10,9-Oxaboraphenanthrenes as luminescent fluorophores

Article abstract of DOI:10.1016/j.tet.2016.01.054

Reactions of 9-chloro-10,9-oxaboraphenanthrene (1) with the phenyl-, p-tolyl-, m-xylyl-, mesityl-, 2,4,6-tri-iso-propylphenyl-, 3,5-bis(trifluoromethyl)phenyl-, and pentafluorophenyl-Grignard reagents resulted in the formation of the corresponding oxaboraphenanthrene derivatives namely 9-phenyl- (2), 9-p-tolyl- (3), 9-(3,5-dimethylphenyl)- (9-m-xylyl-) (4), 9-mesityl- (5), 9-(2,4,6-tri-iso-propylphenyl)- (6), 9-(3,5-bis(trifluoromethyl)phenyl)- (7), and 9-(pentafluorophenyl)-10,9-oxaboraphenanthrene (8). 9-Trisyl- (9) and 9-supersilyl-10,9-oxaboraphenanthrene (10) were obtained selectively employing 1 and Li[C(SiMe₃)₃] or Na[SitBu₃] as reactants. The compounds 4-9 were characterized by X-ray crystallography. The fluorescence measurements of 5-9 embedded in PMMA show emission bands with λ_maxfrom 341 to 373 nm.

Full text of DOI:10.1016/j.tet.2016.01.054

Tetrahedron 72 (2016) 1477e1484
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10,9-Oxaboraphenanthrenes as luminescent fluorophores
Alexandra Budanow, Esther von Grotthuss, Michael Bolte, Matthias Wagner,
*
Hans-Wolfram Lerner
€
€
Institut fur Anorganische Chemie der Goethe-Universitat, Max-von-Laue-Str. 7, D-60438 Frankfurt, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Reactions of 9-chloro-10,9-oxaboraphenanthrene (1) with the phenyl-, p-tolyl-, m-xylyl-, mesityl-, 2,4,6-
tri-iso-propylphenyl-, 3,5-bis(trifluoromethyl)phenyl-, and pentafluorophenyl-Grignard reagents re-
sulted in the formation of the corresponding oxaboraphenanthrene derivatives namely 9-phenyl- (2), 9-
p-tolyl- (3), 9-(3,5-dimethylphenyl)- (9-m-xylyl-) (4), 9-mesityl- (5), 9-(2,4,6-tri-iso-propylphenyl)- (6),
9-(3,5-bis(trifluoromethyl)phenyl)- (7), and 9-(pentafluorophenyl)-10,9-oxaboraphenanthrene (8). 9-
Trisyl- (9) and 9-supersilyl-10,9-oxaboraphenanthrene (10) were obtained selectively employing 1 and
Li[C(SiMe3)3] or Na[SitBu3] as reactants. The compounds 4e9 were characterized by X-ray crystallog-
raphy. The fluorescence measurements of 5e9 embedded in PMMA show emission bands with lmax from
341 to 373 nm.
Received 14 December 2015
Received in revised form 26 January 2016
Accepted 27 January 2016
Available online 30 January 2016
Keywords:
Oxaboraphenanthrene
Fluorophores
Luminescence
X-ray structure analysis
Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction
with the variation of this donor-acceptor system, a control of the
HOMO-LUMO gap is envisioned which is crucial for optoelectronic
10,9-oxaboraphenanthrenes (Fig. 1) are versatile compounds
which were first published in 1960 by Dewar and Dietz1 and since
then haven been used as antioxidant additives in lubricants,2 as
Lewis acids for use in aldol condensations3 or as fungicides.4 Later
the interest in oxaboraphenanthrenes roses continually since they
can be used as precursors for ortho-phenylenes which are studied
for multiple applications in organic electronics.5
applications.6 Dewar and Dietz’s UV/vis investigations of 9-
substituted oxaboraphenanthrenes in solution showed several ab-
sorption bands, with maxima from the phenyl-substituted oxa-
boraphenanthrene shifted bathochromically compared to those of
a hydroxyl-substituted one.1 While 9-hydroxy-oxaboraphenan-
threne (Fig. 1, R]OH)7 is very stable and therefore has found sev-
eral applications,2e4 it shows only an insignificant fluorescence,
whereas 9-phenyl-10,9-oxaboraphenanthrene (2a) (Fig. 1, R]Ph)
fluoresces strongly.1 Unfortunately 2a was sensitive to hydrolysis
due to the Lewis acidic boron center. Nevertheless, it showed that
the fluorescence is tunable depending on the substituent of the
oxaboraphenanthrene core.
As the oxaboraphenanthrene unit shows interesting optoelec-
tronic properties we synthesized various 9-substituted BOP de-
rivatives and investigated their stability and luminescence
behavior. The emission area would be suitable to use our com-
pounds in UV-OLEDs.8,9 Equally an incorporation of them in OLEDs
as a host material is conceivable in order to suppress luminescence
quenching effects.10,11 Recently Hirai et al. published a boron-
containing polycyclic aromatic compound comparable to ours for
this purpose.12
Fig. 1. 10,9-oxaboraphenanthrene derivatives (oxaboraphenanthrene).
When regarding oxaboraphenanthrene as a derivative of ortho-
phenylene, the additional BeO bond leads to a planar and rigid
structure (Fig. 1).1 In the heterocyclic ring the electron density is
predominantly situated on the electron-rich oxygen atom,
explaining why this part of the oxaboraphenanthrene shows no
distinct aromaticity.1,5
Due to its structural motif the oxaboraphenanthrene is an
asymmetrically-linked donor-acceptor system, whose acceptor
properties can be influenced by the substituent R (Fig. 1). Along
2. Results and discussion
In this study the 9-substituted oxaboraphenanthrenes were
synthesized following a route published by Dewar and Dietz1 and
optimized by Zhou et al.:13 By reacting 2-phenylphenol with an
* Corresponding author. Fax: þ49 69 79829260; e-mail address: lerner@chemie.
uni-frankfurt.de (H.-W. Lerner).
http://dx.doi.org/10.1016/j.tet.2016.01.054
0040-4020/Ó 2016 Elsevier Ltd. All rights reserved.

1478
A. Budanow et al. / Tetrahedron 72 (2016) 1477e1484
excess of BCl3 and catalytic amounts of AlCl3 in hexane, 9-chloro-
10,9-oxaboraphenanthrene (Scheme 1) was obtained for use as the
starting compound for further derivatization reactions.
