inorganic compounds
Tl2Mo9Se11
aSciences Chimiques de Rennes, CSM-INSA, UMR CNRS No. 6226, Université de Rennes I, Avenue du Général Leclerc, 35042 Rennes CEDEX, France
*Correspondence e-mail: Patrick.Gougeon@univ-rennes1.fr
The structure of Tl2Mo9Se11, dithallium nonamolybdenum undecaselenide, is isotypic with Tl2Mo9S11 [Potel et al. (1980). Acta Cryst. B36, 1319–1322]. The structural set-up is characterized by a mixture of Mo6Sei8Sea6 and Mo12Sei14Sea6 cluster units in a 1:1 ratio. Both components are interconnected through interunit Mo—Se bonds. The cluster units are centered at Wyckoff positions 3a and 3b (point-group symmetry .). The two TlI atoms are situated in the voids of the three-dimensional arrangement. Two of the five independent Se atoms and the Tl atoms lie on sites with 3. symmetry (Wyckoff site 6c).
Related literature
For the 2Mo9S11, see: Potel et al. (1980). For details of the i- and a-type ligand notation, see: Schäfer & von Schnering (1964). Ionic radii were compiled by Shannon (1976). For background to the extinction correction, see: Becker & Coppens (1974).
of TlExperimental
Crystal data
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Refinement
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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: JANA2006 (Petříček et al., 2006); molecular graphics: DIAMOND (Brandenburg, 2001); software used to prepare material for publication: JANA2006.
Supporting information
https://doi.org/10.1107/S1600536810026541/wm2368sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810026541/wm2368Isup2.hkl
Single crystals of Tl2Mo9Se11 were prepared from a mixture of MoSe2, TlSe and Mo with the nominal composition Tl2Mo12Se14. Before use, Mo powder was reduced under H2 flowing gas at 1273 K during ten hours in order to eliminate any trace of oxygen. The binaries MoSe2 and TlSe were obtained by heating stoichiometric mixtures of the elements in sealed evacuated silica tubes during about 2 days at 1073 and 573 K, respectively. All handlings of materials were done in an argon-filled
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 48 h, then cooled at 100 K/h down to 1373 K and finally furnace cooled.The highest peak and the deepest hole in the final Fourier map are at 1.67 and 0.83 Å from Tl1 and Se5, respectively.
Potel et al. (1980) reported the
