Tetrakis(trimethylsilyl)tetrahedrane
A R T I C L E S
AC-200 and AM-400 FT spectrometer. Mass spectra were obtained
on a Varian Mat 111 and 311-A.
(trimethylsilyl)cyclopropene (50 mg, 81%) as a pale yellow liquid. 1H
NMR (CDCl3): δ -0.15 (s, 9H, SiMe3), -0.06 (s, 1H, CH, proved by
COSY experiment), 0.15 (s, 18H, SiMe3). 13C NMR (CDCl3): δ -1.5,
-1.1 (SiMe3), 5.8 (CH), 132.7 (CdC). IR (film): 2960, 2900, 1730,
Trimethylsilyl[1,2,3-tris(trimethylsilyl)-2-cycloprop-1-enyl]di-
azomethane 7. To the yellow solution of (trimethylsilyl)diazo-
methane (9.9 mmol) in 120 mL of dry ether was added methyllithium
(10.5 mmol) at 0 °C under argon. After 30 min, the temperature was
lowered to -90 °C, and tris(trimethylsilyl)cyclopropenylium hexa-
chloroantimonate 4 (6.0 g, 10.17 mmol) was added. The dark brown
mixture was warmed slowly to -20 °C, and diisopropylamine (269
mg, 2 mmol) and pentane (200 mL) were added. The crude product
was washed two times with 300 mL of ice-cold saturated NaCl solution
and two times with water, and was then separated from the water.
Removal of the solvent in vacuo at 0 °C gave a yellow crude product,
which on high vacuum evaporation yielded bis(trimethylsilyl)acetylene
13 (390 mg, 23.2%) and bis(trimethylsilyl)diazomethane 16 (225 mg,
12.2%). The residue was separated by chromatography (aluminum oxide
neutral, low activity, -25° C, pentane) to give five fractions:
Trimethylsilyl[1,2,3-tris(trimethylsilyl)-2-cycloprop-1-enyl]di-
azomethane 7 (390 mg, 10.7%) as a yellow oil. 1H NMR (CDCl3): δ
-0.03 (s, 9H, SiMe3), 0.15 (s, 9H, SiMe3), 0.26 (s, 18H, SiMe3). 13C
NMR (toluene-d8): δ -0.4, -0.35, -0.1 (SiMe3), 16.5 (quart. C), 38.6
(CdN2), 141.1 (CdC). IR (film): 2960, 2900, 2020, 1705, 1250, 840
cm-1. MS: m/z 368 (M+), 340 (M+ - N2), 255, 155, 73 (SiMe3). HRMS
calcd for C16H36N2Si4 368.1898, found 368.1955.
1250, 840 cm-1. MS: m/z 256 (M+), 241 (M+ - CH3), 183 (M+
-
SiMe3), 168, 153, 73 (SiMe3). HRMS calcd for C12H28Si3 256.1499,
found 256.1513. These spectroscopic data differ from those reported
by Garratt.39
Tetrakis(trimethylsilyl)cyclobutadiene 8 (via Diazo Compound
7). A sample of diazomethane 7 (30 mg, 0.0815 mmol) in 1 mL of
benzene-d6 or methylcyclohexane-d14 was degassed in a tube by four
vacuum freeze-thaw cycles, and then the tube was sealed under argon.
Heating to 60 °C for 8 h gave a red-brown solution of 8 (according to
NMR spectroscopy analysis 45% yield) and the bis(ketenimine) 11.
Tetrakis(trimethylsilyl)cyclobutadiene 8. 1H NMR (C7D14): δ 0.09
(s, 36H, SiMe3). 13C NMR (C7D14): δ 0.08 (SiMe3), 171.59 (CdC).
MS: m/z 340 (M+), 268 (M+ - SiMe3). Under high vacuum conditions,
it is possible to capture preferentially imine 11.
