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Acta Crystallogr Sect E Struct Rep Online. 2009 May 1; 65(Pt 5): i34.
Published online 2009 April 18. doi:  10.1107/S1600536809012495
PMCID: PMC2977540

The Chevrel phase HgMo6S8

Abstract

The crystal structure of HgMo6S8, mercury(II) hexa­molybdenum octa­sulfide, is based on (Mo6S8)S6 cluster units (An external file that holds a picture, illustration, etc.
Object name is e-65-00i34-efi1.jpg symmetry) inter­connected through inter­unit Mo—S bonds. The Hg2+ cations occupy large voids between the different cluster units and are covalently bonded to two S atoms. The Hg atoms and one S atom lie on sites with crystallographic An external file that holds a picture, illustration, etc.
Object name is e-65-00i34-efi1.jpg and 3 symmetry, respectively. Refinement of the occupancy factor of the Hg atom led to the composition Hg0.973 (3)Mo6S8.

Related literature

For isotypic structures, see: Chevrel & Sergent (1982 [triangle]). For a previous report on the title compound as a polycrystalline material, see: Tarascon et al. (1983 [triangle]). For crystallographic background, see: Becker & Coppens (1974 [triangle]); Johnson & Levy (1974 [triangle]).

Experimental

Crystal data

  • Hg0.973Mo6S8
  • M r = 1027.3
  • Trigonal, An external file that holds a picture, illustration, etc.
Object name is e-65-00i34-efi3.jpg
  • a = 9.4319 (3) Å
  • c = 10.7028 (3) Å
  • V = 824.57 (4) Å3
  • Z = 3
  • Mo Kα radiation
  • μ = 21.62 mm−1
  • T = 293 K
  • 0.08 × 0.07 × 0.06 mm

Data collection

  • Nonius KappaCCD diffractometer
  • Absorption correction: analytical (de Meulenaer & Tompa, 1965 [triangle]) T min = 0.298, T max = 0.384
  • 5784 measured reflections
  • 1121 independent reflections
  • 1069 reflections with I > 2σ(I)
  • R int = 0.044

Refinement

  • R[F 2 > 2σ(F 2)] = 0.025
  • wR(F 2) = 0.026
  • S = 1.74
  • 1121 reflections
  • 31 parameters
  • Δρmax = 2.64 e Å−3
  • Δρmin = −1.57 e Å−3

Data collection: COLLECT (Nonius, 1998 [triangle]); cell refinement: COLLECT; data reduction: EVALCCD (Duisenberg et al., 2003 [triangle]); program(s) used to solve structure: SIR97 (Altomare et al., 1999 [triangle]); program(s) used to refine structure: JANA2000 (Petříček & Dušek, 2000 [triangle]); molecular graphics: DIAMOND (Bergerhoff, 1996 [triangle]); software used to prepare material for publication: JANA2000.

Table 1
Selected bond lengths (Å)

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809012495/wm2226sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809012495/wm2226Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

Intensity data were collected on the Nonius KappaCCD X-ray diffactometer system of the Centre de diffractométrie de l’Université de Rennes I (www.cdifx.univ-rennes1.fr).

supplementary crystallographic information

Comment

The superconducting compound HgMo6S8 was first synthesized as a powder sample by Tarascon et al. (1983), but no details were given on its crystal structure. In the present study, we present the crystal structure refinement of HgMo6S8 that has been determined from single-crystal X-ray diffraction data. The title compound is isostructural with the hexagonal Chevrel phases MMo6X8 where M is a large cation (M = alkali metal, alkaline earth, lanthanide, actinide etc.; X = S, Se, Te) [see, for instance, Chevrel & Sergent (1982)]. As a consequence its crystal structure consists of octahedral Mo6 clusters surrounded by fourteen sulfur atoms with eight of them forming a distorted cube (i-type ligands) and the remaining six capping the faces of the S8 cube (a-type ligands). In the structure of HgMo6S8, a part of the chalcogen atoms of the Mo6Si8Sa6 unit are shared according to the formula Mo6Si2Si-a6/2Sa-i6/2 to form the three-dimensional Mo—S network. The Mo6S8 cluster unit is centered at Wyckoff position 6b (3 symmetry). The Mo—Mo distances within the Mo6 clusters are 2.7184 (3) Å for the intra-triangle distances (distances within the Mo3 triangles formed by the Mo atoms related through the threefold axis) and 2.7515 (3) Å for the inter-triangle distances. Each Mo atom is surrounded by five S atoms (4 S1 and 1 S2) forming a distorted square-based pyramid. The apex of the pyramid is shared with an adjacent unit and thus ensures the three-dimensional cohesion. Consequently, each Mo6S8 unit is interconnected to 6 Mo6S8 units to form the Mo—S framework. It results from this arrangement that the shortest intercluster Mo1—Mo1 distances between the Mo6 clusters is 3.2934 (3) Å, indicating only weak metal-metal interaction. The Hg2+ cations reside in the large eight-coordinate voids formed by the chalcogen atoms from eight different Mo6S8 units. They are covalently bonded to two S2 atoms at a distance of 2.3914 (8) Å.

