N-aryl- and N-thienylcarbazoles with dimesitylboryl and 1,3,2-benzodiazaborolyl functions

Article abstract of DOI:10.1002/ejic.201100123

The reaction of the N-lithiated 3,6-di-tert-butylcarbazole with fluorodimesitylborane afforded the N-carbazolyl-functionalized dimesitylborane 1 as a colorless solid in 70 % yield. [4-(3,6-Di-tert-butylcarbazol-9-yl)phenyl] dimesitylborane (2) was synthes

Full text of DOI:10.1002/ejic.201100123

FULL PAPER
DOI: 10.1002/ejic.201100123
N-Aryl- and N-Thienylcarbazoles with Dimesitylboryl and 1,3,2-
Benzodiazaborolyl Functions
Lothar Weber,*[a] Johannes Halama,[a] Lena Böhling,[a] Anna Chrostowska,*[b]
Alain Dargelos,[b] Hans-Georg Stammler,[a] and Beate Neumann[a]
Keywords: Boron / Carbazoles / Density functional calculations / Photophysics
The reaction of the N-lithiated 3,6-di-tert-butylcarbazole
with fluorodimesitylborane afforded the N-carbazolyl-func-
tionalized dimesitylborane 1 as a colorless solid in 70% yield.
[4-(3,6-Di-tert-butylcarbazol-9-yl)phenyl]dimesitylborane (2)
was synthesized in 59% yield by the lithiation of N-(4-bro-
mophenyl)-3,6-di-tert-butylcarbazole and the subsequent
treatment of the organolithium compound with fluorodimes-
itylborane. Synthesis of yellow crystalline [5-(carbazol-9-yl)-
2-thienyl]dimesitylborane 3 was effected in 66% yield by the
lithiation of 3,6-di-tert-butyl-N-(2-thienyl)carbazole and the
subsequent reaction with fluorodimesitylborane. Coupling of
N-(4-bromophenyl)-3,6-di-tert-butylcarbazole and 2-bromo-
1,3-diethyl-1,3,2-benzodiazaborole with magnesium metal in
boiling THF in the presence of lithium chloride led to the
formation of the functionalized benzodiazaborole 5 as a col-
orless solid in 68% yield. Compounds 1–3 and 5 were charac-
terized by elemental analyses, IR and NMR spectroscopy (1H,
11B, 13C) and mass spectrometry. The molecular structures of
1 and 3 were elucidated by X-ray diffraction analyses. The
borylated systems show intense blue luminescence. The
spectroscopic results were reproduced by TD-DFT calcula-
tions at the [B3LYP/6-311G(d,p)] level of theory. Thus, it was
discovered that the LUMOs of 1–3 are located on the vacant
2pz orbital of the boron atom with contributions of the π*
orbital of the phenyl (in 2) or thiophene (in 3) unit, whereas
the HOMOs are mainly represented by the carbazolyl unit.
closed that the 1,3,2-benzodiazaborolyl group does not
function as a π-acceptor as originally anticipated, but in-
stead behaves as a π-donor substituent. The HOMOs of the
molecules under investigation were mainly represented by
the B/N heterocycle, whereas the LUMOs were located at
the organic π-scaffold. Thus, the absorptions were ex-
plained by intramolecular charge-transfer processes. In
keeping with this, the emission bands were subject to a pro-
nounced solvatochromism.[8]
In a recent paper, we tried to design push–pull molecules
in which the benzodiazaborolyl unit should be forced into
the role of an acceptor by a carbazole as a prominent donor
substituent at the other end of a π-system. To our surprise,
the HOMO and LUMO of these species were both located
on the carbazole part of the molecules, and the absorption
spectrum showed transitions without the participation of
the boron heterocycle.[10] In this context, it was interesting
to replace the 1,3,2-benzodiazaborolyl moiety by the
strongly π-accepting dimesitylboryl substituent and to
study the photophysical behavior of the resulting molecules
under otherwise comparable conditions.
Introduction
Conjugated organic molecules and polymers containing
three-coordinate boron have attracted considerable interest
because of their optical and electronic properties, which
make them potentially useful in functional materials.[1]
Three-coordinate boron generally behaves as a π-acceptor
due to its vacant pz orbital, which stabilizes the LUMO of
an adjacent conjugated π-electron skeleton and thus lowers
the HOMO–LUMO gap of these molecules. Thereby the
dimesitylboryl (BMes2) function (Mes = 2,4,6-Me3C5H2) is
the preferred substituent in which the coordinatively and
electronically deficient boron center experiences the steric
shielding of four o-methyl groups.[2–5] In the course of our
studies on the chemical and physico-chemical properties of
1,3,2-diazaboroles and 1,3,2-benzodiazaboroles,[6] it was
demonstrated that arenes, biphenyls, thiophenes, dithio-
phenes and arylalkynes functionalized by 1,3,2-benzodiaza-
borol-2-yl units exhibit intense blue luminescence upon UV
irradiation with Stokes shifts up to 9500 cm–1 and quantum
efficiencies up to 0.99.[7–9] Our studies, however, have dis-
[a] Fakultät für Chemie der Univerität Bielefeld,
33615 Bielefeld, Germany
E-mail: lothar.weber@uni-bielefeld.de
Results and Discussion
[b] Equipe Chimie Physique, IPREM, UMR 5254, Université de
Pau et des Pays de l’Adour,
2 Av. du président Angot, B. P. 1155, 64013 Pau Cédex, France
E-mail: anna.chrostowska@univ-pau.fr
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201100123.
The reaction of in situ generated N-lithiated 3,6-di-tert-
butylcarbazole[11] with an equimolar amount of fluorodi-
mesitylborane[12] in n-pentane at room temperature led to
Eur. J. Inorg. Chem. 2011, 3091–3101
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L. Weber, A. Chrostowska et al.
FULL PAPER
the generation of the (carbazol-9-yl)dimesitylborane 1 as a
colorless solid in 70% yield.
Lithiation of N-(4-bromophenyl)-3,6-di-tert-butylcarb-
azole was achieved by treatment with an equimolar amount
of n-butyllithium in diethyl ether at –78 °C. After warming
the mixture to –20 °C, a solution of fluorodimesitylborane
in n-pentane was added. After hydrolysis, crude 2 was iso-
lated from the organic layer and purified by crystallization
from n-hexane. Pure 2 was obtained as colorless crystals in
59% yield.
The synthesis of [5-(carbazol-9-yl)-2-thienyl]dimesityl-
borane 3 was effected by the lithiation of 3,6-di-tert-butyl-
N-(2-thienyl)carbazole[13] with n-butyllithium in diethyl
ether at room temperature and the subsequent treatment of
the resulting reaction mixture with an equivalent of fluoro-
dimesitylborane. After the addition of water to the reaction
mixture, yellow crystalline 3 was isolated by diethyl ether
extraction, removal of volatile compounds from the extract,
and crystallization of the residue from n-hexane at 4 °C
(66% yield) (Scheme 1).