The oxaboraphenanthrene 4 was crystallized from a concen-
trated THF solution at ꢀ30 ꢁC, whereas crystals of 5 and 6 were
obtained by slow evaporation of hexane solutions at room tem-
perature (see Fig. 2). The compound 4 crystallizes in the ortho-
rhombic space group Pba2 and 5 in the orthorhombic space group
P212121. Both compounds contain two crystallographically in-
dependent molecules in the asymmetric unit. Since most structural
parameters of molecules 4 as well as 5 are closely similar, in each
case the structure of only one molecule of 4 and 5 is shown in Fig. 2.
The oxaboraphenanthrene 6 crystallizes in the monoclinic space
group P21/c.
Scheme 1. Synthesis of 9-chloro-10,9-oxaboraphenanthrene (1) in the reaction of 2-
phenylphenol with BCl3 and catalytic amounts of AlCl3.
The molecular structures of the oxaboraphenanthrenes 7 and 8,
which bear electron withdrawing groups on the B center, are shown
in Fig. 3 below. Crystals of 7 (see Fig. 3) were grown from hexane at
room temperature and belong to the monoclinic space group P21/c.
X-ray quality crystals of 8 (monoclinic, P21/c space group) were
obtained from a hexane/diethyl ether solution at room temperature
(see Fig. 3).
By slow evaporation of the solvent of a saturated benzene so-
lution, single crystals of 9 were grown, which were suitable for an
investigation by X-ray crystallography. The compound 9 crystallizes
in the monoclinic space group P21/c with two crystallographically
independent molecules in the asymmetric unit. Fig. 4 represents
the structure of one of two crystallographically independent mol-
ecules of 9 (selected bond lengths in caption of Fig. 4).
2.1. Synthesis of 9-substituted 10,9-oxaboraphenanthrenes
The substitution with bulky groups at the 9-position should on
the one hand lead to (hydrolysis-) stable products and on the other
enhance their emission. Therefore we synthesized a series of aryl-
and silyl-substituted oxaboraphenanthrenes and investigated their
steric shielding effect on the boron atom. As the insertion of an aryl
substituent can change the electronic properties of the oxabor-
aphenanthrene, we tested if there is any effect of electron with-
drawing and donating aryl groups on the emission characteristics
of the oxaboraphenanthrene (Scheme 2).
Conformation of the aryl-substituted oxaboraphenanthrene
derivatives 4e8 are shown in Fig. 5. In contrast to the structures of
5, 6, and 8 (top) the aryl substituent in 4 and 7 (bottom) lies in the
plane of the oxaboraphenanthrene units.
While in the oxaboraphenanthrene derivatives 5, 6, 8, and 9 the
boron atoms are shielded (Figs. 2e5), in 9-(3,5-bis(trifluoromethyl)
phenyl)-oxaboraphenanthrene (7) as well as in the moisture-
sensitive 9-(m-xylyl)-oxaboraphenanthrene (4) the boron center
is more accessible (Fig. 5). Nevertheless, 5, 6, 8, and 9 as well as 7
turned out to be relatively stable towards hydrolysis and could be
stored for some weeks under air.
Scheme 2. Reaction of 9-chloro-oxaboraphenanthrene (1) with phenyl lithium in THF.
2.2. Luminescence investigations of the
oxaboraphenanthrene-derivatives 5e9
For
the
substitution
reactions
on
9-chloro-10,9-
oxaboraphenanthrene (1) both organolithium as well as Grignard
reagents are suitable. Nevertheless, we investigated the case of
sterically less demanding aryl substituents, up to m-xylyl, and
found that the corresponding organolithium species lead to double
addition and therefore to product mixtures. For instance, treatment
of 1 with 1.1 equiv of Li[Ph] in THF at ꢀ78 ꢁC afforded a mixture of 9-
phenyl-10,9-oxaboraphenanthrene (2a) and the related lithium
borate 2b, as shown in Scheme 2. We identified the borate 2b by its
spectral characteristics and by X-ray structure analysis of single
crystals.
By contrast the reactions of 1 with the phenyl-, p-tolyl-, m-xylyl-,
mesityl-, 2,4,6-tri-iso-propylphenyl-, 3,5-bis(trifluoromethyl)phe-
nyl-, and pentafluorophenyl-Grignard reagent gave only the corre-
sponding oxaboraphenanthrene derivatives, as shown in Scheme 3.
In addition we also investigated the reaction of 1 with the bulky
carbanionic reagent Li[C(SiMe3)3] (trisyl lithium)14,15 and the ste-
rically crowded silanide Na[SitBu3] (supersilyl sodium),16,17 re-
spectively. In both reactions the corresponding 9-substituted-
oxaboraphenanthrenes 9 and 10 were formed in good yields (see
Scheme 4).
In general, for application in OLEDs, compounds are preferred
which fluoresce with high quantum yields and are oxygen- and
moisture-insensitive. Furthermore, they have to form homoge-
neous layers either alone or in a matrix material, e.g. polymethyl
methacrylate (PMMA).18,19
As the oxaboraphenanthrene derivatives 5e9 proved to be air-
and moisture-stable these compounds were tested for their suit-
ability as emitters for organic electronics. The oxaboraphenan-
threnes form homogeneous layers when embedded in PMMA and
show an emission in the near-UV area with moderate quantum
yields (see the experimental section for more details).
The spectra of 5e9 possess almost identical absorption maxima
(see Table 1 and Fig. 6). However, the oxaboraphenanthrenes 5, 6
and 9 with electron donating groups reveal an additional absorp-
tion band (see Fig. 6). Even the emission maxima of the oxabor-
aphenanthrenes 5 and 6 with electron donating groups differ
slightly from those of the oxaboraphenanthrenes 7 and 8 with
electron withdrawing groups (see Table 2 and Fig. 7). Interestingly,
the compounds 5e9 emit light of short wavelengths in the range of
the near-UV area.
In particular 9-mesityl-oxaboraphenanthrene (5), 9-(2,4,6-tris-
iso-propylphenyl)-oxaboraphenanthrene (6), and 9-trisyl-oxabor-
aphenanthrene (9) show an extraordinary stability towards nu-
cleophiles like water. This can be explained using the crystal
structure of 5, 6, and 9: in all these compounds the substituents
shield the boron center from nucleophilic attacks (see Figs. 2e5).
This indicates that electron withdrawing substituents in oxa-
boraphenanthrenes 7 and 8 effect a bathochromic shift of the
emission maximum up to 25 nm compared with these of oxabor-
aphenanthrenes with electron donating substituents (5 and 6). In
consequence the oxaboraphenanthrenes 7 and 8 reveal marginally
larger Stokes shifts than do 5 and 6.

