7,8-Digermabicyclo[2.2.2]octadienes
Su m m a r y a n d Con clu sion s
Organometallics, Vol. 19, No. 17, 2000 3385
the same reaction conditions for the case of 1,1,2,2-tetra-
methyl-3,6-diphenyl-1,2-digermacyclohexa-3,5-diene: bp 152
1
Photolysis of 2,3-benzo-7,7,8,8-tetralkyl-7,8-digermabi-
cyclo[2.2.2]octadienes in solutions gives tetraalkyldi-
germenes and naphthalene in the triplet excited state
as a major process. The 1,2-germyl rearranged products,
2,3-benzo-6,6,7,7-tetraalkyl-6,7-digermatricyclo[3.3.0.0]-
octane, are formed as a minor process. The laser flash
photolysis and matrix isolation studies show that the
UV peaks of the digermenes are at ca. 380 nm. The
digermenes react with 1,3-butadienes, a digermene
trapping agent, to give 1,2-digermecyclohex-4-enes in
good yields. The quenching reactions of digermenes with
carbon teterachloride and ethanol and oxygen are 100
times and 1000 times, respectively, faster than those
with 1,3-butadienes. Product analyses of the quenching
reactions of digermenes with several substrates are
carried out by steady-state methods.
°C/0.5 mmHg; H NMR (δ in C6D6) 0.84-1.17 (m, 20 H), 6.76
(s, 2 H), 7.06-7.23 (m, 10 H); 13C NMR (δ in C6D6) 7.5, 10.7,
126.5, 126.8, 128.6, 139.3, 145.2, 146.8; MS m/z M+ 466. Anal.
Calcd for C24H32Ge2: C, 61.90; H, 6.92. Found: C, 62.12; H,
7.02.
P r ep a r a tion of 1,4-Dip h en yl-2,3-ben zo-7,7,8,8-tetr a -
m eth yl-7,8-d iger m a bicyclo[2.2.2]octa d ien e (1a ).3q To a
mixture of 1,1,2,2-tetramethyl-3,6-diphenyl-1,2-digermacyclo-
hexa-3,5-diene (2.13 g, 5.2 mmol) and 1-aminobenzotriazole
(1.05 g, 7.8 g) in dichloromethane (27 mL) was added lead
tetraacetate (3.87 g, 8.0 mmol) in dichloromethane (30 mL) at
-78 °C during a period of 40 min. As soon as the addition was
completed, the reaction mixture was filtered through silica gel
(Wako gel C 200) and washed with benzene, and the solvent
was removed in vacuo. The residue was purified by rapid
chromatography with silica gel treated with triethylamine and
washed with hexane, and the solvent was removed in vacuo.
The final product was pure solid 7,8-digermabicyclo[2.2.2]-
octadiene (0.79 g, 1.46 mmol, 28.0%): mp 150-153 °C; 1H
NMR (δ in C6D6) 0.24 (s, 6 H), 0.40 (s, 6 H), 6.04 (s, 2 H), 6.63-
6.77 (m, 4 H), 7.17-7.54 (m, 10 H); 13C NMR (δ in C6D6) -3.99,
-2.22, 52.1, 125.0-132.6, 141.0, 146.1; MS m/z M+ 486; UV
(cyclohexane) λ max/nm (log ꢀ) 213 (4.66), 235 (sh, 4.15), 285
(3.31). Anal. Calcd for C26H28Ge2: C, 64.30; H, 5.81. Found:
C, 64.55; H, 5.92.
P r ep a r a tion of 1,4-Dip h en yl-2,3-ben zo-7,7,8,8-tetr a -
eth yl-7,8-d iger m a bicyclo[2.2.2]octa d ien e (1b). 1,4-Diphen-
yl-2,3-benzo-7,7,8,8-tetraethyl-7,8-digermabicyclo[2.2.2]-
octadiene was similarly prepared by the reaction of 1,1,2,2-
tetraethyl-3,6-diphenyl-1,2-digermacyclohexa-3,5-diene (1.15
g, 2.46 mmol), 1-aminobenzotriazole (0.60 g, 4.61 g), and lead
tetraacetate (2.23 g, 4.61 mmol) in 54.0% yield: mp 119-123
°C; 1H NMR (δ in C6D6) 0.88-1.21 (m, 20 H), 6.07 (s, 2 H),
6.68-6.75 (m, 4 H), 7.18-7.57 (m, 10 H); 13C NMR (δ in C6D6)
8.0, 9.3, 10.5, 11.1, 53.0, 124.9, 125.5, 126.6, 128.9, 131.4, 131.5,
141.5, 146.5; MS m/z M+ 542. UV(cyclohexane) λ max/nm (log
Exp er im en ta l Section
NMR spectra were obtained on a Varian Unity Inova 400
MHz NMR spectrometer. GC-MS spectra were measured on
a J EOL J MS-DX 303 mass spectrometer. The infrared spectra
were recorded with a Shimadzu FT IR 4200 spectrometer. The
UV and UV-vis spectra were recorded on a Shimadzu UV
2200 spectrometer. Gas chromatography was performed on a
Shimadzu GC 8A with a 1 m 20% SE30 column. Liquid
chromatography was performed on a Twincle with an Asa-
hipak GS 310 column.
Cyclohexane, cyclohexane-d12, benzene, benzene-d6, 2,3-
dimethylbuta-1,3-diene, 2-methylbuta-1,3-diene, methanol,
ethanol, ethanol-d1, 2-propanol, tert-butyl alcohol, carbon
tetrachloride, chloroform, dichloromethane, triethylsilane,
1-hexyne, and 3-methylpentane were distilled under argon
after refluxing over calcium hydride, sodium, or magnesium
for 1-2 days. 1,4-Diphenylnaphthalene, hexachloroethane, and
1-aminobenzotriazole were commercially available.