Figure 1. Compounds 4a,b, 5 and 6a,b.
Compounds 4a,b and 6a,b have been the subject of a
recent paper.[10] The missing link, the 1,3,2-benzodiazabor-
ole derivative 5, was synthesized by the magnesium metal
mediated coupling of equimolar quantities of 2-bromo-1,3-
diethyl-1,3,2-benzodiazaborole and N-(4-bromophenyl)-
3,6-di-tert-butylcarbazole[14] in boiling THF for 18 h
(Scheme 2).
Compounds 1–3 are stable to oxygen and moisture,
whereas 5 slowly decomposes when exposed to air. These
new compounds are well soluble in common aprotic organic
solvents. In the 11B{1H}NMR spectrum of 1 a singlet was
observed at δ = 51.0 ppm, whereas the respective singlet
resonances of 2 and 3 are more deshielded (δ = 64.9 and
71.3 ppm, respectively). For benzodiazaborole 5, an
11B{1H}NMR resonance at δ = 28.9 ppm was observed.
X-ray Structural Analysis of 1
Single crystals of 1 suitable for an X-ray structural study
(Table 5) were grown from an n-pentane solution at 4 °C.
The compound crystallizes in the monoclinic space group
C2/c. The molecule (Figure 2) may be described as a dimes-
itylborane in which the third coordination site is occupied
by
a planar carbazole ring. The bond B(1)–N(1)
[1.440(3) Å] is slightly shorter than the average B–N bond
in the corresponding 2-(carbazol-9-yl)-1,3,2-benzodiaza-
Scheme 1. Syntheses of 1–3.
For the validation of the capability of the dimesitylboryl borole 4a [1.468(5) Å].[10] For the average B–N bond length
and 1,3,2-benzodiazaborolyl groups as substituents on vari- in a sterically unhindered acyclic aminoborane, a value of
ous luminescent carbazoles, the comparison of 1–3 with de- 1.41 Å is given in the literature.[15] A particularly short B=N
rivatives 4–6 is indispensable (Figure 1).
bond was measured in (CF3)2B=NiPr2 [1.37(1) Å].[16]
Scheme 2. Synthesis of 5.
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Carbazoles with Dimesitylboryl and 1,3,2-Benzodiazaborolyl Functions
N(1)–C(12) distances [1.422(3), 1.427(3) Å], larger values
were observed than in 4a [1.402(5), 1.404(5) Å]. The C–C
bond lengths within the five-membered ring in 1 [1.399(3),
1.402(3), 1.452(3) Å] are well comparable to those in 4a
[1.396(6), 1.407(5), 1.443(6) Å].
X-ray Structural Analysis of 3
Single crystals of 3 were grown from an n-hexane solu-
tion at 4 °C. The compound crystallizes in the monoclinic
space group P21/c. The molecule (Figure 4) consists of a
planar thiophene ring in which the 2-position is linked to
the planar carbazole fragment by a single N(1)–C(21) bond
[1.394(3) Å]. Both rings enclose an interplanar angle of
33.3°, which differs from the respective angle in 6a (41.4°).
Figure 2. Molecular structure of 1. Selected bond lengths [Å] and
angles [°]: B(1)–N(1) 1.440(3), B(1)–C(21) 1.578(3), B(1)–C(30)
1.577(3), N(1)–C(1) 1.422(3), N(1)–C(12) 1.427(3), C(1)–C(6)
1.402(3), C(6)–C(7) 1.452(3), C(7)–C(12) 1.399(3), C(21)–C(22)
1.420(3), C(21)–C(26) 1.415(3), C(22)–C(23) 1.390(3), C(23)–C(24)
1.395(3), C(24)–C(25) 1.389(3), C(25)–C(26) 1.393(3), C(30)–C(31)
1.407(3), C(31)–C(32) 1.390(3), C(32)–C(33) 1.393(3), C(33)–C(34)
1.386(3), C(34)–C(35) 1.389(3), C(35)–C(30) 1.412(3); N(1)–B(1)–
C(21) 119.6(2), C(21)–B(1)–C(30) 121.6(2), N(1)–B(1)–C(30)
118.8(2), B(1)–N(1)–C(1) 126.6(2), B(1)–N(1)–C(12) 127.6(2),
C(1)–N(1)–C(12) 105.7(2), N(1)–C(1)–C(6) 110.0(2), C(1)–C(6)–
C(7) 107.1(2), N(1)–C(12)–C(7) 110.2(2), C(6)–C(7)–C(12)
106.9(2); C(1)–N(1)–B(1)–C(21) 153.9, C(1)–N(1)–B(1)–C(30)
–25.0, C(12)–N(1)–B(1)–C(21) –30.6, C(12)–N(1)–B(1)–C(30)
150.5.
Figure 4. Molecular structure of 3. Selected bond lengths [Å] and
angles [°]: B(1)–C(24) 1.536(3), B(1)–C(25) 1.579(3), B(1)–C(34)
1.583(4), S(1)–C(24) 1.738(2), S(1)–C(21) 1.724(2), C(21)–C(22)
1.389(3), C(22)–C(23) 1.394(3), C(23)–C(24) 1.378(3), N(1)–C(21)
1.394(3), N(1)–C(1) 1.417(3), N(1)–C(12) 1.414(3), C(1)–C(6)
1.404(3), C(6)–C(7) 1.452(3), C(7)–C(12) 1.402(3), C(25)–C(26)
1.418(3), C(26)–C(27) 1.389(3), C(27)–C(28) 1.386(3), C(28)–C(29)
1.385(5), C(29)–C(30) 1.392(3), C(25)–C(30) 1.410(3), C(34)–C(35)
1.420(3), C(35)–C(36) 1.390(3), C(36)–C(37) 1.388(3), C(37)–C(38)
1.382(3), C(38)–C(39) 1.390(3), C(34)–C(39) 1.422(3); C(24)–B(1)–
Obviously, in 1 an optimal π-interaction between the 2pz
orbitals at the boron atom and the carbazole part is pre-
vented by the nonplanarity of the molecule. The plane of
the carbazole and the plane defined by the N(1), C(30), and
C(21) atoms enclose a dihedral angle of 28.2° and compares
with the dihedral angles between the BC3 planes and the
fluorenyl plane (32.7° and 21.2°) in compound 7 (Fig-
ure 3).[17] These angles are markedly smaller than those be- C(25) 117.8(2), C(24)–B(1)–C(34) 118.6(2), C(25)–B(1)–C(34)
123.5(2), B(1)–C(24)–S(1) 120.2(2), B(1)–C(24)–C(23) 130.2(2),
C(21)–S(1)–C(24) 92.7(1), S(1)–C(21)–C(22) 110.8(2), C(21)–
C(22)–C(23) 112.1(2), C(22)–C(23)–C(24) 115.3(2), S(1)–C(21)–
N(1) 121.9(2), C(22)–C(21)–N(1) 127.3(2), C(21)–N(1)–C(1)
tween the NBC2 plane and the mesityl rings in 1 (65.6° and
58.1°) and those between the BC3 plane and the mesityl
rings in 7 (51.8° and 54.9°). Mesityl relevant B–C bond
lengths in 1 [B(1)–C(21) 1.578(3), B(1)–C(30) 1.577(3) Å]
are well comparable to those in 7 [1.571(11)–1.592(10) Å],
8 [1.571(3), 1.581(3) Å] and 9 [1.573(3)–1.580(3) Å] (Fig-
ure 3).[18] Thus, molecule 1 is closer to planarity than the
four conformers of the carbazole derivative 4a (interplanar
124.8(2), C(21)–N(1)–C(12) 126.7(2), C(1)–N(1)–C(12) 107.9(2),
N(1)–C(1)–C(6) 108.7(2), C(1)–C(6)–C(7) 107.2(2), C(6)–C(7)–
C(12) 107.5(2), N(1)–C(12)–C(7) 108.7(2); S(1)–C(24)–B(1)–C(25)
–17.2, S(1)–C(24)–B(1)–C(34) 165.2, C(23)–C(24)–B(9)–C(34)
–24.4, C(23)–C(24)–B(1)–C(25) 153.3, S(1)–C(21)–N(1)–C(12)
38.0, S(1)–C(21)–N(1)–C(1) –152.0, C(22)–C(21)–N(1)–C(12)
angles 55.9–77.7°; av. 66.6°).[10] For the N(1)–C(1) and –141.9, C(22)–C(21)–N(1)–C(1) 28.1.
