Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270110000247/fn3045sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270110000247/fn3045Isup2.hkl |
The sample was prepared by sintering the elemental constituents [Molar ratio?], of purity better than 99.9 wt.%, in an evacuated quartz ampoule in a tube furnace. The ampoule was heated at a rate of 30 K h^{-1} to a maximum temperature of 1370 K and kept at this temperature for 4 h. It was then cooled slowly (10 K h^{-1}) to 770 K and annealed at this temperature for 500 h. After annealing the ampoule, the sample was quenched in cold water. A diffraction-quality single crystal of the title compound was selected from the sample.
The formation of La_{2}Pb(SiS_{4})_{2} was established during the investigation of the phase relations in the respective La_{2}S_{3}–PbS–SiS_{2} system. The systematic absences were found to be consistent with the space group R3c which was applied for the crystal structure determination. One position for La and Pb, one position for Si and two positions for S were determined at the first stage of refinement. However, a statistical mixture of the La and Pb was assumed in the refinement, with the same anisotropic displacement parameters for the La and Pb atoms. The site-occupancy factors for the positions of the La and Pb atoms refined to 0.69 (1) and 0.31 (1), respectively [Please check rounding - 0.696 (9) and 0.304 (9) in CIF tables]. These values are in good agreement with the requirements of charge balance. The positions of the other atoms are fully occupied.
Data collection: CrysAlis CCD (Oxford Diffraction, 2007); cell refinement: CrysAlis RED (Oxford Diffraction, 2007); data reduction: CrysAlis RED (Oxford Diffraction, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2009); software used to prepare material for publication: publCIF (Westrip, 2010).
La_{2}Pb(SiS_{4})_{2} | D_{x} = 4.153 Mg m^{−}^{3} |
M_{r} = 797.67 | Mo Kα radiation, λ = 0.71073 Å |
Trigonal, R3c | Cell parameters from 475 reflections |
Hall symbol: -R 3 2"c | θ = 3.0–27.5° |
a = 9.0522 (13) Å | µ = 21.19 mm^{−}^{1} |
c = 26.964 (5) Å | T = 295 K |
V = 1913.5 (5) Å^{3} | Prism, yellow |
Z = 6 | 0.25 × 0.15 × 0.08 mm |
F(000) = 2112 |
Kuma KM-4 with CCD area-detector diffractometer | 487 independent reflections |
Radiation source: fine-focus sealed tube | 475 reflections with I > 2σ(I) |
Graphite monochromator | R_{int} = 0.034 |
Detector resolution: 1024x1024 with blocks 2x2, 33.133pixel/mm pixels mm^{-1} | θ_{max} = 27.5°, θ_{min} = 3.0° |
ω scans | h = −11→11 |
