Luminescent Boron Compounds
FULL PAPER
for C32H38B2N2S: C 76.21, H 7.59, N 5.55; found: C 76.09, H 7.73, N 5.50.
Experimental Section
5-(Dimesitylboryl)-5’-(1“,3”-diethyl-1“,3”,2“-benzodiazaborol-2”-yl)-2,2’-
dithiophene (4): A solution of 1.6m n-butyllithium (1.79 mL, 2.87 mmol)
in n-hexane was added to a chilled solution (ꢀ788C) of 7 (1.35 g,
2.74 mmol) in n-hexane (30 mL). After stirring for 30 min, the mixture
was warmed to ambient temperature and stirring was pursued for anoth-
er 3 h. A sample of neat 5 (0.69 g, 2.74 mmol) was added and stirring of
the mixture was continued for 16 h at 208C. The resulting slurry was fil-
tered, and the filtrate was freed from solvent and volatile components in
vacuo. The solid residue was dissolved in a minimum amount of boiling
n-hexane and after cooling to room temperature, the solution was stored
overnight at ꢀ358C to give a yellow solid 4 (1.34 g, 71% yield). Elemen-
tal analysis calcd (%) for C36H40B2N2S2: C 73.73, H 6.87, N 4.78; found:
C 73.68, H 6.74, N 4.60.
All manipulations were performed under an atmosphere of dry oxygen-
free argon using Schlenk techniques. All solvents were dried with the
usual drying agents and then freshly distilled prior to use. The com-
pounds 4-bromophenyldimesitylborane,[17] 2-bromo-1,3-diethyl-1,3,2-ben-
zodiazaborole (5),[24] 4’-bromo-4-dimesitylboryl-biphenyl,[37] dimesityl-
fluoroborane (8),[38] and 5,5’-dibromodithiophene[60] were prepared ac-
cording to literature methods, and 4,4’-dibromobiphenyl and 1,4-dibro-
mobenzene were purchased from Acros. NMR spectra were recorded
from solutions at room temperature in C6D6 or CDCl3 (unless otherwise
stated) on a Bruker AM Avance DRX500 spectrometer (1H, 11B, 13C)
.
with SiMe4 (1H,13C) and BF3 OEt2 (11B) as external standards. Some ex-
pected broad 13C peaks corresponding to the carbon attached to boron
were not detected above the noise levels. Mass spectra were obtained
with a VG Autospec sector field mass spectrometer (Micromass). For de-
tailed spectroscopic data see the Supporting Information. Absorption
spectra were measured with a UV/VIS double-beam spectrometer (Shi-
madzu UV-2550). For details see the Supporting Information.
2-Dimesitylborylthiophene (6):
A solution of 1.6m n-butyllithium
(4.33 mL, 6.93 mmol) in n-hexane was added to a solution of thiophene
(0.53 g, 6.30 mmol) in THF (30 mL) at ꢀ788C. The mixture was warmed
to 208C and stirred for 1 h before a solution of 8 (1.69 g, 6.30 mmol) in
THF (20 mL) was added. After stirring over night, the solution was
washed with water (100 mL) and the aqueous phase was extracted with
diethyl ether. (2ꢄ100 mL). The combined organic fractions were dried
over anhydrous Na2SO4 and volatiles were removed in vacuo. The re-
maining oil was purified by column chromatography at silica gel, and 6
were obtained as colorless oil (1.23 g, 59% yield). Compound 6 was iden-
4-(Dimesitylboryl)-1-(1’,3’-diethyl-1’,3’,2’-benzodiazaborol-2’-yl)benzene
(1): A solution of 1.6m n-butyllithium (1.90 mL, 3.04 mmol) in n-hexane
was added to a solution (ꢀ788C) of (4-bromophenyl)(dimesityl)borane
(0.79 g, 2.95 mmol) in THF (25 mL). The mixture was stirred 1 h at
ꢀ788C before a sample of neat 5 (0.75 g, 2.96 mmol) was added. The re-
action mixture was warmed to ambient temperature with stirring for
16 h. Solvent and volatile components were removed in vacuo. The solid
residue was triturated three times with boiling n-hexane. The filtrate was
evaporated to dryness and the residue was crystallized from n-hexane to
afford a colorless microcrystalline solid 1 (0.99 g, 67% yield). Elemental
analysis calcd (%) for C34H40B2N2: C 81.95, H 8.09, N 5.62; found: C
81.89, H 7.99, N 5.43.
1
tified by H and 11B NMR spectroscopy.
