Acta Cryst. (2012). E68, i2 [ doi:10.1107/S1600536811051919 ]
The title compound, tricaesium heptasamarium(III) dodecaselenide, is setting a new starting point for realization of the channel structure of the Cs3M7Se12 series, now with M = Sm, Gd-Er. This Cs3Y7Se12-type arrangement is structurally based on the Z-type sesquiselenides M2Se3 adopting the Sc2S3 structure. Thus, the structural set-up of Cs3Sm7Se12 consists of edge- and vertex-connected [SmSe6]9- octahedra [dØ(Sm3+ - Se2-) = 2.931 Å], forming a rock-salt-related network [Sm7Se12]3- with channels along [001] that are apt to take up monovalent cations (here Cs+) with coordination numbers of 7 + 1 for one and of 6 for the second cation. The latter cation has a trigonal-prismatic coordination and shows half-occupancy, resulting in an impossible short distance [2.394 (4) Å] between symmetrically coupled Cs+ cations of the same kind. While one Sm atom occupies Wyckoff position 2b with site symmetry ..2/m, all other 11 crystallographically different atoms (namely 2 × Cs, 3 × Sm and 6 × Se) are located at Wyckoff positions 4g with site symmetry ..m.
Yellow, transparent, needle-shaped single crystals of Cs3Sm7Se12 were obtained as the main product of a reaction between 0.10 g Sm, 0.08 g Se and 0.50 g CsCl added as flux and caesium source upon heating at 1073 K for 10 days in a sealed, evacuated fused-silica vessel.
In the final difference Fourier map the highest peak is 1.24 Å away from Se2 and the deepest hole is located 0.83 Å away from Sm2.
Data collection: DIF4 (Stoe & Cie, 1992); cell refinement: DIF4 (Stoe & Cie, 1992); data reduction: REDU4 (Stoe & Cie, 1992); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2006); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).
![[Figure 1]](./wm2561fig1thm.gif)
| Fig. 1. Channel-structure representation of Cs3Sm7Se12 as octahedral framework with indicated unit cell. |
![[Figure 2]](./wm2561fig2thm.gif)
| Fig. 2. Coordination spheres of the Cs1+ (left) and Cs2+ (right) cations in Cs3Sm7Se12. Displacement ellipsoids are drawn at the 90% probability level. Symmetry codes: (i) -x+1/2, y-1/2, z+1/2; (ii) -x+1/2, y-1/2, z-1/2; (iii) -x+1, -y+1, -z; (viii) -x+1, -y, -z; (ix) x+1/2, -y+1/2, -z-1/2; (x) x+1/2, -y+1/2, -z+1/2. |
![[Figure 3]](./wm2561fig3thm.gif)
