A gadolinium and niobium oxide sulfide, Gd₃NbS₃O₄

The structure of the title compound, trigadolinium niobium tri­sulfide tetraoxide, Gd₃NbS₃O₄, was determined by single-crystal X-ray diffraction. Gd₃NbS₃O₄ crystallizes in the non-centrosymmetric space group Pn2₁a (No.33) of the orthorhombic system. It is isostructural with Sm₃NbS₃O₄.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](Nb-O) = 0.005 Å
• R factor = 0.030
• wR factor = 0.061
• Data-to-parameter ratio = 30.7

checkCIF results

No syntax errors found


 Alert Level A:



PLAT_111  Alert A ADDSYM Detects (Pseudo) Centre of Symmetry .....        100 PerFit

Author response: The structure solution in the non centrosymmetric space group Pn21a is better than the structure solution in the centrosymmetric space group Pnma, see _publ_section_comment

PLAT_112  Alert A ADDSYM Detects Additional (Pseudo) Symm. Elem...          m

Author response: The structure solution in the non centrosymmetric space group Pn21a is better than the structure solution in the centrosymmetric space group Pnma, see _publ_section_comment

PLAT_113  Alert A ADDSYM Suggests Possible Pseudo/New Spacegroup .          Pnma

Author response: The structure solution in the non centrosymmetric space group Pn21a is better than the structure solution in the centrosymmetric space group Pnma, see _publ_section_comment

 Alert Level C:



STRVAL_01
         From the CIF: _refine_ls_abs_structure_Flack    0.554
         From the CIF: _refine_ls_abs_structure_Flack_su    0.014
           Alert C Flack test results are ambiguous.

General Notes



ABSTM_02  The ratio of expected to reported Tmax/Tmin(RR) is > 1.10
          Tmin and Tmax reported:      0.192     0.641
          Tmin and Tmax expected:      0.130     0.639
          RR =      1.466
          Please check that your absorption correction is appropriate.

REFLT_03
         From the CIF: _diffrn_reflns_theta_max           34.96
         From the CIF: _reflns_number_total               3130
         Count of symmetry unique reflns         1672
         Completeness (_total/calc)            187.20%
         TEST3: Check Friedels for noncentro structure
         Estimate of Friedel pairs measured      1458
         Fraction of Friedel pairs measured     0.872
         Are heavy atom types Z>Si present          yes
          Please check that the estimate of the number of Friedel pairs is
          correct. If it is not, please give the correct count in the
          _publ_section_exptl_refinement section of the submitted CIF.


 3 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 1 Alert Level C = Please check

---

S1. Comment

Recent explorations in the field of oxychalcogenides have revealed novel interesting layered intergrowth compounds with structures based on the staking of chalcogenide and oxide layers (Zhu & Hor, 1997; Otzschi et al., 1999; Boyer et al., 1999; Goga et al., 1999). As the combination of both type layers could lead to materials with interesting electronic and magnetic properties, we were looking for new layered intergrowth compounds. We are currently investigating several quaternary systems containing rare earths and transition elements and during our investigation of the Gd–Nb–S–O system we obtained Gd₃NbS₃O₄ as a side product. A yellow transparent platelet-shaped crystal was mounted on the diffractometer for data collection.

The observed systematic conditions (k+l = 2n for 0kl; and h = 2n for hk0) led to only two possible space groups Pn2₁a (No. 33) and Pnma (No. 62). As the intensity statistics were rather indicating a centrosymmetric space group, we first supposed that Gd₃NbS₃O₄ was isostructural with Sm₃NbSe₃O₄ (Meerschaut et al., 1998) and tried to refine the structure using Pnma (No. 62). However, the refinement led to bad reliability factors (R = 0.0634 and wR = 0.1439). Subsequently, we considered that Gd₃NbS₃O₄ could be isostructural with Sm₃NbS₃O₄ (Boyer-Candalen et al., 2000), i.e. we tried to refine the structure with the non-centrosymetric space group Pn2₁a. The refinement led to much better reliability factors (R = 0.0297 and wR = 0.0606).