2,3-Bis(trimethylsilyl)-1,3-butadienedione-bis(trimethylsilyl)-
1
imine 11 was isolated as a colorless oil. H NMR (C6D6): δ 0.20 (s,
18H, SiMe3), 0.35 (s, 18H, SiMe3). 13C NMR (C6D12): δ 0.4, 0.5
(SiMe3), 26.3 (CdCdN), 177.1 (CdCdN). IR (argon-matrix, 10 K):
2961.4, 2907.0, 2112.1, 1254.7, 1249.0, 863.8, 839.2, 754.5, 747.5
cm-1. MS: m/z 368 (M+), 296 (M+ - SiMe3), 73 (SiMe3). HRMS
calcd for C16H36N2Si4 368.1956, found 368.1963.
Tris(trimethylsilyl)vinylacetylene 14 (410 mg, 15.5%) as a colorless
liquid. 1H NMR (CDCl3): δ 0.11 (s, 9H, SiMe3), 0.16 (s, 18H, SiMe3),
6.54 (s, 1H, dCH). 13C NMR (CDCl3): δ -2.1, -1.0, -0.1 (SiMe3),
103.7, 107.1, 145.4, 155.4. IR (CCl4): 2960, 2900, 2130, 1405, 1250,
2,3-Bis(methoxycarbonyl)-1,4,5,6-tetrakis(trimethylsilyl)bicyclo-
[2.2.0]hexa-2,5-diene 12. Diazomethane 7 (162 mg, 0.44 mmol) in
1.5 mL of benzene-d6 was heated to 70 °C for 100 min. The red-brown
solution was cooled to room temperature, and dimethyl acetylenedi-
carboxylate (0.7 mL, 0.57 mmol) in 2 mL of benzene-d6 was added
under argon. Upon stirring for 1.5 h, the color changed to yellow, and
purification by HPLC (first run: CN-phase, 10% tert-butylmethyl ether/
90% hexane; second run: CN-phase, 5% tert-butylmethyl ether/95%
hexane) gave 12 as colorless crystals (16.7 mg, 0.0346 mmol), mp 95
1050, 845 cm-1. MS: m/z 268 (M+), 253 (M+ - CH3), 195 (M+
-
SiMe3), 180, 165, 155, 73 (SiMe3). HRMS calcd for C13H28Si3 268.1499,
found 268.1508.
[1,2,3-Tris(trimethylsilyl)-2-cyclopropen-1-yl](trimethylsilyl)-
acetylene 15 (460 mg, 13.1%) as a colorless liquid. 1H NMR
(CDCl3): δ -0.03 (s, 9H, SiMe3), 0.05 (s, 9H, SiMe3), 0.24 (s, 18H,
SiMe3). 13C NMR (CDCl3): δ -2.3, -1.1, 0.5 (SiMe3), 6.1 (quart. C),
73.9, 117.8 (acetylenic C), 132.2 (CdC). IR (film): 2980, 2945, 2135,
1745, 1255, 845 cm-1. MS: m/z 352 (M+), 337 (M+ - CH3), 264,
249, 155, 73 (SiMe3). HRMS calcd for C17H36Si4 352.1894, found
352.1882.
1
°C. H NMR (CDCl3): δ 0.20 (s, 18H, SiMe3), 0.21 (s, 18H, SiMe3),
3.56 (s, 6H, OCH3). 13C NMR (CDCl3): δ 1.3, 1.5 (SiMe3), 51.3
(OCH3), 65.3 (C1,C4), 148.0 (CdC), 163.0 (CdC), 171.9 (CO). IR
(KBr): 2950.5, 2901.4, 2840.2, 1716, 1625.9, 1262.8, 1108.8, 843.3
cm-1. MS: m/z 482 (M+), 467 (M+ - CH3), 451 (M+ - OCH3), 409
(M+ - SiMe3). HRMS calcd for C22H42O4Si4 482.2160, found 482.2130.
3-Cyano-1,2,3-tris(trimethylsilyl)cyclopropene 18 (250 mg, 9%)
as colorless crystals. 1H NMR (CDCl3): δ 0.1 (s, 9H, SiMe3), 0.35 (s,
18H, SiMe3). 13C NMR (CDCl3): δ -2.4, -1.5 (SiMe3), 1.1 (quart.
