metal-organic compounds
Di-μ-chlorido-μ-(dimethyl sulfide)-bis{dichlorido[(dimethyl selenide-κSe)(dimethyl sulfide-κS)(0.65/0.35)]niobium(III)}(Nb—Nb)
aDepartment of Chemistry, Graduate School of Science and Engineering, Saitama University, Shimo-Okubo 255, Sakura-ku, Saitama 338-8570, Japan, bComprehensive Analysis Center for Science, Saitama University, Shimo-Okubo 255, Sakura-ku, Saitama 338-8570, Japan, cDepartment of Chemistry, University of Malaya, 50603 Kuala Lumpur, Malaysia, and dChemistry Department, Faculty of Science, King Abdulaziz University, PO Box 80203 Jeddah, Saudi Arabia
*Correspondence e-mail: fuji@chem.saitama-u.ac.jp
The dinuclear compound, [Nb2Cl6(C2H6S)1.7(C2H6Se)1.3], features an NbIII=NbIII double bond [2.6878 (5) Å]. The molecule lies on a twofold rotation axis that passes through the middle of this bond as well as through the bridging dimethyl sulfide ligand. The NbIII ion exists in an octahedral coordination environment defined by two terminal and two bridging Cl atoms, and (CH3)2Se/(CH3)2S ligands. The (bridging) ligand lying on the twofold rotation axis is an ordered (CH3)2S ligand, whereas the terminal ones on a general position are a mixture of (CH3)2Se and (CH3)2S ligands in a 0.647 (2):0.353 (2) ratio (the methyl C atoms are also disordered).
Related literature
For background to this study, see: Cotton et al. (1985); Kakeya et al. (2006a,b). For the synthesis of the principal reactant, see: Tsunoda & Hubert-Pfalzgraf (1982). For a related structure, see: Babaian-Kibala et al. (1991).
Experimental
Crystal data
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Data collection: APEX2 (Bruker, 2008); cell SAINT (Bruker, 2008); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001); software used to prepare material for publication: publCIF (Westrip, 2010).
Supporting information
10.1107/S1600536812033673/bt5971sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536812033673/bt5971Isup2.hkl
All the reactions were carried out under a dry argon atmosphere by using standard Schlenk tube techniques. [Nb2Cl6(Me2S)3] was prepared by a literature method (Tsunoda & Hubert-Pfalzgraf, 1982). Me2Se (0.10 ml, 1.3 mmol) was added to [Nb2Cl6(Me2S)3] (200 mg, 0.34 mmol) in CH2Cl2 (20 ml) and stirred for 1 d at room temperature. The resulting solution was concentrated to dryness to give red purple powders. The crude product was washed with hexane and dried under reduced pressure. A mixture of [Nb2Cl6(Me2S)3] and a compound believed to be [Nb2Cl6(Me2Se)2(Me2S)] was obtained as red purple powders (130 mg, yield 58% identified by 1H NMR). The latter compound was recrystallized from CH2Cl2–hexane (1:4) to give red crystals. 1H NMR (CDCl3, 300 K): δ 3.33 (6H, bridging-Me2S), 2.49 (12H, terminal-Me2Se). 13C NMR (300 K, CDCl3): δ 30.0 (2 C, bridging-Me2S), 14.1 (4 C, terminal-Me2S). FAB-MS(nitrobenzyl alcohol matrix): m/z = 644 [M—Cl]+.
As the formulation refined to [Nb2Cl6(C2H6Se)1.3(C2H6S)1.7], the crystal is probably not reprensentative of the bulk formulation.
The H atoms were placed in calculated positions, with C—H = 0.98 Å for CH3, and refined using a riding model, with Uiso(H) = 1.5Ueq of the carrier atoms.
The chalcogen ligand on the general position is disordered; the atom refined to a 0.647 (2)Se : 0.353S mixture. The Se1–C distances were restrained to 1.95±0.01 Å and the S1'–C distances to 1.80±0.01 Å. The temperature factors of Se1 and S1' were made identical.
