Structure-property relationships of acylated asymmetric dithienophospholes

Article abstract of DOI:10.1016/j.crci.2010.04.023

Friedel-Crafts acylation was found to be an effective way to selectively access mono-functionalized dithienophospholes. Absorption and emission properties of the acylated compounds exhibited high extinction coefficients, relative to unsubstituted dithieno

Full text of DOI:10.1016/j.crci.2010.04.023

C. R. Chimie 13 (2010) 971–979
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´
Full paper/Memoire
Structure–property relationships of acylated asymmetric
dithienophospholes
*
Terry J. Gordon, Lisa D. Szabo, Thomas Linder, Curtis P. Berlinguette, Thomas Baumgartner
Department of Chemistry, The Institute for Sustainable Energy, Environment & Economy, University of Calgary, 2500 University Drive,
NW, Calgary, Alberta, Canada, T2N 1N4
A R T I C L E I N F O
A B S T R A C T
Article history:
Friedel-Crafts acylation was found to be an effective way to selectively access mono-
functionalized dithienophospholes. Absorption and emission properties of the acylated
compounds exhibited high extinction coefficients, relative to unsubstituted dithieno-
phosphole and bathochromic shifts when in the presence of Lewis-acids, e.g., AlCl3 and BF3,
effectively demonstrating that the emissive characteristics could be tuned. Subsequent
treatment of the asymmetric mono-substituted compounds with N-bromosuccinimide,
yielded materials that were later employed in Ni-catalyzed Yamamoto cross-coupling
reactions. The resulting cross-coupled material exhibited a substantial increase in its
extinction coefficient as well as a further red-shifted absorbance and emission profile,
relative to the mono-functionalized phosphole.
Received 28 January 2010
Accepted after revision 23 April 2010
Available online 8 June 2010
Keywords:
Phosphorus heterocycles
Materials science
Acylation
Fluorescence
Density functional calculations
Cross-coupling
´
ß 2010 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
1. Introduction
accessible through organophosphorus electronics using
the highly luminescent dithieno[3,2-b:20,30-d]phosphole
Organic
p
-conjugated materials are an important class
system [3]. Through our systematic structure-property
studies, we were able to address a variety of important
aspects including tunability of the photophysical proper-
ties, solid-state organization, processability (i.e., through
polymeric architectures), as well as the redox-behavior of
the materials [4]. However, synthetic methods that easily
afford mono-substituted, or asymmetric, oxidized
dithieno[3,2-b:20,30-d]phospholes are still rare [5].
In this contribution, we now report on the synthesis
and characterization of acylated dithieno[3,2-b:20,30-
d]phosphole oxides prepared via Friedel-Crafts acylation.
Interestingly, this reaction provides a facile synthetic
of compounds due to their significant potential for diverse
practical applications in optoelectronics, including light-
emitting diodes, field-effect transistors, and photovoltaic
cells [1]. Their organic nature provides for a plethora of
synthetic possibilities to fine tune the materials’ proper-
ties toward specific applications (addressing, e.g., semi-
conducting behavior, or processability). In recent years,
the use of organophosphorus components (as well as
boron and silicon compounds) has become a promising
new approach in this context, as the presence of the
phosphorus center(s) introduces unique electronic fea-
tures to
p
-conjugated materials, which are not accessible
route to asymmetric, mono-functionalized p-conjugated
in this simplicity with native organic components [2].
Over the past seven years or so, we were able to
comprehensively illustrate the beneficial features
phosphole-based materials. These can be further post-
functionalizated through bromination of the vacant 6-
position of the dithienophosphole scaffold and homo-
coupled under Yamamoto reaction conditions, demon-
strating that extended
p-conjugated oligomers with
further tuned absorption and emission properties can
be realized.
* Corresponding author.
E-mail address: thomas.baumgartner@ucalgary.ca (T. Baumgartner).
1631-0748/$ – see front matter ß 2010 Acade´mie des sciences. Published by Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.crci.2010.04.023