Absorption correction: numerical CrysAlis (Oxford Diffraction, 2007) | k = −11→11 |
T_{min} = 0.059, T_{max} = 0.414 | l = −30→35 |
6359 measured reflections |
Refinement on F^{2} | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F^{2} > 2σ(F^{2})] = 0.015 | w = 1/[σ^{2}(F_{o}^{2}) + (0.0241P)^{2} + 4.5858P] where P = (F_{o}^{2} + 2F_{c}^{2})/3 |
wR(F^{2}) = 0.043 | (Δ/σ)_{max} < 0.001 |
S = 1.22 | Δρ_{max} = 0.53 e Å^{−}^{3} |
487 reflections | Δρ_{min} = −0.67 e Å^{−}^{3} |
23 parameters | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^{*}=kFc[1+0.001xFc^{2}λ^{3}/sin(2θ)]^{-1/4} |
0 restraints | Extinction coefficient: 0.00030 (3) |
La_{2}Pb(SiS_{4})_{2} | Z = 6 |
M_{r} = 797.67 | Mo Kα radiation |
Trigonal, R3c | µ = 21.19 mm^{−}^{1} |
a = 9.0522 (13) Å | T = 295 K |
c = 26.964 (5) Å | 0.25 × 0.15 × 0.08 mm |
V = 1913.5 (5) Å^{3} |
Kuma KM-4 with CCD area-detector diffractometer | 487 independent reflections |
Absorption correction: numerical CrysAlis (Oxford Diffraction, 2007) | 475 reflections with I > 2σ(I) |
T_{min} = 0.059, T_{max} = 0.414 | R_{int} = 0.034 |
6359 measured reflections |
R[F^{2} > 2σ(F^{2})] = 0.015 | 23 parameters |
wR(F^{2}) = 0.043 | 0 restraints |
S = 1.22 | Δρ_{max} = 0.53 e Å^{−}^{3} |
487 reflections | Δρ_{min} = −0.67 e Å^{−}^{3} |
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 F^{2} against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F^{2}, conventional R-factors R are based on F, with F set to zero for negative F^{2}. The threshold expression of F^{2} > σ(F^{2}) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F^{2} 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 | U_{iso}*/U_{eq} | Occ. (<1) | |
La1 | 0.34803 (3) | 0.01470 (3) | 0.0833 | 0.01932 (15) | 0.696 (9) |
Pb1 | 0.34803 (3) | 0.01470 (3) | 0.0833 | 0.01932 (15) | 0.304 (9) |
Si1 | 0.6667 | 0.3333 | −0.00684 (5) | 0.0182 (4) | |
S1 | 0.3333 | −0.3333 | 0.08575 (4) | 0.0215 (4) | |
S2 | 0.43233 (11) | 0.30201 (11) | 0.01982 (3) | 0.0238 (3) |
U^{11} | U^{22} | U^{33} | U^{12} | U^{13} | U^{23} | |
La1 | 0.02208 (17) | 0.02208 (17) | 0.0174 (2) | 0.01376 (11) | −0.00096 (3) | 0.00096 (3) |
Pb1 | 0.02208 (17) | 0.02208 (17) | 0.0174 (2) | 0.01376 (11) | −0.00096 (3) | 0.00096 (3) |
Si1 | 0.0199 (5) | 0.0199 (5) | 0.0148 (6) | 0.0099 (2) | 0.000 | 0.000 |
S1 | 0.0256 (5) | 0.0256 (5) | 0.0133 (6) | 0.0128 (3) | 0.000 | 0.000 |
S2 | 0.0276 (5) | 0.0253 (5) | 0.0229 (4) | 0.0166 (4) | 0.0099 (3) | 0.0074 (3) |
La1—S1 | 3.0868 (5) | Si1—S2^{vii} | 2.1203 (9) |
La1—S1^{i} | 3.0867 (5) | Si1—S2^{v} | 2.1203 (9) |
La1—S2 | 2.8801 (8) | S1—La1^{viii} | 3.0868 (5) |
