inorganic compounds
The Chevrel phase HgMo_{6}S_{8}
^{a}Laboratoire de Chimie du Solide et Inorganique Moléculaire, URA CNRS No. 6511, Université de Rennes I, Avenue du Général Leclerc, 35042 Rennes CEDEX, France
^{*}Correspondence email: Patrick.Gougeon@univrennes1.fr
The _{6}S_{8}, mercury(II) hexamolybdenum octasulfide, is based on (Mo_{6}S_{8})S_{6} cluster units ( symmetry) interconnected through interunit Mo—S bonds. The Hg^{2+} 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 and 3 symmetry, respectively. of the occupancy factor of the Hg atom led to the composition Hg_{0.973 (3)}Mo_{6}S_{8}.
of HgMoRelated literature
For isotypic structures, see: Chevrel & Sergent (1982). For a previous report on the title compound as a polycrystalline material, see: Tarascon et al. (1983). For crystallographic background, see: Becker & Coppens (1974); Johnson & Levy (1974).
Experimental
Crystal data

Refinement

Data collection: COLLECT (Nonius, 1998); cell COLLECT; data reduction: EVALCCD (Duisenberg et al., 2003); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: JANA2000 (Petříček & Dušek, 2000); molecular graphics: DIAMOND (Bergerhoff, 1996); software used to prepare material for publication: JANA2000.
Supporting information
10.1107/S1600536809012495/wm2226sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536809012495/wm2226Isup2.hkl
HgMo_{6}S_{8} was obtained in three steps involving, first, the syntheses of singlecrystal of InMo_{6}S_{8} by solid state reaction, then the preparation of the binary compound Mo_{6}S_{8} by 'chimie douce' methods and, finally, the synthesis of the title compound by inserting mercury into the Mo_{6}S_{8} host structure at low temperatures. Single crystals of InMo_{6}S_{8} were obtained from a stoichiometric mixture of In_{2}S_{3}, MoS_{2} and Mo. All handlings of materials were done in an argonfilled
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 arcwelding 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. Mo_{6}S_{8} was obtained by oxidation of singlecrystals of InMo_{6}S_{8} 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 InI_{3} and I_{2} were obtained at the cooler end of the tube. Finally, HgMo_{6}S_{8} was prepared by diffusion of mercury into crystals of Mo_{6}S_{8} in a silica glass tube sealed under vacuum at 673 K during 96 h.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. Fourthorder tensors in the GramCharlier 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.
of the occupancy factor of the Hg atom led to the final composition Hg_{0.973 (3)}Mo_{6}S_{8}.Data collection: COLLECT (Nonius, 1998); cell
