUiso*/Ueq
K11/32/30.58969 (14)0.01743 (18)
Sb11/32/30.15516 (3)0.00913 (12)
Al1000.21158 (14)0.0081 (2)
O10.16874 (17)0.83126 (17)0.2895 (2)0.0152 (3)
O20000.0206 (9)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
K10.0176 (2)0.0176 (2)0.0172 (4)0.00879 (12)00
Sb10.00929 (13)0.00929 (13)0.00879 (15)0.00465 (6)00
Al10.0068 (3)0.0068 (3)0.0107 (5)0.00340 (14)00
O10.0194 (6)0.0194 (6)0.0153 (6)0.0159 (7)0.0001 (3)0.0001 (3)
O20.0257 (14)0.0257 (14)0.0104 (17)0.0129 (7)00
Geometric parameters (Å, º) top
K1—O12.900 (2)Sb1—K1ix3.8456 (8)
K1—O1i2.900 (2)Sb1—K1iv3.8456 (8)
K1—O1ii2.900 (2)Sb1—K1vi3.8456 (9)
K1—O1iii2.9792 (8)Al1—O21.7022 (12)
K1—O1iv2.9792 (8)Al1—O1i1.7616 (18)
K1—O1v2.9792 (9)Al1—O1x1.7616 (18)
K1—O1vi2.9792 (8)Al1—O1xi1.7616 (18)
K1—O1vii2.9792 (9)Al1—K1ix3.6237 (10)
K1—O1viii2.9792 (8)Al1—K1xii3.6237 (10)
K1—Sb13.4959 (14)Al1—K1vi3.6237 (10)
K1—K1ix3.5577 (10)O1—Al1xiii1.7616 (18)
K1—K1vi3.5578 (11)O1—K1iv2.9792 (8)
Sb1—O1ii1.9358 (17)O1—K1vi2.9792 (8)
Sb1—O1i1.9358 (17)O2—Al1xiv1.7022 (12)
Sb1—O11.9358 (17)
O1—K1—O1i57.31 (6)O1v—K1—K1vi51.75 (3)
O1—K1—O1ii57.31 (6)O1vi—K1—K1vi51.75 (3)
O1i—K1—O1ii57.31 (6)O1vii—K1—K1vi151.34 (3)
O1—K1—O1iii79.64 (6)O1viii—K1—K1vi97.96 (3)
O1i—K1—O1iii136.62 (3)Sb1—K1—K1vi66.07 (3)
O1ii—K1—O1iii105.54 (4)K1ix—K1—K1vi104.67 (4)
O1—K1—O1iv105.54 (4)O1ii—Sb1—O1i91.84 (7)
O1i—K1—O1iv136.62 (3)O1ii—Sb1—O191.84 (7)
O1ii—K1—O1iv79.64 (6)O1i—Sb1—O191.84 (7)
O1iii—K1—O1iv55.65 (7)O1ii—Sb1—K156.05 (5)
O1—K1—O1v79.64 (6)O1i—Sb1—K156.05 (5)
O1i—K1—O1v105.54 (4)O1—Sb1—K156.05 (5)
O1ii—K1—O1v136.62 (3)O1ii—Sb1—K1ix49.546 (15)
O1iii—K1—O1v57.18 (7)O1i—Sb1—K1ix49.546 (16)
O1iv—K1—O1v109.90 (4)O1—Sb1—K1ix113.79 (5)
O1—K1—O1vi105.54 (4)K1—Sb1—K1ix57.738 (16)
O1i—K1—O1vi79.64 (6)O1ii—Sb1—K1iv49.546 (15)
O1ii—K1—O1vi136.62 (3)O1i—Sb1—K1iv113.79 (5)
O1iii—K1—O1vi109.90 (4)O1—Sb1—K1iv49.546 (16)
O1iv—K1—O1vi141.92 (8)K1—Sb1—K1iv57.738 (16)
O1v—K1—O1vi55.65 (7)K1ix—Sb1—K1iv94.16 (2)
O1—K1—O1vii136.62 (3)O1ii—Sb1—K1vi113.79 (6)
O1i—K1—O1vii105.54 (4)O1i—Sb1—K1vi49.546 (15)
O1ii—K1—O1vii79.64 (6)O1—Sb1—K1vi49.546 (15)
O1iii—K1—O1vii109.90 (4)K1—Sb1—K1vi57.738 (17)
O1iv—K1—O1vii57.18 (7)K1ix—Sb1—K1vi94.16 (2)
O1v—K1—O1vii141.92 (8)K1iv—Sb1—K1vi94.16 (2)
O1vi—K1—O1vii109.90 (4)O2—Al1—O1i110.86 (7)
O1—K1—O1viii136.62 (3)O2—Al1—O1x110.85 (7)
O1i—K1—O1viii79.64 (6)O1i—Al1—O1x108.05 (7)
O1ii—K1—O1viii105.54 (4)O2—Al1—O1xi110.86 (7)
O1iii—K1—O1viii141.92 (8)O1i—Al1—O1xi108.05 (7)
O1iv—K1—O1viii109.90 (4)O1x—Al1—O1xi108.05 (7)
O1v—K1—O1viii109.90 (4)O2—Al1—K1ix116.18 (3)
O1vi—K1—O1viii57.18 (7)O1i—Al1—K1ix54.80 (2)
O1vii—K1—O1viii55.65 (7)O1x—Al1—K1ix132.96 (8)
O1—K1—Sb133.62 (4)O1xi—Al1—K1ix54.80 (2)
O1i—K1—Sb133.62 (4)O2—Al1—K1xii116.18 (3)
O1ii—K1—Sb133.62 (4)O1i—Al1—K1xii132.96 (8)
O1iii—K1—Sb1109.04 (4)O1x—Al1—K1xii54.80 (2)
O1iv—K1—Sb1109.04 (4)O1xi—Al1—K1xii54.80 (2)
O1v—K1—Sb1109.04 (4)K1ix—Al1—K1xii102.01 (3)
O1vi—K1—Sb1109.04 (4)O2—Al1—K1vi116.18 (3)
O1vii—K1—Sb1109.04 (4)O1i—Al1—K1vi54.80 (2)
O1viii—K1—Sb1109.04 (4)O1x—Al1—K1vi54.80 (2)
O1—K1—K1ix99.69 (6)O1xi—Al1—K1vi132.96 (8)
O1i—K1—K1ix53.78 (3)K1ix—Al1—K1vi102.01 (3)
O1ii—K1—K1ix53.78 (3)K1xii—Al1—K1vi102.01 (3)
O1iii—K1—K1ix151.34 (3)Al1xiii—O1—Sb1125.19 (10)
O1iv—K1—K1ix97.96 (3)Al1xiii—O1—K1144.48 (9)
O1v—K1—K1ix151.34 (3)Sb1—O1—K190.33 (6)
O1vi—K1—K1ix97.96 (3)Al1xiii—O1—K1iv96.30 (4)
O1vii—K1—K1ix51.75 (3)Sb1—O1—K1iv100.82 (4)
O1viii—K1—K1ix51.75 (3)K1—O1—K1iv74.47 (4)
Sb1—K1—K1ix66.07 (3)Al1xiii—O1—K1vi96.30 (4)
O1—K1—K1vi53.78 (3)Sb1—O1—K1vi100.82 (4)
O1i—K1—K1vi53.78 (3)K1—O1—K1vi74.47 (4)
O1ii—K1—K1vi99.69 (6)K1iv—O1—K1vi141.92 (8)
O1iii—K1—K1vi97.96 (3)Al1—O2—Al1xiv180.0
O1iv—K1—K1vi151.34 (3)
Symmetry codes: (i) y+1, xy+1, z; (ii) x+y, x+1, z; (iii) xy+1, x+1, z+1; (iv) x+1, y+2, z+1; (v) y1, x+y, z+1; (vi) x, y+1, z+1; (vii) y, x+y, z+1; (viii) xy+1, x, z+1; (ix) x+1, y+1, z+1; (x) x+y1, x, z; (xi) x, y1, z; (xii) x, y, z+1; (xiii) x, y+1, z; (xiv) x, y, z.