Dimethyl Tetrakis(trimethylsilyl)phthalate. Dewarbenzene 12 (10
mg) was heated to 90 °C for 5.5 h. The phthalate was obtained
C), 126.6 (CN), 127.5 (CdC). IR (CCl4): 2200, 1750, 1250, 850 cm-1
.
1
quantitatively as colorless crystals, mp 165 °C. H NMR (CDCl3): δ
HRMS calcd for C13H27NSi3 281.1451, found 281.1473. In some cases,
cyclopropene 17 was found.
0.28 (s, 18H, SiMe3), 0.32 (s, 18H, SiMe3), 3.79 (s, 6H, OCH3). 13C
NMR (CDCl3): δ 3.4, 4.6 (SiMe3), 52.2 (OCH3), 135.7, 144.9, 166.9
(CdC), 171.3 (CO). IR (KBr): 2992.6, 2949.2, 2902.7, 1733.4, 1250.0,
1105.9, 847.1 cm-1. MS: m/z 482 (M+), 467 (M+ - CH3), 451 (M+
- OCH3), 409 (M+ - SiMe3). HRMS calcd for C22H42O4Si4 482.2160,
found 482.2180.
3-Methyl-1,2,3-tris(trimethylsilyl)cyclopropene 17 could also be
prepared in the following way: To a suspension of tris(trimethylsilyl)-
cyclopropenylium hexachloroantimonate 4 (100 mg, 0.17 mmol) in 3
mL of dry ether was added methyllithium (0.32 mmol) under argon at
-78° C. After the mixture was stirred for 15 min, the temperature was
raised to 0 °C, and a small amount of water was added. The residue
was extracted with ether, dried over MgSO4, and the solvent was
evaporated. High vacuum distillation gave the cyclopropene 17 (30
mg, 65%) as a colorless liquid. 1H NMR (CDCl3): δ 0.11 (s, 9H,
SiMe3), 0.14 (s, 18H, SiMe3), 0.92 (s, 3H, CH3). 13C NMR (CDCl3):
δ -2.00, -0.65 (SiMe3), 10.92 (quart. C), 25.8 (CH3), 141.84 (CdC).
IR (film): 2970, 2915, 2860, 1715, 1255, 840 cm-1. MS: m/z 270
(M+), 255 (M+ - CH3), 197 (M+ - SiMe3), 73 (SiMe3). HRMS calcd
for C13H30Si3 270.1640, found 270.1655.
1,2,3-Tris(trimethylsilyl)cyclopropene. To a suspension of tris-
(trimethylsilyl)cyclopropenylium hexachloroantimonate 4 (140 mg, 0.24
mmol) in 15 mL of dry ether was added lithium aluminum hydride
(10 mg, 0.26 mmol) under argon. After being stirred for 30 min, the
mixture was cooled to 0 °C and hydrolyzed with water. The residue
was filtered, washed with 20 mL of ether, and dried over MgSO4. The
solvent was evaporated, and high vacuum distillation gave 1,2,3-tris-
Tetrakis(trimethylsilyl)cyclobutadiene 8 (via Dianion 9). The
crystals of tetrakis(trimethylsilyl)cyclobutadiene cobalt complex 6 (3.0
g, 6.5 mmol) and an excess amount of lithium metal (1.0 g, 0.14 mol)
were placed in a reaction tube with a magnetic stirrer and degassed.
Dry oxygen-free THF (30 mL) was introduced by vacuum transfer,
and the mixture was stirred at room temperature for 24 h to give a
dark brown solution containing tetrakis(trimethylsilyl)cyclobutadiene
dianion 9. The solvent was evaporated, and then degassed hexane (40
mL) was introduced by vacuum transfer. After the filtration of the
residual lithium pieces and insoluble dark materials in a glovebox,
degassed THF (10 mL) and 1,2-dibromoethane (2.1 g, 11 mmol) were
introduced by vacuum transfer. The mixture was stirred for a short
time (ca. 1 min). The solvent was removed in vacuo, and then again
degassed hexane (5 mL) was introduced by vacuum transfer. After
(39) Garratt, P. J.; Tsotinis, A. J. Org. Chem. 1990, 55, 84-88.
9
J. AM. CHEM. SOC. VOL. 124, NO. 46, 2002 13825