The
led to an Nb1–Se1 distance of 2.72 Å but a much longer Nb1–S1' distance of 2.79 Å (a normal Nb–S bond is approximately 2.40 Å). then proceeded by setting the Nb1–S1 (ordered sulfur) and the N1b–S1' (disordered sulfur) bond distances to be within 0.01 Å of each other. The two methyl groups were each split into two components, and the temperature factors of the primed atoms were set to those of the unprimed ones. Additionally, the anisotropic temperature factors were tightly restrained to be nearly isotropic. This model gave distances of 2.420 (1) Å for the ordered atom and 2.543 (6) Å for the disordered atom.The failure of the Hirshfeld test for the Nb1–Se1 and Nb1–S1' bonds is attributed to the tight restraints imposed on the disordered ligand.
Arising from the
the compound is formulated as [Nb2Cl6(C2H6Se)1.3(C2H6S)1.7].Data collection: APEX2 (Bruker, 2008); cell
SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001); software used to prepare material for publication: publCIF (Westrip, 2010).Fig. 1. Thermal ellispoid plot (Barbour, 2001) plot of [Nb2Cl6(C2H6Se)1.3(C2H6S)1.7] at the 70% probability level. The disorder is not shown and symmetry-related atoms are not labeled. |
[Nb2Cl6(C2H6S)1.7(C2H6Se)1.3] | F(000) = 1238 |
Mr = 645.87 | Dx = 2.219 Mg m−3 |
Orthorhombic, Pbcn | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2n 2ab | Cell parameters from 3921 reflections |
a = 13.3314 (11) Å | θ = 2.9–28.5° |
b = 13.5952 (12) Å | µ = 4.63 mm−1 |
c = 10.6649 (9) Å | T = 150 K |
V = 1932.9 (3) Å3 | Block, red |
Z = 4 | 0.10 × 0.09 × 0.08 mm |
Bruker APEXII CCD area-detector diffractometer | 2218 independent reflections |
Radiation source: Bruker TXS fine-focus rotating anode | 1975 reflections with I > 2σ(I) |
Bruker Helios multilayer confocal mirror monochromator | Rint = 0.028 |
Detector resolution: 8.333 pixels mm-1 | θmax = 27.5°, θmin = 2.1° |
ϕ and ω scans | h = −15→17 |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | k = −16→17 |
Tmin = 0.655, Tmax = 0.709 | l = −12→13 |
10299 measured reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.023 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.057 | H-atom parameters constrained |
S = 1.03 | w = 1/[σ2(Fo2) + (0.0281P)2 + 2.0744P] where P = (Fo2 + 2Fc2)/3 |
2218 reflections | (Δ/σ)max = 0.001 |
85 parameters | Δρmax = 0.61 e Å−3 |
17 restraints | Δρmin = −0.53 e Å−3 |
[Nb2Cl6(C2H6S)1.7(C2H6Se)1.3] | V = 1932.9 (3) Å3 |
Mr = 645.87 | Z = 4 |
Orthorhombic, Pbcn | Mo Kα radiation |
a = 13.3314 (11) Å | µ = 4.63 mm−1 |
b = 13.5952 (12) Å | T = 150 K |