Figure 3. Compounds 7–9.
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FULL PAPER
In the 5-position, the thiophene ring is attached to a dimes-
The formal insertion of a phenylene unit into the B–N
itylboryl group by a B(1)–C(14) single bond [1.536(3) Å]. bond of 1 provides an elongated π-electron scaffold for mo-
For comparison, the B–C(thiophene) bond in 6a was found lecule 2. The cyclohexane solution of 2 displays three ab-
to be slightly longer [1.557(2) Å]. Mesityl relevant B–C sorptions in the UV/Vis spectrum at λ = 296 (ε = 16364),
bond lengths in 3 are in the expected range [B(1)–C(25) 330 (9494), and 374 nm (18120 Lmol–1 cm–1). The CT band
1.579(3), B(1)–C(34) 1.583(4) Å]. The plane defined by the at lowest energy, which reflects the HOMO–LUMO transi-
C(24), C(25), and C(34) atoms, including the boron atom, tion, experiences a redshift of 50 nm compared with 1. In
is twisted out of the plane of the thiophene ring by 21.8°. the related compound 10 (Figure 5), the corresponding CT
The interplanar angles between this plane and the mesityl band was observed at 362 nm.[19] The bands at λ = 330 and
groups are 64.4° and 48.3°. Bond angles and bond lengths 296 nm are tentatively assigned to the carbazole-centered
within the carbazole part of 3 are similar to those of com- HOMO Ǟ LUMO+1 and HOMO–1 Ǟ LUMO+1 transi-
pound 1. In summary, molecule 3 is closer to planarity than tions, respectively.
the diazaborolyl analog 6a. This observation and the
shorter B–C(thiophene) bonds point an increased π-com-
munication within 3.
UV/Vis and Luminescence Spectra
Figure 5. Compound 10.
Table 1 lists selected photophysical data for compounds
1–3, all of which exhibit intense blue luminescence under
The CT absorption band in 2 shows a slight negative
UV irradiation. For comparison, the photophysical data for solvatochromism with λmax = 367 (THF) and 363 nm
the analogous systems with the 1,3,2-benzodiazaborolyl (CH2Cl2). Such negative solvatochromic behavior was also
function 4a,b, 5 and 6a,b are also included.
reported for 10 and other acceptor-substituted carba-
As reported previously, the UV/Vis spectrum of zoles[20,21] and is most likely due to a dipole inversion upon
3,6-di-tert-butylcarbazole (in cyclohexane) is dominated S0ǞS1 excitation. In the absence of effective π-conjugation,
by a strong absorption band at λ = 296 nm (ε = the ground-state polarization of 2 is essentially determined
18114 Lmol–1 cm–1) and a significantly weaker band at λ by inductive effects with the boron atom as a σ-donor and
= 337 nm (ε = 2672 Lmol–1 cm–1). In line with theoretical the nitrogen atom as σ-acceptor (μg,calcd. = 0.83 D). Upon
calculations, the band at λ = 296 nm was assigned to a tran- excitation of 2, the direction of the dipole-moment vector
sition from the HOMO–1 into the LUMO of the molecule, reverses, because charge is transferred from the nitrogen
whereas that at λ = 337 nm reflects the HOMO–LUMO atom to the boron atom. Thus, the solvent molecules have
transition.[10] In the UV/Vis spectrum of 1 (in cyclohexane), an energetically unfavorable orientation and need to be re-
an intense band was observed at λ = 288 nm (ε = organized at the expense of energy, particularly in polar me-
21800 Lmol–1 cm–1) in addition to a less intense band at λ dia. In contrast, the emission band of 2 shows the expected
= 324 nm (ε = 14072 Lmol–1 cm–1). The high intensity of positive solvatochromism. Bands in the luminescence spec-
the latter band may indicate the superposition of a CT band tra at λ = 394 (cyclohexane), 452 (THF), and 461 nm
and a transition within the carbazole system. The positions (CH2Cl2) with Stokes shifts of 1400 (cyclohexane), 5400
of these absorptions are virtually the same for THF or (THF) and 6100 cm–1 (CH2Cl2) are diagnostic for a polar
CH2Cl2 solutions of 1. The absence of solvatochromism excited state of 2 (μg,calcd. = 12.61 D). The quantum effi-
points to a low dipole moment of the compound in the ciencies are quite high (Φ = 0.78 in cyclohexane, 0.77 in
ground state (μg,calcd. = 0.21 D). In the luminescence spec- THF, 0.70 in CH2Cl2). Derivative 10 gave rise to blue emis-
trum of 1 (in cyclohexane), a strong band was observed at sion at λ = 387 nm with a quantum yield of Φ = 0.62 and
λ = 450 nm (Stokes shift 9000 cm–1), which in a THF or a Stokes shift of 1800 cm–1 in cyclohexane.[19]
CH2Cl2 solution is redshifted to 479 (Stokes shift
In compound 5, which is derived from 2 by the replace-
10200 cm–1) or 492 nm (10700 cm–1), respectively. The large ment of the dimesitylboryl group by the 1,3-diethyl-1,3,2-
Stokes shifts and the solvatochromism are consistent with benzodiazaborolyl unit, UV/Vis absorption bands were ob-
a more polar excited state resulting from an intramolecular served in cyclohexane, THF and CH2Cl2 at λ = 298 and
charge transfer (μg,calcd. = 3.70 D).