HgMo6S8 was found to be superconducting at 8 K from DC-susceptibility measurements on a batch of single crystals.

Experimental

HgMo6S8 was obtained in three steps involving, first, the syntheses of single-crystal of InMo6S8 by solid state reaction, then the preparation of the binary compound Mo6S8 by 'chimie douce' methods and, finally, the synthesis of the title compound by inserting mercury into the Mo6S8 host structure at low temperatures. Single crystals of InMo6S8 were obtained from a stoichiometric mixture of In2S3, MoS2 and Mo. All handlings of materials were done in an argon-filled glove box. The initial mixture (ca 5 g) was cold pressed and loaded into a molybdenum crucible, which was sealed under a low argon pressure using an arc-welding system. The charge was heated at the rate of 300 K/h up to 1773 K, the temperature which was held for six hours, then cooled at 100 K/h down to 1273 K and finally furnace cooled. Mo6S8 was obtained by oxidation of single-crystals of InMo6S8 by iodine in a glass tube sealed under vacuum. The end of the tube containing the crystals of the In compound and an excess of iodine was placed in a furnace with about 3 cm of the other end sticking out of the furnace, at about room temperature. The furnace was then heated at 523 K for 96 h. At the end of the reaction, crystals of InI3 and I2 were obtained at the cooler end of the tube. Finally, HgMo6S8 was prepared by diffusion of mercury into crystals of Mo6S8 in a silica glass tube sealed under vacuum at 673 K during 96 h.

Refinement

The structure was refined using an anisotropic approximation and converged at an reliability factor R(F) = 0.034. Analyses of the difference Fourier maps revealed positive and negative residual peaks around the Hg atom. Fourth-order tensors in the Gram-Charlier expansion (Johnson & Levy, 1974) of the mercury displacement factor were used to describe the electron density around this site. The resulting R value dropped to 0.025 for only five additional parameters. Refinement of the occupancy factor of the Hg atom led to the final composition Hg0.973 (3)Mo6S8.

Figures

Fig. 1.
: View of HgMo6S8 along [110].
Fig. 2.
: Plot showing the atom-numbering scheme and the interunit linkage of the (Mo6S8)S6 cluster units. Displacement ellipsoids are drawn at the 97% probability level.

Crystal data

Hg0.973Mo6S8Dx = 6.204 (1) Mg m3
Mr = 1027.3Mo Kα radiation, λ = 0.71069 Å
Trigonal, R3Cell parameters from 7043 reflections
Hall symbol: -R 3θ = 2.0–42.1°
a = 9.4319 (3) ŵ = 21.62 mm1
c = 10.7028 (3) ÅT = 293 K
V = 824.57 (4) Å3Truncated cube, black
Z = 30.08 × 0.07 × 0.06 mm
F(000) = 1374

Data collection

Nonius KappaCCD diffractometer1121 independent reflections
Radiation source: fine-focus sealed tube1069 reflections with I > 2σ(I)
horizontally mounted graphite crystalRint = 0.044
Detector resolution: 9 pixels mm-1θmax = 39.8°, θmin = 3.1°
ω– and [var phi]–scansh = −16→16
Absorption correction: analytical (de Meulenaer & Tompa, 1965)k = −16→16
Tmin = 0.298, Tmax = 0.384l = −13→19
5784 measured reflections

Refinement

Refinement on FWeighting scheme based on measured s.u.'s w = 1/σ2(F)
R[F2 > 2σ(F2)] = 0.025(Δ/σ)max = 0.001
wR(F2) = 0.026Δρmax = 2.64 e Å3
S = 1.74Δρmin = −1.57 e Å3
1121 reflectionsExtinction correction: B-C type 1 Lorentzian isotropic (Becker & Coppens, 1974)
31 parametersExtinction coefficient: 0.020681