| Fig. 3. Interplay of the Cs+ cations situated in the triple-channels of the crystal structure of Cs3Sm7Se12. Displacement ellipsoids are drawn at the 90% probability level. |
| Cs3Sm7Se12 | F(000) = 2014 |
| Mr = 2398.70 | Dx = 5.408 Mg m−3 |
| Orthorhombic, Pnnm | Mo Kα radiation, λ = 0.71069 Å |
| Hall symbol: -P 2 2n | Cell parameters from 5000 reflections |
| a = 13.0387 (9) Å | θ = 2.1–29.3° |
| b = 26.6742 (19) Å | µ = 32.19 mm−1 |
| c = 4.2351 (3) Å | T = 293 K |
| V = 1472.95 (18) Å3 | Needle, yellow |
| Z = 2 | 0.10 × 0.07 × 0.05 mm |
| Stoe IPDS-I diffractometer | 2135 independent reflections |
| Radiation source: fine-focus sealed tube | 1587 reflections with I > 2σ(I) |
| graphite | Rint = 0.065 |
| imaging plate detector system scans | θmax = 29.0°, θmin = 2.8° |
| Absorption correction: numerical (X-SHAPE; Stoe & Cie, 1999) | h = −17→17 |
| Tmin = 0.115, Tmax = 0.216 | k = −36→36 |
| 15080 measured reflections | l = −5→5 |
| Refinement on F2 | Primary atom site location: structure-invariant direct methods |
| Least-squares matrix: full | Secondary atom site location: difference Fourier map |
| R[F2 > 2σ(F2)] = 0.035 | w = 1/[σ2(Fo2) + (0.0371P)2] where P = (Fo2 + 2Fc2)/3 |
| wR(F2) = 0.072 | (Δ/σ)max = 0.014 |
| S = 0.97 | Δρmax = 2.09 e Å−3 |
| 2135 reflections | Δρmin = −1.78 e Å−3 |
| 72 parameters | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
| 0 restraints | Extinction coefficient: 0.00017 (4) |
| Cs3Sm7Se12 | V = 1472.95 (18) Å3 |
| Mr = 2398.70 | Z = 2 |
| Orthorhombic, Pnnm | Mo Kα radiation |
| a = 13.0387 (9) Å | µ = 32.19 mm−1 |
| b = 26.6742 (19) Å | T = 293 K |
| c = 4.2351 (3) Å | 0.10 × 0.07 × 0.05 mm |
| Stoe IPDS-I diffractometer | 2135 independent reflections |
| Absorption correction: numerical (X-SHAPE; Stoe & Cie, 1999) | 1587 reflections with I > 2σ(I) |
| Tmin = 0.115, Tmax = 0.216 | Rint = 0.065 |
| 15080 measured reflections | θmax = 29.0° |
| R[F2 > 2σ(F2)] = 0.035 | Δρmax = 2.09 e Å−3 |
| wR(F2) = 0.072 | Δρmin = −1.78 e Å−3 |
| S = 0.97 | Absolute structure: ? |
| 2135 reflections | Flack parameter: ? |
| 72 parameters | Rogers parameter: ? |
| 0 restraints |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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. |
| x | y | z | Uiso*/Ueq | Occ. (<1) | |
| Cs1 | 0.28796 (6) | 0.36600 (3) | 0.0000 | 0.0252 (2) | |
| Cs2 | 0.56532 (14) | 0.03154 (7) | 0.0000 | 0.0311 (5) | 0.50 |
| Sm1 | 0.0000 | 0.0000 | 0.5000 | 0.0124 (2) | |