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T.J. Gordon et al. / C. R. Chimie 13 (2010) 971–979
Scheme 1. Synthetic route to asymmetric and symmetric carbonyl-substituted dithieno[3,2-b:20,30-d]phospholes, compounds 2 through 5, and compound
6, respectively.
2. Results and discussion
example (Scheme 1). The resulting compound 6, was
found to possess the desired red-shifted absorption and
emission properties (vide infra), however, exhibited
limited solubility in common organic solvents making
more extensive optical and electronic characterizations
difficult.
2.1. Synthesis
Friedel-Crafts acylation of dithienophosphole oxides
has successfully been employed for the preparation of
symmetric and asymmetric luminescent materials. As
shown in Scheme 1, the synthetic route utilized the
treatment of the dithieno[3,2-b:20,30-d]phosphole oxide 1
with the appropriate acyl chlorides in the presence of
excess AlCl3 under mild reaction conditions in dichloro-
methane to afford compounds 2, and 3. Surprisingly,
even an excess of the acyl chloride (ꢀ3.0 equivalents),
yielded only mono-functionalized phospholes, with the
exception of the formation of a minor amount of the 2,6-
difunctionalized phosphole (< 5%), when the acylation
reagent was acetyl chloride, denoted as compound 2x. The
disubstituted species 2x could be selectively crystallized
from an ethyl acetate/hexanes solution at room tempera-
ture. Reactions employing thiophene-2-carbonyl chlo-
ride, on the other hand, did not form the corresponding
difunctionalized phosphole, even under extended reac-
tion times (> 2 days). The identity of the mono-functio-
nalized species was supported by the heteronuclear NMR
studies.
2.2. Crystal structures
As stated in section 2.1, a minor quantity of the diacetyl
product (2x) was isolated through crystallization from a
concentrated ethyl acetate/hexanes solution and suitable
for single crystal X-ray structure analysis. The molecular
structure and crystal packing of 2x are shown in Fig. 1.
Suitable single crystals of
3 were obtained from a
concentrated ethanol solution, and its molecular structure
and packing are shown in Fig. 2. Table 1 summarizes
selected bond lengths for compounds 2x and 3.
The molecular structures of 2x and 3 exhibit similar
characteristics with respect to the planarity of the
conjugated backbone with the exception that the carbon-
yl-thiophene in 3 twists slightly out of the plane by
approximately 48, whereas the respective orientation of
the pendant P-phenyl moiety is rotated approximately 908
relative to 2x, likely due to packing effects. Both
compounds also exhibit similar orientations of the
carbonyl moieties, lying in the same plane as the thiophene
S atoms, similar to a diformyl-functionalized phosphole
reported earlier [7]. The thiophene carbonyl bond lengths
and twisting are similar to those found in a related di-2-
thienyl ketone [8]. However, the molecules of 2x show
little direct overlap in the solid-state presumably due to
the bulkier terminal methyl moieties. Interestingly, mono-
substitution of 3 imparts chirality about the P atom and
Subsequent treatment of 2 and 3 with N-bromosuccin-
imide (NBS) in acetic acid/chloroform yielded mono-
brominated compounds 4 and 5 in good yields after a
short silica column using ethyl acetate as an eluent or
crystallization from acetone, respectively. In order to
demonstrate that the mono-brominated acylated phos-
pholes could also be used to yield materials with more
extended conjugation, nickel-catalyzed Yamamoto coup-
ling [6] was employed using
5 as a representative

T.J. Gordon et al. / C. R. Chimie 13 (2010) 971–979
973
Fig. 1. Molecular structure (top) and packing (bottom) of 2x in the solid state (50% probability level, H atoms omitted for clarity).
both enantiomers are observed interacting in a slip-
stacked pair packing arrangement as shown in Fig. 2.
absorbance and photoluminescence spectra are depicted
in Fig. 3. As shown by the black plots of compounds 1, 2 and
(Fig. 3), the absorption maxima exhibit
bathochromic shift with the addition of acetyl (2;
max = 381 nm) and thiophene-2-carbonyl (3;
max = 393 nm), relative to unsubstituted dithienophos-
phole (1; max = 361 nm, [3]). The red-shift is attributed to
3
(lmax
)
a
2.3. UV-vis and fluorescence spectroscopy
l
l
Solution absorption and fluorescence data for com-
pounds 1 through 6 are summarized in Table 2 and the
l
Fig. 2. Molecular structure (left) and packing (right) of 3 in the solid state (50% probability level, H atoms omitted for clarity).

