Kim et al.
(TMS)-ethynyl sulfide, and better control of the volatile SCl2
this step. Then, the first trap was warmed to -41 °C and
simultaneously vacuum-distilled into the deposition apparatus
cooled at -180 °C for another hour. Afterward, the deposition tube
was warmed to -78 °C and left under vacuum for another hour.
Finally, CDCl3 was added through the side arm of the deposition
tube for the product analysis. 1H NMR (300 MHz, CDCl3): δ 3.01
(s, 2H),48 as well as residual peaks at δ 0-2, possibly due to n-butyl
ethynyl sulfide or mono-deprotected TMS-ethynyl ethynyl sulfide.
13C NMR (75 MHz, CDCl3): δ 85.1, 66.8, as well as traces of
peaks at δ 82.0, 77.4, 35.0, 31.4, 21.6, 13.7, possibly due to the
side products. Note in the NMR spectrum the presence of
discernible side products, unavoidably produced during cycles of
bulb-to-bulb distillation. Samples of 3 in a deposition tube were
exposed to vacuum via several freeze-pump-thaw cycles and then
co-deposited with N2 gas for 45 min onto CsI cold window (21
K), while the deposition tube was kept in dry ice/acetone bath (-78
°C). Then, the matrix was slowly cooled to 10 K.
during the addition.
The revised procedures are as follows: To a flame-dried 100
mL round-bottom flask containing a bulky stirring bar were added
8 mL of THF (dried over Na/benzophenone) and an excess of
TMS-acetylene (4 mL, 29 mmol plus the extra volume of the
needle). The solution was cooled to -41 °C, then 12.2 mL (28
mmol) of n-BuLi (2.3 M) was added dropwise and stirred for 1 h.
Meanwhile, an excess of SCl2 (>0.9 mL, 14 mmol) was freshly
distilled from stock bottle (tech. 80%) and subsequently admixed
with 2 mL of THF. Then, the SCl2/THF mixture was kept at -30
°C and syringe-transferred dropwise to the mother solution flask
cooled at dry ice/acetone bath, at such rate that temperature inside
the flask did not exceed -60 °C during the entire addition period.
Twenty minutes after the addition, the brownish solution was
allowed to warm to room temperature and quenched with 40 mL
of deionized water. The ether extraction yielded 200 mL of reddish
ethereal solution, which was then dried over MgSO4 and gravity-
filtered. Analysis of the organic layer after workup was performed
via TLC with KMnO4 staining, as well as GC-MS to ensure the
purity of product. Solvent was removed by rotary evaporation, and
the crude product was then subjected to fractional vacuum distil-
lation; after a few drops of forerun, clear liquid was distilled at
Preparation of 3,4-Thiophenedicarboxylic Acid Anhydride
(11). As described in the literature,49 ca. 0.55 g of 3,4-thiophene-
dicarboxylic acid (97%) was mixed with 8 mL of freshly distilled
acetic anhydride (distilled from P2O5), and the solution mixture
was vigorously refluxed for 2 h. After cooling, excess acetic
anhydride was removed by vacuum distillation, leaving yellowish-
brown solids in the flask. Subsequently, the solids were transferred
to a 10 mL Erlenmeyer flask and recrystallized with a benzene
and hexane mixture. Upon cooling, white needles precipitated out
of solution, which were collected by vacuum filtration and rinsed
with cold benzene. Light brown needles (300 mg, 61.6%) were
obtained. Then, the crude anhydride was placed in a sublimation
chamber and sublimed 3 h at 80-90 °C (oil bath) and 0.07 mmHg
onto a water-cooled cold finger. Subsequently, white crystals (240
1
50-56 °C (distillation head), 0.5 mmHg. H NMR (300 MHz,
1
mg) were scraped off from the cold finger. H NMR (300 MHz,
CDCl3): δ 0.21 (s, 18H). 13C NMR (75 MHz, CDCl3): δ 104.1,
86.0, -0.2. MS (EI) m/z (relative intensity): 226 (M+, 46), 211
(100), 121 (82), 98 (34), 97 (37), 73 (80). UV/vis (λmax, CH3CN):
219 nm (ꢀ ) 3600 M-1 cm-1), 229 nm (ꢀ ) 5910 M-1 cm-1), 239
nm (ꢀ ) 6450 M-1 cm-1).
CDCl3): δ 8.10 (s, 2H).50 13C NMR (75 MHz, CDCl3): δ 156.5,
135.5, 129.5.50 MS (EI) m/z (relative intensity): 154 (M+, 47%),
110 (100%), 82 (47%).50 UV/vis (λmax, CH3CN): 225 nm (ꢀ )
38350 M-1 cm-1), 250 nm (ꢀ ) 5020 M-1 cm-1), and a broad
shoulder around 280 nm. Given such low vapor pressure of the
anhydride (mp 144-146 °C),49 a special apparatus was designed
to deposit the matrix sample (see Supporting Information).
2,5-Diiodothiophene (10) is commercially available. The sample
was sublimed at room temperature and co-deposited with N2 to
form a matrix.
Diethynyl Sulfide (3). It cost several experimental failures to
develop an optimal procedure for the preparation of 3 and the
deposition of a sample suitable for IR matrix-isolation spectroscopy.
To a 25 mL round-bottom flask were added 5 mL of ethylene glycol
and ca. 0.5 mL of bis(trimethylsilylethynyl) sulfide. To the well-
stirred solution was added dropwise 2 equiv of Bu4NF‚3H2O
dissolved in 2 mL of ethylene glycol. The reaction mixture was
stirred 20 min, prior to vacuum distillation (0.5 mmHg) of volatile
substances into the first trap cooled at -78 °C for an hour.
Typically, a white coating forms inside the trapping flask during
Acknowledgment. We gratefully acknowledge the financial
support of the National Science Foundation. H.I. thanks Prof.
S. Oishi (Kitasato University) for support. We thank Prof. Adam
Matzger (University of Michigan), Sugumar Venkataramani
(Ruhr-Universita¨t Bochum), and Prof. Wolfram Sander (Ruhr-
Universita¨t Bochum) for stimulating discussions.
(45) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Zakrzewski, V. G.; Montgomery, J. A., Jr.;
Stratmann, R. E.; Burant, J. C.; Dapprich, S.; Millam, J. M.; Daniels, A.
D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J.; Barone, V.; Cossi,
M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo, C.; Clifford, S.;
Ochterski, J.; Petersson, G. A.; Ayala, P. Y.; Cui, Q.; Morokuma, K.; Malick,
D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.; Cioslowski, J.;
Ortiz, J. V.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi,
I.; Gomperts, R.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.;
Peng, C. Y.; Nanayakkara, A.; Gonzalez, C.; Challacombe, M.; Gill, P. M.
W.; Johnson, B. G.; Chen, W.; Wong, M. W.; Andres, J. L.; Head-Gordon,
M.; Replogle, E. S.; Pople, J. A. Gaussian 98, revision A.6; Gaussian,
Inc.: Pittsburgh, PA, 1998.
Supporting Information Available: Details concerning ex-
perimental matrix-isolation techniques; natural resonance theory
analysis of diethynyl sulfide (3); computed electronic transitions
of butatrienethione (5); matrix IR spectra for photolysis of diethynyl
sulfide (3). This material is available free of charge via the Internet
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