A projection of the structure of Gd₃NbS₃O₄ is shown in Fig. 1. A l l metal atoms are found in mixed environments of oxygen and sulfur. Nb1 and Gd1 are involved in similar coordination polyhedra (very distorted prism with eight surrounding atoms, viz. four O and four S atoms). These polyhedra are connected by edge-sharing and alternate regularly along the b axis. In the same way, Gd2 and Gd3 are located in slightly different bicapped trigonal prisms that are alternate along the b axis.

The difference between the sulfur and selenium compounds is related to the position of the chalcogen in the structure. In the Sm₃NbSe₃O₄ compound, atom Se3 sits on the inversion center (special position 4a) and is octahedrally coordinated. On the contrary, in Gd₃NbS₃O₄, atom S3 deviates from this position and no longer occupies the center of the octahedron but a square pyramid. These structural characteristics lead to the absence of a mirror plane in the structure. Finally, we refined a Flack (1983) parameter close to 1/2, which indicates that we have a racemic twin.

S2. Experimental

A mixture of Gd₂S₃, Gd₂O₃, Nb₂O₅, and Nb, weighted in the proportion 1.33:1.67:1:0.5, was pressed into a pellet and sealed in a silica tube under vacuum. The tube was progressively heated (100 K h⁻¹) to 1273 K and maintained at that temperature for 12 h. To favor crystallization, a small amount of iodine (<5 mg cm⁻³) was added to the intermediate reaction product which was reheated in a temperature gradient furnace at 1273 K for 10 d. Yellow transparent platelet-shaped crystals were obtained as a by-product. Chemical analyses performed on these crystals using an EDS-equipped scanning electron microscope revealed the following atomic percentages (except for oxygen): Gd 42.8, Nb 12.7 and S 44.5, in good agreement with the theoretical values Gd 42.8, Nb 14.3 and S 42.8 calculated for Gd₃NbS₃O₄.

S3. Refinement

Refinement of the opposite enantiomer leads to identical R values and a complementary Flack parameter [0.446 (14)].

Computing details

Data collection: COLLECT (Nonius, 1997-2000); cell refinement: HKL SCALEPACK (Otwinowski & Minor, 1997); data reduction: HKL DENZO (Otwinowski & Minor, 1997) and SCALEPACK; program(s) used to solve structure: not used (isotypic); molecular graphics: DIAMOND (Brandenburg, 2001); software used to prepare material for publication: SHELXTL (Bruker, 2001).

Figures

Fig. 1. A projection of the structure of Gd3NbS3O4 along the b axis, ellipsoids drawn at the 80% probability level.

Tridadolinium niobium trisulfide tetraoxide

Crystal data

Gd3NbS3O4	F(000) = 1252
Mr = 724.84	Dx = 6.734 Mg m^−3
Orthorhombic, Pn21a	Mo Kα radiation, λ = 0.71069 Å
Hall symbol: P -2ac -2n	Cell parameters from 21073 reflections
a = 6.6451 (1) Å	θ = 2.9–35.0°
b = 7.5873 (2) Å	µ = 29.85 mm^−1
c = 14.1809 (3) Å	T = 293 K
V = 714.98 (3) Å^3	Platelet, yellow
Z = 4	0.09 × 0.06 × 0.02 mm

Data collection

Nonius KappaCCD diffractometer	3130 independent reflections
Radiation source: fine-focus sealed tube	2839 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.054
Detector resolution: 9 pixels mm^-1	θmax = 35.0°, θmin = 3.0°
CCD scans	h = −10→10
Absorption correction: gaussian (SHELXTL; Bruker, 2001)	k = −12→12
Tmin = 0.192, Tmax = 0.641	l = −22→21
18460 measured reflections