A. Budanow et al. / Tetrahedron 72 (2016) 1477e1484
1479
Scheme 3. 9-Aryl-substituted oxaboraphenanthrenes synthesized starting from 9-chloro-oxaboraphenanthrene (1) and Grignard-reagents (red: electron withdrawing groups,
green: electron donating groups). For the synthesis of 9-phenyl-10,9-oxaboraphenanthrene (2), see Ref. 1.
10 were obtained by selectively employing 1 and Li[C(SiMe3)3] or
Na[SitBu3] as reactants. The oxaboraphenanthrene derivatives 4e9
were characterized by X-ray crystallography. The UV/vis measure-
ments of 5e9 embedded in PMMA show four to five absorption
bands. Interestingly, the compounds 5e9 emit light of short
wavelengths in the range of the near-UV area. In addition to that we
observed a dependency between the quantum yields and the steric
bulkiness of the substituent. Thus, oxaboraphenanthrenes are
considered to be promising candidates for UV-OLED material.
4. Experimental section
4.1. General materials and methods
All reactions and manipulations were carried out under dry,
Scheme 4. 9-Alkyl- and 9-silyl-substituted oxaboraphenanthrenes synthesized start-
oxygen-free nitrogen by using standard Schlenk ware or in an
argon-filled M. Braun glovebox. The solvents THF, Et2O, Bu2O,
pentane, toluene, benzene and [D6]-benzene were stirred over
sodium/benzophenone and distilled prior to use. CHCl3 and CH2Cl2
were dried over CaH2 and distilled before use.
The NMR spectra were recorded on Bruker DPX 250, Avance 300,
Avance 400, and Avance 500 spectrometers. Elemental analyses
were performed at the microanalytical laboratories of the Univer-
sity Frankfurt. The UV/Vis absorption spectra measurements were
carried out at a Varian Cary 500 UV/Vis spectrophotometer, the
fluorescence spectra as well as the quantum yields at a Jasco FP-
8300.
For the luminescence investigations a parent solution was pre-
pared consisting of a mixture of 10 weight percent of the analyte in
PMMA, dissolved in methylene chloride (spectrophotometric
grade). The results described above are based on parent solutions of
8 mg of the analyte, 72 mg PMMA in 3.6 mL methylene chloride.
ing from 9-chloro-oxaboraphenanthrene (1) and trisilyl lithium and supersilyl sodium.
Additionally, these results show that oxaboraphenanthrenes
with sterically demanding groups show a higher quantum yield
even when the concentrations used were lower.20 This effect may
be explained with a higher stability of their molecular scaffolds.
3. Conclusion
In summary, convenient access to oxaboraphenanthrenes with
sophisticated substituents on the boron center was established.
Reactions of 9-chloro-10,9-oxaboraphenanthrene (1) with the p-
tolyl-, m-xylyl-, mesityl-, 2,4,6-tri-iso-propylphenyl-, 3,5-
bis(trifluoromethyl)phenyl-, and penta-fluorophenyl-Grignard re-
agent resulted in the formation of the corresponding oxabor-
aphenanthrene derivatives 3e8. Under the same conditions, 9 and

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A. Budanow et al. / Tetrahedron 72 (2016) 1477e1484
Fig. 2. Solid-state structures of 4 (orthorhombic space group Pba2; one of two crystallographically independent molecules), 5 (orthorhombic space group P212121; one of two
crystallographically independent molecules), and 6 (monoclinic space group P21/c). Displacement ellipsoids are drawn at the 50% probability level. H atoms have been omitted for
ꢀ
clarity. Selected bond lengths (A) and bond angles (deg) 4: B(1)eO(1) 1.377(2), B(1)eC(11) 1.562(2), B(1)eC(21) 1.569(3), O(1)eC(1) 1.375(2), CeCbiphenyl 1.373(3)e1.416(2), C(2)e
C(12) 1.469(2), CeCxylyl/aryl 1.386(3)e1.402(2), O(1)eB(1)eC(11) 115.95(15), O(1)eB(1)eC(21) 111.39(14), C(11)eB(1)eC(21) 132.66(14), C(1)eO(1)eB(1) 124.97(13), O(1)eC(1)eC(6)
116.05(14), O(1)eC(1)eC(2) 121.19(14), CeCeCbiphenyl 115.78(14) ꢀ124.54(15), C(16)eC(11)eB(1) 124.31(15), C(12)eC(11)eB(1) 118.21(14), CeCeCXylyl/aryl 116.31(15)e122.95(15),
C(26)eC(21)eB(1) 126.57(15), C(22)eC(21)eB(1) 117.11(14). 5: B(1)eO(1) 1.375(4), B(1)eC(11) 1.540(4), B(1)eC(21) 1.568(4), O(1)eC(1) 1.375(3), CeCbiphenyl 1.377(4)e1.408(4),
C(2)eC(12) 1.475(4), CeCmesityl/aryl 1.384(4)e1.409(4); O(1)eB(1)eC(11) 117.9(3), O(1)eB(1)eC(21) 117.2(2), C(11)eB(1)eC(21) 124.9(3), B(1)eO(1)eC(1) 122.3(2), O(1)eC(1)eC(6)
115.8(2), O(1)eC(1)eC(2) 122.4(2), CeCeCbiphenyl 116.9(2)e123.1(2), C(16)eC(11)eB(1) 121.8(2), C(12)eC(11)eB(1) 119.6(2), CeCeCmesityl/aryl 118.1(3)e121.8(3), C(22)eC(21)eB(1)
120.6(3). 6: B(1)eO(1) 1.380(4), B(1)eC(1) 1.533(5), B(1)eC(21) 1.582(4), O(1)eC(11) 1.379(3), CeCbiphenyl 1.366(5)e1.419(4), C(2)eC(12) 1.468(5), CeCtip/aryl 1.378(3)e1.406(4);
O(1)eB(1)eC(1) 118.2(3), O(1)eB(1)eC(21) 116.5(3), C(1)eB(1)eC(21) 125.3(3), C(11)eO(1)eB(1) 122.1(5), CeCeCbiphenyl 116.2(3)e123.6(5), O(1)eC(11)eC(12) 121.7(3), O(1)e
C(11)eC(16) 116.0(3), CeCeCtip/aryl 117.8(3)e122.3(3), C(26)eC(21)eB(1) 119.6(3), C(22)eC(21)eB(1) 121.6(3).