COLLECT (Nonius, 1998); data reduction: EVALCCD (Duisenberg et al., 2003); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: Jana2000 (Petříček & Dušek, 2000); molecular graphics: DIAMOND (Bergerhoff, 1996); software used to prepare material for publication: Jana2000 (Petříček & Dušek, 2000).Hg_{0.973}Mo_{6}S_{8}  D_{x} = 6.204 (1) Mg m^{−}^{3} 
M_{r} = 1027.3  Mo Kα radiation, λ = 0.71069 Å 
Trigonal, R3  Cell parameters from 7043 reflections 
Hall symbol: R 3  θ = 2.0–42.1° 
a = 9.4319 (3) Å  µ = 21.62 mm^{−}^{1} 
c = 10.7028 (3) Å  T = 293 K 
V = 824.57 (4) Å^{3}  Truncated cube, black 
Z = 3  0.08 × 0.07 × 0.06 mm 
F(000) = 1374 
Nonius KappaCCD diffractometer  1121 independent reflections 
Radiation source: finefocus sealed tube  1069 reflections with I > 2σ(I) 
Horizontally mounted graphite crystal monochromator  R_{int} = 0.044 
Detector resolution: 9 pixels mm^{1}  θ_{max} = 39.8°, θ_{min} = 3.1° 
ω– and ϕ–scans  h = −16→16 
Absorption correction: analytical (de Meulenaer & Tompa, 1965)  k = −16→16 
T_{min} = 0.298, T_{max} = 0.384  l = −13→19 
5784 measured reflections 
Refinement on F  Weighting scheme based on measured s.u.'s w = 1/σ^{2}(F) 
R[F^{2} > 2σ(F^{2})] = 0.025  (Δ/σ)_{max} = 0.001 
wR(F^{2}) = 0.026  Δρ_{max} = 2.64 e Å^{−}^{3} 
S = 1.74  Δρ_{min} = −1.57 e Å^{−}^{3} 
1121 reflections  Extinction correction: BC type 1 Lorentzian isotropic (Becker & Coppens, 1974) 
31 parameters  Extinction coefficient: 0.020681 
Hg_{0.973}Mo_{6}S_{8}  Z = 3 
M_{r} = 1027.3  Mo Kα radiation 
Trigonal, R3  µ = 21.62 mm^{−}^{1} 
a = 9.4319 (3) Å  T = 293 K 
c = 10.7028 (3) Å  0.08 × 0.07 × 0.06 mm 
V = 824.57 (4) Å^{3} 
Nonius KappaCCD diffractometer  1121 independent reflections 
Absorption correction: analytical (de Meulenaer & Tompa, 1965)  1069 reflections with I > 2σ(I) 
T_{min} = 0.298, T_{max} = 0.384  R_{int} = 0.044 
5784 measured reflections 
R[F^{2} > 2σ(F^{2})] = 0.025  31 parameters 
wR(F^{2}) = 0.026  Δρ_{max} = 2.64 e Å^{−}^{3} 
S = 1.74  Δρ_{min} = −1.57 e Å^{−}^{3} 
1121 reflections 
x  y  z  U_{iso}*/U_{eq}  Occ. (<1)  
Hg1  0  0  0  0.0339 (4)  0.973 (3) 
Mo1  −0.01555 (2)  −0.17363 (2)  −0.394419 (15)  0.00748 (7)  
S1  0  0  −0.22344 (8)  0.0113 (2)  
S2  −0.03460 (6)  −0.31591 (7)  −0.58775 (4)  0.00933 (17) 
U^{11}  U^{22}  U^{33}  U^{12}  U^{13}  U^{23}  
Hg1  0.0384 (4)  0.0384 (4)  0.0249 (6)  0.0192 (2)  0  0 
Mo1  0.00780 (9)  0.00831 (9)  0.00617 (10)  0.00391 (6)  0.00003 (5)  −0.00036 (5) 
S1  0.0126 (2)  0.0126 (2)  0.0088 (3)  0.00628 (12)  0  0 
S2  0.0097 (2)  0.0096 (2)  0.0087 (2)  0.00476 (17)  0.00067 (15)  −0.00032 (15) 