c = 10.6649 (9) Å | 0.10 × 0.09 × 0.08 mm |
Bruker APEXII CCD area-detector diffractometer | 2218 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 1975 reflections with I > 2σ(I) |
Tmin = 0.655, Tmax = 0.709 | Rint = 0.028 |
10299 measured reflections |
R[F2 > 2σ(F2)] = 0.023 | 17 restraints |
wR(F2) = 0.057 | H-atom parameters constrained |
S = 1.03 | Δρmax = 0.61 e Å−3 |
2218 reflections | Δρmin = −0.53 e Å−3 |
85 parameters |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Nb1 | 0.468766 (18) | 0.233109 (19) | 0.36981 (2) | 0.01461 (9) | |
Se1 | 0.43903 (16) | 0.38286 (10) | 0.54126 (16) | 0.0169 (2) | 0.647 (2) |
S1' | 0.4374 (8) | 0.3682 (6) | 0.5299 (8) | 0.0169 (2) | 0.353 |
Cl1 | 0.57325 (6) | 0.16964 (6) | 0.53247 (6) | 0.02378 (16) | |
Cl2 | 0.31130 (5) | 0.16593 (6) | 0.42645 (7) | 0.02496 (17) | |
Cl3 | 0.38916 (5) | 0.33927 (5) | 0.20578 (6) | 0.02154 (16) | |
S1 | 0.5000 | 0.08504 (7) | 0.2500 | 0.0173 (2) | |
C1 | 0.3683 (5) | 0.3155 (6) | 0.6751 (7) | 0.0327 (8) | 0.647 (2) |
H1A | 0.3411 | 0.2533 | 0.6434 | 0.049* | 0.647 (2) |
H1B | 0.3133 | 0.3570 | 0.7053 | 0.049* | 0.647 (2) |
H1C | 0.4148 | 0.3021 | 0.7442 | 0.049* | 0.647 (2) |
C2 | 0.3289 (7) | 0.4616 (8) | 0.4702 (10) | 0.0240 (12) | 0.647 (2) |
H2A | 0.2946 | 0.4234 | 0.4051 | 0.036* | 0.647 (2) |
H2B | 0.3562 | 0.5219 | 0.4333 | 0.036* | 0.647 (2) |
H2C | 0.2812 | 0.4785 | 0.5367 | 0.036* | 0.647 (2) |
C1' | 0.3660 (7) | 0.3227 (8) | 0.6639 (10) | 0.0327 (8) | 0.353 |
H2D | 0.2942 | 0.3330 | 0.6490 | 0.049* | 0.3532 (16) |
H2E | 0.3863 | 0.3584 | 0.7396 | 0.049* | 0.3532 (16) |
H2F | 0.3791 | 0.2524 | 0.6751 | 0.049* | 0.3532 (16) |
C2' | 0.3338 (14) | 0.4497 (16) | 0.489 (2) | 0.0240 (12) | 0.353 |
H3D | 0.2715 | 0.4241 | 0.5255 | 0.036* | 0.3532 (16) |
H3E | 0.3273 | 0.4534 | 0.3981 | 0.036* | 0.3532 (16) |
H3F | 0.3470 | 0.5156 | 0.5231 | 0.036* | 0.3532 (16) |
C3 | 0.4005 (2) | 0.0020 (2) | 0.2071 (3) | 0.0246 (6) | |
H3A | 0.3415 | 0.0398 | 0.1811 | 0.037* | |
H3B | 0.3831 | −0.0393 | 0.2793 | 0.037* | |
H3C | 0.4227 | −0.0398 | 0.1376 | 0.037* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Nb1 | 0.01621 (14) | 0.01427 (14) | 0.01335 (13) | −0.00034 (9) | −0.00035 (9) | 0.00066 (9) |
Se1 | 0.0202 (2) | 0.0139 (6) | 0.0167 (4) | −0.0004 (4) | 0.0026 (3) | −0.0051 (3) |
S1' | 0.0202 (2) | 0.0139 (6) | 0.0167 (4) | −0.0004 (4) | 0.0026 (3) | −0.0051 (3) |
Cl1 | 0.0265 (4) | 0.0263 (4) | 0.0185 (3) | 0.0031 (3) | −0.0059 (3) | 0.0021 (3) |
Cl2 | 0.0209 (4) | 0.0286 (4) | 0.0254 (4) | −0.0064 (3) | 0.0031 (3) | −0.0001 (3) |