La1—S2^{i} | 2.8800 (8) | S1—Pb1^{viii} | 3.0868 (5) |
La1—S2^{ii} | 3.0143 (9) | S1—La1^{ix} | 3.0868 (5) |
La1—S2^{iii} | 3.0144 (9) | S1—Pb1^{ix} | 3.0868 (5) |
La1—S2^{iv} | 3.2784 (10) | S2—Pb1^{x} | 3.0144 (9) |
La1—S2^{v} | 3.2784 (10) | S2—La1^{x} | 3.0144 (9) |
Si1—S1^{vi} | 2.1277 (17) | S2—La1^{vii} | 3.2784 (10) |
Si1—S2 | 2.1203 (9) | ||
S2^{i}—La1—S2 | 108.54 (4) | Si1^{vi}—S1—La1 | 88.79 (2) |
S2^{i}—La1—S2^{ii} | 76.180 (19) | Si1^{vi}—S1—La1^{viii} | 88.79 (2) |
S2—La1—S2^{ii} | 125.02 (2) | La1—S1—La1^{viii} | 119.956 (1) |
S2^{i}—La1—S2^{iii} | 125.02 (2) | Si1^{vi}—S1—Pb1^{viii} | 88.79 (2) |
S2—La1—S2^{iii} | 76.179 (19) | La1—S1—Pb1^{viii} | 119.956 (1) |
S2^{ii}—La1—S2^{iii} | 146.66 (3) | Si1^{vi}—S1—La1^{ix} | 88.79 (2) |
S2^{i}—La1—S1^{i} | 142.28 (2) | La1—S1—La1^{ix} | 119.956 (2) |
S2—La1—S1^{i} | 80.23 (2) | La1^{viii}—S1—La1^{ix} | 119.956 (1) |
S2^{ii}—La1—S1^{i} | 69.45 (2) | Pb1^{viii}—S1—La1^{ix} | 119.956 (1) |
S2^{iii}—La1—S1^{i} | 92.63 (3) | Si1^{vi}—S1—Pb1^{ix} | 88.79 (2) |
S2^{i}—La1—S1 | 80.23 (2) | La1—S1—Pb1^{ix} | 119.956 (2) |
S2—La1—S1 | 142.28 (2) | La1^{viii}—S1—Pb1^{ix} | 119.956 (1) |
S2^{ii}—La1—S1 | 92.63 (3) | Pb1^{viii}—S1—Pb1^{ix} | 119.956 (1) |
S2^{iii}—La1—S1 | 69.45 (2) | Si1—S2—La1 | 96.78 (3) |
S1^{i}—La1—S1 | 115.736 (8) | Si1—S2—Pb1^{x} | 90.88 (4) |
S2^{i}—La1—S2^{iv} | 67.90 (3) | La1—S2—Pb1^{x} | 135.29 (3) |
S2—La1—S2^{iv} | 68.01 (3) | Si1—S2—La1^{x} | 90.88 (4) |
S2^{ii}—La1—S2^{iv} | 63.78 (3) | La1—S2—La1^{x} | 135.29 (3) |
S2^{iii}—La1—S2^{iv} | 144.16 (2) | Si1—S2—La1^{vii} | 85.82 (3) |
S1^{i}—La1—S2^{iv} | 83.023 (17) | La1—S2—La1^{vii} | 108.26 (3) |
S1—La1—S2^{iv} | 143.63 (2) | Pb1^{x}—S2—La1^{vii} | 116.23 (3) |
S2^{i}—La1—S2^{v} | 68.01 (3) | La1^{x}—S2—La1^{vii} | 116.23 (3) |
S2—La1—S2^{v} | 67.89 (3) | S2^{v}—Si1—S2^{vii} | 109.12 (4) |
S2^{ii}—La1—S2^{v} | 144.16 (2) | S2^{v}—Si1—S2 | 109.12 (4) |
S2^{iii}—La1—S2^{v} | 63.77 (3) | S2^{vii}—Si1—S2 | 109.12 (4) |
S1^{i}—La1—S2^{v} | 143.63 (2) | S2^{v}—Si1—S1^{vi} | 109.82 (4) |
S1—La1—S2^{v} | 83.022 (17) | S2^{vii}—Si1—S1^{vi} | 109.82 (4) |
S2^{iv}—La1—S2^{v} | 100.00 (3) | S2—Si1—S1^{vi} | 109.82 (4) |
S2^{i}—La1—S1—Si1^{vi} | −126.859 (18) | S2^{iv}—La1—S2—Si1 | 107.53 (4) |
S2—La1—S1—Si1^{vi} | −19.13 (3) | S2^{v}—La1—S2—Si1 | −3.95 (4) |
S2^{ii}—La1—S1—Si1^{vi} | 157.651 (16) | S2^{i}—La1—S2—Pb1^{x} | 149.99 (4) |
S2^{iii}—La1—S1—Si1^{vi} | 6.495 (18) | S2^{ii}—La1—S2—Pb1^{x} | −124.18 (5) |
S2^{iv}—La1—S1—Si1^{vi} | −155.47 (3) | S2^{iii}—La1—S2—Pb1^{x} | 27.24 (4) |