ꢀ) 213 (4.70), 235 (sh, 4.17), 285 (3.43). Anal. Calcd for C30H34
-
Ge2: C, 66.75; H, 6.35. Found: C, 67.01; H, 6.15.
1,1,2,2-Tetramethyl-3,6-diphenyl-1,2-digermacyclohexa-3,5-
diene,3q 1,4-diphenyl-2,3-benzo-7,7,8,8-tetramethyl-7,8-digerma-
bicyclo[2.2.2]octadiene,3q dimethyldichlorogermane,27 and 1,2-
dichlorotetramethyldigermane28 were prepared as reported in
the literature.
P r ep a r a tion of 1,1,2,2,4,5-Hexa m eth yl-1,2-d iger m a cy-
cloh ex-4-en e. A mixture of 1,1,2,2-tetramethyl-1,2-dichloro-
digermane (1.5 g, 5.4 mmol), 2,3-dimethylbuta-1,3-diene (0.56
g, 6.8 mmol), and lithium metal (56 mg, 8 mmol) in ether (45
mL)-THF (9 mL) was stirred at room temperature for 12 h.
The mixture was then hydrolyzed, and the organic layer was
separated and dried over anhydrous sodium sulfate. The
solvent was removed in vacuo, and the residual brown oil was
placed in a distilling flask. Fractional distillation gave 0.2 g
(0.7 mmol, 13.0%) of pure 1,1,2,2,4,5-hexamethyl-1,2-diger-
macyclohex-4-ene: bp 160 °C/27 mmHg; NMR (δ in C6D6) 0.26
(s, 6 H), 1.59 (s, 4 H), 1.75 (s, 6 H); 13C NMR (δ in C6D6) -4.2,
22.2, 24.2, 123.9; MS m/z M+ 288. Anal. Calcd for C10H22Ge2:
C, 41.78; H, 7.71. Found: C, 41.84; H, 7.92.
P h ot olysis of 1,4-Dip h en yl-2,3-b en zo-7,7,8,8-t et r a -
m eth yl-7,8-d iger m a bicyclo[2.2.2]octa d ien e (1a ). A de-
gassed sealed Pyrex tube containing a benzene (1 mL) solution
of 7,8-digermabicyclo[2.2.2]octadiene (1a ) (20 mg, 0.04 mmol)
was irradiated with a 120 W low-pressure Hg arc lamp (Sen
Tokushu Kogen Co. Ltd.) for 3 h at room temperature. NMR,
GC, and GC-MS analysis of the resulting mixture showed the
presence of 1,4-diphenylnaphthalene (3, 81%), rearranged
product (4a , 6%), 1-oxa-2,3,4,5-tetragermacyclopentane (6a ,
29%), cyclotetragermane (5a , <0.1%), 1,4-dioxa-2,3,5,6- tet-
ragermacyclohexane (7a , <0.1%), and oligo(tetramethyldiger-
menes)s (8a ). 4a : NMR (δ in C6D6) -0.34 (s, 3 H), 0.39 (s, 3
H), 0.46 (s, 3 H), 0.47 (s, 3 H), 1.63 (d, J ) 8.6 Hz, 1 H), 2.69
(d, J ) 8.6 Hz, 1 H), 6.90-7.55 (m, 14 H); MS m/z M+ 486.
The structures of oligogermanes 5a and 7a were very carefully
assigned by comparing with their GC data reported previ-
ously.15,16 The compound 5a was very quickly oxidized to give
P r ep a r a tion of 1,1,2,2-Tetr a m eth yl-3,6-d ip h en yl-1,2-
d iger m a cycloh exa -3,5-d ien e.3q To a suspension of 1,4-
dibromo-1,4-diphenylbutadiene (5.26 g, 14.5 mmol) in 29 mL
of ether, cooled in an ice-bath, was added 22.8 mL of 1.27 N
n-butyllithium dropwise during a period of 20 min. The
solution was allowed to come to room temperature. THF (48
mL) was added, and the solution was again cooled in an ice
bath. During a period of 45 min, 1,2-dichloro-1,1,2,2-tetra-
methyldigermane (4.0 g, 14.5 mmol) in 19 mL of THF was
added dropwise, and the mixture was stirred overnight at room
temperature and then refluxed for 4 h. The mixture was then
hydrolyzed, and the organic layer was separated and dried over
anhydrous sodium sulfate. The solvent was removed in vacuo,
and the residual brown oil was placed in a distilling flask.
Fractional distillation gave 3.71 g (8.85 mmol, 61.0%) of pure
1,2-digermacyclohexa-3,5-diene: bp 152 °C/1.0 mmHg; 1H
NMR (δ in C6D6) 0.41 (s, 12 H), 6.81 (s, 2 H), 7.07-7.29 (m, 10
H); MS m/z M+ 412.
P r ep a r a tion of 1,1,2,2-Tetr a eth yl-3,6-d ip h en yl-1,2-d i-
ger m a cycloh exa -3,5-d ien e. 1,2-Dichloro-1,1,2,2-tetraethyl-
digermane28 (3.85 g, 11.6 mmol) reacted with 1,4-dilithio-1,4-
diphenylbutadiene to give 1,1,2,2-tetraethyl-3,6-diphenyl-1,2-
digermacyclohexa-3,5-diene (1.15 g, 2.46 mmol, 21.2%) under
(27) Finholt, A. E. Nucl. Sci. Abstr. 1957, 6, 617.
(28) Kumada, M.; Sakamoto, S.; Ishikawa, M. J . Organomet. Chem.
1969, 17, 235.