Hg1—S1  2.3914 (8)  Mo1—Mo1^{ix}  2.7184 (3) 
Hg1—S1^{i}  2.3914 (8)  Mo1—Mo1^{x}  2.7515 (3) 
Hg1—S2^{ii}  3.2056 (4)  Mo1—Mo1^{xi}  2.7184 (4) 
Hg1—S2^{iii}  3.2056 (4)  Mo1—Mo1^{xii}  2.7515 (2) 
Hg1—S2^{iv}  3.2056 (7)  Mo1—S1  2.4108 (7) 
Hg1—S2^{v}  3.2056 (7)  Mo1—S2  2.4236 (6) 
Hg1—S2^{vi}  3.2056 (8)  Mo1—S2^{xiii}  2.4896 (8) 
Hg1—S2^{vii}  3.2056 (8)  Mo1—S2^{x}  2.4933 (6) 
Mo1—Mo1^{viii}  3.8679 (3)  Mo1—S2^{xii}  2.4340 (8) 
Mo1—Mo1^{iii}  3.2131 (2)  
S1—Hg1—S1^{i}  180  Mo1^{x}—Mo1—Mo1^{iii}  97.693 (7) 
S1—Hg1—S2^{ii}  105.278 (8)  Mo1^{x}—Mo1—Mo1^{ix}  90 
S1—Hg1—S2^{iii}  74.722 (8)  Mo1^{x}—Mo1—Mo1^{xi}  60.398 (8) 
S1—Hg1—S2^{iv}  105.278 (9)  Mo1^{x}—Mo1—Mo1^{xii}  59.205 (7) 
S1—Hg1—S2^{v}  74.722 (9)  Mo1^{x}—Mo1—S1  115.964 (15) 
S1—Hg1—S2^{vi}  105.278 (9)  Mo1^{x}—Mo1—S2  55.677 (18) 
S1—Hg1—S2^{vii}  74.722 (9)  Mo1^{x}—Mo1—S2^{xiii}  138.626 (14) 
S1^{i}—Hg1—S1  180  Mo1^{x}—Mo1—S2^{x}  54.776 (13) 
S1^{i}—Hg1—S2^{ii}  74.722 (8)  Mo1^{x}—Mo1—S2^{xii}  114.515 (14) 
S1^{i}—Hg1—S2^{iii}  105.278 (8)  Mo1^{xi}—Mo1—Mo1^{iii}  96.739 (8) 
S1^{i}—Hg1—S2^{iv}  74.722 (9)  Mo1^{xi}—Mo1—Mo1^{ix}  60.000 (8) 
S1^{i}—Hg1—S2^{v}  105.278 (9)  Mo1^{xi}—Mo1—Mo1^{x}  60.398 (8) 
S1^{i}—Hg1—S2^{vi}  74.722 (9)  Mo1^{xi}—Mo1—Mo1^{xii}  90 
S1^{i}—Hg1—S2^{vii}  105.278 (9)  Mo1^{xi}—Mo1—S1  55.682 (12) 
S2^{ii}—Hg1—S2^{iii}  180  Mo1^{xi}—Mo1—S2  116.065 (18) 
S2^{ii}—Hg1—S2^{iv}  113.319 (18)  Mo1^{xi}—Mo1—S2^{xiii}  135.971 (18) 
S2^{ii}—Hg1—S2^{v}  66.681 (18)  Mo1^{xi}—Mo1—S2^{x}  55.48 (2) 
S2^{ii}—Hg1—S2^{vi}  113.319 (17)  Mo1^{xi}—Mo1—S2^{xii}  117.362 (19) 
S2^{ii}—Hg1—S2^{vii}  66.681 (17)  Mo1^{xii}—Mo1—Mo1^{iii}  148.317 (7) 
S2^{iii}—Hg1—S2^{ii}  180  Mo1^{xii}—Mo1—Mo1^{ix}  60.398 (6) 
S2^{iii}—Hg1—S2^{iv}  66.681 (18)  Mo1^{xii}—Mo1—Mo1^{x}  59.205 (7) 
S2^{iii}—Hg1—S2^{v}  113.319 (18)  Mo1^{xii}—Mo1—Mo1^{xi}  90 
S2^{iii}—Hg1—S2^{vi}  66.681 (17)  Mo1^{xii}—Mo1—S1  115.964 (13) 
S2^{iii}—Hg1—S2^{vii}  113.319 (17)  Mo1^{xii}—Mo1—S2  57.184 (12) 
S2^{iv}—Hg1—S2^{ii}  113.319 (18)  Mo1^{xii}—Mo1—S2^{xiii}  133.837 (19) 
S2^{iv}—Hg1—S2^{iii}  66.681 (18)  Mo1^{xii}—Mo1—S2^{x}  113.894 (15) 
S2^{iv}—Hg1—S2^{v}  180  Mo1^{xii}—Mo1—S2^{xii}  55.318 (14) 
S2^{iv}—Hg1—S2^{vi}  113.319 (19)  S1—Mo1—S2  170.65 (2) 
S2^{iv}—Hg1—S2^{vii}  66.681 (19)  S1—Mo1—S2^{xiii}  93.53 (2) 
S2^{v}—Hg1—S2^{ii}  66.681 (18)  S1—Mo1—S2^{x}  90.323 (17) 
S2^{v}—Hg1—S2^{iii}  113.319 (18)  S1—Mo1—S2^{xii}  91.758 (14) 
S2^{v}—Hg1—S2^{iv}  180  S2—Mo1—S2^{xiii}  95.79 (2) 
S2^{v}—Hg1—S2^{vi}  66.681 (19)  S2—Mo1—S2^{x}  87.39 (2) 
S2^{v}—Hg1—S2^{vii}  113.319 (19)  S2—Mo1—S2^{xii}  88.750 (19) 