329 nm. Again, the band at lower energy is assigned to the
This clearly contrasts with the photophysical behavior of HOMO–LUMO and the second band to a HOMO–1 Ǟ
the 2-(carbazol-9-yl)-1,3,2-benzodiazaboroles 4a,b in which LUMO transition; the absence of solvatochromism is obvi-
Stokes shifts of only 500–700 cm–1 (in cyclohexane) were ous.
observed. The virtual absence of solvatochromism was con-
The fluorescence spectrum of 2 shows a positive solva-
firmed by quantum-chemical calculations, which point to tochromism with bands at λ = 366 (cyclohexane), 370
electronic transitions within the carbazole fragment without (THF), and 372 nm (CH2Cl2). Markedly, larger Stokes
the participation of the B/N heterocycle. Thus, no signifi- shifts of 3200 (cyclohexane) to 3600 cm–1 (CH2Cl2) may be
cant dipole moment of the molecule was present in the ex- explained by an extensive reorganization of the structure of
cited state.[10]
5 in the excited state.
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Carbazoles with Dimesitylboryl and 1,3,2-Benzodiazaborolyl Functions
Table 1. Selected photophysical data of compounds 1–3, 4a,b, 5, and 6a,b.
Compound
λmax,abs [nm]
λmax,abs [cm–1]
ε [Lmol–1 cm–1]
λmax,em [nm]
λmax,em [cm–1]
Stokes shift [cm–1]
Φf[d]
1[a]
288
324
288
325
288
325
296
330
374
296
333
367
297
335
363
295
327
390
294
327
390
295
327
387
297
340
296
340
296
341
296
335
297
336
296
337
298
329
298
329
298
329
296
321
296
323
297
320
296
328
296
330
297
330
34700
30900
34700
30800
34700
30800
33800
30300
26700
33800
30000
27200
33700
29900
27500
33900
30600
25600
34000
30600
25600
33900
30600
25800
33700
29400
33800
29400
33800
29300
33800
29800
33700
29800
33700
30800
33600
30400
33600
30400
33600
30400
33800
31100
33800
31000
33700
31300
33800
30500
33800
30300
33700
30300
21800
14072
18553
12209
16720
11030
16364
9494
18120
21049
13255
22111
11433
7552
11977
18256
10858
25663
20663
11253
25472
16443
9397
8427
16676
2643
23080
4251
17990
2900
17336
1532
15895
3149
19945
3329
31650
6580
15023
5389
17662
5292
14488
9509
13661
9509
22780
15760
22628
9931
28555
13194
15380
10710
450
479
492
21900
20600
20100
9000
0.15
0.19
0.31
1[b]
1[c]
2[a]
10200
10700
394
452
461
414
445
25300
21800
21400
24000
22300
1400
5400
6100
1600
3300
0.78
0.77
0.70
0.43
0.41
2[b]
2[c]
3[a]
3[b]
3[c]
452
345
348
349
342
344
346
366
370
372
371
389
395
386
388
396
21900
29900
28700
28600
29100
29000
28800
27200
26900
26800
25800
25200
25000
25500
25300
25000
3900
500
0.32
0.37
0.09
0.44
0.41
0.33
0.46
0.48
0.40
0.40
0.14
0.15
0.21
0.13
4a[a]
4a[b]
4a[c]
4b[a]
4b[b]
4b[c]
5[a]
700
700
700
800
2000
3200
3500
3600
5300
5800
6300
5000
5000
5300
5[b]
5[c]
6a[a]
6a[b]
6a[c]
6b[a]
6b[b]
6b[c]
0.15
0.18
[a] In cyclohexane. [b] In THF. [c] In CH2Cl2. [d] Against standard POPOP (Φ = 0.93).
The UV/Vis spectrum of 3 in cyclohexane is charac- comparison with 2, this absorption band is redshifted by
terized by bands at λ = 295 nm (ε = 18256), 327 (10858), λ = 26 nm; for the corresponding 1,3,2-benzodiazaborole
and 390 nm (25663 Lmol–1 cm–1). In THF and CH2Cl2 derivative 6a, this band is redshifted by λ = 69 nm. In the
solutions of 3, no significant shifts of these absorptions are luminescence spectrum of 3 in cyclohexane, a band at λ =
noted. Accordingly, the ground-state dipole moment is cal- 414 nm is observed, which is redshifted in THF and CH2Cl2
culated as μg,calcd. = 0.21 D. The CT band with the lowest to λ = 445 and 452 nm, respectively. The increased polarity
energy is attributed to the HOMO–LUMO transition. In of the excited state was confirmed computationally by a
Eur. J. Inorg. Chem. 2011, 3091–3101
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L. Weber, A. Chrostowska et al.
FULL PAPER
dipole moment of μg,calcd. = 9.93 D. These data correspond
For compound 1, the experimentally determined bond
to Stokes shifts of 1600 (cyclohexane), 3300 (THF), and lengths and valence angles (Table 2) are not essentially dif-
3900 cm–1 (CH2Cl2).
ferent from those calculated, with the exception of the
In the UV/Vis spectrum of 2-[5-(carbazol-9-yl)-2-thi- C(21)–C(22) and C(30)–C(35) bond lengths for which the
enyl]-1,3-diethyl-1,3,2-benzodiazaborole 6a, absorption calculated value 1.391 Å is slightly shorter than the experi-
bands in cyclohexane were encountered at λ = 296 (ε = mental ones [1.420(3) and 1.407(3) Å]. The same holds for
14488) and 321 nm (9509 Lmol–1 cm–1). The luminescence the C(21)–B(1)–C(30) angle [calcd. 120.2°; exp. 121.6(2)°].
spectrum of 6a was characterized by intense emissions at In contrast to this, the calculated value for the C(30)–B(1)–
λ = 371 (cyclohexane), 389 (THF), and 395 nm (CH2Cl2), N(1) angle (119.9°) is slightly more obtuse than the experi-
combined with Stokes shifts of 5300, 5800, and 6300 cm–1, mentally determined one [118.8(2)°]. The calculated value
respectively. The larger Stokes shifts in 6a compared with 3 of the N–C bond length in the carbazole (1.386 Å) increases
underlines that, in the ground state, molecule 3, with only marginally from 1.401 Å [exp. av. 1.403(5) Å] in 6a to
two linked-ring systems, is closer to planarity than the di- 1.420 Å [exp. av. 1.425(3) Å] in 1.
azaborole analogue 6a. This finding and the shorter B–
The calculated absorption maxima from TD-DFT com-
C(thiophene) bonds point to an increased π-communication putations, carried out on the optimized geometries of 1–3,
within 3.
and the corresponding oscillator strengths f are displayed
in Table 3. The calculation for 1 gave a lowest energy band
at λ = 288 nm for an allowed S0ǞS1 electronic absorption
with an oscillator strength f = 0.31, which corresponds to
DFT Calculations
Table 2 contains selected [CAM-B3LYP/6-311G(d,p)] the HOMOǞLUMO transition. This calculated value dif-
calculated geometrical parameters for 1 and 3 in addition fers from the observed absorption maximum at λ = 324 nm
to their experimental structural data.
by 36 nm. The redshift may be due to the fact that in solu-
Table 2. Selected experimental and calculated [CAM-B3LYP/6-311G(d,p)] bond lengths [Å] and angles [°] for 1 and 3.