Refinement

Refinement on F^2	w = 1/[σ^2(Fo^2) + (0.0207P)^2 + 6.6189P] where P = (Fo^2 + 2Fc^2)/3
Least-squares matrix: full	(Δ/σ)max = 0.002
R[F^2 > 2σ(F^2)] = 0.030	Δρmax = 2.23 e Å^−3
wR(F^2) = 0.061	Δρmin = −2.11 e Å^−3
S = 1.05	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
3130 reflections	Extinction coefficient: 0.00103 (6)
102 parameters	Absolute structure: (Flack, 1983)
1 restraint	Absolute structure parameter: 0.554 (14)
Primary atom site location: isomorphous structure methods

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
Gd1	0.77583 (4)	0.24993 (9)	0.58180 (2)	0.00675 (6)
Gd2	0.21841 (5)	−0.00586 (3)	0.65757 (3)	0.00756 (8)
Gd3	0.22626 (5)	0.50511 (4)	0.66538 (3)	0.00857 (8)
Nb1	0.81637 (8)	0.74064 (13)	0.57250 (4)	0.00674 (10)
S1	0.5013 (2)	0.2443 (3)	0.72724 (10)	0.0080 (2)
S2	0.5457 (2)	0.7568 (3)	0.70274 (10)	0.0092 (2)
S3	0.4791 (3)	0.0219 (3)	0.49464 (13)	0.0118 (4)
O1	0.8565 (6)	0.7551 (13)	0.4376 (3)	0.0099 (8)
O2	0.8755 (8)	−0.0289 (8)	0.6154 (4)	0.0118 (11)
O3	0.8798 (8)	0.5231 (8)	0.6323 (4)	0.0109 (11)
O4	0.1330 (6)	0.7415 (12)	0.5731 (3)	0.0092 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Gd1	0.00683 (11)	0.00576 (10)	0.00767 (12)	0.0003 (2)	0.00051 (9)	0.0000 (2)
Gd2	0.00659 (17)	0.00641 (16)	0.00968 (15)	−0.00030 (18)	0.00006 (11)	−0.00003 (18)
Gd3	0.00713 (17)	0.00623 (17)	0.01234 (15)	−0.00007 (19)	0.00058 (12)	0.00069 (18)
Nb1	0.0087 (2)	0.0058 (2)	0.00570 (19)	−0.0015 (4)	0.00000 (16)	0.0000 (3)
S1	0.0076 (5)	0.0090 (5)	0.0075 (5)	−0.0002 (9)	0.0000 (4)	0.0001 (9)
S2	0.0088 (6)	0.0095 (6)	0.0092 (5)	−0.0002 (8)	0.0002 (4)	−0.0001 (8)
S3	0.0119 (8)	0.0135 (12)	0.0101 (6)	−0.0047 (7)	0.0010 (6)	−0.0018 (7)
O1	0.0106 (17)	0.0116 (18)	0.0076 (16)	−0.003 (3)	0.0002 (14)	−0.001 (3)
O2	0.010 (2)	0.009 (3)	0.017 (2)	0.0001 (19)	−0.0056 (19)	0.001 (2)
O3	0.008 (2)	0.008 (3)	0.017 (2)	−0.001 (2)	−0.0035 (17)	0.000 (2)
O4	0.0091 (16)	0.012 (2)	0.0064 (16)	0.004 (3)	−0.0004 (13)	0.000 (3)

Geometric parameters (Å, º)