Cl3 | 0.0244 (4) | 0.0224 (4) | 0.0179 (3) | 0.0073 (3) | 0.0008 (3) | 0.0027 (3) |
S1 | 0.0198 (5) | 0.0147 (5) | 0.0174 (5) | 0.000 | −0.0024 (4) | 0.000 |
C1 | 0.045 (2) | 0.0319 (19) | 0.0213 (18) | −0.0017 (16) | 0.0105 (15) | 0.0018 (15) |
C2 | 0.0259 (18) | 0.022 (3) | 0.024 (4) | 0.0093 (15) | −0.0041 (18) | 0.003 (2) |
C1' | 0.045 (2) | 0.0319 (19) | 0.0213 (18) | −0.0017 (16) | 0.0105 (15) | 0.0018 (15) |
C2' | 0.0259 (18) | 0.022 (3) | 0.024 (4) | 0.0093 (15) | −0.0041 (18) | 0.003 (2) |
C3 | 0.0249 (15) | 0.0219 (16) | 0.0270 (16) | −0.0055 (12) | −0.0045 (13) | 0.0007 (12) |
Nb1—Cl2 | 2.3676 (7) | C1—H1A | 0.9800 |
Nb1—Cl1 | 2.3863 (7) | C1—H1B | 0.9800 |
Nb1—S1 | 2.4204 (8) | C1—H1C | 0.9800 |
Nb1—Cl3 | 2.5039 (7) | C2—H2A | 0.9800 |
Nb1—Cl3i | 2.5140 (7) | C2—H2B | 0.9800 |
Nb1—S1' | 2.543 (6) | C2—H2C | 0.9800 |
Nb1—Nb1i | 2.6878 (5) | C1'—H2D | 0.9800 |
Nb1—Se1 | 2.7650 (10) | C1'—H2E | 0.9800 |
Se1—C1 | 1.941 (6) | C1'—H2F | 0.9800 |
Se1—C2 | 1.968 (6) | C2'—H3D | 0.9800 |
S1'—C1' | 1.825 (9) | C2'—H3E | 0.9800 |
S1'—C2' | 1.822 (9) | C2'—H3F | 0.9800 |
Cl3—Nb1i | 2.5140 (7) | C3—H3A | 0.9800 |
S1—C3 | 1.801 (3) | C3—H3B | 0.9800 |
S1—C3i | 1.801 (3) | C3—H3C | 0.9800 |
S1—Nb1i | 2.4204 (8) | ||
Cl2—Nb1—Cl1 | 101.10 (3) | C3—S1—Nb1i | 120.94 (10) |
Cl2—Nb1—S1 | 88.07 (2) | C3i—S1—Nb1i | 121.93 (10) |
Cl1—Nb1—S1 | 89.00 (2) | C3—S1—Nb1 | 121.93 (10) |
Cl2—Nb1—Cl3 | 91.42 (3) | C3i—S1—Nb1 | 120.94 (10) |
Cl1—Nb1—Cl3 | 164.53 (3) | Nb1i—S1—Nb1 | 67.46 (3) |
S1—Nb1—Cl3 | 100.57 (2) | Se1—C1—H1A | 109.5 |
Cl2—Nb1—Cl3i | 166.23 (3) | Se1—C1—H1B | 109.5 |
Cl1—Nb1—Cl3i | 90.05 (3) | H1A—C1—H1B | 109.5 |
S1—Nb1—Cl3i | 100.29 (2) | Se1—C1—H1C | 109.5 |
Cl3—Nb1—Cl3i | 76.37 (3) | H1A—C1—H1C | 109.5 |
Cl2—Nb1—S1' | 87.8 (2) | H1B—C1—H1C | 109.5 |
Cl1—Nb1—S1' | 82.5 (3) | Se1—C2—H2A | 109.5 |
S1—Nb1—S1' | 169.6 (2) | Se1—C2—H2B | 109.5 |
Cl3—Nb1—S1' | 89.0 (3) | H2A—C2—H2B | 109.5 |
Cl3i—Nb1—S1' | 85.7 (2) | Se1—C2—H2C | 109.5 |
Cl2—Nb1—Nb1i | 121.15 (2) | H2A—C2—H2C | 109.5 |
Cl1—Nb1—Nb1i | 120.69 (2) | H2B—C2—H2C | 109.5 |
S1—Nb1—Nb1i | 56.272 (14) | S1'—C1'—H2D | 109.5 |
Cl3—Nb1—Nb1i | 57.795 (18) | S1'—C1'—H2E | 109.5 |
Cl3i—Nb1—Nb1i | 57.431 (17) | H2D—C1'—H2E | 109.5 |
S1'—Nb1—Nb1i | 133.6 (2) | S1'—C1'—H2F | 109.5 |
Cl2—Nb1—Se1 | 89.33 (4) | H2D—C1'—H2F | 109.5 |
Cl1—Nb1—Se1 | 82.48 (5) | H2E—C1'—H2F | 109.5 |
S1—Nb1—Se1 | 170.45 (5) | S1'—C2'—H3D | 109.5 |
Cl3—Nb1—Se1 | 88.67 (5) | S1'—C2'—H3E | 109.5 |
Cl3i—Nb1—Se1 | 84.11 (4) | H3D—C2'—H3E | 109.5 |
S1'—Nb1—Se1 | 1.6 (3) | S1'—C2'—H3F | 109.5 |
