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The title compound, tetra­rubidium tetra­oxa­tin(IV), crystallizes with the Na4CoO4 structure type, showing discrete SnO44- anions as main building blocks. The structure is thus isotypic with a series of corresponding A4MO4 compounds(A = alkali metal and M = group IV element).

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270199013700/br1266sup1.cif
Contains datablocks I, br1266

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270199013700/br1266Isup2.hkl
Contains datablock I

Comment top

Rb4SnO4 crystallizes in the triclinic spacegroup P1 and is isotypic with the Na4CoO4 structure type (Jansen, 1975). Corresponding alkaline metal oxotetrelates(IV) with the same structure type are the stannates K4SnO4 (Marchand et al., 1975) and Cs4SnO4 (Bernet & Hoppe, 1990), the plumbates of Na, K and Rb (Brandes & Hoppe, 1994; Nowitzki & Hoppe, 1983) the germanates of Na and K (Halwax & Völlenkle, 1985) and Na4SiO4 (Baur et al., 1986).

The Sn atoms in Rb4SnO4 are coordinated by four O atoms in a slightly distorted tetrahedral environment, with Sn—O distances ranging from 1.934 (10)? to 1.977 (9) Å and O—Sn—O angles from 105.1 (4) to 115.1 (4)°. As in all stannates of the type A4SnO3 and A4SnO4 (A = alkaline metal), all the O ligands are coordinated by five alkali metal atoms and one Sn atom in a distorted octahedral geometry (Fig. 1). The Sn—O distances in the title compound are thus comparable with those observed in the stannates(IV) K4SnO4 (Sn—O 1.95–1.96 Å) or Cs4SnO4 (Sn—O 1.94–1.97 Å) and they differ significantly from those observed in the stannates(II) K4SnO3 (Sn—O 2.041–2.052 Å; Röhr, 1995) or Cs4SnO3 (Sn—O 2.028–2.049 Å; Röhr & Zönnchen, 1998).

A view of the unit cell of Rb4SnO4 is given in Fig. 2. The coordination numbers of the Rb cations vary from 4 (Rb1) to 4 + 1 (Rb4) and 5 (Rb2, Rb3). A similar description of the packing as given for Cs4PbO4 (Müller et al., 1991) or Cs4SnO3 (Röhr & Zönnchen, 1998) is also possible for Rb4SnO4: Rb and Sn atoms together form planes of nearly hexagonal close-packed layers running perpendicular to the [100] direction. These layers are stacked in the sequence A—B, where the stacking is in between the hexagonal closed-packed arrangement and the α-U structure type observed for the packing of Cs and Sn in Cs4SnO3 (Fig. 3).

The Raman spectrum of Rb4SnO4 recorded at room temperature shows four bands that can be assigned to the four normal modes of an ideal tetrahedron XY4. The totally symmetric stretching mode (ν1, A1) is observed at 638 cm−1 and the asymmetric stretching mode (ν3, F2) is observed as a weak band at 620 cm−1. The symmetric (ν2, E) and the antisymmetric (ν4, F2) bending modes are observed at 188 cm−1 and 137 cm−1, respectively. This assignment is consistent in the series of MO4 silicates, germanates and stannates (Nyquist & Kagel, 1997).

Experimental top

Single crystals of Rb4SnO4 were formed by the reduction of a mixture of RbO2 and SnO with elemental rubidium. Liquid rubidium (756.9 mg, 8.856 mmol; Maassen, 99°) was reacted with RbO2 (346.8 mg, 2.952 mmol) and powdered SnO (399.3 mg, 2.965 mmol; ABCR, 99°) in corundum crucibles under an argon atmosphere. The mixtures were heated up to 1000 K within 5 h and cooled to room temperature at a rate of 4 K/h. The thick honey-yellow hygroscopic crystals of the title compound were handled in a dry box and prepared in capillaries filled with dried oil. The X-ray powder pattern of the sample could be indexed on the basis of the reported single-crystal data of Rb4SnO4 but show additional reflections of Rb2SnO2 (Braun & Hoppe, 1982). The room-temperature Raman spectrum of a single-crystal sealed in a Lindemann capillary was recorded with a Raman microscope attached to an FT spectrometer (Bruker IFS66V).

Refinement top

Δρmax and Δπmin lie within 0.8 Å of the Sn atoms.