1 calcd.
1 exp.
3 calcd.
3 exp.
B(1)–N(1)
B(1)–C(21)
B(1)–C(30)
C(21)–C(26)
C(21)–C(22)
C(30)–C(31)
C(30)–C(35)
N(1)–C(12)
N(1)–C(1)
C(12)–C(11)
C(12)–C(7)
C(1)–C(12)
C(1)–C(6)
C(6)–C(7)
C(21)–B(1)–N(1)
C(30)–B(1)–N(1)
C(21)–B(1)–C(30)
B(1)–N(1)–C(12)
B(1)–N(1)–C(1)
C(1)–N(1)–C(12)
N(1)–C(1)–C(6)
C(1)–C(6)–C(7)
C(2)–C(1)–C(6)
C(1)–N(1)–B(1)–C(21)
C(12)–N(1)–B(1)–C(21)
C(12)–N(1)–B(1)–C(30)
C(35)–C(30)–B(1)–N(1)
C(22)–C(21)–B(1)–N(1)
1.438
1.580
1.580
1.409
1.391
1.391
1.409
1.420
1.420
1.392
1.398
1.392
1.398
1.448
119.9
119.9
120.2
127.1
127.1
105.8
110.1
107.0
119.6
154.2
25.8
1.440(3)
1.578(3)
1.577(3)
1.415(3)
1.420(3)
1.407(3)
1.412(3)
1.427(3)
1.422(3)
1.395(3)
1.399(3)
1.390(3)
1.402(3)
1.452(3)
119.6(2)
118.8(2)
121.6(2)
127.6(2)
126.6(2)
105.7(2)
110.0(2)
107.1(2)
119.8(2)
153.9
B(1)–C(24)
B(1)–C(25)
B(1)–C(34)
S(1)–C(24)
1.542
1.579
1.580
1.741
1.731
1.369
1.410
1.376
1.393
1.399
1.399
1.401
1.401
1.449
119.4
117.4
123.2
122.5
128.0
92.1
1.536(3)
1.579(3)
1.583(4)
1.738(2)
1.724(2)
1.389(3)
1.394(3)
1.378(3)
1.394(3)
1.414(3)
1.417(3)
1.402(3)
1.404(3)
1.452(3)
117.8(2)
118.6(2)
123.5(2)
120.2(2)
130.2(2)
92.7(1)
S(1)–C(21)
C(21)–C(22)
C(22)–C(23)
C(23)–C(24)
N(1)–C(21)
N(1)–C(12)
N(1)–C(1)
C(12)–C(7)
C(1)–C(6)
C(6)–C(7)
C(24)–B(1)–C(25)
C(24)–B(1)–C(34)
C(25)–B(1)–C(34)
B(1)–C(24)–S(1)
B(1)–C(24)–C(23)
C(21)–S(1)–C(24)
S(1)–C(21)–C(22)
S(1)–C(21)–N(1)
N(1)–C(12)–C(7)
111.5
121.8
109.1
110.8(2)
121.9(2)
108.7(2)
30.6
–150.5
59.2
51.0
C(12)–C(7)–C(6)
106.9
107.5(2)
–154.2
58.6
58.6
C(25)–B(1)–C(24)–S(1)
S(1)–C(21)–N(1)–C(12)
16.4
–57.2
17.2
38.0
Table 3. Comparison of [CAM-B3LYP/6-311G(d,p)] calculated data for optimized geometries of 1–3 and observed UV/Vis absorption
maxima (in cyclohexane); calculated values of dipole moment of ground and excited states [Debye].
Compound
λmax
(calcd.)
[nm]
Oscillator strength (f)
(calcd.)
λmax
(exp.)
[nm]
Δλmax
(calcd. – exp.)
[nm]
Ground-state
dipole moment
[μg]
Excited-state
dipole moment
[μg]
1
288.0
314.5
329.5
0.31
0.59
0.53
324
374
390
–36
–59.5
–60.5
0.21
0.83
0.21
3.70
12.61
9.93
2
3Ͼ
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Eur. J. Inorg. Chem. 2011, 3091–3101

Carbazoles with Dimesitylboryl and 1,3,2-Benzodiazaborolyl Functions
tion an ensemble of rotational isomers exist, including perimentally determined value (λ = 374 nm) by 59.5 nm.
planar geometries. Moreover, one should also consider the For 3, this lowest energy absorption is calculated at
possibility that the calculations simply overestimate these the longest wavelength (λ = 329.5 nm) and differs from
energies.
the experimental value (λ = 390 nm) by 60.5 nm. The com-
In the case of compound 2, the most intense absorption puted HOMOǞLUMO transition of 3 is thus red-
corresponding to the HOMOǞLUMO transition is shifted by 41.5 nm or 15 nm in comparison to 1 or 2,
calculated at λ = 314.5 nm and thus differs from the ex- respectively.
Table 4. [CAM-B3LYP/6-311G(d,p)] calculated MO energies εKS (LUMO+2, LUMO+1, LUMO, HOMO, HOMO–1, HOMO–2,
HOMO–LUMO gaps) and first four ΔSCF/TDDFT ionization energies of 1, 2, and 3. Contour values are plotted at Ϯ(0.04 e/bohr3)1/2
.
Eur. J. Inorg. Chem. 2011, 3091–3101
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3097

L. Weber, A. Chrostowska et al.
FULL PAPER
Table 4 displays the [CAM-B3LYP/6-311G(d,p)] calcu- resented by the 2pz orbital of the boryl group, whereas the
lated MO energies (LUMO, HOMO, HOMO–1) of 1–3, as HOMO remains on the carbazole part.
well as the HOMO–LUMO gaps, and the four first ΔSCF/
The different nature of the dimesitylboryl and the 1,3,2-
TDDFT ionization energies. The LUMOs of 1–3 are lo- benzodiazaborolyl substituents is substantiated by the val-
cated on the vacant 2pz orbital of the boron atom with π*- ues of the HOMO energies of the free carbazole (–7.01 eV),
orbital contributions of the phenyl (in 2) or thiophene (in compound 1 (–7.26 eV), and the 2-(carbazol-9-yl)-1,3,2-
3) unit, whereas the HOMO and HOMO–1 energies corre- benzodiazaborole 4a (–6.62 eV). Destabilization of the
spond to π1(crb) and π2(crb), respectively, and are located HOMO energy of 1 was effected by the insertion of a phen-
on the carbazole part in the three molecules.