| Sm2 | 0.21848 (5) | 0.08314 (2) | 0.0000 | 0.01316 (15) | |
| Sm3 | 0.40590 (4) | 0.71214 (2) | 0.0000 | 0.01224 (15) | |
| Sm4 | 0.07792 (5) | 0.68240 (2) | 0.0000 | 0.01271 (15) | |
| Se1 | 0.25592 (8) | 0.19644 (4) | 0.0000 | 0.0125 (3) | |
| Se2 | 0.12980 (9) | 0.57736 (4) | 0.0000 | 0.0142 (3) | |
| Se3 | 0.43019 (9) | 0.60350 (4) | 0.0000 | 0.0129 (3) | |
| Se4 | 0.05307 (8) | 0.78890 (4) | 0.0000 | 0.0133 (3) | |
| Se5 | 0.15051 (9) | 0.98065 (4) | 0.0000 | 0.0142 (3) | |
| Se6 | 0.42742 (9) | 0.82140 (4) | 0.0000 | 0.0133 (3) |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| Cs1 | 0.0214 (4) | 0.0295 (4) | 0.0247 (6) | −0.0002 (3) | 0.000 | 0.000 |
| Cs2 | 0.0266 (9) | 0.0273 (9) | 0.0393 (14) | 0.0114 (7) | 0.000 | 0.000 |
| Sm1 | 0.0147 (4) | 0.0109 (4) | 0.0116 (6) | −0.0030 (3) | 0.000 | 0.000 |
| Sm2 | 0.0153 (3) | 0.0135 (3) | 0.0107 (4) | −0.0027 (2) | 0.000 | 0.000 |
| Sm3 | 0.0137 (3) | 0.0117 (3) | 0.0113 (4) | −0.0018 (2) | 0.000 | 0.000 |
| Sm4 | 0.0131 (3) | 0.0130 (3) | 0.0121 (4) | 0.0034 (2) | 0.000 | 0.000 |
| Se1 | 0.0123 (5) | 0.0153 (5) | 0.0101 (7) | −0.0004 (4) | 0.000 | 0.000 |
| Se2 | 0.0147 (6) | 0.0142 (5) | 0.0137 (8) | 0.0007 (4) | 0.000 | 0.000 |
| Se3 | 0.0154 (5) | 0.0096 (5) | 0.0138 (7) | 0.0007 (4) | 0.000 | 0.000 |
| Se4 | 0.0144 (5) | 0.0128 (5) | 0.0126 (8) | 0.0000 (4) | 0.000 | 0.000 |
| Se5 | 0.0155 (5) | 0.0129 (5) | 0.0141 (8) | −0.0004 (4) | 0.000 | 0.000 |
| Se6 | 0.0140 (5) | 0.0134 (5) | 0.0124 (8) | 0.0008 (4) | 0.000 | 0.000 |
| Cs1—Se4i | 3.6071 (12) | Sm1—Se5xi | 2.9328 (8) |
| Cs1—Se4ii | 3.6071 (12) | Sm1—Se5xii | 2.9328 (8) |
| Cs1—Se6ii | 3.7129 (12) | Sm1—Se5xiii | 2.9328 (8) |
| Cs1—Se6i | 3.7129 (12) | Sm2—Se5xiii | 2.8738 (13) |
| Cs1—Se3iii | 3.7639 (14) | Sm2—Se2i | 2.9020 (10) |
| Cs1—Se5i | 3.8053 (12) | Sm2—Se2ii | 2.9020 (10) |
| Cs1—Se5ii | 3.8053 (12) | Sm2—Se3ii | 2.9217 (9) |
| Cs1—Se1 | 4.5421 (14) | Sm2—Se3i | 2.9217 (9) |
| Cs1—Cs1iv | 4.2351 (3) | Sm2—Se1 | 3.0614 (13) |
| Cs1—Cs1v | 4.2351 (3) | Sm3—Se4xiv | 2.8578 (9) |
| Cs2—Cs2vi | 2.394 (4) | Sm3—Se4xv | 2.8578 (9) |
| Cs2—Se2ii | 3.5286 (16) | Sm3—Se3 | 2.9152 (13) |
| Cs2—Se2i | 3.5286 (16) | Sm3—Se6 | 2.9279 (13) |
| Cs2—Se2vii | 3.6917 (17) | Sm3—Se1xvi | 3.0185 (9) |
| Cs2—Se2viii | 3.6917 (17) | Sm3—Se1xvii | 3.0185 (9) |
| Cs2—Se5iii | 3.719 (2) | Sm4—Se4 | 2.8591 (13) |