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)

xyzUiso*/UeqOcc. (<1)
Hg10000.0339 (4)0.973 (3)
Mo1−0.01555 (2)−0.17363 (2)−0.394419 (15)0.00748 (7)
S100−0.22344 (8)0.0113 (2)
S2−0.03460 (6)−0.31591 (7)−0.58775 (4)0.00933 (17)

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
Hg10.0384 (4)0.0384 (4)0.0249 (6)0.0192 (2)00
Mo10.00780 (9)0.00831 (9)0.00617 (10)0.00391 (6)0.00003 (5)−0.00036 (5)
S10.0126 (2)0.0126 (2)0.0088 (3)0.00628 (12)00
S20.0097 (2)0.0096 (2)0.0087 (2)0.00476 (17)0.00067 (15)−0.00032 (15)

Geometric parameters (Å, °)

Hg1—S12.3914 (8)Mo1—Mo1ix2.7184 (3)
Hg1—S1i2.3914 (8)Mo1—Mo1x2.7515 (3)
Hg1—S2ii3.2056 (4)Mo1—Mo1xi2.7184 (4)
Hg1—S2iii3.2056 (4)Mo1—Mo1xii2.7515 (2)
Hg1—S2iv3.2056 (7)Mo1—S12.4108 (7)
Hg1—S2v3.2056 (7)Mo1—S22.4236 (6)
Hg1—S2vi3.2056 (8)Mo1—S2xiii2.4896 (8)
Hg1—S2vii3.2056 (8)Mo1—S2x2.4933 (6)
Mo1—Mo1viii3.8679 (3)Mo1—S2xii2.4340 (8)
Mo1—Mo1iii3.2131 (2)
S1—Hg1—S1i180Mo1x—Mo1—Mo1iii97.693 (7)
S1—Hg1—S2ii105.278 (8)Mo1x—Mo1—Mo1ix90
S1—Hg1—S2iii74.722 (8)Mo1x—Mo1—Mo1xi60.398 (8)
S1—Hg1—S2iv105.278 (9)Mo1x—Mo1—Mo1xii59.205 (7)
S1—Hg1—S2v74.722 (9)Mo1x—Mo1—S1115.964 (15)
S1—Hg1—S2vi105.278 (9)Mo1x—Mo1—S255.677 (18)
S1—Hg1—S2vii74.722 (9)Mo1x—Mo1—S2xiii138.626 (14)
S1i—Hg1—S1180Mo1x—Mo1—S2x54.776 (13)
S1i—Hg1—S2ii74.722 (8)Mo1x—Mo1—S2xii114.515 (14)
S1i—Hg1—S2iii105.278 (8)Mo1xi—Mo1—Mo1iii96.739 (8)
S1i—Hg1—S2iv74.722 (9)Mo1xi—Mo1—Mo1ix60.000 (8)
S1i—Hg1—S2v105.278 (9)Mo1xi—Mo1—Mo1x60.398 (8)
S1i—Hg1—S2vi74.722 (9)Mo1xi—Mo1—Mo1xii90
S1i—Hg1—S2vii105.278 (9)Mo1xi—Mo1—S155.682 (12)
S2ii—Hg1—S2iii180Mo1xi—Mo1—S2116.065 (18)
S2ii—Hg1—S2iv113.319 (18)Mo1xi—Mo1—S2xiii135.971 (18)
S2ii—Hg1—S2v66.681 (18)Mo1xi—Mo1—S2x55.48 (2)
S2ii—Hg1—S2vi113.319 (17)Mo1xi—Mo1—S2xii117.362 (19)
S2ii—Hg1—S2vii66.681 (17)Mo1xii—Mo1—Mo1iii148.317 (7)
S2iii—Hg1—S2ii180Mo1xii—Mo1—Mo1ix60.398 (6)
S2iii—Hg1—S2iv66.681 (18)Mo1xii—Mo1—Mo1x59.205 (7)
S2iii—Hg1—S2v113.319 (18)Mo1xii—Mo1—Mo1xi90
S2iii—Hg1—S2vi66.681 (17)Mo1xii—Mo1—S1115.964 (13)
S2iii—Hg1—S2vii113.319 (17)Mo1xii—Mo1—S257.184 (12)
S2iv—Hg1—S2ii113.319 (18)Mo1xii—Mo1—S2xiii133.837 (19)
S2iv—Hg1—S2iii66.681 (18)Mo1xii—Mo1—S2x113.894 (15)
S2iv—Hg1—S2v180Mo1xii—Mo1—S2xii55.318 (14)