974
T.J. Gordon et al. / C. R. Chimie 13 (2010) 971–979
Table 1
methane solutions of 1, 2, and 3; however, most values
range between PL = 11–31%, which is significantly lower
than usually observed for dithienophospholes ( PL = 35–
Selected bond lengths for compounds 2x and 3.
f
f
2x
3
90%) [3,4]. The lower values can be attributed to the
quenching character of the incorporated ketone func-
tionalities, opening up significant non-radiative relaxa-
tion pathways, and are in line with earlier observations
˚
˚
(O1 – P1)
(C3 – P1)
(C9 – P1)
(C1 – C2)
(C1 – C15)
(C4 – C5)
(C15 – O2)
(C15 – C16)
1.483(1) A
(O1 – P1)
(C3 – P1)
(C6 – P1)
(C14 – P1)
(C4 – C5)
(C5 – C6)
(C8 – C9)
(C9 – O2)
(C9 – C10)
1.483(7) A
˚
˚
1.820(5) A
1.810(2) A
˚
˚
1.789(2) A
1.806(2) A
˚
˚
1.802(2) A
1.377(3) A
˚
˚
1.472(3) A
1.456(3) A
for
a diformyl-functionalized dithienophosphole [7].
˚
˚
1.384(4) A
1.460(3) A
Surprisingly, after bromination of compounds 2 and 3,
the quantum yield was found to increase. DFT-calculated
molecular orbitals of compound 4 (not shown) support
˚
˚
1.218(3) A
1.467(3) A
˚
˚
1.499(3) A
1.228(3) A
˚
1.472(3) A
that bromine is an integral component of the
p– and p*–
system. However, the calculations also show that
bromination only effects the energy level of the LUMO
by lowering it to ꢁ2.58 eV (4) from ꢁ2.44 eV (2),
whereas the energy of the HOMO remains essentially
unchanged at ꢁ6.05 eV (cf. 2: ꢁ6.04 eV). This suggests
that bromine acts as an electron acceptor. Although a
rare phenomenon, Havlas and Michl have recently
reported that the heavy atom effects of bromine can
indeed be inverted when the bromine behaves as an
electron acceptor [10]. Thus, it is plausible that a similar
mechanism may apply in the present study. Photo-
an extension of the
p-system with the addition of the
ketone moiety. The brominated compounds 4 and 5 exhibit
a further red-shift in absorbance, as compared to the
acylated derivatives, shifting by Dlmax = 13 and
Dlmax = 11 nm,respectively. Extinctioncoefficients(
extracted from max for compounds 1, 2 and 3 (Table 2). The
unsubstituted dithienophosphole 1 exhibits the lowest
extinction coefficient at
= 6250 Mꢁ1cmꢁ1, relative to the
acylated and brominated compounds 2 through 5. The value
for compounds 2 (
= 12,444 Mꢁ1 cmꢁ1) nearly doubles to
(4) = 24,444 Mꢁ1 cmꢁ1 upon bromination. Compounds 3
and 5 showed similar absorption characteristics increasing
the extinction via
(3) = 14,909 Mꢁ1 cmꢁ1 after acylation, to
(5) = 23,880 Mꢁ1 cmꢁ1 post-bromination. Surprisingly, the
of compound 5 is slightly lower than compound 4 possibly
e)were
l
e
e
e
luminescence life times (h) were also measured for
compounds 1 through 5, and show typical values for
organophosphorus-based conjugated materials (Table 2)
[11].
e
e
e
During the synthesis of 2 and 3, the emission color of
the reaction mixtures shifted from blue to yellow upon
addition of AlCl3 leading us to explore whether it was
possible to further tune the emission color of the
resulting phospholes in the presence of Lewis acids.
Therefore, the photophysical properties of compounds 1,
2 and 3 in the presence of BF3 were investigated to
examine the spectral response, which was believed to
originate from a Lewis-acid complex to the oxygen
atoms of the P O and/or C O functional groups of the
scaffold. As shown in the red and blue plots of Fig. 3a, c,
and e, compounds 1 and 2 exhibited a red-shifted
absorbance profile upon addition of the Lewis-acid. The
indicating that the thiophene moiety is not completely
coplanar with the phosphole unit. Yamamoto coupling of 5
increases the extinction coefficient to a greater extent,
nearly tripling, increasing to
max = 438 nm). The increase, relative to the unsubstituted
e
(6) = 60,000 Mꢁ1 cmꢁ1
(l
phosphole and brominated compound, is attributed to the
extended absorption cross-section of the molecule and
extended
p-system. Density Functional Theory (DFT)
calculations, at the B3LYP/6-31G(d) level of theory [9],
indicate that the lone pair(s) at the Br atom contribute to the
p– and p*- system, thereby extending the frontier orbitals
(HOMO, LUMO) and the absorption cross-section.
Photoluminescence spectra for compounds 1, 2, and 3
also exhibit red-shifted characteristics, shifting from
shifts in lmax for compounds 1 and 2 were Dlmax = 7 and
Dlmax = 4 nm for the initial addition of Lewis-acid and
Dlmax = 15 and Dlmax = 7 nm after the addition of a large
excess of boron trifluoride (employed as diethyl ethe-
rate), relative to the position of lmax of the neat
solutions, respectively. It should be noted that the initial
addition of boron trifluoride was chosen to be approxi-
l
em = 447 nm (unsubstituted 1, [3]) to
em = 469 nm for the non-brominated compounds 2 and
3, and em = 478 and em = 483 nm for the brominated
compounds 4 and 5, respectively. Photoluminescence
lem = 463 and
l
l
l
quantum yields
(fPL) were obtained for dichloro-
Table 2
Photophysical data of compounds 1– 6 in dichloromethane solution.
Compound
lmax/nm
e
/Mꢁ1 cmꢁ1
lem/nm
fPL
h/ns
1
2
3
4
5
361
381
394
393
404
6250
447
463
478
469
483
0.21
0.26
0.11
0.46
0.30
13
6
12,444
24,444
14,909
23,880
1
6
2
6
438 (520)
60,000
560 (605)
0.31
NA
l
max: maximum wavelength of absorption;
e
: extinction coefficient;
l
em: maximum wavelength of emission; fPL: fluorescence quantum yield of emission
in dichloromethane (absolute values, using an integrating sphere;
absorption or emission profiles).
h: fluorescence emission life time; bracketed wavelengths indicate shoulders in the