of Tl2Mo9S11 that was the first compound containing a transition metal cluster with a nuclearity higher than 9, namely the trioctahedral Mo12 cluster. The latter cluster, which results from the uniaxial face-sharing of three Mo6 octahedra, coexists with the octahedral Mo6 cluster in equal proportion. We present here the of the isotypic selenide, Tl2Mo9Se11.The Mo—Se framework of Tl2Mo9Se11 consists of an equal mixture of Mo6Sei8Sea6 and Mo12Sei14Sea6 cluster units interconnected through Mo—Se bonds (Fig.1 and 2). Details of the i- and a-type ligand notation were reported by Schäfer & von Schnering (1964). The first unit can be described as an Mo6 octahedron surrounded by 8 face-capping inner Sei and 6 apical Sea ligands. The Mo12 core of the second unit results from the face sharing of 3 octahedral Mo6 clusters. The Mo12 cluster is surrounded by 14 Sei atoms capping the faces of the bioctahedron and 6 apical Sea ligands above the ending Mo atoms. The Mo6Sei8Sea6 and Mo12Sei14Sea6 units are centered at 3a and 3b positions and have point-group symmetry 3. The Mo—Mo distances within the Mo6 clusters are 2.6897 (7) Å for the intra-triangle distances (distances within the Mo3 triangles formed by the Mo1 atoms related through the threefold axis) and 2.7609 (6) Å for the inter-triangle distances. In the sulfide, the two later values are slightly larger, viz. 2.693 (1) and 2.780 (5) Å. The Mo—Mo distances within the Mo12 clusters are 2.6382 (5) and 2.6780 (7) Å for the distances in the triangles formed by the Mo2 and Mo3 atoms, respectively. In Tl2Mo9S11, the corresponding distances are equal to 2.658 (1) and 2.688 (1) Å, respectively. The distances between the triangles formed by the Mo2 and Mo3 atoms are 2.7397 (7) and 2.7901 (7) Å and those between the Mo33 triangles, 2.6796 (6) Å. The average Mo—Mo distance within the Mo12 cluster is similar in Tl2Mo9S11 and Tl2Mo9Se11 and amounts to 2.705 Å. The Se atoms bridge either one (Se1, Se2, Se4 and Se5) or two (Se3) Mo triangular faces of the clusters. Moreover, the Se1 and Se2 atoms are linked to a Mo atom of a neighboring cluster. The Mo—Se bond distances range from 2.5269 (8) to 2.6247 (8) Å within the Mo6Sei8Sea6 unit and from 2.5129 (8) to 2.7025 (8) Å within the Mo12Sei14Sea6 ubit. Each Mo12Sei14Sea6 unit is interconnected to 6 Mo6Sei8Sea6 units (and vice versa) via Mo2—Se1 bonds (respectively Mo1—Se2) to form the three-dimensional Mo—Se framework, the overall connectivity formula of which is Mo12Sei8Sei-a6/2Sea-i6/2, Mo6Sei2Sei-a6/2Sea-i6/2. It results from this arrangement that the shortest intercluster Mo1—Mo2 distance between the Mo6 and Mo12 clusters is 3.4239 (8) Å compared to 3.217 (1) in Tl2Mo9S11, indicating only weak metal-metal interaction. The Tl atoms occupy large voids delimited by four Mo6Sei8Sea6 units and four Mo12Sei14Sea6 units. The Tl1 and Tl2 cations have a very similar environment which consists of