Nb1i—Nb1—Se1 | 132.31 (4) | H3D—C2'—H3F | 109.5 |
C1—Se1—C2 | 100.2 (3) | H3E—C2'—H3F | 109.5 |
C1—Se1—Nb1 | 102.0 (3) | S1—C3—H3A | 109.5 |
C2—Se1—Nb1 | 104.6 (4) | S1—C3—H3B | 109.5 |
C1'—S1'—C2' | 89.8 (9) | H3A—C3—H3B | 109.5 |
C1'—S1'—Nb1 | 111.5 (5) | S1—C3—H3C | 109.5 |
C2'—S1'—Nb1 | 113.9 (10) | H3A—C3—H3C | 109.5 |
Nb1—Cl3—Nb1i | 64.77 (2) | H3B—C3—H3C | 109.5 |
C3—S1—C3i | 102.3 (2) | ||
Cl2—Nb1—Se1—C1 | 35.3 (2) | Cl1—Nb1—Cl3—Nb1i | 89.16 (10) |
Cl1—Nb1—Se1—C1 | −66.0 (2) | S1—Nb1—Cl3—Nb1i | −38.270 (17) |
Cl3—Nb1—Se1—C1 | 126.7 (2) | Cl3i—Nb1—Cl3—Nb1i | 59.87 (2) |
Cl3i—Nb1—Se1—C1 | −156.8 (2) | S1'—Nb1—Cl3—Nb1i | 145.7 (2) |
Nb1i—Nb1—Se1—C1 | 168.8 (2) | Se1—Nb1—Cl3—Nb1i | 144.13 (4) |
Cl2—Nb1—Se1—C2 | −68.8 (4) | Cl2—Nb1—S1—C3 | 16.75 (12) |
Cl1—Nb1—Se1—C2 | −170.1 (4) | Cl1—Nb1—S1—C3 | 117.89 (12) |
Cl3—Nb1—Se1—C2 | 22.7 (4) | Cl3—Nb1—S1—C3 | −74.34 (12) |
Nb1i—Nb1—Se1—C2 | 64.8 (4) | Cl3i—Nb1—S1—C3 | −152.23 (12) |
Cl2—Nb1—S1'—C1' | 33.1 (6) | S1'—Nb1—S1—C3 | 83.3 (13) |
Cl1—Nb1—S1'—C1' | −68.4 (6) | Nb1i—Nb1—S1—C3 | −113.40 (12) |
S1—Nb1—S1'—C1' | −33.5 (19) | Cl2—Nb1—S1—C3i | −115.09 (12) |
Cl3—Nb1—S1'—C1' | 124.6 (6) | Cl1—Nb1—S1—C3i | −13.95 (12) |
Cl3i—Nb1—S1'—C1' | −159.0 (7) | Cl3—Nb1—S1—C3i | 153.82 (12) |
Nb1i—Nb1—S1'—C1' | 165.8 (4) | Cl3i—Nb1—S1—C3i | 75.93 (12) |
Cl2—Nb1—S1'—C2' | −66.7 (10) | S1'—Nb1—S1—C3i | −48.6 (14) |
Cl1—Nb1—S1'—C2' | −168.2 (10) | Nb1i—Nb1—S1—C3i | 114.76 (12) |
S1—Nb1—S1'—C2' | −133.3 (13) | Cl2—Nb1—S1—Nb1i | 130.15 (2) |
Cl3—Nb1—S1'—C2' | 24.8 (10) | Cl1—Nb1—S1—Nb1i | −128.71 (2) |
Cl3i—Nb1—S1'—C2' | 101.2 (10) | Cl3—Nb1—S1—Nb1i | 39.061 (18) |
Nb1i—Nb1—S1'—C2' | 66.0 (11) | Cl3i—Nb1—S1—Nb1i | −38.832 (17) |
Cl2—Nb1—Cl3—Nb1i | −126.58 (2) | S1'—Nb1—S1—Nb1i | −163.3 (13) |
Symmetry code: (i) −x+1, y, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | [Nb2Cl6(C2H6S)1.7(C2H6Se)1.3] |
Mr | 645.87 |
Crystal system, space group | Orthorhombic, Pbcn |
Temperature (K) | 150 |
a, b, c (Å) | 13.3314 (11), 13.5952 (12), 10.6649 (9) |
V (Å3) | 1932.9 (3) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 4.63 |
Crystal size (mm) | 0.10 × 0.09 × 0.08 |
Data collection | |
Diffractometer | Bruker APEXII CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.655, 0.709 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 10299, 2218, 1975 |
Rint | 0.028 |
(sin θ/λ)max (Å−1) | 0.649 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.023, 0.057, 1.03 |
No. of reflections | 2218 |
No. of parameters | 85 |
No. of restraints | 17 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.61, −0.53 |
