Alkaline metal oxoantimonates(III), A₃[SbO₃] (A = K or Cs)

The two title trialkaline trioxoantimonates(III), tripotassium trioxoantimonate(III), K₃[SbO₃], (I), and tricaesium trioxo­antimonate(III), Cs₃[SbO₃], (II), crystallize in the cubic Na₃[AsS₃] structure type in space group P2₁3. The structures show discrete Ψ-tetrahedral [SbO₃]³⁻ anions with C_3v point-group symmetry. The Sb—O distances are 1.923 (4) Å in (I) and 1.928 (2) Å in (II), and the O—Sb—O bond angles are 99.5 (2)° in (I) and 100.4 (1)° in (II).

S1. Comment

The oxoantimonates(III), ASbO₂ [A = K, Rb (Hirschle & Röhr, 2000) or Cs (Hirschle & Röhr, 1998)], are isotypic with the corresponding bismuthates [A = K, Rb or Cs (Zoche & Jansen, 1998)] and contain, in accordance with the lone pair on Sb^III/Bi^III, the group V atoms coordinated by four O atoms in a Ψ-trigonal bipyramidal geometry. In the compounds A₄[Sb₂O₅] [A = K, Rb or Cs (Hirschle & Röhr, 2000)], two [SbO₃] Ψ tetrahedra are connected via an oxygen ligand to form [O₂Sb—O-SbO₂]^4- `butterfly' anions. In contrast, K₄[Bi₂O₅] (Zoche et al., 1998) contains [Bi₄O₁₀]^8- anions, with Bi both in Ψ-trigonal bipyramidal and Ψ-tetrahedral coordination by oxygen. The bismuthates A₃[BiO₃], with Ψ-tetrahedral anions as characteristic building blocks, are known for the whole series of alkaline metals A. The isotypic sodium (Stöver & Hoppe, 1980) and potassium (Zoche & Jansen, 1997b) compounds can be described as defect NaCl variants, [A₃Bi][O₃], i.e. the cations A and Bi form a face-centred cubic sublattice (Cu₃Al type). In the rubidium (Zoche & Jansen, 1997b) and caesium (Zoche & Jansen, 1997a) phases, the cations are arranged in a body-centered cubic sublattice (Fe₃Al type). For the corresponding oxoantimonate series A₃[SbO₃], only the sodium compound has been described in the literature to date (Stöver & Hoppe, 1980): Na₃[SbO₃] is isotypic with the Na and K bismuthates mentioned above. We present here the structures of two further oxoantimonates, K₃[SbO₃], (I), and Cs₃[SbO₃], (II). \sch

The isotypic compounds (I) and (II) crystallize in the cubic spacegroup P2₁3 with the Na₃[AsS₃] structure type (Palazzi, 1976), and are thus isotypic with the Rb and Cs oxobismuthates and most alkaline metal thio- and selenoarsenates, -antimonates and -bismuthates. Rb₃[SbO₃] forms the same structure type, with a lattice constant (refined from X-ray powder data) of 8.9523 (6) Å.

The crystal structures of (I) and (II) contain [SbO₃]^3- anions with crystallographic C_3v point group symmetry and nearly equal Sb—O distances for the two compounds; the O—Sb—O bond angles are also very similar. The bond lengths are thus slightly longer than those observed in the sodium phase (Sb—O 1.890 Å).

The oxygen ligands are octahedrally coordinated by one Sb atom and five A cations (Fig. 1). The oxoantimonate ions form a face-centred cubic arrangement (Fig. 2), in which the alkaline metal cations occupy all tetrahedral and octahedral interstices. In an alternative description of the structure according to the concept of O'Keeffe & Hyde (1985), the A and Sb atoms form a 3:1 superstructure of a body-centred cubic lattice, the Fe₃Al structure type. Whereas the corresponding K₃Sb phase (Emmerling & Röhr, 2001) crystallizes with a superstructure of the hexagonal Cu₃P type, the direct analogy of the metal atom arrangement in the intermetallic phase and the oxide is observed for Cs₃Sb (Emmerling & Röhr, 2001) and (II). The unit cell volumes are also comparable [762.8 (1) ų in (II) and 763.7 (1) ų in Cs₃Sb].