Experimental details

Crystal data
Chemical formulaK2[Al2Sb2O7]
Mr487.66
Crystal system, space groupTrigonal, P3m1
Temperature (K)293
a, c (Å)5.6325 (8), 8.045 (2)
V3)221.04 (7)
Z1
Radiation typeMo Kα
µ (mm1)7.25
Crystal size (mm)0.10 × 0.07 × 0.03
Data collection
DiffractometerEnraf-Nonius CAD-4
diffractometer
Absorption correctionψ-scans
(North et al., 1968)
Tmin, Tmax0.589, 0.805
No. of measured, independent and
observed [I > 2σ(I)] reflections
1691, 342, 319
Rint0.085
(sin θ/λ)max1)0.753
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.018, 0.044, 1.14
No. of reflections342
No. of parameters19
Δρmax, Δρmin (e Å3)1.28, 0.81

Computer programs: CAD-4 Software (Enraf-Nonius, 1989), CAD-4 Software, HELENA (Spek, 1993), SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), ORTEP (Johnson, 1968) and DRAWxtl (Finger & Kroeker, 1997), SHELXL97.

Selected geometric parameters (Å, º) top
K1—O12.900 (2)Al1—O21.7022 (12)
K1—O1i2.9792 (8)Al1—O1iii1.7616 (18)
Sb1—O1ii1.9358 (17)
O1ii—Sb1—O1iii91.84 (7)Al1v—O1—Sb1125.19 (10)
O2—Al1—O1iii110.86 (7)Al1—O2—Al1vi180.0
O1iii—Al1—O1iv108.05 (7)
Symmetry codes: (i) xy+1, x+1, z+1; (ii) x+y, x+1, z; (iii) y+1, xy+1, z; (iv) x+y1, x, z; (v) x, y+1, z; (vi) x, y, z.
 

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