S2^{v}—La1—S1—Si1^{vi} | −58.065 (14) | S1^{i}—La1—S2—Pb1^{x} | −67.94 (4) |
S2^{i}—La1—S1—La1^{viii} | 145.23 (4) | S1—La1—S2—Pb1^{x} | 51.89 (5) |
S2—La1—S1—La1^{viii} | −107.04 (4) | S2^{iv}—La1—S2—Pb1^{x} | −154.31 (3) |
S2^{ii}—La1—S1—La1^{viii} | 69.74 (4) | S2^{v}—La1—S2—Pb1^{x} | 94.21 (4) |
S2^{iii}—La1—S1—La1^{viii} | −81.41 (4) | S2^{i}—La1—S2—La1^{x} | 149.99 (4) |
S2^{iv}—La1—S1—La1^{viii} | 116.62 (3) | S2^{ii}—La1—S2—La1^{x} | −124.18 (5) |
S2^{v}—La1—S1—La1^{viii} | −145.97 (4) | S2^{iii}—La1—S2—La1^{x} | 27.24 (4) |
S2^{i}—La1—S1—Pb1^{viii} | 145.23 (4) | S1^{i}—La1—S2—La1^{x} | −67.94 (4) |
S2—La1—S1—Pb1^{viii} | −107.04 (4) | S1—La1—S2—La1^{x} | 51.89 (5) |
S2^{ii}—La1—S1—Pb1^{viii} | 69.74 (4) | S2^{iv}—La1—S2—La1^{x} | −154.31 (3) |
S2^{iii}—La1—S1—Pb1^{viii} | −81.41 (4) | S2^{v}—La1—S2—La1^{x} | 94.21 (4) |
S2^{iv}—La1—S1—Pb1^{viii} | 116.62 (3) | S2^{i}—La1—S2—La1^{vii} | −35.995 (14) |
S2^{v}—La1—S1—Pb1^{viii} | −145.97 (4) | S2^{ii}—La1—S2—La1^{vii} | 49.84 (3) |
S2—La1—S1—La1^{ix} | 68.78 (5) | S2^{iii}—La1—S2—La1^{vii} | −158.74 (2) |
S2^{ii}—La1—S1—La1^{ix} | −114.44 (4) | S1^{i}—La1—S2—La1^{vii} | 106.08 (3) |
S2^{iii}—La1—S1—La1^{ix} | 94.40 (4) | S1—La1—S2—La1^{vii} | −134.09 (2) |
S1^{i}—La1—S1—La1^{ix} | 177.15 (5) | S2^{iv}—La1—S2—La1^{vii} | 19.71 (3) |
S2^{iv}—La1—S1—La1^{ix} | −67.57 (5) | S2^{v}—La1—S2—La1^{vii} | −91.77 (2) |
S2^{v}—La1—S1—La1^{ix} | 29.84 (3) | La1—S2—Si1—S2^{v} | 5.99 (6) |
S2—La1—S1—Pb1^{ix} | 68.78 (5) | Pb1^{x}—S2—Si1—S2^{v} | −129.86 (5) |
S2^{ii}—La1—S1—Pb1^{ix} | −114.44 (4) | La1^{x}—S2—Si1—S2^{v} | −129.86 (5) |
S2^{iii}—La1—S1—Pb1^{ix} | 94.40 (4) | La1^{vii}—S2—Si1—S2^{v} | 113.91 (4) |
S1^{i}—La1—S1—Pb1^{ix} | 177.15 (5) | La1—S2—Si1—S2^{vii} | −113.16 (4) |
S2^{iv}—La1—S1—Pb1^{ix} | −67.57 (5) | Pb1^{x}—S2—Si1—S2^{vii} | 110.99 (6) |
S2^{v}—La1—S1—Pb1^{ix} | 29.84 (3) | La1^{x}—S2—Si1—S2^{vii} | 110.99 (6) |
S2^{i}—La1—S2—Si1 | 51.83 (3) | La1^{vii}—S2—Si1—S2^{vii} | −5.24 (5) |
S2^{ii}—La1—S2—Si1 | 137.66 (3) | La1—S2—Si1—S1^{vi} | 126.418 (17) |
S2^{iii}—La1—S2—Si1 | −70.92 (5) | Pb1^{x}—S2—Si1—S1^{vi} | −9.43 (2) |
S1^{i}—La1—S2—Si1 | −166.10 (4) | La1^{x}—S2—Si1—S1^{vi} | −9.43 (2) |
S1—La1—S2—Si1 | −46.27 (5) |
Symmetry codes: (i) y+1/3, x−1/3, −z+1/6; (ii) −x+y+1/3, y−1/3, z+1/6; (iii) y, −x+y, −z; (iv) x−y+1/3, −y+2/3, −z+1/6; (v) −y+1, x−y, z; (vi) −x+1, −y, −z; (vii) −x+y+1, −x+1, z; (viii) −y, x−y−1, z; (ix) −x+y+1, −x, z; (x) x−y, x, −z. |
Experimental details
Crystal data | |
Chemical formula | La_{2}Pb(SiS_{4})_{2} |
M_{r} | 797.67 |
Crystal system, space group | Trigonal, R3c |
Temperature (K) | 295 |