seven Se atoms as nearest neighbors with Tl—Se distances in the ranges 3.0737 (10) - 3.5840 (6) Å and 3.0483 (9) - 3.4032 (6) Å for the Tl1 and Tl2 sites, respectively. These seven Se atoms form a monocapped octahedron compressed along the threefold axis. Three additional Se atoms at 4.3543 (6) and 4.2446 (6) Å from Tl1 and Tl2, respectively, are also observed (Figure 3). The average Tl—Se values are 3.72 and 3.54 Å for the Tl1 and Tl2 sites, respectively. Values of 3.57 and 3.68 Å are expected from the sum of the ionic radii for Se2- and Tl+ for coordination numbers 8 and 12 (Shannon, 1976).
For the
of Tl2Mo9S11, see: Potel et al. (1980). For details of the i- and a-type ligand notation, see: Schäfer & von Schnering (1964). Ionic radii were compiled by Shannon (1976). For background to the extinction correction, see: Becker & Coppens (1974).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: JANA2006 (Petříček et al., 2006); molecular graphics: DIAMOND (Brandenburg, 2001); software used to prepare material for publication: JANA2006 (Petříček et al., 2006).Fig. 1. : View of Tl2Mo9Se11 along [110]. | |
Fig. 2. : Plot showing the atom-numbering scheme and the linkage of the Mo12Se14Se6 and Mo6Se8Se6 cluster units. Displacement ellipsoids are drawn at the 97% probability level. Symmetry codes are as in Table 1. | |
Fig. 3. : Environment of the Tl atoms. Symmetry codes are as in Table 1. |
Tl2Mo9Se11 | Dx = 7.321 Mg m−3 |
Mr = 2140.8 | Mo Kα radiation, λ = 0.71069 Å |
Trigonal, R3 | Cell parameters from 10017 reflections |
Hall symbol: -R 3 | θ = 1–40.3° |
a = 9.6212 (1) Å | µ = 42.73 mm−1 |
c = 36.3316 (7) Å | T = 293 K |
V = 2912.55 (7) Å3 | Irregular block, black |
Z = 6 | 0.13 × 0.12 × 0.11 mm |
F(000) = 5484 |
Nonius KappaCCD diffractometer | 4097 independent reflections |
Radiation source: fine-focus sealed tube | 3156 reflections with I > 2σ(I) |
Horizontally mounted graphite crystal monochromator | Rint = 0.087 |
Detector resolution: 9 pixels mm-1 | θmax = 40.2°, θmin = 1.7° |
φ– and ω–scans | h = −16→17 |
Absorption correction: multi-scan (PLATON; Spek, 2009) | k = −16→17 |
Tmin = 0.033, Tmax = 0.108 | l = −58→66 |
21097 measured reflections |
Refinement on F2 | 0 constraints |
R[F > 3σ(F)] = 0.043 | Weighting scheme based on measured s.u.'s w = 1/[σ2(I) + 0.0004I2] |
wR(F) = 0.092 | (Δ/σ)max = 0.033 |
S = 1.37 | Δρmax = 3.92 e Å−3 |
4097 reflections | Δρmin = −2.89 e Å−3 |
69 parameters | Extinction correction: B-C type 1 Gaussian isotropic (Becker & Coppens, 1974) |
0 restraints | Extinction coefficient: 2320 (40) |
Tl2Mo9Se11 | Z = 6 |
Mr = 2140.8 | Mo Kα radiation |