Gd1—O2	2.267 (6)	Gd3—S3^iii	2.9996 (19)
Gd1—O4^i	2.279 (4)	Gd3—Nb1^vii	3.5139 (7)
Gd1—O3	2.299 (6)	Gd3—Gd2^xi	3.7124 (4)
Gd1—O1^ii	2.459 (4)	Gd3—Gd1^vii	3.7567 (5)
Gd1—S1	2.7536 (14)	Nb1—O2^xi	1.893 (6)
Gd1—S3^iii	2.882 (2)	Nb1—O3	1.903 (6)
Gd1—S3	2.899 (2)	Nb1—O1	1.935 (4)
Gd1—S1^iv	3.0952 (14)	Nb1—O4^v	2.104 (4)
Gd1—Nb1^ii	3.4838 (6)	Nb1—S2	2.5809 (15)
Gd1—Gd2^v	3.6838 (6)	Nb1—S3^iii	2.7415 (19)
Gd1—Gd3^v	3.7567 (5)	Nb1—Gd1^xii	3.4838 (6)
Gd1—Gd2^iii	3.8675 (6)	Nb1—Gd2^xiii	3.5060 (8)
Gd2—O4^vi	2.331 (8)	Nb1—Gd3^v	3.5139 (7)
Gd2—O2^vii	2.363 (5)	S1—Gd2^iv	2.890 (2)
Gd2—O1^i	2.447 (8)	S1—Gd3^iv	2.910 (2)
Gd2—S1	2.848 (2)	S1—Gd1^viii	3.0952 (14)
Gd2—S1^viii	2.890 (2)	S2—Gd2^xi	2.895 (2)
Gd2—S2^vi	2.895 (2)	S2—Gd2^xiv	2.913 (2)
Gd2—S3	2.8957 (19)	S2—Gd3^iv	2.930 (2)
Gd2—S2^ix	2.913 (2)	S3—Nb1^i	2.7415 (19)
Gd2—Nb1^x	3.5060 (8)	S3—Gd1^i	2.882 (2)
Gd2—Gd1^vii	3.6838 (6)	S3—Gd3^i	2.9996 (19)
Gd2—Gd3^vi	3.7125 (4)	O1—Gd2^iii	2.447 (8)
Gd2—Gd1^i	3.8675 (6)	O1—Gd3^iii	2.456 (8)
Gd3—O4	2.305 (7)	O1—Gd1^xii	2.459 (4)
Gd3—O3^vii	2.354 (5)	O2—Nb1^vi	1.893 (6)
Gd3—O1^i	2.456 (8)	O2—Gd2^v	2.363 (5)
Gd3—S1	2.833 (2)	O3—Gd3^v	2.354 (5)
Gd3—S2	2.904 (2)	O4—Nb1^vii	2.104 (4)
Gd3—S1^viii	2.910 (2)	O4—Gd1^iii	2.279 (4)
Gd3—S2^viii	2.930 (2)	O4—Gd2^xi	2.331 (8)
O2—Gd1—O4^i	95.7 (3)	O2^vii—Gd2—S2^ix	75.32 (14)
O2—Gd1—O3	133.47 (16)	O1^i—Gd2—S2^ix	142.66 (10)
O4^i—Gd1—O3	104.2 (3)	S1—Gd2—S2^ix	115.86 (5)
O2—Gd1—O1^ii	75.4 (3)	S1^viii—Gd2—S2^ix	79.92 (6)
O4^i—Gd1—O1^ii	68.19 (14)	S2^vi—Gd2—S2^ix	76.17 (5)
O3—Gd1—O1^ii	73.9 (3)	S3—Gd2—S2^ix	145.43 (6)
O2—Gd1—S1	91.24 (16)	O4—Gd3—O3^vii	65.09 (19)
O4^i—Gd1—S1	153.82 (11)	O4—Gd3—O1^i	101.71 (17)
O3—Gd1—S1	88.83 (15)	O3^vii—Gd3—O1^i	72.97 (19)
O1^ii—Gd1—S1	137.92 (10)	O4—Gd3—S1	153.21 (11)
O2—Gd1—S3^iii	156.77 (14)	O3^vii—Gd3—S1	137.16 (17)
O4^i—Gd1—S3^iii	79.28 (19)	O1^i—Gd3—S1	77.83 (15)
O3—Gd1—S3^iii	69.41 (15)	O4—Gd3—S2	77.79 (16)
