J. J. Eisch, B. W. Kotowicz
FULL PAPER
solid identified as a mixture of trimethyltin chloride (5.0 mmol,
fine, pale yellow precipitate settled out. The colorless supernatant
44%) and dimethyltin dichloride (2.3 mmol, 40%). From the solu- solution was decanted and the precipitate dried under vacuum. The
tion the solvents were removed in vacuo to give 1.23 g of a yellow
oil. Since the separation of the substances present in the residue
precipitate was identified by spectral data as pure 36 (0.12 g, 23%).
Ϫ
1H NMR (C6H6): δ ϭ 1.09 (t, J ϭ 8.2 Hz, 6 H), 1.89 (q, J ϭ
was unsuccessful, the components were identified spectroscopically. 8.2 Hz, 4 H), 7.33 (dd, J ϭ 5.4, 3.2 Hz, 4 H), 8.01 (dd, J ϭ 5.3,
3.4 Hz, 4 H). Ϫ 13C NMR (C6H6): δ ϭ 10.3 (CH3), 12.4 (br., B-
1-Dichloroboryl-2-[chloro(methyl)boryl]benzene (40 mol-%)
CH2), 132.7, 136.0, 145.6 (br., Car-B). Ϫ 11B NMR (C6H6): δ ϭ
(24): 1H NMR (C6D6): δ ϭ 1.21 (s, 3 H), 7.19 (dd, J ϭ 5.5, 3.3
67.5.
Hz, 2 H), 8.18 (dd, J ϭ 5.5, 3.3 Hz, 2 H). Ϫ 13C NMR (C6D6):
δ
ϭ 9.5, 133.9, 136.4. Ϫ δ ϭ 33. Ϫ 1-
11B (C6H6):
1,3-Bis(diethylboryl)benzene (28): A solution of 1,3-bis(trimeth-
ylstannyl)benzene (1.46 g, 3.6 mmol) in 3 ml of dry pentane and
diethylboron chloride (0.85 g, 8.1 mmol) were stirred at room tem-
perature for 1 h. Thereupon the reaction mixture was heated under
atmospheric pressure until the pentane started to distill. Then, the
reaction mixture was stirred and heated to 70°C for 3 h. Volatiles
were removed under vacuum to leave a yellowish, oily residue that
was identified as essentially pure 1,3-bis(diethylboryl)benzene (0.67
[Chloro(methyl)boryl]-2-(chlorodimethylstannyl)benzene (65 mol-
%) (23): 1H NMR (C6D6): δ ϭ 0.24 (s, 6 H), 1.21 (s, 3 H), 7.42 (d,
1 H) 7.86 (td, 1 H), 7.92 (d, 1 H) 8.36 (td, 1 H). Ϫ 13C NMR
(C6D6): δ ϭ Ϫ0.3 (Sn-CH3), 10.0 (B-CH3), 132.8, 133.8, 135.8,
136.4. Ϫ 11B (C6H6): δ ϭ 38.7. Ϫ 119Sn (C6H6): δ ϭ 172.1. Ϫ 9,10-
Dichloro-9,10-Dihydro-9,10-diboraanthracene (22)[19] (ca. 10 mol-
%). Ϫ 1H NMR (C6D6): δ ϭ 7.27 (dd, J ϭ 5.55, 3.5 Hz, 4 H), 7.68
(dd, J ϭ 5.5, 3.5 Hz, 4 H). Ϫ 13C NMR (C6D6): δ ϭ 132.9, 137.1.
1
g, 87%). Ϫ H NMR (C6D6): δ ϭ 1.07 (t, J ϭ 7.9 Hz, 12 H), 1.62
(q, J ϭ 7.8 Hz, 8 H), 7.35 (t, J ϭ 7.5 Hz, 1 H), 7.87 (d, J ϭ 7.3
Hz, 2 H), 8.45 (s, 1 H). Ϫ 13C NMR (C6D6): δ ϭ 8.8 (CH3), 17.3
(br., B-CH2), 127.7, 137.8, 139.4, 140.3. Ϫ 11B NMR (C6D6): δ ϭ
78.5. Ϫ Attempts to further purify the crude product by distillation
failed and resulted in its significant decomposition with the liber-
ation of triethylborane.