Trigonal, R3 | µ = 42.73 mm−1 |
a = 9.6212 (1) Å | T = 293 K |
c = 36.3316 (7) Å | 0.13 × 0.12 × 0.11 mm |
V = 2912.55 (7) Å3 |
Nonius KappaCCD diffractometer | 4097 independent reflections |
Absorption correction: multi-scan (PLATON; Spek, 2009) | 3156 reflections with I > 2σ(I) |
Tmin = 0.033, Tmax = 0.108 | Rint = 0.087 |
21097 measured reflections |
R[F > 3σ(F)] = 0.043 | 69 parameters |
wR(F) = 0.092 | 0 restraints |
S = 1.37 | Δρmax = 3.92 e Å−3 |
4097 reflections | Δρmin = −2.89 e Å−3 |
x | y | z | Uiso*/Ueq | ||
Tl1 | 0.333333 | 0.666667 | 0.495781 (14) | 0.04933 (17) | |
Tl2 | 0 | 0 | 0.267672 (12) | 0.02611 (11) | |
Mo1 | −0.18022 (5) | 0.31787 (5) | 0.364749 (12) | 0.01129 (13) | |
Mo2 | 0.16529 (5) | 0.15027 (5) | 0.406587 (12) | 0.01120 (13) | |
Mo3 | 0.15606 (5) | −0.00891 (5) | 0.469882 (12) | 0.01087 (13) | |
Se1 | −0.04118 (6) | 0.29911 (6) | 0.306626 (15) | 0.01295 (17) | |
Se2 | 0.03067 (6) | 0.32633 (6) | 0.411871 (15) | 0.01342 (17) | |
Se3 | 0.32150 (6) | 0.30388 (6) | 0.467628 (15) | 0.01463 (17) | |
Se4 | −0.333333 | 0.333333 | 0.41962 (2) | 0.01559 (19) | |
Se5 | 0 | 0 | 0.35157 (2) | 0.01474 (19) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Tl1 | 0.0620 (2) | 0.0620 (2) | 0.0239 (2) | 0.03102 (12) | 0 | 0 |
Tl2 | 0.02704 (13) | 0.02704 (13) | 0.0242 (2) | 0.01352 (7) | 0 | 0 |
Mo1 | 0.01119 (17) | 0.01064 (17) | 0.01168 (17) | 0.00518 (13) | 0.00061 (13) | −0.00028 (13) |
Mo2 | 0.01129 (17) | 0.01096 (17) | 0.01107 (17) | 0.00535 (14) | 0.00023 (13) | 0.00051 (13) |
Mo3 | 0.01081 (16) | 0.01111 (16) | 0.01077 (17) | 0.00553 (13) | 0.00040 (13) | 0.00014 (13) |
Se1 | 0.0120 (2) | 0.0136 (2) | 0.0140 (2) | 0.00691 (17) | 0.00193 (16) | 0.00090 (16) |
Se2 | 0.0145 (2) | 0.0121 (2) | 0.0140 (2) | 0.00685 (17) | −0.00087 (17) | 0.00125 (16) |
Se3 | 0.0121 (2) | 0.0135 (2) | 0.0151 (2) | 0.00408 (17) | 0.00057 (17) | 0.00032 (17) |
Se4 | 0.0181 (2) | 0.0181 (2) | 0.0106 (3) | 0.00905 (12) | 0 | 0 |
Se5 | 0.0167 (2) | 0.0167 (2) | 0.0108 (3) | 0.00835 (11) | 0 | 0 |
Tl1—Tl2i | 3.5164 (7) | Mo1—Mo1xiv | 2.7609 (7) |
Tl1—Se2 | 4.3543 (6) | Mo1—Mo2viii | 3.4239 (8) |
Tl1—Se2ii | 4.3543 (7) | Mo1—Se1 | 2.5540 (8) |
Tl1—Se2iii | 4.3543 (7) | Mo1—Se1x | 2.6143 (8) |
Tl1—Se3 | 3.5840 (6) | Mo1—Se1xiv | 2.5757 (6) |
Tl1—Se3ii | 3.5840 (5) | Mo1—Se2 | 2.6247 (8) |
Tl1—Se3iii | 3.5840 (8) | Mo1—Se4 | 2.5269 (8) |
Tl1—Se3iv | 3.4547 (6) | Mo2—Mo2viii | 2.6382 (6) |
Tl1—Se3v | 3.4547 (8) | Mo2—Mo2ix | 2.6382 (5) |
Tl1—Se3vi | 3.4547 (5) | Mo2—Mo3 | 2.7397 (7) |
Tl1—Se4vii | 3.0737 (10) | Mo2—Mo3viii | 2.7901 (7) |
Tl2—Se1 | 3.4032 (7) | Mo2—Se1i | 2.6597 (6) |
Tl2—Se1viii | 3.4032 (6) | Mo2—Se2 | 2.6034 (9) |