| Cs2—Se6iii | 3.924 (2) | Sm4—Se2 | 2.8823 (13) |
| Cs2—Sm2vi | 4.1597 (18) | Sm4—Se6xviii | 2.8888 (9) |
| Sm1—Se3i | 2.9070 (11) | Sm4—Se6xix | 2.8888 (9) |
| Sm1—Se3ix | 2.9070 (11) | Sm4—Se1xvii | 3.0526 (9) |
| Sm1—Se5x | 2.9328 (8) | Sm4—Se1xvi | 3.0526 (9) |
| Se4i—Cs1—Se4ii | 71.90 (3) | Se2ii—Sm2—Se1 | 86.77 (3) |
| Se4i—Cs1—Se6ii | 125.93 (3) | Se3ii—Sm2—Se1 | 85.54 (3) |
| Se4ii—Cs1—Se6ii | 85.24 (2) | Se3i—Sm2—Se1 | 85.54 (3) |
| Se4i—Cs1—Se6i | 85.24 (2) | Se4xiv—Sm3—Se4xv | 95.63 (4) |
| Se4ii—Cs1—Se6i | 125.93 (3) | Se4xiv—Sm3—Se3 | 85.26 (3) |
| Se6ii—Cs1—Se6i | 69.55 (3) | Se4xv—Sm3—Se3 | 85.26 (3) |
| Se4i—Cs1—Se3iii | 64.04 (3) | Se4xiv—Sm3—Se6 | 86.87 (3) |
| Se4ii—Cs1—Se3iii | 64.04 (3) | Se4xv—Sm3—Se6 | 86.87 (3) |
| Se6ii—Cs1—Se3iii | 143.874 (16) | Se3—Sm3—Se6 | 168.27 (4) |
| Se6i—Cs1—Se3iii | 143.874 (16) | Se4xiv—Sm3—Se1xvi | 171.05 (4) |
| Se4i—Cs1—Se5i | 90.60 (2) | Se4xv—Sm3—Se1xvi | 87.03 (2) |
| Se4ii—Cs1—Se5i | 131.59 (3) | Se3—Sm3—Se1xvi | 86.44 (3) |
| Se6ii—Cs1—Se5i | 137.25 (3) | Se6—Sm3—Se1xvi | 101.84 (3) |
| Se6i—Cs1—Se5i | 95.72 (2) | Se4xiv—Sm3—Se1xvii | 87.03 (2) |
| Se3iii—Cs1—Se5i | 67.69 (3) | Se4xv—Sm3—Se1xvii | 171.05 (4) |
| Se4i—Cs1—Se5ii | 131.59 (3) | Se3—Sm3—Se1xvii | 86.44 (3) |
| Se4ii—Cs1—Se5ii | 90.60 (2) | Se6—Sm3—Se1xvii | 101.84 (3) |
| Se6ii—Cs1—Se5ii | 95.72 (2) | Se1xvi—Sm3—Se1xvii | 89.10 (3) |
| Se6i—Cs1—Se5ii | 137.25 (3) | Se4—Sm4—Se2 | 172.93 (4) |
| Se3iii—Cs1—Se5ii | 67.69 (3) | Se4—Sm4—Se6xviii | 87.59 (3) |
| Se5i—Cs1—Se5ii | 67.63 (2) | Se2—Sm4—Se6xviii | 97.20 (3) |
| Se2ii—Cs2—Se2vii | 95.31 (3) | Se4—Sm4—Se6xix | 87.59 (3) |
| Se2i—Cs2—Se2vii | 141.35 (6) | Se2—Sm4—Se6xix | 97.20 (3) |
| Se2ii—Cs2—Se2viii | 141.35 (6) | Se6xviii—Sm4—Se6xix | 94.28 (4) |
| Se2i—Cs2—Se2viii | 95.31 (3) | Se4—Sm4—Se1xvii | 87.63 (3) |
| Se2vii—Cs2—Se2viii | 70.00 (4) | Se2—Sm4—Se1xvii | 87.29 (3) |
| Se2ii—Cs2—Se5iii | 138.46 (3) | Se6xviii—Sm4—Se1xvii | 174.23 (4) |
| Se2i—Cs2—Se5iii | 138.46 (3) | Se6xix—Sm4—Se1xvii | 88.74 (2) |
| Se2vii—Cs2—Se5iii | 72.81 (4) | Se4—Sm4—Se1xvi | 87.63 (3) |
| Se2viii—Cs2—Se5iii | 72.81 (4) | Se2—Sm4—Se1xvi | 87.29 (3) |
| Se2ii—Cs2—Se6iii | 70.80 (4) | Se6xviii—Sm4—Se1xvi | 88.74 (2) |
| Se2i—Cs2—Se6iii | 70.80 (4) | Se6xix—Sm4—Se1xvi | 174.23 (4) |
| Se2vii—Cs2—Se6iii | 141.36 (3) | Se1xvii—Sm4—Se1xvi | 87.85 (3) |