Computer programs: APEX2 (Bruker, 2008), SAINT (Bruker, 2008), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), X-SEED (Barbour, 2001), publCIF (Westrip, 2010).
Acknowledgements
This work was partly supported by the programs of the Grants-in-Aid for Scientific Research (to FT, No. 23510115) from the Japan Society for the Promotion of Science.
References
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The chemistry of the lower oxidation states of niobium in discrete complexes remains relatively unexplored. Our research group has already carried out X-ray crystallographic determinations of the complexes of the general formula [Nb2Cl6L3] (L= tetrahydrothiophene C4H8S, dimethyl sulfide (Kakeya et al., 2006a, 2006b). These complexes have a triply bridged face-sharing dioctahedral structure with one thioether as a bridging ligand and two terminal Cl- and thioether. A series of ligand substitution reactions of these complexes with monodentate oxygen donors and substituted phosphanes has been explored. The structures of the face-sharing dioctahedral complexes preserve their original geometry in the case of reaction with monodentate ligands and ligand substitution occurred only at terminal positions (Cotton et al., 1985). We report here the first success in determining the structure of [Nb2Cl6(C2H6Se)1.3(C2H6S)1.7 (Scheme I), which has selenoether as ligands at terminal positions.
The molecule has dinuclear bridging unit [Nb2(µ-Cl)2(µ-Me2X)] (X = mixture of S, Se) with the terminal Me2X ligands in a trans orientation to the bridging Me2S (Fig. 1). The average Nb—(µ-Cl) and Nb—(µ-Me2S) distances fall within the range of those for [Nb2(µ-Cl)2Cl4(µ-Me2S)(Me2S)2], which has the same bridging unit (Kakeya et al., 2006a, 2006b). The terminal Nb—Cl lengths are shorter than the corresponding distances to the bridging atoms. If the terminal metal-chalcogen bond were purely ionic, the distance should coincide with the sum of ionic radii of metal and chalcogen. Since the ionic radii of the trivalent niobium, Se2– and S2– given in the literature are 0.72 Å, 1.98 Å and 1.84 Å, the bond distances of the metal and chalcogen is 2.70 Å for Se2– and 2.56 Å for S2–. We find that the difference between bond lengths and sum of the those radii is smaller in the title compound than in [Nb2Cl6(Me2S)3]. This difference is ascribed to the influence of the covalency of the metal-chalcogen interactions. Other geometrical parameters also lie within the same ranges as in analogous dinuclear niobium complexes (Kakeya et al., 2006a, 2006b).