Tl2—Se1ix | 3.4032 (8) | Mo2—Se2ix | 2.6124 (10) |
Tl2—Se2i | 3.1441 (4) | Mo2—Se3 | 2.6721 (6) |
Tl2—Se2x | 3.1441 (7) | Mo2—Se5 | 2.5129 (8) |
Tl2—Se2xi | 3.1441 (7) | Mo3—Mo3viii | 2.6780 (9) |
Tl2—Se3i | 4.2446 (7) | Mo3—Mo3ix | 2.6780 (7) |
Tl2—Se3x | 4.2446 (6) | Mo3—Mo3xv | 2.6796 (6) |
Tl2—Se3xi | 4.2446 (8) | Mo3—Mo3vi | 2.6796 (7) |
Tl2—Se5 | 3.0483 (9) | Mo3—Se2ix | 2.5634 (8) |
Mo1—Mo1xii | 2.6897 (9) | Mo3—Se3 | 2.6090 (6) |
Mo1—Mo1xiii | 2.6897 (7) | Mo3—Se3ix | 2.6112 (6) |
Mo1—Mo1x | 2.7609 (6) | Mo3—Se3xv | 2.7025 (8) |
Mo1xii—Mo1—Mo1xiii | 60.000 (18) | Mo2—Mo3—Mo3ix | 90.11 (2) |
Mo1xii—Mo1—Mo1x | 90 | Mo2—Mo3—Mo3xv | 147.49 (3) |
Mo1xii—Mo1—Mo1xiv | 60.85 (2) | Mo2—Mo3—Mo3vi | 111.83 (2) |
Mo1xiii—Mo1—Mo1x | 60.849 (16) | Mo2ix—Mo3—Mo3viii | 89.04 (2) |
Mo1xiii—Mo1—Mo1xiv | 90 | Mo2ix—Mo3—Mo3ix | 60.094 (17) |
Mo1x—Mo1—Mo1xiv | 58.302 (17) | Mo2ix—Mo3—Mo3xv | 110.275 (17) |
Mo2viii—Mo2—Mo2ix | 60.00 (2) | Mo2ix—Mo3—Mo3vi | 145.90 (3) |
Mo2viii—Mo2—Mo3 | 90.953 (18) | Mo3viii—Mo3—Mo3ix | 60.000 (18) |
Mo2viii—Mo2—Mo3viii | 60.546 (16) | Mo3viii—Mo3—Mo3xv | 90 |
Mo2ix—Mo2—Mo3 | 62.472 (16) | Mo3viii—Mo3—Mo3vi | 60.02 (2) |
Mo2ix—Mo2—Mo3viii | 89.850 (19) | Mo3ix—Mo3—Mo3xv | 60.019 (16) |
Mo3—Mo2—Mo3viii | 57.92 (2) | Mo3ix—Mo3—Mo3vi | 90 |
Mo2—Mo3—Mo2ix | 56.983 (15) | Mo3xv—Mo3—Mo3vi | 59.962 (18) |
Mo2—Mo3—Mo3viii | 61.982 (19) |
Symmetry codes: (i) −x+1/3, −y+2/3, −z+2/3; (ii) −y+1, x−y+1, z; (iii) −x+y, −x+1, z; (iv) −x+1, −y+1, −z+1; (v) y, −x+y+1, −z+1; (vi) x−y, x, −z+1; (vii) −x, −y+1, −z+1; (viii) −y, x−y, z; (ix) −x+y, −x, z; (x) y−2/3, −x+y−1/3, −z+2/3; (xi) x−y+1/3, x−1/3, −z+2/3; (xii) −y, x−y+1, z; (xiii) −x+y−1, −x, z; (xiv) x−y+1/3, x+2/3, −z+2/3; (xv) y, −x+y, −z+1. |
Experimental details
Crystal data | |
Chemical formula | Tl2Mo9Se11 |
Mr | 2140.8 |
Crystal system, space group | Trigonal, R3 |
Temperature (K) | 293 |
a, c (Å) | 9.6212 (1), 36.3316 (7) |
V (Å3) | 2912.55 (7) |
Z | 6 |
Radiation type | Mo Kα |
µ (mm−1) | 42.73 |
Crystal size (mm) | 0.13 × 0.12 × 0.11 |
Data collection | |
Diffractometer | Nonius KappaCCD |
Absorption correction | Multi-scan (PLATON; Spek, 2009) |
Tmin, Tmax | 0.033, 0.108 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 21097, 4097, 3156 |
Rint | 0.087 |
(sin θ/λ)max (Å−1) | 0.909 |
Refinement | |
R[F > 3σ(F)], wR(F), S | 0.043, 0.092, 1.37 |
No. of reflections | 4097 |
No. of parameters | 69 |
Δρmax, Δρmin (e Å−3) | 3.92, −2.89 |
Computer programs: COLLECT (Nonius, 1998), EVALCCD (Duisenberg et al., 2003), SIR97 (Altomare et al., 1999), JANA2006 (Petříček et al., 2006), DIAMOND (Brandenburg, 2001).