T.J. Gordon et al. / C. R. Chimie 13 (2010) 971–979
975
Fig. 3. UV-vis absorption and photoluminescence spectra of compounds 1 a) and b), 2 c) and d), and 3 e) and f) in dichloromethane solution.
mately 10 times that of the phosphole concentration in
order to observe any spectral shift more easily, as adding
one equivalent per carbonyl moiety did not perturb the
spectral properties in a measurable way. Interestingly,
compound 3 did not exhibit a shift in absorbance even
with the addition of a large excess of boron trifluoride.
An interesting trend that is observed for compounds 1, 2
and 3, after the addition of boron trifluoride, is the red-
Contrary to the absorption spectroscopy results, all of
the photoluminescence spectra for compounds 1, 2 and 3
exhibited red-shifted emission characteristics upon addi-
tion of boron trifluoride. Compound 1 exhibited the
strongest red-shift in emission, shifting from
to em = 490 nm, whereas compounds 2 and 3, exhibited
nearly similar shifts, shifting from em = 463 to
em = 493 nm and em = 469 to em = 495 nm, respectively.
31P and 13C NMR spectroscopy experiments were
employed to investigate the coordination of BF3 to the
O and/or C O moieties in chloroform solutions of
lem = 447 nm
l
l
l
l
l
shift in
lmax, as compared with the neat solutions,
decreases as the extent of conjugation of the molecules
increases.
P