S2^{vi}—Hg1—S2^{ii}  113.319 (17)  S2^{xiii}—Mo1—S2  95.79 (2) 
S2^{vi}—Hg1—S2^{iii}  66.681 (17)  S2^{xiii}—Mo1—S2^{x}  99.70 (2) 
S2^{vi}—Hg1—S2^{iv}  113.319 (19)  S2^{xiii}—Mo1—S2^{xii}  91.39 (2) 
S2^{vi}—Hg1—S2^{v}  66.681 (19)  S2^{x}—Mo1—S2  87.39 (2) 
S2^{vi}—Hg1—S2^{vii}  180  S2^{x}—Mo1—S2^{xiii}  99.70 (2) 
S2^{vii}—Hg1—S2^{ii}  66.681 (17)  S2^{x}—Mo1—S2^{xii}  168.58 (2) 
S2^{vii}—Hg1—S2^{iii}  113.319 (17)  S2^{xii}—Mo1—S2  88.750 (19) 
S2^{vii}—Hg1—S2^{iv}  66.681 (19)  S2^{xii}—Mo1—S2^{xiii}  91.39 (2) 
S2^{vii}—Hg1—S2^{v}  113.319 (19)  S2^{xii}—Mo1—S2^{x}  168.58 (2) 
S2^{vii}—Hg1—S2^{vi}  180  Hg1—S1—Mo1  139.382 (14) 
Mo1^{viii}—Mo1—Mo1^{iii}  133.459 (8)  Hg1—S1—Mo1^{ix}  139.382 (13) 
Mo1^{viii}—Mo1—S1  85.136 (14)  Hg1—S1—Mo1^{xi}  139.382 (14) 
Mo1^{viii}—Mo1—S2  85.600 (16)  Mo1—S1—Mo1^{ix}  68.64 (2) 
Mo1^{viii}—Mo1—S2^{xiii}  176.394 (13)  Mo1—S1—Mo1^{xi}  68.64 (2) 
Mo1^{viii}—Mo1—S2^{x}  83.677 (18)  Mo1^{ix}—S1—Mo1  68.64 (2) 
Mo1^{viii}—Mo1—S2^{xii}  85.310 (16)  Mo1^{ix}—S1—Mo1^{xi}  68.64 (2) 
Mo1^{iii}—Mo1—Mo1^{viii}  133.459 (8)  Mo1^{xi}—S1—Mo1  68.64 (2) 
Mo1^{iii}—Mo1—Mo1^{ix}  147.479 (10)  Mo1^{xi}—S1—Mo1^{ix}  68.64 (2) 
Mo1^{iii}—Mo1—Mo1^{x}  97.693 (7)  Hg1^{xiv}—S2—Mo1  125.450 (18) 
Mo1^{iii}—Mo1—Mo1^{xi}  96.739 (8)  Hg1^{xiv}—S2—Mo1^{x}  98.407 (18) 
Mo1^{iii}—Mo1—Mo1^{xii}  148.317 (7)  Hg1^{xiv}—S2—Mo1^{xv}  97.225 (18) 
Mo1^{iii}—Mo1—S1  92.988 (11)  Hg1^{xiv}—S2—Mo1^{xii}  156.59 (2) 
Mo1^{iii}—Mo1—S2  92.457 (12)  Mo1—S2—Mo1^{x}  69.005 (19) 
Mo1^{iii}—Mo1—S2^{xiii}  49.898 (13)  Mo1—S2—Mo1^{xv}  132.74 (2) 
Mo1^{iii}—Mo1—S2^{x}  49.797 (18)  Mo1—S2—Mo1^{xii}  68.041 (15) 
Mo1^{iii}—Mo1—S2^{xii}  141.203 (18)  Mo1^{x}—S2—Mo1  69.005 (19) 
Mo1^{ix}—Mo1—Mo1^{iii}  147.479 (10)  Mo1^{x}—S2—Mo1^{xv}  129.09 (2) 
Mo1^{ix}—Mo1—Mo1^{x}  90  Mo1^{x}—S2—Mo1^{xii}  66.955 (19) 
Mo1^{ix}—Mo1—Mo1^{xi}  60.000 (8)  Mo1^{xv}—S2—Mo1  132.74 (2) 
Mo1^{ix}—Mo1—Mo1^{xii}  60.398 (6)  Mo1^{xv}—S2—Mo1^{x}  129.09 (2) 
Mo1^{ix}—Mo1—S1  55.682 (11)  Mo1^{xv}—S2—Mo1^{xii}  80.305 (15) 
Mo1^{ix}—Mo1—S2  117.489 (13)  Mo1^{xii}—S2—Mo1  68.041 (15) 
Mo1^{ix}—Mo1—S2^{xiii}  131.337 (14)  Mo1^{xii}—S2—Mo1^{x}  66.955 (19) 
Mo1^{ix}—Mo1—S2^{x}  115.28 (2)  Mo1^{xii}—S2—Mo1^{xv}  80.305 (15) 
Mo1^{ix}—Mo1—S2^{xii}  57.566 (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, x−y−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) x−y−1/3, x+1/3, −z−2/3; (viii) −x, −y, −z−1; (ix) −y, x−y, z; (x) y, −x+y, −z−1; (xi) −x+y, −x, z; (xii) x−y, x, −z−1; (xiii) −y−1/3, x−y−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. 