S2. Experimental

Crystals of (I) were grown from a mixture containing KO₂ (Fluka AG, 99.0%), K (Alkali-Metallhandel GmbH Bonn, 98.0%) and Sb powder (Sigma-Aldrich, 99.8%) in a molar ratio of 0.5:1.5:2. The mixture was heated up to 973 K and then cooled down to 573 K at a rate of 5 K h^-1. Then the furnace was turned off. For (II), CsO₂ (803 mg, 4.87 mmol) was reacted with powdered Sb (198 mg, 1.62 mmol) in a corundum crucible under an argon atmosphere. The mixture was heated up to 973 K within 3.5 h and then cooled down to room temperature at a rate of 5 K h^-1. The X-ray powder pattern of the sample (Stadi P diffractometer with linear PSD; Stoe & Cie, Darmstadt) could be indexed with the single-crystal data of (II) and showed weak reflections of Cs₃[SbO₄] and elemental Sb. Both title compounds formed hydroscopic colourless crystals, which were handled in a dry box under argon and prepared in capillaries filled with dried oil.

Computing details

For both compounds, data collection: CAD-4 Software (Enraf-Nonius, 1989) Query; cell refinement: CAD-4 Software Query; data reduction: HELENA (Spek, 1996); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP (Johnson, 1968) and DRAWxtl (Finger & Kroeker, 1999); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The molecular view of the [SbO3]^3- Ψ tetrahedron together with the coordinating Cs cations in (II) (75% probability ellipsoids).
	Fig. 2. A view of the unit cell of the compounds A3[SbO3] (small light grey balls: K or Cs; dark grey balls: O)

(I) Tripotassium trioxoantimonate(III)

Crystal data

K3[SbO3]	Dx = 3.272 Mg m^−3
Mr = 287.05	Mo Kα radiation, λ = 0.71070 Å
Cubic, P213	Cell parameters from 25 reflections
Hall symbol: P 2ac 2ab 3	θ = 3.8–29.3°
a = 8.352 (5) Å	µ = 6.77 mm^−1
V = 582.7 (5) Å^3	T = 293 K
Z = 4	Prism, colourless
F(000) = 528	0.1 × 0.1 × 0.1 mm

Data collection

Enraf-Nonius CAD-4 diffractometer	377 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.090
Graphite monochromator	θmax = 27.4°, θmin = 4.2°
ω/2θ scans	h = 0→10
Absorption correction: ψ scan (North et al., 1968)	k = −10→10
Tmin = 0.497, Tmax = 0.508	l = −10→0
1510 measured reflections	3 standard reflections every 120 min
455 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	w = 1/[σ^2(Fo^2) + (0.0219P)^2] where P = (Fo^2 + 2Fc^2)/3
R[F^2 > 2σ(F^2)] = 0.026	(Δ/σ)max < 0.001
wR(F^2) = 0.054	Δρmax = 0.72 e Å^−3
S = 1.04	Δρmin = −1.03 e Å^−3
455 reflections	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
20 parameters	Extinction coefficient: 0.0025 (9)
0 restraints	Absolute structure: Flack (1983), 189 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: −0.03 (11)

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
Sb	0.51456 (4)	0.51456 (4)	0.51456 (4)	0.01377 (18)
K1	0.7890 (2)	0.7890 (2)	0.7890 (2)	0.0192 (5)
K2	0.2839 (2)	0.2839 (2)	0.2839 (2)	0.0177 (5)
K3	0.02565 (16)	0.02565 (16)	0.02565 (16)	0.0242 (4)
O1	0.0051 (5)	0.2108 (4)	0.4391 (4)	0.0206 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Sb	0.01377 (18)	0.01377 (18)	0.01377 (18)	−0.00078 (16)	−0.00078 (16)	−0.00078 (16)
K1	0.0192 (5)	0.0192 (5)	0.0192 (5)	0.0025 (8)	0.0025 (8)	0.0025 (8)
K2	0.0177 (5)	0.0177 (5)	0.0177 (5)	−0.0006 (7)	−0.0006 (7)	−0.0006 (7)
K3	0.0242 (4)	0.0242 (4)	0.0242 (4)	−0.0008 (5)	−0.0008 (5)	−0.0008 (5)
O1	0.0165 (19)	0.0179 (17)	0.0274 (17)	−0.003 (2)	−0.0001 (19)	0.0076 (13)

Geometric parameters (Å, º)