When the reaction was repeated by employing 6.0 mmol of 1,2-
bis(trimethylstannyl)benzene and 24.0 mmol of boron trichloride,
Me3SnCl and Me2SnCl2 were filtered off from the chilled reaction
solution (Ϫ40°C), the filtrate freed of volatiles and the residue dis-
tilled under vacuum to yield 80% of 24.
Diethyl(phenyl)borane: A solution of trimethyl(phenyl)tin (2.65
g, 11 mmol) in 10 ml of dry pentane was added dropwise to a
stirred solution of diethylboron bromide (1.80 g, 12 mmol) in 10
ml of pentane at room temperature. The reaction mixture was
heated under atmospheric pressure until pentane started to distill.
When distillation stopped, the reaction was heated and stirred at
70°C for 3 h. The volatiles were removed under vacuum to give a
clear, brownish liquid which was identified as nearly pure diethyl-
(phenyl)borane (1.43 g, 89%). Ϫ 1H NMR (C6D6): δ ϭ 1.01 (t, J ϭ
7.8 Hz, 6 H), 1.54 (q, J ϭ 7.8 Hz, 4 H), 7.25 (m, 3 H), 7.75 (d, J ϭ
6.5 Hz, 2 H). Ϫ 13C NMR (C6D6): δ ϭ 8.8 (-CH3), 16.0 (br., B-
CH2), 128.2, 132.1, 134.5, 139.3 (Car-B). Ϫ 11B NMR (C6D6):
δ ϭ 78.1.
A parallel procedure was conducted with 1,4-bis(trimethylstan-
nyl)benzene (8) and diethylboron chloride to provide a 90% yield
of 1,4-bis(diethylboryl)benzene (29) at the stage where volatiles had
been removed from the reaction mixture. Attempted distillation
again led to the evolution of triethylborane.
2-(Diethylboryl)-Ͱ-(trimethylstannyl)toluene (30): At room tem-
perature a solution of α,2-bis(trimethylstannyl)toluene (1.71 g, 4
mmol) in 3 ml of dry pentane was added dropwise to a neat sample
of diethylboron chloride (0.85 g, 8 mmol). The reaction mixture
was stirred at room temperature for 1 h and then heated gradually
until pentane started to distill. The reaction mixture then was
stirred and heated at 70°C for 3 h. After that, volatiles were re-
moved under reduced pressure to leave a pale yellow, oily mixture
of 30 and unreacted tin derivative in approximately a 1:1 molar
ratio. The residue was then allowed to react further with an excess
of Et2BCl (1.0 g, 10 mmol). After stirring the mixture at 60°C for
12 h, the volatiles were removed in vacuo. The clear yellow oil was
identified by spectral data as 2-(diethylboryl)-α-(trimethylstannyl)-
toluene. Further purification of the crude product by distillation
resulted in its partial decomposition. Ϫ 1H NMR (C6D6): δ ϭ 0.03
(s, JSn-H ϭ 52 Hz, 9 H), 1.03 (t, J ϭ 7.6 Hz, 6 H), 1.49 (q, J ϭ 7.6
Hz, 4 H), 2.20 (s, 2 H, JSn-H ϭ 72 Hz), 6.93 (t, J ϭ 7.5 Hz, 1 H),
6.94 (d, J ϭ 6.2 Hz, 1 H), 7.00 (t, J ϭ 7.4 Hz, 1 H), 7.12 (td, J ϭ
7.4, 1.2 Hz, 1 H). Ϫ 13C NMR (C6D6): δ ϭ Ϫ9.5 (Sn-CH3, J ϭ
324, 308 Hz), 8.95 (B-CH2-CH3), 21.6 (Sn-CH2, J ϭ 300, 244 Hz),
22.0 (br., CH2), 123.1, 127.6, 128.36, 128.42, 143.1 (CHar-B). Ϫ 11B
NMR (C6D6): δ ϭ 85.3. Ϫ 119Sn NMR (C6D6): δ ϭ 3.7.