The attachment of the electron-withdrawing dimesityl- HOMO energies of –6.73 (in 2) and –6.81 eV (in 3).
boryl group to the nitrogen atom of the carbazole led to The lack of significant solvatochromsim in the ground
ylene or thiophene spacer into the B–N bond yielding
the stabilization of its HOMO (π1, –7.01 eV) by 0.25 eV. states of 1–3 was confirmed by the low calculated dipole
In contrast, the linkage of the benzodiazaborole ring was moments (0.21–0.83 D). The fluorescence spectra of 1–3 (in
accompanied by a destabilization of 0.38 eV, reflecting the cyclohexane) display bands at λ = 450 (1), 394 (2), and
electron-releasing character of the B/N heterocycle. The in- 414 nm (3) connected with Stokes shifts of 9000, 1400, and
troduction of the phenylene unit between the dimesitylboryl 1600 cm–1, respectively. Significant redshifts of the emission
and the carbazole fragments effects a destabilization of the bands in polar solvents (THF, CH2Cl2) are in line with sig-
HOMO (in 2) by 0.34 eV, whereas the thiophenediyl unit nificant polarities in the excited states, as also documented
(in 3) evokes only half this effect (0.16 eV) with respect to by calculated dipole moments of 3.70 (1), 12.61 (2), and
the (carbazol-9-yl)dimesitylborane 1. This destabilization is 9.93 D (3).
due to the +M effect of these two spacers.
Thus, benzodiazaborolyl and dimesitylboryl groups are
The position of HOMO–1 is insensitive towards substitu- contrasting building blocks in π-conjugated organic mole-
tion and is only very slightly stabilized in 2 (0.005 eV) and cules. The idea to place both on the ends of push–pull mole-
in 3 (0.082 eV) in comparison with 1. The HOMO–LUMO cules is challenging. Attempts to impose π-acceptor proper-
gap is significantly smaller in 2 (5.979 eV – 207.6 nm) and ties on the benzodiazaborole core involve the introduction
in 3 (5.990 eV – 207.2 nm) than in 1 (6.880 eV – 180.4 nm). of fluorinated aryl substituents at the nitrogen atoms of the
The most important difference in the calculated ionization molecules.
energies (IE) is noted for 1 and highlights the influence of
the acceptor properties of the boron atom directly linked to
Experimental Section
the nitrogen atom of carbazole (IE = 7.258 eV). The formal
insertion of a phenylene or a thiophene unit into the B–N
bond of 1 provides a lowering of the IE [6.907 (2) and
6.984 eV (3)] due to the donating properties of these two
rings. Deeper energy ionizations seem practically unper-
turbed by their environment.
General: All manipulations were performed under dry, oxygen-free
argon by using Schlenk techniques. All solvents were dried by stan-
dard methods and freshly distilled prior to use. The compounds 2-
bromo-1,3-diethyl-1,3,2-benzodiazaborole,[22] fluorodimesitylbor-
ane,[12] 3,6-di-tert-butylcarbazole,[11] 3,6-di-tert-butyl-N-(2-thi-
enyl)carbazole,[13] and 1-bromo-4-(3,6-di-tert-butylcarbazol-9-yl)-
benzene[14] were prepared according to literature methods. NMR
spectra were recorded at room temperature with a BrukerAM Av-
ance DRX-500 spectrometer (1H, 11B, 13C) by using TMS and
BF3·OEt2 as external standards. Mass spectra were taken with a
VG autospec sector field mass spectrometer (Micromass). The UV/
Vis spectra were recorded with a Thermo Evolution 300 UV/Vis
spectrometer and the emission spectra with a Hitachi F-4500 fluo-
rescence spectrometer.
Conclusion
Dimesitylborane derivatives 1–3 with carbazol-9-yl, 4-
(carbazol-9-yl)phenyl, and 5-(carbazol-9-yl)-2-thienyl sub-
stituents have been synthesized. Molecules 1 and 3 have
nonplanar geometries in the crystalline phase, as evidenced
by X-crystallography, as well as in the gas phase, according
to DFT calculations. In the UV/Vis spectra the low energy
bands at λ = 324 (1), 374 (2), and 390 nm (3) are assigned to
HOMOǞLUMO charge-transfer transitions, whereby the
3,6-Di-tert-butyl-N-(dimesitylboryl)carbazole (1): A solution of 3,6-
di-tert-butylcarbazole (0.559 g, 2.0 mmol) in n-pentane (30 mL)
was combined at 20 °C with an equimolar amount of an n-butyl-
lithium solution in n-hexane (1.6 m, 1.25 mL, 2.0 mmol). After stir-
HOMOs are located at the carbazolyl part of the molecules. ring the mixture for 1 h, an n-pentane solution (10 mL) of fluorodi-
mesitylborane (0.540 g, 2.0 mmol) was added. The slurry was
stirred overnight, filtered, and the solvent and volatile components
were removed from the filtrate. Purification of the residue was ef-
fected by column chromatography on silica with n-pentane. Product
1 (Rf = 0.25) was crystallized from n-pentane to give 0.753 g (70%)
The LUMOs are mainly represented by the vacant 2pz or-
bital of the boron atom with π*-orbital contributions of the
phenyl or thiophene unit in 2 or 3, respectively. Obviously,
the replacement of the π-electron-donating 1,3,2-benzodi-
azaborolyl substituent by the efficient π-accepting dimes-
itylboryl group led to a significant change in the nature of
the frontier orbitals. In the N-(benzodiazaborolyl)carbazole
4, the HOMO and LUMO are located on the carbazole
part of the molecule with no participation of the boron-
1
of pure 1 as a colorless solid. H NMR (CDCl3): δ = 1.42 (s, 18
H, tBu), 2.07 (s, 12 H, o-CH3), 2.36 (s, 6 H, p-CH3), 6.84 (m, 6
H, mesityl-H and tBuCCH=CH), 7.13 (dd, J = 1.7, 8.8 Hz, 2 H,
tBuCCH=CH), 7.98 (d, J = 1.7 Hz, 2 H, tBuCCHC) ppm. 13C{1H}
NMR (CDCl3): δ = 21.3 (s, p-CH3), 21.9 (s, o-CH3), 31.8 [s, C-
containing moiety. In 1, however, the LUMO is mainly rep- (CH3)3], 34.6 [s, C(CH3)3], 114.9 (s, tBuCCHCH), 115.4 (s,
3098
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Carbazoles with Dimesitylboryl and 1,3,2-Benzodiazaborolyl Functions
tBuCCHC), 123.8 (s, tBuCCHCH), 128.6 [s, BCCCHC(CH3)],
2-[4-(3,6-Di-tert-butylcarbazol-9-yl)phenyl]-1,3-diethyl-1,3,2-benzo-
128.1, 141.0, 141.6 (3 s, tBuCCHCC), 138.8, 145.5 [2 s, BCC(CH3)- diazaborole (5): Samples of 1-bromo-4-(3,6-di-tert-butylcarbazol-9-
CHC(CH3)] ppm. 11B{1H}NMR (CDCl3): δ = 51.0 ppm. IR (ATP,
yl)benzene (1.00 g, 2.3 mmol) and 2-bromo-1,3-diethyl-1,3,2-
diamond): ν = 3027 (w), 2949 (s), 2918 (s), 1606 (m), 1690 (m), benzodiazaborole (0.65 g, 2.6 mmol) were added to a mixture of
˜
1467 (s), 1392 (s), 1298 (m), 850 (s), 818 (s) cm–1. MS/EI: m/z (%)
magnesium metal (0.20 g, 8.2 mmol) and LiCl (0.13 g, 3.0 mmol)
= 527.4 (100) [M]+, 512.4 (41) [M – CH3]+, 249.2 (68) [B – in THF (30 mL). The resulting mixture was heated under reflux for
Mes2]+. C38H46BN (527.61): calcd. C 86.51, H 8.79, N 2.65; found
C 86.50, H 9.01, N 2.40.