Into a lying quartz cuvette (39ꢂ11ꢂ11 mm3) 100
m
L of methy-
resulting reacting mixture was additionally stirred for 1 h at ꢀ90 ꢁC.
After warming to room temperature, the yellow suspension was
filtered and the white precipitate was washed with hexane
(3ꢂ2 mL). All volatiles were removed from the combined organic
layers in vacuo. According to the 11B NMR spectrum 9-phenyl-10,9-
oxaboraphenanthrene (2a) and the borate 2b were thereby formed
(integral ratio of the signals: 2a: 2b¼3: 7). The residue was a yellow
oil from which X-ray quality crystals were obtained at room-
temperature after approx. 3 weeks under nitrogen atmosphere
(yield: 34%, 0.482 g, 0.85 mmol).21
lene chloride and 10 mL of the parent solution were filled. After
evaporation of the solvent a homogeneous layer of PMMA and the
luminophore was formed which was analyzed in regard to its lu-
minescence behavior.
By adding the parent solution in 10
mL steps dissolved in
methylene chloride onto the existing layer and evaporating the
solvent thicker layers can be formed and analyzed.
9-Chloro-10,9-oxaboraphenanthrene,8 Li[C(SiMe3)3]$2 THF,14,15
and Na[SitBu3]16,17 were synthesized following literature known
methods.
1H NMR (300.0 MHz, C6D6):
(m, 2H), 7.50 (m, 4H), 7.27 (m, 4H), 7.10 (m, 2H), 3.46 (m, 12H,
OCH2), 1.10 (m, 12H, CH2); 11B NMR (96.3 MHz, C6D6):
d¼8.06 (m, 5H), 7.95 (m, 1H), 7.55
d¼3.3; ele-
4.2. Synthesis protocols and characterization data
mental Anal. Calcd (%) for C38H40BLiO3 (562.45): 81.14, H, 7.17;
found: C 81.04, H 7.24.
4.2.1. Synthesis of the lithium borate of 2. To a solution of (0.541 g,
2.52 mmol, 1.0 equiv) 9-chloro-oxaboraphenanthrene (1) in THF
4.2.2. Synthesis of 9-p-tolyl-10,9-oxaboraphenanthrene (3). To a so-
lution of (0.523 g, 2.43 mmol, 1.0 equiv) 9-chloro-
(20 mL) a phenyl lithium solution (1.8 mL, 1.52
M in Bu2O;
2.77 mmol, 1.1 equiv) was added (90 min) at ꢀ90 ꢁC and the

A. Budanow et al. / Tetrahedron 72 (2016) 1477e1484
1481
Fig. 3. Solid-state structures of 7 (monoclinic space group P21/c) and 8 (monoclinic space group P21/c). Displacement ellipsoids are drawn at the 50% probability level. Selected bond
ꢀ
lengths (A) and bond angles (deg) 7: O(1)eC(1) 1.370(3), O(1)eB(1) 1.377(4), B(1)eC(11) 1.549(4), B(1)eC(21) 1.585(4), CeCbiphenyl 1.376(4)e1.424(4), C(2)eC(12) 1.475(4), CeCphenyl
1.383(4)e1.402(4); C(1)eO(1)eB(1) 124.6(2), O(1)eB(1)eC(11) 117.2(2), O(1)eB(1)eC(21) 110.7(2), C(11)eB(1)eC(21) 132.0(2), O(1)eC(1)eC(6) 116.5(2), O(1)eC(1)eC(2) 121.0(2),
CeCeCbiphenyl 116.2(3)e124.0(2). 8: O(1)eB(1) 1.361(2), O(1)eC(11) 1.383(2), B(1)eC(1) 1.533(3), B(1)eC(21) 1.585(2), CeCbiphenyl 1.373(3)e1.419(2), C(2)eC(12) 1.472(3), CeCphenyl
1.374(3)e1.397(2), B(1)eO(1)eC(11) 122.26(14), O(1)eB(1)eC(1) 119.60(15), O(1)eB(1)eC(21) 114.60(15), C(1)eB(1)eC(21) 125.77(16), CeCeCbiphenyl 116.38(17)e123.36(16), C(6)e
C(1)eB(1) 123.75(16), C(2)eC(1)eB(1) 117.55(16), O(1)eC(11)eC(16) 115.96(16), O(1)eC(11)eC(12) 121.45(16).
a
yellowish, hydrolysis-sensitive powder in 88% (0.580 g,
2.15 mmol) yield.
1H NMR (300.0 MHz, C6D6):
d
¼8.10 (d, 3JHH¼7.8 Hz, 1H), 8.31 (d,
3JHH¼7.4 Hz, 4H), 7.79 (d, JHH¼7.4 Hz, 1H), 7.64 (m, 2H), 7.34 (m,
3
2H), 7.04 (m, 2H), 2.10 (s, 3H, CH3); 11B NMR (96.3 MHz, C6D6):
d
¼42.6 (br, h1/2¼530 Hz); 13C NMR (75.5 MHz, C6D6):
¼141.5,
d
135.4, 135.1, 130.2, 129.2, 128.9, 128.4, 125.8, 125.3, 123.7, 123.2,
122.7, 112.35, 21.2; elemental Anal. Calcd (%) for C19H15BO (270.13):
84.48, H 5.60; found: C 84.45, H 5.47.
4.2.3. Synthesis of 9-m-xylyl-10,9-oxaboraphenanthrene (4). To
a solution of (0.723 g, 3.36 mmol, 1.0 equiv) 9-chloro-oxabor-
aphenanthrene (1) in THF (15 mL) 10.0 mL (0.27 m in THF;
4.00 mmol, 1.2 equiv) of an m-xylyl-Grignard solution were added
(5 min) at room temperature. The resulting yellow reaction mixture
was heated for 2.5 h at ꢀ70 ꢁC and was filtered after cooling to
room temperature over Celite using Schlenk technique. The filtrate
was concentrated whereupon colorless plates appropriate for X-ray
crystallography were obtained by storing the saturated THF solu-
tion of the product at ꢀ30 ꢁC overnight. After evaporation of the
solvent under reduced pressure the product was obtained as
a colorless powder in a yield of 52% (0.521 g, 1.75 mmol).