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 [SnO4]4− anion in Rb4SnO4, together with the coordination spheres of the O atoms. Displacement ellipsoids are shown at the 50% probability level.
[Figure 2] Fig. 2. View of the unit cell of the crystal structure of Rb4SnO4. Small spheres denote Rb, while tetrahedra denote SnO4.
[Figure 3] Fig. 3. Hexagonal closed-packed Rb4Sn nets in Rb4SnO4 (stacking: A—B; circles indicate Sn positions) running perpendicular to the [100] direction.
tetrarubidiumtetraoxatin(IV) top
Crystal data top
Rb4SnO4Z = 2
Mr = 524.57F(000) = 460
Triclinic, P1Dx = 4.312 Mg m3
a = 6.773 (2) ÅMo Kα radiation, λ = 0.71070 Å
b = 6.776 (3) ÅCell parameters from 25 reflections
c = 10.122 (3) Åθ = 7.3–21.4°
α = 71.72 (3)°µ = 27.05 mm1
β = 79.48 (2)°T = 293 K
γ = 66.64 (2)°Plate, pale yellow
V = 404.0 (2) Å30.10 × 0.07 × 0.04 mm
Data collection top
Enraf-Nonius CAD-4
diffractometer
Rint = 0.049
Radiation source: fine-focus sealed tubeθmax = 26°, θmin = 5.2°
Graphite monochromatorh = 08
ω/2θ scansk = 78
Absorption correction: ψ-scan
(North et al., 1968)
l = 1212
Tmin = 0.109, Tmax = 0.3393 standard reflections every 120 min
1710 measured reflections intensity decay: none
1575 independent reflections
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)] = 0.056 w = 1/[σ2(Fo2) + (0.1006P)2 + 1.5556P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.150(Δ/σ)max < 0.001
S = 1.10Δρmax = 4.13 e Å3
1575 reflectionsΔρmin = 4.37 e Å3
83 parametersExtinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.0139 (17)
Crystal data top
Rb4SnO4γ = 66.64 (2)°
Mr = 524.57V = 404.0 (2) Å3
Triclinic, P1Z = 2
a = 6.773 (2) ÅMo Kα radiation
b = 6.776 (3) ŵ = 27.05 mm1
c = 10.122 (3) ÅT = 293 K
α = 71.72 (3)°0.10 × 0.07 × 0.04 mm
β = 79.48 (2)°
Data collection top
Enraf-Nonius CAD-4
diffractometer
1575 independent reflections
Absorption correction: ψ-scan
(North et al., 1968)
Rint = 0.049
Tmin = 0.109, Tmax = 0.3393 standard reflections every 120 min
1710 measured reflections intensity decay: none
Refinement top
R[F2 > 2σ(F2)] = 0.05683 parameters
wR(F2) = 0.1500 restraints
S = 1.10Δρmax = 4.13 e Å3
1575 reflectionsΔρmin = 4.37 e Å3
Special details top

Experimental. Absorption correction based on 12 psi-scans (North et al., 1968)