| Se2viii—Cs2—Se6iii | 141.36 (3) | Sm3ii—Se1—Sm3i | 89.10 (3) |
| Se5iii—Cs2—Se6iii | 93.63 (5) | Sm3ii—Se1—Sm4i | 178.80 (4) |
| Se3i—Sm1—Se3ix | 180.000 (14) | Sm3i—Se1—Sm4i | 91.519 (12) |
| Se3i—Sm1—Se5x | 92.43 (3) | Sm3ii—Se1—Sm4ii | 91.519 (12) |
| Se3ix—Sm1—Se5x | 87.57 (3) | Sm3i—Se1—Sm4ii | 178.80 (4) |
| Se3i—Sm1—Se5xi | 87.57 (3) | Sm4i—Se1—Sm4ii | 87.85 (3) |
| Se3ix—Sm1—Se5xi | 92.43 (3) | Sm3ii—Se1—Sm2 | 91.46 (3) |
| Se5x—Sm1—Se5xi | 180.00 (4) | Sm3i—Se1—Sm2 | 91.46 (3) |
| Se3i—Sm1—Se5xii | 92.43 (3) | Sm4i—Se1—Sm2 | 89.55 (3) |
| Se3ix—Sm1—Se5xii | 87.57 (3) | Sm4ii—Se1—Sm2 | 89.55 (3) |
| Se5x—Sm1—Se5xii | 92.44 (3) | Sm4—Se2—Sm2xvii | 96.22 (3) |
| Se5xi—Sm1—Se5xii | 87.56 (3) | Sm4—Se2—Sm2xvi | 96.22 (3) |
| Se3i—Sm1—Se5xiii | 87.57 (3) | Sm2xvii—Se2—Sm2xvi | 93.72 (4) |
| Se3ix—Sm1—Se5xiii | 92.43 (3) | Sm1viii—Se3—Sm3 | 167.99 (5) |
| Se5x—Sm1—Se5xiii | 87.56 (3) | Sm1viii—Se3—Sm2xvi | 91.79 (3) |
| Se5xi—Sm1—Se5xiii | 92.44 (3) | Sm3—Se3—Sm2xvi | 96.47 (3) |
| Se5xii—Sm1—Se5xiii | 180.0 | Sm1viii—Se3—Sm2xvii | 91.79 (3) |
| Se5xiii—Sm2—Se2i | 99.19 (3) | Sm3—Se3—Sm2xvii | 96.47 (3) |
| Se5xiii—Sm2—Se2ii | 99.19 (3) | Sm2xvi—Se3—Sm2xvii | 92.90 (4) |
| Se2i—Sm2—Se2ii | 93.72 (4) | Sm3xviii—Se4—Sm3xix | 95.63 (4) |
| Se5xiii—Sm2—Se3ii | 88.41 (3) | Sm3xviii—Se4—Sm4 | 93.81 (3) |
| Se2i—Sm2—Se3ii | 172.31 (4) | Sm3xix—Se4—Sm4 | 93.81 (3) |
| Se2ii—Sm2—Se3ii | 86.18 (2) | Sm2xx—Se5—Sm1xxi | 92.23 (3) |
| Se5xiii—Sm2—Se3i | 88.41 (3) | Sm2xx—Se5—Sm1xx | 92.23 (3) |
| Se2i—Sm2—Se3i | 86.18 (2) | Sm1xxi—Se5—Sm1xx | 92.44 (3) |
| Se2ii—Sm2—Se3i | 172.31 (4) | Sm4xiv—Se6—Sm4xv | 94.28 (4) |
| Se3ii—Sm2—Se3i | 92.90 (4) | Sm4xiv—Se6—Sm3 | 91.72 (3) |
| Se5xiii—Sm2—Se1 | 171.21 (4) | Sm4xv—Se6—Sm3 | 91.72 (3) |
| Se2i—Sm2—Se1 | 86.77 (3) |
| Symmetry codes: (i) −x+1/2, y−1/2, z+1/2; (ii) −x+1/2, y−1/2, z−1/2; (iii) −x+1, −y+1, −z; (iv) x, y, z−1; (v) x, y, z+1; (vi) −x+1, −y, −z; (vii) x+1/2, −y+1/2, −z−1/2; (viii) x+1/2, −y+1/2, −z+1/2; (ix) x−1/2, −y+1/2, −z+1/2; (x) −x, −y+1, −z; (xi) x, y−1, z+1; (xii) −x, −y+1, −z+1; (xiii) x, y−1, z; (xiv) x+1/2, −y+3/2, −z+1/2; (xv) x+1/2, −y+3/2, −z−1/2; (xvi) −x+1/2, y+1/2, z−1/2; (xvii) −x+1/2, y+1/2, z+1/2; (xviii) x−1/2, −y+3/2, −z−1/2; (xix) x−1/2, −y+3/2, −z+1/2; (xx) x, y+1, z; (xxi) x, y+1, z−1. |
| Cs1—Se4i | 3.6071 (12) | Cs2—Cs2iv | 2.394 (4) |
| Cs1—Se4ii | 3.6071 (12) | Cs2—Se2ii | 3.5286 (16) |