Fig. 4. Solid-state structure of 9 (monoclinic space group P21/c). Displacement ellip-
soids are drawn at the 50% probability level. Selected bond lengths (A) and bond angles
ꢀ
1H NMR (300.0 MHz, C6D6):
(m, 1H), 7.45 (m, 1H), 7.23 (m, 3H), 7.10 (m, 2H), 7.04 (m, 1H), 2.26
d
¼8.44 (m, 1H), 7.74 (m, 2H), 7.55
(deg) of one of two crystallographically independent molecules: SieCMe 1.867(4)
ꢀ1.886(3), SieC(7) 1.919e1.933(3), B(1)eO(1) 1.384(4), B(1)eC(1) 1.561(4), B(1)eC(7)
1.580(4), O(1)eC(11) 1.373(4), C(1)eC(6) 1.403(4), CeCbiphenyl 1.366(5)e1.424(4), C(2)e
C(12) 1.457(5); CeSieC 102.21(16)e107.22(16), CeSieC(7) 109.96(14) ꢀ117.17(16),
O(1)eB(1)eC(1) 114.3(3), O(1)eB(1)eC(7) 114.0(3), C(1)eB(1)eC(7) 131.4(3), C(11)e
O(1)eB(1) 126.0(2), CeCeCbiphenyl 115.7(3)e122.7(3), C(6)eC(1)eB(1) 123.5(3), C(2)e
C(1)eB(1) 119.1(3), B(1)eC(7)eSi 106.6(2)e114.4(2), SieC(7)eSi 107.77 (14)e
111.60(14), O(1)eC(11)eC(16) 116.4(3), O(1)eC(11)eC(12) 120.9(3).
(m, 6H, 2 CH3); 11B NMR (96.3 MHz, C6D6):
d
¼44.3 (br, h1/
¼780 Hz); 13C NMR (75.5 MHz, C6D6):
d
¼152.1, 139.8, 137.8, 137.2,
2
133.0, 132.8, 132.2, 130.2, 129.3, 128.5, 127.3, 126.4, 123.9, 123.7,
123.5, 122.1, 120.8, 21.5 (2 CH3); elemental Anal. Calcd (%) for
C20H17BO (284.16): C 84.53; H, 6.03; found: C 84.55, H 6.87.
4.2.4. Synthesis of 9-mesityl-10,9-oxaboraphenanthrene (5). To
a solution of (0.526 g, 2.45 mmol, 1.0 equiv) 9-chloro-oxabor-
oxaboraphenanthrene (1) in THF (5 mL) a p-tolyl-Grignard solution
aphenanthrene (1) in THF (10 mL) 3.8 mL (0.67
M in THF;
(0.8 mL, 0.30
M in THF; 2.80 mmol, 1.1 equiv) was added (10 min) at
2.55 mmol, 1.2 equiv) of a mesityl-Grignard solution were added
(2 min) at room temperature. The resulting colorless suspension
was stirred for 30 min at room temperature, mixed with water
(50 mL) and the layers were separated. The aqueous layer was
treated with diethyl ether (3ꢂ20 mL), the combined organic layers
room temperature and the resulting reacting mixture was stirred
for 1 h at 60 ꢁC. After cooling to room temperature, the colorless
suspension was filtered and the white precipitate was washed
with hexane (3ꢂ2 mL). All volatiles were removed from the
combined organic layers in vacuo. The product was obtained as

1482
A. Budanow et al. / Tetrahedron 72 (2016) 1477e1484
Fig. 5. Conformation of aryl-substituted oxaboraphenanthrene derivatives 4e8.
Table 1
Table 2
Absorption data of 5e9 in PMMA films
Data for the emission measurements of 5e9 in PMMA films which showed no
emission itself in the observed wavelengths area
5
6
7
8
9
Excitation
lext nm
Emission
lem nm
Concentration
mmol/L
Substance
fmax %
Wavelengths/nm
262
271
293
309
321
262
272
293
308
319
259
269
295
308
260
269
296
307
262
271
295
309
322
10ꢀ6 mmol
5
6
7
8
9
268
262
266
266
260
348
341
373
361
344
7.4
5.8
5.6
6.4
5.4
0.148
0.058
0.224
0.064
0.011
25.2
34.8
29.5
16.1
47.3
dried over MgSO4 and the solvent evaporated under reduced
pressure. The oxaboraphenanthrene 5 was obtained as a colorless
powder with a yield of 92% (0.678 g, 2.27 mmol). Slow evaporation
of a saturated hexane solution of 5 over Granopent lead to colorless
crystal blocks which were suitable for an investigation by X-ray
crystallography.
1H NMR (300.0 MHz, C6D6):
d
¼8.03 (m, 2H), 7.86 (d,
3JHH¼6.8 Hz, 1H), 7.55 (dd, 3JHH¼8.1 Hz, JHH¼1.1 Hz, 1H), 7.42 (m,
4
1H), 7.20e7.07 (m, 3H), 6.87 (s, 2H), 2.26 (s, 3H, CH3), 2.18 (s, 6H, 2
CH3); 11B NMR (96.3 MHz, C6D6):
d
¼46.1 (br, h1/2¼730 Hz); 13C NMR
(75.5 MHz, C6D6):
d
¼152.4, 140.3, 139.1, 138.1, 137.7, 133.5, 129.3,
127.8, 127.7, 124.9, 123.7, 123.7, 121.9, 121.0, 22.6 (2 CH3), 21.4 (1
CH3); elemental Anal. Calcd (%) for C21H19BO (298.15): C 84.59, H
6.42; found: C 84.55, H 6.87.
4.2.5. Synthesis of 9-(2,4,6-tri-iso-propylphenyl)-10,9-
oxaboraphenanthrene (6). To a solution of (0.522 g, 2.43 mmol,
1.0 equiv) 9-chloro-oxaboraphenanthrene (1) in THF (10 mL)
Fig. 6. Absorption spectra of 5e9 from PMMA layers of same thickness and same
weight percent content of the analyte see Table 1.
a 2,4,6-tri-iso-propylphenyl-Grignard solution (0.20
M in THF;

A. Budanow et al. / Tetrahedron 72 (2016) 1477e1484
1483
(%) for C20H11BF6O (392.10): C 61.26, H 2.83; found: C 61.26, H
3.00.