Tl1—Tl2i | 3.5164 (7) | Mo1—Mo1x | 2.7609 (6) |
Tl1—Se2 | 4.3543 (6) | Mo1—Mo2viii | 3.4239 (8) |
Tl1—Se2ii | 4.3543 (7) | Mo1—Se1 | 2.5540 (8) |
Tl1—Se2iii | 4.3543 (7) | Mo1—Se1x | 2.6143 (8) |
Tl1—Se3 | 3.5840 (6) | Mo1—Se1xiii | 2.5757 (6) |
Tl1—Se3ii | 3.5840 (5) | Mo1—Se2 | 2.6247 (8) |
Tl1—Se3iii | 3.5840 (8) | Mo1—Se4 | 2.5269 (8) |
Tl1—Se3iv | 3.4547 (6) | Mo2—Mo2ix | 2.6382 (5) |
Tl1—Se3v | 3.4547 (8) | Mo2—Mo3 | 2.7397 (7) |
Tl1—Se3vi | 3.4547 (5) | Mo2—Mo3viii | 2.7901 (7) |
Tl1—Se4vii | 3.0737 (10) | Mo2—Se1i | 2.6597 (6) |
Tl2—Se1 | 3.4032 (7) | Mo2—Se2 | 2.6034 (9) |
Tl2—Se1viii | 3.4032 (6) | Mo2—Se2ix | 2.6124 (10) |
Tl2—Se1ix | 3.4032 (8) | Mo2—Se3 | 2.6721 (6) |
Tl2—Se2i | 3.1441 (4) | Mo2—Se5 | 2.5129 (8) |
Tl2—Se2x | 3.1441 (7) | Mo3—Mo3ix | 2.6780 (7) |
Tl2—Se2xi | 3.1441 (7) | Mo3—Mo3xiv | 2.6796 (6) |
Tl2—Se3i | 4.2446 (7) | Mo3—Se2ix | 2.5634 (8) |
Tl2—Se3x | 4.2446 (6) | Mo3—Se3 | 2.6090 (6) |
Tl2—Se3xi | 4.2446 (8) | Mo3—Se3ix | 2.6112 (6) |
Tl2—Se5 | 3.0483 (9) | Mo3—Se3xiv | 2.7025 (8) |
Mo1—Mo1xii | 2.6897 (7) |
Symmetry codes: (i) −x+1/3, −y+2/3, −z+2/3; (ii) −y+1, x−y+1, z; (iii) −x+y, −x+1, z; (iv) −x+1, −y+1, −z+1; (v) y, −x+y+1, −z+1; (vi) x−y, x, −z+1; (vii) −x, −y+1, −z+1; (viii) −y, x−y, z; (ix) −x+y, −x, z; (x) y−2/3, −x+y−1/3, −z+2/3; (xi) x−y+1/3, x−1/3, −z+2/3; (xii) −x+y−1, −x, z; (xiii) x−y+1/3, x+2/3, −z+2/3; (xiv) y, −x+y, −z+1. |
Acknowledgements
Intensity data were collected at the `Centre de diffractométrie de l'Université de Rennes I' (www.cdifx.univ-rennes1.fr).
References
Altomare, A., Burla, M. C., Camalli, M., Cascarano, G. L., Giacovazzo, C., Guagliardi, A., Moliterni, A. G. G., Polidori, G. & Spagna, R. (1999). J. Appl. Cryst. 32, 115–119. Web of Science CrossRef CAS IUCr Journals Google Scholar
Becker, P. J. & Coppens, P. (1974). Acta Cryst. A30, 129–147. CrossRef IUCr Journals Web of Science Google Scholar
Brandenburg, K. (2001). DIAMOND. Crystal Impact GbR, Bonn, Germany. Google Scholar
Duisenberg, A. J. M., Kroon-Batenburg, L. M. J. & Schreurs, A. M. M. (2003). J. Appl. Cryst. 36, 220–229. Web of Science CrossRef CAS IUCr Journals Google Scholar
Nonius (1998). COLLECT. Nonius BV, Delft, The Netherlands. Google Scholar
Petříček, V., Dušek, M. & Palatinus, L. (2006). JANA2006. Institute of Physics, Praha, Czech Republic. Google Scholar
Potel, M., Chevrel, R. & Sergent, M. (1980). Acta Cryst. B36, 1319–1322. CrossRef CAS IUCr Journals Web of Science Google Scholar
Schäfer, H. & von Schnering, H. G. (1964). Angew. Chem. 76, 833–845. Google Scholar
Shannon, R. D. (1976). Acta Cryst. A32, 751–767. CrossRef CAS IUCr Journals Web of Science Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar
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Potel et al. (1980) reported the crystal structure of Tl2Mo9S11 that was the first compound containing a transition metal cluster with a nuclearity higher than 9, namely the trioctahedral Mo12 cluster. The latter cluster, which results from the uniaxial face-sharing of three Mo6 octahedra, coexists with the octahedral Mo6 cluster in equal proportion. We present here the crystal structure of the isotypic selenide, Tl2Mo9Se11.