5-Bromo-5’-dimesitylboryl-2,2’-dithiophene (7): A solution 1.6m n-butyl-
lithium (2.9 mL, 4.7 mmol) in n-hexane was added dropwise to a solution
of 5,5’-dibromo-2,2’-dithiophene (1.34 g, 4.24 mmol) in THF (40 mL) at
ꢀ788C and the resulting mixture was then stirred for 30 min. The mixture
was warmed to room temperature, stirred for 1 h and then cooled to
ꢀ788C. Then a solution of 8 (1.11 g, 4.24 mmol) in n-pentane (30 mL)
was added and the mixture was warmed to 208C. After stirring overnight,
the reaction mixture was added to water (100 mL), the organic layer was
separated and the aqueous layer was washed with diethyl ether (2ꢄ
200 mL). The combined organic extracts were dried over anhydrous
Na2SO4. The solvents were removed in vacuo. The crude residue was pu-
rified by column chromatography on silica gel with cyclohexane to afford
4’-Dimesitylboryl-4-(1’’,3’’,2’’-benzodiazaborole-2’’-yl)-biphenyl (2): A so-
lution of 1.6m n-butyllithium (2.40 mL, 3.84 mmol) in n-hexane was
added to
a
solution (ꢀ788C) of 4’-bromo-4-dimesitylborylbiphenyl
(1.80 g, 3.74 mmol) in THF (40 mL). The mixture was stirred 1 h at
ꢀ788C before a sample of neat 5 (0.97 g, 3.84 mmol) was added. Stirring
was continued for 1 h at ꢀ788C and for 16 h at room temperature. After
evaporation to dryness the residue was
suspended in toluene (30 mL) and the
obtained slurry was filtered. The fil-
trate was concentrated and stored at
ꢀ358C for 2 d and a colorless micro-
Table 10. Crystallographic data for compounds 2, 3, and 4.
2
3
4
.
formula
C40H44B2N2 CH2Cl2
659.32
C32H38B2N2S
504.32
0.16ꢄ0.12ꢄ0.04
triclinic
C36H40B2N2S2
586.44
0.30ꢄ0.16ꢄ0.05
orthorhombic
Pna21
35.908(11)
11.664(5)
7.749(3)
90
90
90
3246(2)
4
1.200
0.192
1248
3.2-27.5
31152
7028
0.1133
4142
387
crystalline product
2 was obtained
Mr [gmolꢀ1
]
(1.16 g, 54% yield). Elemental analysis
calcd (%) for C40H44B2N2·0.5CH2Cl2:
crystal size [mm]
crystal system
space group
a [ꢃ]
b [ꢃ]
c [ꢃ]
0.30ꢄ0.26ꢄ0.24
monoclinic
P21/n
9.6086(2)
36.0766(7)
31.4181(6)
90
C 74.69,
H 7.03, N 4.25; found: C
¯
P1
74.98; H 7.30, N 4.14.
9.1341(2)
16.4987(4)
19.1034(4)
89.1668(12)
88.3439(12)
89.5897(13)
2877.32(11)
4
1.164
0.136
1080
3.0-27.5
62524
13184
0.049
9643
683
1.025
0.0479
0.1248
0.276/ꢀ0.309
2-Dimesitylboryl-5-(1’,3’,2’-benzodia-
zaborol-2’-yl)-thiophene (3):
A solu-
tion of 1.6m n-butyllithium (1.75 mL,
2.81 mmol) in n-hexane was added to
a solution (ꢀ788C) of 2-dimesitylbor-
ylthiophene (6) (0.85 g, 2.56 mmol) in
THF (40 mL). Stirring was continued
for 15 min and for another 60 min at
ambient temperature. The reaction
mixture was re-cooled to ꢀ788C and
then neat 5 (0.65 g, 2.56 mmol) was
added. The solution was warmed to
room temperature and stirred for 6 h.
After removing solvent and volatile
components in vacuo, the remaining
green oil was purified by short-path
distillation (3508C, 10ꢀ6 bar) to give an
off-white solid. Recrystallization of the
solid from n-pentane at ꢀ358C gave
a [8]
b [8]
95.3049(6)
90
10844.3(4)
12
1.212
0.211
4200
3.0-25.0
93795
19032
0.040
g [8]
V [ꢃ3]
Z
1calcd [gcmꢀ3
]
m [nmꢀ1
F (000)
q [8]
]
reflns collected
unique reflns
R (int)
reflns observed [I>2s(I)]
parameters
15447
1299
GOF
1.025
1.014
RF [I>2s(I)]
wRF2 (all data)
0.0501
0.1358
0.899/ꢀ0.633
0.0594
0.1297
0.322/ꢀ0.236
colorless crystals of
3 (0.80 g, 67%
D1max/min [eꢃꢀ3
]
yield). Elemental analysis calcd (%)
Chem. Eur. J. 2012, 18, 1369 – 1382
ꢂ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1379
Weber, Lothar