Sb—O1^i	1.923 (4)	K2—O1^i	2.961 (5)
Sb—O1^ii	1.923 (4)	K2—O1^iii	2.961 (5)
Sb—O1^iii	1.923 (4)	K2—O1^ii	2.961 (5)
K1—O1^iv	2.758 (5)	K3—O1^xii	2.659 (4)
K1—O1^v	2.758 (5)	K3—O1^xiii	2.659 (4)
K1—O1^vi	2.758 (5)	K3—O1^xiv	2.659 (4)
K1—O1^vii	2.922 (5)	O1—Sb^xv	1.923 (4)
K1—O1^viii	2.922 (5)	O1—K3^xvi	2.659 (4)
K1—O1^ix	2.922 (5)	O1—K1^xvii	2.758 (5)
K2—O1^x	2.734 (4)	O1—K1^xviii	2.922 (5)
K2—O1^xi	2.734 (4)	O1—K2^xv	2.961 (5)
K2—O1	2.734 (4)
O1^i—Sb—O1^ii	99.50 (15)	O1^ii—Sb—O1^iii	99.51 (15)
O1^i—Sb—O1^iii	99.50 (15)

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

(II) Tricaesium trioxoantimonate(III)

Crystal data

Cs3[SbO3]	Dx = 4.950 Mg m^−3
Mr = 568.48	Mo Kα radiation, λ = 0.71070 Å
Cubic, P213	Cell parameters from 25 reflections
Hall symbol: P 2ac 2ab 3	θ = 2.3–32.8°
a = 9.1369 (10) Å	µ = 17.65 mm^−1
V = 762.78 (14) Å^3	T = 293 K
Z = 4	Prism, colourless
F(000) = 960	0.11 × 0.08 × 0.06 mm

Data collection

Enraf-Nonius CAD-4 diffractometer	540 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.063
Graphite monochromator	θmax = 27.4°, θmin = 4.5°
ω/2θ scans	h = −11→11
Absorption correction: ψ scan (North et al., 1968)	k = −11→11
Tmin = 0.197, Tmax = 0.347	l = 0→11
3665 measured reflections	3 standard reflections every 120 min
586 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	w = 1/[σ^2(Fo^2) + 0.2365P] where P = (Fo^2 + 2Fc^2)/3
R[F^2 > 2σ(F^2)] = 0.014	(Δ/σ)max = 0.001
wR(F^2) = 0.036	Δρmax = 0.68 e Å^−3
S = 1.07	Δρmin = −0.59 e Å^−3
750 reflections	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
23 parameters	Extinction coefficient: 0.00079 (8)
0 restraints	Absolute structure: Flack (1983), 240 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.06 (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
Cs1	0.77732 (3)	0.77732 (3)	0.77732 (3)	0.02308 (10)
Cs2	0.27318 (3)	0.27318 (3)	0.27318 (3)	0.02379 (11)
Cs3	0.01855 (3)	0.01855 (3)	0.01855 (3)	0.02933 (10)
Sb1	0.50362 (2)	0.50362 (2)	0.50362 (2)	0.01958 (8)
O1	0.0055 (3)	0.2041 (3)	0.4592 (3)	0.0295 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cs1	0.02308 (10)	0.02308 (10)	0.02308 (10)	0.00097 (10)	0.00097 (10)	0.00097 (10)
Cs2	0.02379 (11)	0.02379 (11)	0.02379 (11)	−0.00051 (9)	−0.00051 (9)	−0.00051 (9)
Cs3	0.02933 (10)	0.02933 (10)	0.02933 (10)	−0.00225 (10)	−0.00225 (10)	−0.00225 (10)
Sb1	0.01958 (8)	0.01958 (8)	0.01958 (8)	−0.00125 (9)	−0.00125 (9)	−0.00125 (9)
O1	0.0282 (13)	0.0266 (11)	0.0336 (12)	−0.0037 (10)	−0.0021 (12)	0.0089 (11)

Geometric parameters (Å, º)

Cs1—O1^i	3.077 (2)	Cs3—O1^xii	2.888 (2)
Cs1—O1^ii	3.077 (2)	Cs3—O1^xiii	2.888 (2)
Cs1—O1^iii	3.077 (2)	Cs3—O1^xiv	2.888 (2)
Cs1—O1^iv	3.191 (3)	Sb1—O1^ix	1.928 (2)
Cs1—O1^v	3.191 (2)	Sb1—O1^x	1.928 (2)
Cs1—O1^vi	3.191 (2)	Sb1—O1^xi	1.928 (2)
Cs2—O1^vii	3.044 (3)	O1—Sb1^xv	1.928 (2)
Cs2—O1^viii	3.044 (3)	O1—Cs3^xvi	2.888 (2)
Cs2—O1	3.044 (3)	O1—Cs1^xvii	3.077 (2)
Cs2—O1^ix	3.245 (3)	O1—Cs1^xviii	3.191 (2)
Cs2—O1^x	3.245 (3)	O1—Cs2^xv	3.245 (3)
Cs2—O1^xi	3.245 (3)
O1^ix—Sb1—O1^x	100.43 (9)

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