a, c (Å) | 9.0522 (13), 26.964 (5) |
V (Å^{3}) | 1913.5 (5) |
Z | 6 |
Radiation type | Mo Kα |
µ (mm^{−}^{1}) | 21.19 |
Crystal size (mm) | 0.25 × 0.15 × 0.08 |
Data collection | |
Diffractometer | Kuma KM-4 with CCD area-detector diffractometer |
Absorption correction | Numerical CrysAlis (Oxford Diffraction, 2007) |
T_{min}, T_{max} | 0.059, 0.414 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 6359, 487, 475 |
R_{int} | 0.034 |
(sin θ/λ)_{max} (Å^{−}^{1}) | 0.649 |
Refinement | |
R[F^{2} > 2σ(F^{2})], wR(F^{2}), S | 0.015, 0.043, 1.22 |
No. of reflections | 487 |
No. of parameters | 23 |
Δρ_{max}, Δρ_{min} (e Å^{−}^{3}) | 0.53, −0.67 |
Computer programs: CrysAlis CCD (Oxford Diffraction, 2007), CrysAlis RED (Oxford Diffraction, 2007), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 2009), publCIF (Westrip, 2010).
La1—S1 | 3.0868 (5) | La1—S2^{iv} | 3.2784 (10) |
La1—S1^{i} | 3.0867 (5) | La1—S2^{v} | 3.2784 (10) |
La1—S2 | 2.8801 (8) | Si1—S1^{vi} | 2.1277 (17) |
La1—S2^{i} | 2.8800 (8) | Si1—S2 | 2.1203 (9) |
La1—S2^{ii} | 3.0143 (9) | Si1—S2^{vii} | 2.1203 (9) |
La1—S2^{iii} | 3.0144 (9) |
Symmetry codes: (i) y+1/3, x−1/3, −z+1/6; (ii) −x+y+1/3, y−1/3, z+1/6; (iii) y, −x+y, −z; (iv) x−y+1/3, −y+2/3, −z+1/6; (v) −y+1, x−y, z; (vi) −x+1, −y, −z; (vii) −x+y+1, −x+1, z. |
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The synthesis of compounds with increasingly complex compositions, such as ternary, quaternary etc., has become a principal direction in modern material sciences (Eliseev & Kuzmichyeva, 1990; Mitchell & Ibers, 2002). Among multicomponent systems an important place belongs to the complex rare-earth chalcogenides. They have been intensively studied over recent years owing to their specific thermal, electrical and optical properties, which make them prospective materials in the field of IR and nonlinear optics. Therefore, the synthesis and investigation of the crystal structures of complex chalcogenides are important in the search for new materials. So far, the series of quarternary rare-earth chalcogenides with Pb have been obtained from the R_{2}S_{3}–PbS–SnS_{2} system (Marchuk et al., 2007; Gulay et al., 2008). These R_{2}Pb_{3}Sn_{3}S_{12} (R = La–Nd, Sm, Gd–Tm) compounds crystallize in the non-centrosymmetric space group Pmc2_{1} (Y_{2}Pb_{3}Sn_{3}S_{12} structure type). However, a thorough investigation of the similar La_{2}S_{3}–PbS–SiS_{2} system shows that a different quarternary compound of formula La_{2}Pb(SiS_{4})_{2} can be obtained. The crystal structure of this new chalcogenide is presented here.