| Cs1—Se6ii | 3.7129 (12) | Cs2—Se2i | 3.5286 (16) |
| Cs1—Se6i | 3.7129 (12) | Cs2—Se2v | 3.6917 (17) |
| Cs1—Se3iii | 3.7639 (14) | Cs2—Se2vi | 3.6917 (17) |
| Cs1—Se5i | 3.8053 (12) | Cs2—Se5iii | 3.719 (2) |
| Cs1—Se5ii | 3.8053 (12) | Cs2—Se6iii | 3.924 (2) |
| Cs1—Se1 | 4.5421 (14) |
| Symmetry codes: (i) −x+1/2, y−1/2, z+1/2; (ii) −x+1/2, y−1/2, z−1/2; (iii) −x+1, −y+1, −z; (iv) −x+1, −y, −z; (v) x+1/2, −y+1/2, −z−1/2; (vi) x+1/2, −y+1/2, −z+1/2. |
This work was supported by the State of Baden-Württemberg (Stuttgart) and the German Research Foundation (DFG; Bonn) within the funding programme Open Access Publishing. We thank Dr Falk Lissner for the data collection.
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Cs3Sm7Se12 crystallizes isotypically to the large family of ternary A3M7Ch12 representatives with a channel-like structure. For Ch = S, A = K, Rb, M = Er, see: Lissner et al. (2002); for Ch = Se, A = Rb, M = Dy, Yb, see: Folchnandt & Schleid (2000), Kim et al. (1996); for Ch = Se, A = Cs, M = Y, Gd – Er, see: Folchnandt & Schleid (1996, 1997, 1998); for Ch = Te, A = Cs, M = Sm, Gd, Tb, see: Tougaît et al. (2001).
In the title compound, [SmSe6]9- octahedra (d(Sm3+–Se2-) = 2.8578 (9)–3.0614 (13) Å) are connected via edges and corners to form a [Sm7Se12]3- network with triple-channels occupied by Cs+ cations (Fig. 1). This network represents a defect rock-salt-type structure strongly related to that of the Z-type sesquiselenides M2Se3 (Dismukes & White, 1964) according to the formula [□]4[M]8[Se]12. In tricaesium heptasamarium(III) dodecaselenide three Cs+ cations replace one Sm3+ for charge balance. The triple-channels are arranged in a herringbone pattern and run through the structure parallel to [001]. They are filled with two crystallographically different Cs+ cations (Fig. 2). While Cs1+ exhibits a coordination number of 7+1 with an extra secondary contact (d(Cs1+–Se2-) = 3.6071 (12)–3.8053 (12) Å and 4.5421 (14) Å; Fig. 2, left), the Cs2+ cations have only six selenide anions as nearest neighbours in the shape of a trigonal prism (d(Cs2+–Se2-) = 3.5286 (16) – 3.924 (2) Å; Fig. 2, right). Owing to the very close distances between these Cs2+ cations (d(Cs2+···Cs2+) = 2.394 (4) Å) only a half-occupation of this position is possible (Fig. 2, right and Fig. 3) and stoichiometrically meaningful.