4.2.7. Synthesis of 9-(pentafluorophenyl)-10,9-oxaboraphenanthrene
(8). To a solution of (0.701 g, 3.27 mmol, 1.0 equiv) 9-chloro-oxa-
boraphenanthrene (1) in toluene (20 mL) 20.0 mL (0.18
M in THF;
3.59 mmol, 1.1 equiv) of a pentafluorophenyl-Grignard solution
were added (30 min) at room temperature, whereby the reddish 9-
chloro-oxaboraphenanthrene (1) solution turned immediately
yellow. After the entire dose of the Grignard reagent the mixture
was stirred for 2 h at room temperature and quenched with water
(50 mL). The layers were separated, the aqueous layer was treated
with diethyl ether (3ꢂ20 mL) and the combined organic layers
were dried over MgSO4. Removing the solvent under reduced
pressure the crude product was obtained as a brownish crystalline
solid. By elution of the solid in hexane (20 mL) and the dropwise
addition of diethyl ether (ca. 2 mL) until the solid was completely
dissolved and after slow evaporation of the solvent at room tem-
perature colorless crystal blocks of 8 were obtained in a yield of 85%
(0.961 g, 2.77 mmol) which were suitable for X-ray crystallography.
Fig. 7. Emission spectra of 5e9. Measurement with the highest obtained quantum
yield with normalized intensities see Table 2.
1H NMR (300.0 MHz, C6D6):
1H), 7.47e7.38 (m, 2H), 7.20 (td, JHH¼7.4 Hz, JHH¼1.0 Hz, 1H),
d
¼7.92e7.89 (m, 2H), 7.78e7.75 (m,
3 4
7.17e7.03 (m, 2H); 11B NMR (96.3 MHz, C6D6):
d
¼41.1 (br., h1/
2.93 mmol, 1.2 equiv) was added (1 h) at room temperature and
stirred for 2 h at 60 ꢁC. After cooling to room temperature, the re-
action solution was quenched with water (30 mL) and the layers
were separated. The aqueous layer was treated with diethyl ether
(3ꢂ20 mL) and the combined organic layers were dried with
MgSO4. After evaporation of the solvent in vacuo, the product was
obtained as a colorless powder with a yield of 79% (0.737 g,
1.93 mmol). By slow evaporation colorless crystal blocks which
were suitable for an investigation by X-ray crystallography were
grown from a saturated hexane solution of 6.
¼450 Hz); 13C NMR (75.5 MHz, C6D6):
d
¼151.5, 139.7, 137.1, 134.4,
2
133.9, 132.6, 129.6, 129.1, 127.7, 124.4, 124.0, 123.4, 122.8, 123.7,
122.1, 121.8, 120.8, 120.0; 19F NMR (282.3 MHz, C6D6):
d
¼ꢀ131.30
(m, 2 o-PhF), e151.93 (p-PhF), e161.53 (2 m-PhF); elemental Anal.
Calcd (%) for C18H8BF5O (346.06): C 62.47, H, 2.33; found: C 62.43, H
2.58.
4.2.8. Synthesis of 9-trisyl-10,9-oxaboraphenanthrene (9). To
a slurry of (1.357 g, 2.87 mmol) Li[C(SiMe3)3]$2 THF in toluene at
ꢀ78 ꢁC (0.502 g, 2.34 mmol) 1 in toluene (20 mL) was added over
a period of 1.5 h and the colorless suspension was warmed to room
temperature overnight. The solvent was removed under reduced
pressure, the precipitate eluted with hexane (20 mL) and the
resulted slurry filtered over Celite. After removal of the solvent 9
was obtained as a colorless powder 65% (0.624 g, 1.52 mmol). By
slow evaporation of a saturated benzene solution colorless crystal
1H NMR (300.0 MHz, C6D6):
d
¼8.02 (m, 2H), 7.86 (d,
3JHH¼7.4 Hz, 1H), 7.58 (d, 3JHH¼8.0 Hz,1H), 7.41 (t, 3JHH¼7.6 Hz, 1H),
7.24 (s, 2H, m-PhH), 7.20e7.07 (m, 3H), 2.93 (m, 1H, CH-iPr), 2.77
(m, 2H, CH-iPr), 1.34 (d, 6H, CH3-iPr), 1.22 (d, 6H, CH3-iPr) 1.16 (d,
6H, CH3-iPr); 11B NMR (96.3 MHz, C6D6):
d
¼46.7 (br, h1/2¼1700 Hz);
13C NMR (75.5 MHz, C6D6):
129.3, 127.8, 127.7, 124.9, 123.7, 123.7, 121.9, 121.0, 22.6 (2 CH3), 21.4
(1 CH3); elemental Anal. Calcd (%) for C27H31BO (382.35): C 84.82, H
8.17; found: C 84.66, H 8.14.
d
¼152.4, 140.3, 139.1, 138.1, 137.7, 133.5,
blocks were grown, which were suitable for X-ray crystallography.
1H NMR (300.0 MHz, C6D6):
d
¼8.54 (dd, JHH¼7.7 Hz,
3
4JHH¼1.1 Hz, 1H)), 7.94 (t, JHH¼8.3 Hz, 2H), 7.48 (dd, JHH¼8.1 Hz,
4JHH¼1.1 Hz, 1H), 7.41e7.31 (m, 1H), 7.30e7.22 (m, 1H), 7.20e7.11
(m,1H), 7.06e6.99 (m,1H), 0.40 (s, 27H, 9 CH3); 11B NMR (96.3 MHz,
3
3
4.2.6. Synthesis of 9-(3,5-bis(trifluoromethyl)phenyl)-10,9-
oxaboraphenanthrene (7). To a solution of (0.824 g, 3.84 mmol,
1.0 equiv) 9-chloro-oxaboraphenanthrene (1) in toluene (40 mL)
C6D6):
d
¼45.1 (br., h1/2¼550 Hz); 13C NMR (75.5 MHz, C6D6):
20.0 mL (0.23
bis(trifluoromethyl)phenyl-Grignard
M
in THF; 4.52 mmol, 1.2 equiv) of
solution were
a
3,5-
d
¼151.3, 138.9, 138.6, 132.4, 129.3, 129.3, 128.6, 125.7, 123.9, 123.3,
123.0, 122.3, 119.7, 6.6 (9 CH3); 29Si NMR (59.6 MHz, C6D6):
d¼ ꢀ1.4
added
(30 min) at room temperature, whereby the reddish solution of 9-
chloro-oxaboraphenanthrene (1) immediately turned yellow. After
adding the entire dose of the Grignard solution the brown reaction
mixture was stirred for 2.5 h at 70 ꢁC. The now clear yellow reacting
solution was cooled to room temperature and quenched with water
(50 mL). The separated aqueous layer was treated with diethyl
ether (3ꢂ20 mL), the combined organic layers were dried over
MgSO4 and the solvent removed in vacuo which resulted in
a brownish oil. After some hours at room temperature colorless
crystal needles of 7 could be obtained from the oil which were
suitable for X-ray crystallography. Analytically pure 7 was obtained
by crystallization in hexane at room temperature in a yield of 93%
(1.401 g, 3.57 mmol).