1,2-Bis(diethylboryl)benzene (27): A solution of 1,2-bis(trimeth-
ylstannyl)benzene (1.81 g, 4.5 mmol) in 5 ml of dry pentane was
added dropwise to a refluxing solution of diethylboron bromide
(1.78 g, 12 mmol) in 10 ml of pentane. After the addition, the
reaction mixture was heated at reflux for 1 h. The pentane and
unreacted Et2BBr were removed under reduced pressure and a fresh
10-ml portion of dry pentane was added to the yellow residue and
the solution was cooled to Ϫ78°C. Upon cooling a precipitate was
formed and was filtered off at Ϫ78°C. The pentane was removed
from the filtrate under vacuum to give a crude product as a lemon-
colored oil (1.16 g). Distillation of the crude product yielded 27 as
a yellowish, viscous liquid (0.81 g, 84%). During distillation partial
decomposition with the evolution of some triethylborane was ob-
1
served. Ϫ H NMR (C6D6): δ ϭ 1.00 (t, J ϭ 8 Hz, 12 H), 1.35 (q,
J ϭ 8 Hz, 8 H), 7.24 (dd, J ϭ 5.0, 3.0 Hz, 2 H), 7.35 (dd, J ϭ 5.0,
3.0 Hz, 2 H). Ϫ 13C NMR (C6D6): δ ϭ 8.2 (CH2-CH3), 21.6 (br.,
B-CH2-CH3), 128.6, 130.3, 139.7 (Car-B). Ϫ 11B NMR (C6D6):
δ ϭ 80.8.
2-(Diethylboryl)-Ͱ-(bromodimethylstannyl)toluene (31): A solu-
tion of α,2-bis(trimethylstannyl)toluene (2.11 g, 5 mmol) in 5 ml of
dry pentane was added to a solution of diethylboron bromide (1.78
g, 12 mmol) in 5 ml of pentane at room temperature. The reaction
mixture was heated at reflux for 3 h and then the pentane was
9,10-Diethyl-9,10-dihydro-9,10-diboraanthracene (36): A solution
of 1,2-bis(diethylboryl)benzene (27) (0.98 g, 4.6 mmol) in dry hep-
tane (10 ml) was heated under reflux for 12 h. The solvent was then partly distilled off under atmospheric pressure. The residue was
gradually distilled off as the reaction temperature rose to 140°C.
The residue was stirred at 140Ϫ150°C for 6 h and the volatiles
further heated at 70°C for 4 h. The volatiles were removed under
vacuum to leave a colorless oil of almost pure 31 (1.75 g, 90%). Ϫ
then were removed under vacuum. The oily, yellow residue (0.63 g) 1H NMR (C6D6): δ ϭ 0.31 (s, JSn-H ϭ 55 Hz, 6 H), 0.97 (t, J ϭ
contained (36) and unreacted (27) in an approximate molar ratio
of 1.0:0.3. Freshly distilled pentane (10 ml) was added to the resi-
7.5 Hz, 6 H), 1.44 (q, J ϭ 7.5 Hz, 4 H), 2.58 (s, 2 H, JSn-H ϭ 68
Hz); 6.85Ϫ7.05 (m, 4 H). Ϫ 13C NMR (C6D6): δ ϭ Ϫ2.6 (Sn-CH3),
due and the resulting solution was cooled to Ϫ78°C, whereupon a 8.9 (B-CH2-CH3), 22.1 (br., B-CH2), 27.9 (Sn-CH2), 124.3, 127.9,
768 Eur. J. Inorg. Chem. 1998, 761Ϫ769