S2iv—Hg1—S2vi113.319 (19)S1—Mo1—S2170.65 (2)
S2iv—Hg1—S2vii66.681 (19)S1—Mo1—S2xiii93.53 (2)
S2v—Hg1—S2ii66.681 (18)S1—Mo1—S2x90.323 (17)
S2v—Hg1—S2iii113.319 (18)S1—Mo1—S2xii91.758 (14)
S2v—Hg1—S2iv180S2—Mo1—S2xiii95.79 (2)
S2v—Hg1—S2vi66.681 (19)S2—Mo1—S2x87.39 (2)
S2v—Hg1—S2vii113.319 (19)S2—Mo1—S2xii88.750 (19)
S2vi—Hg1—S2ii113.319 (17)S2xiii—Mo1—S295.79 (2)
S2vi—Hg1—S2iii66.681 (17)S2xiii—Mo1—S2x99.70 (2)
S2vi—Hg1—S2iv113.319 (19)S2xiii—Mo1—S2xii91.39 (2)
S2vi—Hg1—S2v66.681 (19)S2x—Mo1—S287.39 (2)
S2vi—Hg1—S2vii180S2x—Mo1—S2xiii99.70 (2)
S2vii—Hg1—S2ii66.681 (17)S2x—Mo1—S2xii168.58 (2)
S2vii—Hg1—S2iii113.319 (17)S2xii—Mo1—S288.750 (19)
S2vii—Hg1—S2iv66.681 (19)S2xii—Mo1—S2xiii91.39 (2)
S2vii—Hg1—S2v113.319 (19)S2xii—Mo1—S2x168.58 (2)
S2vii—Hg1—S2vi180Hg1—S1—Mo1139.382 (14)
Mo1viii—Mo1—Mo1iii133.459 (8)Hg1—S1—Mo1ix139.382 (13)
Mo1viii—Mo1—S185.136 (14)Hg1—S1—Mo1xi139.382 (14)
Mo1viii—Mo1—S285.600 (16)Mo1—S1—Mo1ix68.64 (2)
Mo1viii—Mo1—S2xiii176.394 (13)Mo1—S1—Mo1xi68.64 (2)
Mo1viii—Mo1—S2x83.677 (18)Mo1ix—S1—Mo168.64 (2)
Mo1viii—Mo1—S2xii85.310 (16)Mo1ix—S1—Mo1xi68.64 (2)
Mo1iii—Mo1—Mo1viii133.459 (8)Mo1xi—S1—Mo168.64 (2)
Mo1iii—Mo1—Mo1ix147.479 (10)Mo1xi—S1—Mo1ix68.64 (2)
Mo1iii—Mo1—Mo1x97.693 (7)Hg1xiv—S2—Mo1125.450 (18)
Mo1iii—Mo1—Mo1xi96.739 (8)Hg1xiv—S2—Mo1x98.407 (18)
Mo1iii—Mo1—Mo1xii148.317 (7)Hg1xiv—S2—Mo1xv97.225 (18)
Mo1iii—Mo1—S192.988 (11)Hg1xiv—S2—Mo1xii156.59 (2)
Mo1iii—Mo1—S292.457 (12)Mo1—S2—Mo1x69.005 (19)
Mo1iii—Mo1—S2xiii49.898 (13)Mo1—S2—Mo1xv132.74 (2)
Mo1iii—Mo1—S2x49.797 (18)Mo1—S2—Mo1xii68.041 (15)
Mo1iii—Mo1—S2xii141.203 (18)Mo1x—S2—Mo169.005 (19)
Mo1ix—Mo1—Mo1iii147.479 (10)Mo1x—S2—Mo1xv129.09 (2)
Mo1ix—Mo1—Mo1x90Mo1x—S2—Mo1xii66.955 (19)
Mo1ix—Mo1—Mo1xi60.000 (8)Mo1xv—S2—Mo1132.74 (2)
Mo1ix—Mo1—Mo1xii60.398 (6)Mo1xv—S2—Mo1x129.09 (2)
Mo1ix—Mo1—S155.682 (11)Mo1xv—S2—Mo1xii80.305 (15)
Mo1ix—Mo1—S2117.489 (13)Mo1xii—S2—Mo168.041 (15)
Mo1ix—Mo1—S2xiii131.337 (14)Mo1xii—S2—Mo1x66.955 (19)
Mo1ix—Mo1—S2x115.28 (2)Mo1xii—S2—Mo1xv80.305 (15)
Mo1ix—Mo1—S2xii57.566 (18)

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

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: WM2226).

References

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