The Mo—Se framework of Tl2Mo9Se11 consists of an equal mixture of Mo6Sei8Sea6 and Mo12Sei14Sea6 cluster units interconnected through Mo—Se bonds (Fig.1 and 2). Details of the i- and a-type ligand notation were reported by Schäfer & von Schnering (1964). The first unit can be described as an Mo6 octahedron surrounded by 8 face-capping inner Sei and 6 apical Sea ligands. The Mo12 core of the second unit results from the face sharing of 3 octahedral Mo6 clusters. The Mo12 cluster is surrounded by 14 Sei atoms capping the faces of the bioctahedron and 6 apical Sea ligands above the ending Mo atoms. The Mo6Sei8Sea6 and Mo12Sei14Sea6 units are centered at 3a and 3b positions and have point-group symmetry 3. The Mo—Mo distances within the Mo6 clusters are 2.6897 (7) Å for the intra-triangle distances (distances within the Mo3 triangles formed by the Mo1 atoms related through the threefold axis) and 2.7609 (6) Å for the inter-triangle distances. In the sulfide, the two later values are slightly larger, viz. 2.693 (1) and 2.780 (5) Å. The Mo—Mo distances within the Mo12 clusters are 2.6382 (5) and 2.6780 (7) Å for the distances in the triangles formed by the Mo2 and Mo3 atoms, respectively. In Tl2Mo9S11, the corresponding distances are equal to 2.658 (1) and 2.688 (1) Å, respectively. The distances between the triangles formed by the Mo2 and Mo3 atoms are 2.7397 (7) and 2.7901 (7) Å and those between the Mo33 triangles, 2.6796 (6) Å. The average Mo—Mo distance within the Mo12 cluster is similar in Tl2Mo9S11 and Tl2Mo9Se11 and amounts to 2.705 Å. The Se atoms bridge either one (Se1, Se2, Se4 and Se5) or two (Se3) Mo triangular faces of the clusters. Moreover, the Se1 and Se2 atoms are linked to a Mo atom of a neighboring cluster. The Mo—Se bond distances range from 2.5269 (8) to 2.6247 (8) Å within the Mo6Sei8Sea6 unit and from 2.5129 (8) to 2.7025 (8) Å within the Mo12Sei14Sea6 ubit. Each Mo12Sei14Sea6 unit is interconnected to 6 Mo6Sei8Sea6 units (and vice versa) via Mo2—Se1 bonds (respectively Mo1—Se2) to form the three-dimensional Mo—Se framework, the overall connectivity formula of which is Mo12Sei8Sei-a6/2Sea-i6/2, Mo6Sei2Sei-a6/2Sea-i6/2. It results from this arrangement that the shortest intercluster Mo1—Mo2 distance between the Mo6 and Mo12 clusters is 3.4239 (8) Å compared to 3.217 (1) in Tl2Mo9S11, indicating only weak metal-metal interaction. The Tl atoms occupy large voids delimited by four Mo6Sei8Sea6 units and four Mo12Sei14Sea6 units. The Tl1 and Tl2 cations have a very similar environment which consists of seven Se atoms as nearest neighbors with Tl—Se distances in the ranges 3.0737 (10) - 3.5840 (6) Å and 3.0483 (9) - 3.4032 (6) Å for the Tl1 and Tl2 sites, respectively. These seven Se atoms form a monocapped octahedron compressed along the threefold axis. Three additional Se atoms at 4.3543 (6) and 4.2446 (6) Å from Tl1 and Tl2, respectively, are also observed (Figure 3). The average Tl—Se values are 3.72 and 3.54 Å for the Tl1 and Tl2 sites, respectively. Values of 3.57 and 3.68 Å are expected from the sum of the ionic radii for Se2- and Tl+ for coordination numbers 8 and 12 (Shannon, 1976).