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
Sn0.27370 (12)0.15660 (13)0.24574 (8)0.0127 (3)
O10.0399 (13)0.3022 (14)0.3713 (10)0.0212 (19)
O20.4593 (13)0.3337 (15)0.1882 (9)0.0206 (19)
O30.4475 (15)0.1437 (14)0.3495 (10)0.025 (2)
O40.1293 (18)0.158 (2)0.0971 (11)0.038 (3)
Rb10.2378 (2)0.2392 (2)0.03146 (14)0.0250 (4)
Rb20.27554 (19)0.5094 (2)0.44200 (13)0.0195 (4)
Rb30.2156 (2)0.0329 (2)0.37954 (14)0.0233 (4)
Rb40.2620 (2)0.4067 (2)0.16385 (14)0.0260 (4)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Sn0.0129 (5)0.0105 (5)0.0159 (5)0.0067 (3)0.0009 (3)0.0018 (3)
O10.014 (4)0.017 (4)0.032 (5)0.002 (4)0.003 (4)0.009 (4)
O20.015 (4)0.019 (4)0.028 (5)0.010 (4)0.006 (4)0.005 (4)
O30.029 (5)0.011 (4)0.032 (5)0.010 (4)0.004 (4)0.004 (4)
O40.044 (6)0.052 (7)0.030 (6)0.025 (6)0.006 (5)0.014 (5)
Rb10.0229 (7)0.0199 (7)0.0283 (8)0.0026 (5)0.0054 (6)0.0057 (5)
Rb20.0197 (6)0.0196 (7)0.0243 (7)0.0117 (5)0.0020 (5)0.0089 (5)
Rb30.0234 (7)0.0215 (7)0.0261 (7)0.0124 (5)0.0076 (5)0.0013 (5)
Rb40.0263 (7)0.0258 (7)0.0279 (8)0.0133 (6)0.0043 (6)0.0033 (5)
Geometric parameters (Å, º) top
Sn—O41.934 (10)Rb2—O23.024 (9)
Sn—O31.959 (9)Rb3—O2iii2.877 (9)
Sn—O21.962 (8)Rb3—O1vii2.880 (9)
Sn—O11.977 (9)Rb3—O12.947 (8)
Rb1—O4i2.758 (11)Rb3—O3vii3.056 (9)
Rb1—O2ii2.773 (9)Rb3—O3iii3.063 (9)
Rb1—O2iii2.783 (8)Rb4—O4i2.858 (11)
Rb1—O42.797 (11)Rb4—O1viii2.873 (9)
Rb2—O1iv2.764 (9)Rb4—O3iii2.924 (9)
Rb2—O12.802 (8)Rb4—O2ix2.985 (9)
Rb2—O3v2.855 (9)Rb4—O4viii3.252 (12)
Rb2—O3vi2.932 (10)
O4—Sn—O3113.4 (4)O4—Sn—O1105.1 (4)
O4—Sn—O2115.1 (4)O3—Sn—O1109.8 (4)
O3—Sn—O2107.3 (4)O2—Sn—O1105.7 (3)
Symmetry codes: (i) x, y, z; (ii) x, y+1, z; (iii) x1, y, z; (iv) x, y+1, z+1; (v) x, y+1, z; (vi) x+1, y, z+1; (vii) x, y, z+1; (viii) x, y1, z; (ix) x1, y1, z.

Experimental details

Crystal data
Chemical formulaRb4SnO4
Mr524.57
Crystal system, space groupTriclinic, P1
Temperature (K)293
a, b, c (Å)6.773 (2), 6.776 (3), 10.122 (3)
α, β, γ (°)71.72 (3), 79.48 (2), 66.64 (2)
V3)404.0 (2)
Z2
Radiation typeMo Kα
µ (mm1)27.05
Crystal size (mm)0.10 × 0.07 × 0.04
Data collection
DiffractometerEnraf-Nonius CAD-4
diffractometer
Absorption correctionψ-scan
(North et al., 1968)
Tmin, Tmax0.109, 0.339
No. of measured, independent and
observed (?) reflections
1710, 1575, ?
Rint0.049
(sin θ/λ)max1)0.617
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.056, 0.150, 1.10
No. of reflections1575
No. of parameters83
Δρmax, Δρmin (e Å3)4.13, 4.37

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
Sn—O41.934 (10)Rb2—O23.024 (9)
Sn—O31.959 (9)Rb3—O2iii2.877 (9)
Sn—O21.962 (8)Rb3—O1vii2.880 (9)
Sn—O11.977 (9)Rb3—O12.947 (8)
Rb1—O4i2.758 (11)Rb3—O3vii3.056 (9)
Rb1—O2ii2.773 (9)Rb3—O3iii3.063 (9)
Rb1—O2iii2.783 (8)Rb4—O4i2.858 (11)
Rb1—O42.797 (11)Rb4—O1viii2.873 (9)
Rb2—O1iv2.764 (9)Rb4—O3iii2.924 (9)
Rb2—O12.802 (8)Rb4—O2ix2.985 (9)
Rb2—O3v2.855 (9)Rb4—O4viii3.252 (12)
Rb2—O3vi2.932 (10)
O4—Sn—O3113.4 (4)O4—Sn—O1105.1 (4)
O4—Sn—O2115.1 (4)O3—Sn—O1109.8 (4)
O3—Sn—O2107.3 (4)O2—Sn—O1105.7 (3)
Symmetry codes: (i) x, y, z; (ii) x, y+1, z; (iii) x1, y, z; (iv) x, y+1, z+1; (v) x, y+1, z; (vi) x+1, y, z+1; (vii) x, y, z+1; (viii) x, y1, z; (ix) x1, y1, z.
 

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