Experimental details
Crystal data  
Chemical formula  Hg_{0.973}Mo_{6}S_{8} 
M_{r}  1027.3 
Crystal system, space group  Trigonal, R3 
Temperature (K)  293 
a, c (Å)  9.4319 (3), 10.7028 (3) 
V (Å^{3})  824.57 (4) 
Z  3 
Radiation type  Mo Kα 
µ (mm^{−}^{1})  21.62 
Crystal size (mm)  0.08 × 0.07 × 0.06 
Data collection  
Diffractometer  Nonius KappaCCD diffractometer 
Absorption correction  Analytical (de Meulenaer & Tompa, 1965) 
T_{min}, T_{max}  0.298, 0.384 
No. of measured, independent and observed [I > 2σ(I)] reflections  5784, 1121, 1069 
R_{int}  0.044 
(sin θ/λ)_{max} (Å^{−}^{1})  0.900 
Refinement  
R[F^{2} > 2σ(F^{2})], wR(F^{2}), S  0.025, 0.026, 1.74 
No. of reflections  1121 
No. of parameters  31 
No. of restraints  ? 
Δρ_{max}, Δρ_{min} (e Å^{−}^{3})  2.64, −1.57 
Computer programs: COLLECT (Nonius, 1998), EVALCCD (Duisenberg et al., 2003), SIR97 (Altomare et al., 1999), Jana2000 (Petříček & Dušek, 2000), DIAMOND (Bergerhoff, 1996).
Hg1—S1  2.3914 (8)  Mo1—S2  2.4236 (6) 
Mo1—Mo1^{i}  2.7184 (3)  Mo1—S2^{iii}  2.4896 (8) 
Mo1—Mo1^{ii}  2.7515 (3)  Mo1—S2^{ii}  2.4933 (6) 
Mo1—S1  2.4108 (7)  Mo1—S2^{iv}  2.4340 (8) 
Symmetry codes: (i) −y, x−y, z; (ii) y, −x+y, −z−1; (iii) −y−1/3, x−y−2/3, z+1/3; (iv) x−y, x, −z−1. 
Acknowledgements
Intensity data were collected on the Nonius KappaCCD Xray diffactometer system of the Centre de diffractométrie de l'Université de Rennes I (www.cdifx.univrennes1.fr).
References
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This is an openaccess article distributed under the terms of the Creative Commons Attribution (CCBY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
The superconducting compound HgMo_{6}S_{8} 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 HgMo_{6}S_{8} that has been determined from singlecrystal Xray diffraction data. The title compound is isostructural with the hexagonal Chevrel phases MMo_{6}X_{8} 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 Mo_{6} clusters surrounded by fourteen sulfur atoms with eight of them forming a distorted cube (itype ligands) and the remaining six capping the faces of the S_{8} cube (atype ligands). In the structure of HgMo_{6}S_{8}, a part of the chalcogen atoms of the Mo_{6}S^{i}_{8}S^{a}_{6} unit are shared according to the formula Mo_{6}S^{i}_{2}S^{ia}_{6/2}S^{ai}_{6/2} to form the threedimensional Mo—S network. The Mo_{6}S_{8} cluster unit is centered at Wyckoff position 6b (3 symmetry). The Mo—Mo distances within the Mo_{6} clusters are 2.7184 (3) Å for the intratriangle distances (distances within the Mo_{3} triangles formed by the Mo atoms related through the threefold axis) and 2.7515 (3) Å for the intertriangle distances. Each Mo atom is surrounded by five S atoms (4 S1 and 1 S2) forming a distorted squarebased pyramid. The apex of the pyramid is shared with an adjacent unit and thus ensures the threedimensional cohesion. Consequently, each Mo_{6}S_{8} unit is interconnected to 6 Mo_{6}S_{8} units to form the Mo—S framework. It results from this arrangement that the shortest intercluster Mo1—Mo1 distances between the Mo_{6} clusters is 3.2934 (3) Å, indicating only weak metalmetal interaction. The Hg^{2+} cations reside in the large eightcoordinate voids formed by the chalcogen atoms from eight different Mo_{6}S_{8} units. They are covalently bonded to two S2 atoms at a distance of 2.3914 (8) Å.
HgMo_{6}S_{8} was found to be superconducting at 8 K from DCsusceptibility measurements on a batch of single crystals.