(3 SiMe3) elemental Anal. Calcd (%) for C22H35BOSi3 (410.58): C
64.36; H, 8.59, found: C 64.03, H 8.51.
4.2.9. Synthesis of 9-supersilyl-10,9-oxaboraphenanthrene (10). To
a solution of (2.67 mmol, 1.1 equiv) Na[SitBu3]$2 THF in 7 mL tol-
uene at ꢀ78 ꢁC (0.520 g, 2.42 mmol, 1.0 equiv) 1 in toluene (20 mL)
was added over a period of 1.5 h and the yellow solution was
warmed to room temperature overnight. The solvent was removed
under reduced pressure, the precipitate eluted with benzene
(15 mL) and the resulted slurry filtered over Celite. By concentrating
the filtrate 10 was obtained as colorless, dendritic crystals (yield:
90%, g, 2.18 mmol).
1H NMR (300.0 MHz, C6D6):
d
¼8.74 (d, 3JHH¼7.6 Hz, 1H), 7.99 (t,
1H NMR (300.0 MHz, C6D6):
d
¼8.0 (s, 2H), 7.77e7.67 (m, 4H),
3JHH¼9.1 Hz, 2H), 7.58 (dd, JHH¼8.1 Hz, 1H), 7.40 (t, JHH¼7.5 Hz,
3
3
7.22e7.13 (m, 2H), 7.01e6.86 (m, 3H); 11B NMR (96.3 MHz, C6D6):
d
3
1H), 7.32 (t, JHH¼7.3 Hz, 1H), 7.20e7.13 (m, 1H), 7.07 (t,
¼40.4 (br., h1/2¼590 Hz); 13C NMR (75.5 MHz, C6D6):
¼151.3,
d
3JHH¼7.6 Hz, 1H), 1.42 (s, 27H, 9 CH3); 11B NMR (96.3 MHz, C6D6):
¼54.0 (br, h1/2¼500 Hz); 13C NMR (75.5 MHz, C6D6):
¼151.6,139.9
d
140.0, 136.6, 134.4 (br.), 133.7, 131.4, 131.0, 129.6, 127.7, 126.1,
d
124.1, 123.9, 123.7, 123.7, 123.6, 123.5, 122.5, 122.3, 120.8; 19F
(2C), 137.1, 132.9, 129.2, 126.8, 123.0, 123.8, 123.0, 122.2, 120.3, 32.6
(9 CH3), 23.1 (3 CMe3); 29Si NMR (59.6 MHz, C6D6): n.b; elemental
NMR (282.3 MHz, C6D6):
d
¼ ꢀ62.5 (2CF3); elemental Anal. Calcd

1484
A. Budanow et al. / Tetrahedron 72 (2016) 1477e1484
Table 3
Crystal data and refinement details for oxaboraphenanthrenes 4e9
4
C
5
6
7
8
9
Empirical formula
Formula weight
T/K
20H17BO
C21H19BO
298.17
173(2)
MoKa, 0.71073 A
Orthorhombic
P212121
9.4804(5)
13.7252(6)
25.3586(11)
90
90
90
3299.7(3)
8
1.200
C27H31BO
382.33
293(2)
MoKa, 0.71073 A
Monoclinic
P21/c
9.0884(7)
32.123(2)
8.5689(6)
90
110.9690(10)
90
2336.0(3)
4
1.087
824
C20H11BF6O
392.10
173(2)
MoKa, 0.71073 A
Monoclinic
P21/c
12.1297(12)
5.4293(4)
25.144(3)
90
96.922(8)
90
1643.8(3)
4
1.584
792
C18H8BF5O
346.05
173(2)
MoKa, 0.71073 A
Monoclinic
P21/c
15.7080(11)
7.2722(4)
12.5481(10)
90
96.140(6)
90
1425.17(17)
4
1.613
696
C22H35BOSi3
410.58
173(2)
MoKa, 0.71073 A
Monoclinic
P 21/n
16.5118(8)
8.7803(4)
33.5288(16)
90
99.209(4)
90
4798.3(4)
8
1.137
1776
284.15
173(2)
MoKa, 0.71073 A
Orthorhombic
Pba2
15.2162(5)
35.4853(14)
5.5091(2)
90
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Wavelength
Crystal system
Space group
ꢀ
a/A
ꢀ
b/A
ꢀ
c/A
ꢁ
ꢁ
a
b
g
/
/
90
90
ꢁ
/
3
ꢀ
V/A
2974.65(19)
8
1.269
Z
Density calculated g cmꢀ3
F(000)
1200
1264
Index ranges
ꢀ16ꢃhꢃ18
ꢀ42ꢃkꢃ42
ꢀ6ꢃlꢃ6
ꢀ11ꢃhꢃ11
ꢀ16ꢃkꢃ13
ꢀ25ꢃlꢃ30
0.48ꢂ0.46ꢂ0.46
12,830
ꢀ10ꢃhꢃ10
ꢀ38ꢃkꢃ38
ꢀ10ꢃlꢃ10
0.65ꢂ0.50ꢂ0.15
22,779
ꢀ14ꢃhꢃ14
ꢀ6ꢃkꢃ6
ꢀ29ꢃlꢃ30
0.35ꢂ0.32ꢂ0.27
8072
ꢀ19ꢃhꢃ16
ꢀ8ꢃkꢃ8
ꢀ15ꢃlꢃ15
0.28ꢂ0.15ꢂ0.02
10,868
ꢀ20ꢃhꢃ20
ꢀ10ꢃkꢃ10
ꢀ31ꢃlꢃ41
0.42ꢂ0.27ꢂ0.13
35,581
Crystal size/mm3
No. of reflections collected
0.23ꢂ0.15ꢂ0.10
32,715
R1, wR2 [I>2
s
(I)]
0.0387, 0.0943
5518/1/402
0.990
0.0487, 0.1298
5765/0/421
1.027
0.0878, 0.2010
4119/9/261
1.114
0.0638, 0.1509
3016/37/265
1.051
0.0422, 0.0992
2664/0/226
0.946
0.0620, 0.1570
9108/0/515
1.033
Data/restraints/parameter
GOOF on F2
R1, wR2 (all data)
largest diff peak and hole/eA
0.0455, 0.0976
0.168, ꢀ0.140
0.0513, 0.1320
0.0167, ꢀ0.220
0.1168, 0.2165
0.0255, ꢀ0.283
0.0801, 0.1603
0.602, ꢀ0.547
0.0616, 0.1067
0.254, ꢀ0.253
0.0791, 0.1665
0.322, ꢀ0.507
ꢀꢀ3
Anal. Calcd (%) for C24H35BOSi (378.43): 76.17, H, 9.32, found: C
76.09, H 9.57.