18 h, and the volatile components were removed in vacuo. The resi-
due was triturated with n-pentane (30 mL). The filtered solution
was stored at –20 °C whereby colorless crystals of 5 separated.
1
[4-(3,6-Di-tert-butylcarbazol-9-yl)phenyl]dimesitylborane (2):
A
Yield: 0.82 g (68%). H NMR (CDCl3): δ = 1.45 (t, J = 7.1 Hz, 6
solution of n-butyllithium in n-hexane (1.6 m, 1.70 mL, 2.70 mmol)
was added dropwise to a chilled solution (–78 °C) of N-(4-bro-
mophenyl)-3,6-di-tert-butylcarbazole (1.20 g, 2.70 mmol) in diethyl
ether (50 mL). After warming the mixture to –20 °C, a solution of
fluorodimesitylborane (0.72 g, 2.70 mmol) in n-pentane (10 mL)
was added. The reaction mixture was slowly warmed to room tem-
perature and stirred overnight. Water (10 mL) was added and the
separated organic layer was dried with Na2SO4. The solvent was
removed in vacuo from a colorless solid residue, which was sub-
sequently crystallized from n-hexane (25 mL). Yield: 0.97 g (59%)
of 2 as colorless crystals. 1H NMR (CDCl3): δ = 1.59 (s, 18 H,
tBu), 2.22 (s, 12 H, o-CH3), 2.44 (s, 6 H, p-CH3), 6.98 (s, 4 H,
mesityl-H), 7.59 (s, 4 H, tBuCCHCHC), 7.68 (d, J = 8 Hz, 2 H,
NCCHCHCB), 7.84 (d, J = 8 Hz, 2 H, NCCHCHCB), 8.27 (s, 2
H, tBuCCHC) ppm. 13C{1H} NMR (CDCl3): δ = 21.2 (s, p-CH3),
23.5 (s, o-CH3), 31.9 [s, C(CH3)3], 34.7 [s, C(CH3)3], 109.4 (s,
tBuCCHCH), 116.3 (s, tBuCCHC), 123.7 (s, tBuCCHCH), 125.3
(s, NCCHCHCB), 128.2 [s, BCCCHC(CH3)], 137.9 (s,
NCCHCHCB) 123.7, 138.8, 143.2 (3 s, tBuCCHCC), 138.7, 140.8
[2 s, BCC(CH3)CHC(CH3)], 141.4 (s, NCCHCHCB), 141.6 [s,
BCC(CH3)CH], 143.9 (s, NCCHCHCB) ppm. 11B{1H}NMR
H, NCH2CH3), 1.53 [s, 18 H, C(CH3)3], 3.94 (q, J = 7.1 Hz, 4
H, NCH2CH3), 7.13 (m, 2 H, CH=CHCH=CH), 7.21 (m, 2 H,
CH=CHCH=CH), 7.53 (m, 4 H, tBuCCHC, tBuCCHCH), 7.71
(d, J = 8.5 Hz, NCCHCHCB), 7.82 (d, J = 8.5 Hz, NCCHCHCB),
8.2 (s, 2 H, tBuCCHCHC) ppm. 13C{1H} NMR (CDCl3): δ = 16.3
(s, NCH2CH3) 32.0 [s, C(CH3)3], 34.7 [s, C(CH3)3], 37.7 (s,
NCH2CH3), 108.9 (s, CH=CHCH=CH), 109.3 (s, tBuCCHCHC),
116.2 (s, tBuCCHC), 118.8 (s, CH=CHCH=CH), 123.6 (s,
tBuCCHCHC), 126.0 (s, NCCHCHCB), 134.8 (s, NCCHCHCB),
137.1 (s, N2C2), 138.5 (s, NCCHCHCB), 123.4, 139.1, 142.9 (3 s,
tBuCCHCC) ppm. 11B{1H}NMR (CDCl3): δ = 28.6 ppm. IR
(ATP, diamond): ν = 3034 (w), 2956 (s), 2926 (m), 1600 (s), 1519
˜
(s), 1470 (s), 1401 (s), 1371 (s), 1263 (m), 1233 (s), 1045 (m), 875
(w), 809 (s), 667 (m) cm–1. MS/EI: m/z (%) = 527.4 (100) [M]+,
512.4 (69) [M – CH3]+. C42H48BNS (527.57): calcd. C 81.96, H
8.02, N 7.96; found C 81.16, H 8.37, N 7.57.
X-ray Crystallography: Single crystals of 1 and 2 were coated with
a layer of hydrocarbon oil, attached to a glass fiber, and cooled to
100 K for data collection. Crystallographic data were collected with
a Nonius Kappa CCD diffractometer with Mo-Kα radiation
(graphite monochromator), λ = 0.71073 Å. Crystallographic pro-
grams used for the structure solution and refinement were from
SHELX-97.[23] The structure was solved by direct methods and was
refined by using full-matrix least squares on F2 of all unique reflec-
tions with anisotropic thermal parameters for all non-hydrogen
atoms. Hydrogen atoms were included at calculated positions with
U(H) = 1.2Ueq for CH2 groups and U(H) = 1.5Ueq for CH3 groups.