Relevant interatomic distances and coordination numbers of the La, Pb and Si atoms in the structure of La_{2}Pb(SiS_{4})_{2} are listed in Table 1 [Coordination numbers not given - do you wish to add them?]. Overall, the distances are close to the sums of the respective ionic radii (Wiberg, 1995). The Si atom lies on a threefold rotation axis and is surrounded by one S1 and three S2 atoms, resulting in a slightly elongated [Si1S1S2_{3}] tetrahedron of C_{3}_{v} point-group symmetry. A similar, but compressed, environment for an Si atom was found in the recently published hexagonal compound La_{3}Ag_{0.90}SiS_{7} (Daszkiewicz et al., 2008). In the title compound the La and Pb atoms occupy the same site, with occupancy factors of 0.69 (1) and 0.31 (1), respectively. Therefore, these atoms have the same coordination environment of eight S atoms, creating a bicapped trigonal prism, [(La1/Pb1)S1_{2}S2_{6}] (Fig. 1). Similar values for La—S and Pb—S distances have also been observed in the previously reported lanthanum and lead sulfides. For example, the shortest La—S distance in La_{2}S_{3} (Basançon et al., 1969) is 2.91 (1) Å and the shortest Pb—S distance in Ho_{5}Cu_{1+}_{x}Pb_{3-}_{x}_{/2}S_{11} (x = 1/4) is 2.822 (8) Å (Gulay et al., 2007). In the title compound the two longest (La/Pb)—S distances of 3.2784 (10) Å contribute 0.178 of a valence unit (Brown, 1996). However, the bond-valence sums of the La^{3+}, Pb^{2+} and Si^{4+} ions are 2.722, 2.040 and 4.077, respectively. These values suggest that the La^{3+} ion is underbonded in its eight-coordinate site. On the other hand, the bond-valence sums for both symmetry-independent S atoms are 1.901 for S1 and 2.087 for S2. Thus, atom S1 is underbonded and S2 is overbonded, despite both anions having similar pyramidal trigonal surroundings, [(La1/Pb1)_{3}Si1].
The [(La1/Pb1)S1_{2}S2_{6}] bicapped trigonal prisms and [Si1S1S2_{3}] tetrahedra are connected to each other in two ways. Firstly, three prisms connect the tetrahedra by the edges and the prisms are connected to each other only by one corner [denoted (1) in Fig. 1], and secondly three prisms are connected by edges around the threefold axis and an empty trigonal prism exists inside this block [denoted (2) in Fig. 1]. In addition, two [Si1S1S2_{3}] tetrahedra share edges, resulting in a closed empty trigonal prism in the structure. The centre of gravity of this gap is located 2.629 (1) Å from the S atoms, which makes La_{2}Pb(SiS_{4})_{2} a prospective material in crystal engineering.
Overall, the (La+Pb) and Si atoms in the structure of La_{2}Pb(SiS_{4})_{2} form separated two-dimmensional nets which are parallel to the ab plane (Fig. 2). A 3^{6} net is created by the (La+Pb) atoms, whereas the Si atoms form a honeycomb-like 6^{3} net. However, the S atoms do not create a layer. Thus, the cationic (La^{3+}+Pb^{2+}) and Si^{4+} layers are arranged in an alternating manner and they are immersed in the anionic sublattice.