References and notes
1. Dewar, M. J. S.; Dietz, R. J. Chem. Soc. 1960, 1344.
2. Braid, M. U.S. Patent 4 353 807, 1982.
3. Davis, F. A.; Dewar, M. J. S. J. Org. Chem. 1968, 8, 3324.
4.3. X-ray structure determination
4. Kohn, G. K; McMurtry, R. J. U.S. Patent 3 686 398, 1972.
5. He, J.; Crase, J. L.; Wadumethrige, S. H.; Thakur, K.; Dai, L.; Zou, S.; Rathore, R.;
Hartley, C. S. J. Am. Chem. Soc. 2010, 132, 13848.
6. Crossley, D. L.; Cade, I. A.; Clark, E. R.; Escande, A.; Humphries, M. J.; King, S. M.;
Vitorica-Yrezabal, I.; Ingleson, M. J.; Turner, M. L. Chem. Sci. 2015, 6, 5144.
7. Budanow, A.; Sinke, T.; Lerner, H.-W.; Bolte, M. Acta Crystallogr. 2014, C70, 662.
8. Zou, L.; Savvate’ev, V.; Booher, J.; Kim, C.-H.; Shinarb, J. Appl. Phys. Lett. 2001, 79,
2282.
9. Qiu, C. F.; Wang, L. D.; Chen, H. Y.; Wong, M.; Kwok, H. S. Appl. Phys. Lett. 2001,
79, 2276.
10. Liu, H.; Bai, Q.; Yao, L.; Zhang, H.; Xu, H.; Zhang, S.; Li, W.; Gao, Y.; Li, J.; Lu, P.;
Wang, H.; Yang, B.; Mac, Y. Chem. Sci. 2015, 6, 3797.
The data for 6 were collected on a Siemens SMART three-circle
ꢀ
diffractometer using MoKa radiation (
l
¼0.71073 A) and were scaled
using the program SADABS.22
The data for the remaining structures were collected on a STOE
IPDS II two-circle diffractometer with a Genix Microfocus tube with
ꢀ
mirror optics using MoKa radiation (
l
¼0.71073 A) and were scaled
using the frame scaling procedure in the X-AREA program system.23
The structures were solved by direct methods using the program
SHELXS and refined against F2 with full-matrix least-squares tech-
niques using the program SHELXL-97 (see Table 3).24
Due to the absence of anomalous scatterers, the absolute
structure of 4 and 5 could not be determined.
11. Chao, T.-C.; Lin, Y.-T.; Yang, C.-Y.; Hung, T. S.; Chou, H.-C.; Wu, C.-C.; Wong, K.-T.
Adv. Mater. 2005, 17, 992.
12. Hirai, H.; Nakajima, K.; Nakatsuka, S.; Shiren, K.; Ni, J.; Nomura, S.; Ikuta, T.;
Hatakeyama, T. Angew. Chem., Int. Ed. 2015, 54, 13581.
13. Zhou, Q. J.; Worm, K.; Dolle, R. E. J. Org. Chem. 2004, 69, 5147.
14. Cowley, A. H.; Norman, N. C.; Pakulski, M.; Becker, G.; Layh, M.; Kirchner, E.;
Schmidt, M. Inorg. Synth. 1990, 27, 235.
The crystal of 6 was measured at room temperature, because the
crystals did not survive being cooled. One isopropyl group is dis-
ordered over two positions with a site occupation factor of 0.570
(15) for the major occupied site. The disordered atoms were iso-
tropically refined.
One trifluoromethyl group in 7 is disordered over three posi-
tions with site occupation factors of 0.447(3), 0.303(3), and
0.250(3). Bond lengths and angles of the disordered atoms were
restrained to be equal to those of the non-disordered tri-
fluoromethyl group. The disordered atoms were isotropically
refined.
One trimethylsilyl group in 9 is disordered over two positions
with a site occupation factor of 0.644(8) for the major occupied site.
The disordered atoms were isotropically refined.
CCDC deposition numbers: 1410266 (lithium borate 2bꢂ3 THF),
1403456 (4), 1403457 (5), 1403458 (6), 1403459 (7), 1403460 (8),
1403461 (9).
15. Eaborn, C.; Hitchcock, P. B.; Smith, J. D.; Sullivan, A. C. Chem. Commun. 1983, 827.
16. Lerner, H.-W. Coord. Chem. Rev. 2005, 249, 781.
€
17. Wiberg, N.; Amelunxen, K.; Lerner, H.-W.; Schuster, H.; Noth, H.; Krossing, I.;
Schmidt-Amelunxen, M.; Seifert, T. J. Organomet. Chem. 1997, 542, 1.
18. Tang, C. W.; VanSlyke, S. A. Appl. Phys. Lett. 1987, 51, 913.
19. SooKim, H.; Moon, S. I.; Hwang, D. E.; Jeong, K. W.; Kim, C. K.; Moon, D.-G.;
Hong, C. Opt. Laser Technol. 2016, 77, 104.
20. Bahirwar, B. M.; Atram, R. G.; Pode, R. B.; Moharil, S. V. Mater. Chem. Phys. 2007,
106, 364.
21. 2bꢂ3 THF (C38H40BLiO3) crystallizes in the ‘monoclinic’ system, space group ‘P
ꢀ
ꢀ
ꢀ
a
21/n’ with a¼9.7010(8) A, b¼19.0850(11) A, c¼17.7489(15) A,
¼90ꢁ,
b
¼101.
416(7)ꢁ,
g
¼90ꢁ, V¼3221.1(4), M¼562.45, Z¼4, and Dc¼1.160 g cmꢀ3. 24799
reflections (6030 unique) were collected in the range of 3.393e25.703ꢁ at 173 K
giving a final residual value of R1¼0.1021 (all data) wR2¼0.1721 ([I>2
s(I)]);
CCDC 1410266.
22. Sheldrick, G. M. SADABS, A Program for the Scaling of Area Detector Data,
€
Gottingen, Germany, 1996.
23. Stoe, C. X-AREA. Diffractometer Control Program System; Stoe & Cie: Darmstadt,
Germany, 2002.
24. Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112.