Crystal data for the compounds are listed in Table 5. CCDC-
811962 (for 1) and -811963 (for 3) contain the supplementary crys-
tallographic data for this paper. These data can be obtained free of
charge from Cambridge Crystallographic Data Centre via
www.ccd.cam.ac.uk/data_request/cif or as ESI.
(CDCl ): δ = 71.3 ppm. IR (ATP, diamond): ν = 3018 (w), 2959
˜
3
(s), 1605 (m), 1487 (m), 1470 (s), 1390 (s), 1218 (m), 831 (s), 802
(s) cm–1. MS/EI: m/z (%) = 603.4 (100) [M]+, 588.0 (44) [M –
CH3]+. C44H50BN (603.71): calcd. C 87.54, H 8.35, N 2.32; found
C 87.29, H 8.36, N 2.43.
5-(3,6-Di-tert-butylcarbazol-9-yl)-2-(dimesitylboryl)thiophene (3):
An n-hexane solution of n-butyllithium (1.6 m, 2.1 mL, 3.4 mmol)
was added dropwise at room temperature to a well-stirred solution
of 2-(3,6-di-tert-butylcarbazol-9-yl)thiophene (1.2 g, 3.3 mmol) in
diethyl ether (50 mL). After 1 h, an n-pentane solution (10 mL) of
fluorodimesitylborane (0.9 g, 3.3 mmol) was added, and stirring
was continued overnight. The slurry was combined with water
(10 mL). The organic layer was separated and dried with Na2SO4.
The solvent and volatile components were removed in vacuo, and
the yellow, solid residue was recrystallized from n-hexane (40 mL).
Computational Methods: All calculations were performed by using
the Gaussian 09[25] program package with the 6-311G(d,p) basis
set. DFT has been shown to predict various molecular properties
successfully.[26] All geometry optimizations were carried out with
the CAM-B3LYP[27] functional and were followed by frequency
calculations to verify that the stationary points obtained are true
energy minima. Ionization energies (IE) were calculated by using
the CAM-B3LYP functional (which is particularly well suited for
ionization energy evaluations; see for example ref.[9]) with ΔSCF/
TD-DFT, which means that separate SCF calculations were per-
formed to optimize the orbitals of the ground state and the appro-
priate ionic state (IE = Ecation – Eneutral). The advantages of the
most frequently employed ΔSCF/TD-DFT method of calculations
of the first ionization energies have been demonstrated pre-
viously.[28] The TD-DFT[29] approach provides a first principal
method for the calculation of excitation energies within a density
functional context taking into account the low-lying ion calculated
by ΔSCF method.
1
Yield: 1.3 g (66%) of colorless crystalline 3. H NMR (CDCl3): δ
= 1.52 (s, 18 H, tBu), 2.28 (s, 12 H, o-CH3), 2.38 (s, 6 H, p-CH3),
6.92 (s, 4 H, mesityl-H), 7.37 (d, J = 3.8 Hz, 1 H, NCCHCHCS),
7.56 (dd, J = 1.7, 8.5 Hz, 2 H, tBuCCHCHC), 7.58 (d, J = 3.8 Hz,
1 H, NCCHCHCS), 7.70 (d, J = 8.5 Hz, 2 H, tBuCCHCHC), 8.15
(d, J = 1.7 Hz, 2 H, tBuCCHC) ppm. 13C{1H} NMR (CDCl3): δ
= 21.2 (s, p-CH3), 23.5 (s, o-CH3), 31.9 [s, C(CH3)3], 34.7 [s,
C(CH3)3], 110.0 (s, tBuCCHCHC), 116.2 (s, tBuCCHC), 123.5 (s,
NCCHCHCS), 124.0 (s, tBuCCHCHC), 128.2 [s, BCCCHC(CH3)],
140.3 (s, NCCHCHCS) 123.9, 139.0, 141.0 (3 s, tBuCCHCC),
144.1, 145.7 [2 s, BCC(CH3)CHC(CH3)] 152.0 (s, NCCHCHCS)
ppm. 11B{1H}NMR (CDCl3): δ = 64.9 ppm. IR (ATP, diamond):
ν = 2950 (s), 1605 (m), 1518 (m), 1487 (m), 1430 (s), 1363 (s), 1224
˜
(m), 844 (s), 820 (s), 713 (s), 610 (s) cm–1. MS/EI: m/z (%) = 609.5
(100) [M]+, 594.4 (44) [M
–
CH3]+, 248.2 (20) [BMes2]+.
C42H48BNS (609.73): calcd. C 82.74, H 7.94, N 2.30; found C
82.28, H 7.93, N 2.25.
Supporting Information (see footnote on the first page of this arti-
cle): Tables of atomic coordinates for [CAM-B3LYP/6-311G(d,p)]
Eur. J. Inorg. Chem. 2011, 3091–3101
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3099

L. Weber, A. Chrostowska et al.
FULL PAPER
Table 5. Crystallographic data of 1 and 3.
1
3
Empirical formula
Mr [gmol–1]
Crystal dimension [mm]
Crystal system
Space group
a [Å]
C38H46BN·0.5C5H12
C42H48BNS
609.68
0.30ϫ0.13ϫ0.10
monoclinic
P21/c
13.9022(6)
18.3085(9)
13.9814(5)
96.800(2)
3533.6(2)
4
563.64
0.22ϫ0.14ϫ0.12
monoclinic
C2/c
30.4874(11)
20.1111(10)
11.7183(3)
98.155(2)
7112.2(5)
8
b [Å]
c [Å]
β [°]
V [Å3]
Z
ρcalcd. [gcm–3]
1.053
0.059
1.146
0.121
μ [mm–1]
F(000)
Θ [°]
No. refl. collected
No. refl. unique
R(int)
2456
3.0–25.0
19755
6252
0.047
1312
3.0–25.0
26962
6136
0.080
No. refl. [IϾ2σ(I)]
Refined parameter
GOF
RF [I Ͼ 2σ(I)]
wRF2 (all data)
Δρmax/min [eÅ–3]
Remarks
4821
372
0.975
0.0604
0.1739
0.629/–0.390
4136
430
1.007
0.0480
0.1227
0.205/–0.282
0.5 pentane molecules were disordered near an inversion cen- Disorder of tert-butyl group C(18),
ter and could not be satisfactorily refined. The routine C(19), and C(20) on three positions
squeeze of Platon[24] was used to remove the electron density (42:30:28). One idealized disordered
of the solvent, but the empirical formula includes the solvent methyl group [C(32)].
for further calculations. Disorder of C(14), C(15), and C(16)
on two positions (70:30).
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Received: February 4, 2011
Published Online: June 6, 2011
Eur. J. Inorg. Chem. 2011, 3091–3101
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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3101