Alkylation of tetrathiotungstate anions: crystal structures of the alkylthiolatotrithiotungstate complexes [PPh₄]₂[WS₃(Sⁿ Pr)][WS₃(Sⁿ Bu)]·½C₆H₆ and [PPh₄][WS₃(SCH₂C₆H₄CH₂Cl-4)]

2.1 General

All syntheses were performed in oven-dried glassware under a purified nitrogen atmosphere using standard Schlenk techniques. The solvents were purified by conventional methods and degassed prior to use. (NH₄)₂[WS₄], n-propylbromide, n-butylbromide, 1-bromomethyl-4-chloromethyl-benzene, and 1,4-bis-bromomethyl-benzene were purchased from Alfa Aesar Ltd. and used as supplied. [Ph₄P]₂[WS₄] was prepared by the addition of (NH₄)₂[WS₄] in water solution to an aqueous solution of Ph₄PBr. The resulting solid was collected by filtration; washed with water, ethanol, and diethyl ether; and dried in vacuo. All elemental analyses were carried out using a Perkin-Elmer 2400 CHN analyzer. NMR spectra were recorded on a Bruker ALX 400 spectrometer operating at 400 MHz for ¹H. Chemical shifts (δ in ppm) are reported with reference to SiMe₄ (¹H).

2.2 Synthesis of [PPh₄][WS₃(SⁿPr)] (1)

To a solution of [Ph₄P]₂[WS₄] (250 mg, 0.25 mmol) in CH₃CN (20 mL) was added n-propylbromide (0.15 mL, 1.60 mmol) in CH₃CN (5 mL) with stirring at 5°C. The resulting mixture was stirred at room temperature for 1 h, during which the color gradually changed from yellow to red. The solvent was removed in vacuo, and the residue was treated with THF (10 mL) and filtered. The filtrate was layered with 20 mL of Et₂O and allowed to stand at ca. 4°C. Red needle-shaped micro-crystals of 1 were obtained after 5 days, and were isolated by filtration, washed with Et₂O, and dried in vacuo. Yield: 77 mg (46%). – Anal. for C₂₇H₂₇PS₄W: calcd. C 46.69, H 3.92; found C 46.47, H 3.90. – ¹H NMR (CDCl₃, ppm): δ=1.12 (t, 3H, CH₃), 1.65 (m, 2H, SCH₂CH₂), 3.21 (t, 2H, SCH₂), 7.59–7.86 (m, 20H, Ph₄P).

2.3 Synthesis of [PPh₄][WS₃(SⁿBu)] (2)

Compound 2 was synthesized by a procedure similar to that used for 1 except that n-butylbromide (0.63 mL, 1.60 mmol) was added and the mixture was stirred for 3 h before the solvent and volatiles were removed in vacuo. After the residue was extracted with THF (2×5 mL) and the solution concentrated to ca. 5 mL, 20 mL Et₂O was introduced to precipitate 2 as an orange-red solid. Yield: 98 mg (57%). – Anal. for C₂₈H₂₉PS₄W: calcd. C 47.46, H 4.12; found C 47.21, H 4.17. – ¹H NMR (CDCl₃, ppm): δ=0.97 (t, 3H, CH₃), 1.47 (m, 2H, SCH₂CH₂), 1.94 (m, 2H, SCH₂CH₂CH₂), 3.42 (t, 2H, SCH₂), 7.63–7.92 (m, 20H, Ph₄P).

2.4 Synthesis of [PPh₄][WS₃(SCH₂C₆H₄ CH₂Cl-4)] (3)

A solution of 1-bromomethyl-4-chloromethyl-benzene (220 mg, 1.00 mmol) in CH₃CN (5 mL) was added to a CH₃CN solution (20 mL) of [Ph₄P]₂[WS₄] (250 mg, 0.25 mmol), and the mixture was stirred overnight at room temperature, during which the color of the solution slowly changed from yellow to red. From a workup similar to that used for the isolation of 1, red block crystals of 3 were obtained in 3 days. Yield: 100 mg (51%). – Anal. for C₃₂H₂₈PClS₄W: calcd. C 48.58, H 3.57; found C 48.33, H 3.62. – ¹H NMR (CDCl₃, ppm): δ=3.64 (s, 2H, SCH₂), 4.78 (s, 2H, CH₂Cl), 7.01–7.18 (m, 4H, C₆H₄ ), 7.61–7.95 (m, 20H, Ph₄P).

2.5 Synthesis of [PPh₄]₂[WS₃ (μ-SCH₂C₆H₄CH₂S)WS₃] (4)

A solution of 1,4-bis-bromomethyl-benzene (66.5 mg, 0.25 mmol) in CH₃CN (5 mL) was added to a CH₃CN solution (20 mL) of [Ph₄P]₂[WS₄] (250 mg, 0.25 mmol), and the mixture was stirred for 24 h at room temperature, during which the color of the solution gradually changed from yellow to dark red. From a workup similar to that used for the isolation of 3, dark red micro-crystals of 4 were obtained in 2 days. Yield: 85 mg (62%). – Anal. for C₅₆H₄₈P₂S₈W₂: calcd. C 47.80, H 3.44; found C 48.02, H 3.49. – ¹H NMR (CDCl₃, ppm): δ=3.76 (s, 4H, SCH₂), 6.86–6.93 (m, 4H, C₆H₄ ), 7.52–7.91 (m, 40H, Ph₄P).

2.6 X-ray crystallography

As high-quality single crystals of complexes 1 and 2 were difficult to obtain for X-ray diffraction, recrystallization of the mixture of 1 and 2 in a 1:1 ratio (equimolar ratio) from THF-benzene-Et₂O (1:1:2) gave single crystals of 1/2·½C₆H₆ suitable for X-ray diffraction analysis. Crystallographic data and experimental details for [PPh₄]₂[WS₃(Sⁿ Pr)][WS₃(Sⁿ Bu)]·C₆H₆ (1/2·½C₆H₆) and [PPh₄][WS₃(SCH₂C₆H₄CH₂Cl-4)] (3) are summarized in Table 1. Intensity data were collected on a Bruker SMART APEX 2000 CCD diffractometer using graphite-monochromatized MoKα radiation (λ=0.71073 Å) at 296(2) K. The collected frames were processed with the software Saint [9]. The data were corrected for absorption using the program Sadabs [10]. The structures were solved by Direct Methods and refined by full-matrix least squares on F² using the shelxtl software package [11], [12], [13]. All non-hydrogen atoms were refined anisotropically. The positions of all hydrogen atoms were generated geometrically (C_sp3−H=0.97 and C_sp2−H=0.93 Å), assigned isotropic displacement parameters, and allowed to ride on their respective parent carbon or nitrogen atoms before the final cycle of least-squares refinement. The largest peaks in the final difference maps that had heights of 2.02 (for 1/2·½C₆H₆) and 2.09 e Å⁻³ (for 3) are in the vicinity of the tungsten atoms. The selected bond lengths and bond angles of complexes 1–3 were listed in Table 2 for the comparison.

CCDC 1495648 and 1495649 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.