O1^ii—Gd1—S3^iii	122.0 (2)	O3^vii—Gd3—S2	135.51 (17)
S1—Gd1—S3^iii	84.46 (6)	O1^i—Gd3—S2	141.26 (10)
O2—Gd1—S3	74.42 (14)	S1—Gd3—S2	86.06 (6)
O4^i—Gd1—S3	75.71 (16)	O4—Gd3—S1^viii	133.48 (12)
O3—Gd1—S3	151.04 (14)	O3^vii—Gd3—S1^viii	68.97 (15)
O1^ii—Gd1—S3	129.60 (19)	O1^i—Gd3—S1^viii	70.78 (14)
S1—Gd1—S3	81.93 (5)	S1—Gd3—S1^viii	72.20 (5)
S3^iii—Gd1—S3	82.366 (10)	S2—Gd3—S1^viii	136.65 (4)
O2—Gd1—S1^iv	70.24 (15)	O4—Gd3—S2^viii	75.25 (14)
O4^i—Gd1—S1^iv	135.55 (11)	O3^vii—Gd3—S2^viii	71.87 (15)
O3—Gd1—S1^iv	66.07 (15)	O1^i—Gd3—S2^viii	142.29 (10)
O1^ii—Gd1—S1^iv	67.48 (10)	S1—Gd3—S2^viii	121.46 (4)
S1—Gd1—S1^iv	70.441 (9)	S2—Gd3—S2^viii	75.78 (6)
S3^iii—Gd1—S1^iv	128.58 (6)	S1^viii—Gd3—S2^viii	84.20 (6)
S3—Gd1—S1^iv	133.94 (6)	O4—Gd3—S3^iii	73.31 (11)
O4^vi—Gd2—O2^vii	64.80 (18)	O3^vii—Gd3—S3^iii	119.03 (15)
O4^vi—Gd2—O1^i	109.41 (17)	O1^i—Gd3—S3^iii	74.29 (11)
O2^vii—Gd2—O1^i	73.97 (18)	S1—Gd3—S3^iii	80.96 (5)
O4^vi—Gd2—S1	152.51 (11)	S2—Gd3—S3^iii	68.47 (5)
O2^vii—Gd2—S1	140.69 (15)	S1^viii—Gd3—S3^iii	139.46 (7)
O1^i—Gd2—S1	77.67 (15)	S2^viii—Gd3—S3^iii	136.25 (6)
O4^vi—Gd2—S1^viii	135.17 (11)	O2^xi—Nb1—O3	127.8 (2)
O2^vii—Gd2—S1^viii	73.15 (14)	O2^xi—Nb1—O1	103.7 (3)
O1^i—Gd2—S1^viii	71.26 (13)	O3—Nb1—O1	117.3 (3)
S1—Gd2—S1^viii	72.29 (5)	O2^xi—Nb1—O4^v	77.8 (3)
O4^vi—Gd2—S2^vi	77.59 (14)	O3—Nb1—O4^v	77.3 (3)
O2^vii—Gd2—S2^vi	137.28 (16)	O1—Nb1—O4^v	82.28 (16)
O1^i—Gd2—S2^vi	141.08 (10)	O2^xi—Nb1—S2	82.58 (18)
S1—Gd2—S2^vi	80.90 (6)	O3—Nb1—S2	82.91 (17)
S1^viii—Gd2—S2^vi	131.17 (4)	O1—Nb1—S2	143.23 (13)
O4^vi—Gd2—S3	78.19 (12)	O4^v—Nb1—S2	133.95 (11)
O2^vii—Gd2—S3	112.36 (14)	O2^xi—Nb1—S3^iii	145.03 (17)
O1^i—Gd2—S3	67.84 (11)	O3—Nb1—S3^iii	77.78 (17)
S1—Gd2—S3	80.40 (5)	O1—Nb1—S3^iii	77.9 (2)
S1^viii—Gd2—S3	134.58 (7)	O4^v—Nb1—S3^iii	136.0 (2)
S2^vi—Gd2—S3	76.84 (5)	S2—Nb1—S3^iii	77.18 (6)
O4^vi—Gd2—S2^ix	75.24 (14)

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