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T.J. Gordon et al. / C. R. Chimie 13 (2010) 971–979
Table 3
Crystal data and structure refinement for 2x and 3.
2x
3
Formula
C18 H13 O3 P S2
C19 H11 O2 P S3
398.43
Mr
372.37
T
173(2) K
123(2) K
˚
˚
l
0.7107 A
1.54178 A
Crystal system
Monoclinic
Monoclinic
Space group
C2/c
P21/c
˚
˚
a
20.20720(70) A
8.8545(3) A
˚
˚
11.2803(3) A
b
8.24900(29) A
˚
˚
c
20.88330(50) A
908
17.7894(5) A
a
908
b
g
V
97.1208(17)8
908
3454.171(192) A
8
1.432 Mg/m3
0.414 mmꢁ1
1536
106.6930(10)8
908
3
˚
˚
1701.95(9) A3
Z
rcalcd
m
F(000)
Crystal size
u
4
1.555 Mg/m3
4.962 mmꢁ1
816
0.16 ꢂ 0.09 ꢂ 0.06 mm3
1.97 to 27.468
ꢁ25 ꢃ h ꢃ 26
1.178 ꢂ 0.37 ꢂ 0.366 mm3
range
4.7 to 688
Index ranges
ꢁ8 ꢃ h ꢃ 10
ꢁ10 ꢃ k ꢃ 10
ꢁ13 ꢃ k ꢃ 12
ꢁ18 ꢃ K ꢃ 20
10559
ꢁ26 ꢃ K ꢃ 26
Reflections collected
7185
Independent reflections
3883 [R(int) = 0.0216]
98 %
3029 [R(int) = 0.0489]
97.8 %
Completeness to
u
Absorption correction
Max./min. transmission
Data/restraints/parameters
GoF on F2
Semi-empirical
0.9756 and 0.9367
3883/0/225
Numerical
0.4376 and 0.1039
3029/0/226
1.225
1.076
Final R indices [I > 2
s
(I)]
R1 = 0.0436, wR2 ¼ 0:1331
R1 = 0.0488, wR2 ¼ 0:1381
R1 = 0.0448, wR2 ¼ 0:1205
R1 = 0.0453, wR2 ¼ 0:121
R indices (all data)
ꢁ3
ꢁ3
˚
˚
Largest diff. peak/hole
0.524 and ꢁ0.514 eA
0.657 and ꢁ0.511 eA
compounds
1
and 3. Both compounds exhibited
a
2.4. Theoretical calculations
downfield shift of approximately Dd = 20 ppm in their
31P NMR spectra after the addition of BF3. On the contrary,
the 13C NMR resonance peak associated with the carbonyl
moiety, located at ꢀ177 ppm, did not exhibit any shift
upon addition of BF3. These results suggest that the
interaction of the Lewis acid, i.e., BF3, with the dithieno-
phospholes prepared in this study is mostly associated
with the phosphorus-oxygen moiety. The observed optical
responses for compounds 1–3 suggest that the effect of the
functionalized phosphorus center on the photophysical
properties of the materials as a whole diminishes upon
To explore the extent of delocalization in the molecular
orbitals of the acylated dithienophospholes, suggested by
the bathochromic spectroscopic shifts in the absorption
and emission spectra, DFT was employed at the B3LYP/6-
31G(d) level [9]. The resulting isodensity plots are shown
in Fig. 4 for compounds 1, 2 and 3. All of the compounds
display a similar distribution in their respective highest
occupied molecular orbital (HOMO) and lowest unoccu-
pied molecular orbital (LUMO) and extending over the
carbonyl moiety for compounds 2 and 3. The HOMO level
increasing extent of
p
-conjugation, which is supported by
of compounds
EHOMO = ꢁ6.04 eV, 3: EHOMO = ꢁ6.01 eV) and lower in
energy than unsubstituted dithienophosphole (cf.:
EHOMO = ꢁ5.77 eV). The calculated energy levels of the
LUMOs are also markedly different from compound 1,
lowering in energy from ELUMO = ꢁ1.86 eV (1) to
ELUMO = ꢁ2.44 and ꢁ2.52 eV for compounds 2 and 3,
respectively. The difference in ELUMO for 2 and 3 is due to
2 and 3 are nearly degenerate (2:
the frontier orbitals of the three compounds (vide infra).
This feature has also recently been observed with extended
donor/acceptor substituted dithienophospholes that do
not show any shift of the photophysical data upon
significant modification of the phosphorus center (oxida-
tion or complexation to Au) [12].
The observations confirm that the photophysical
properties of acylated and non-acylated dithienophos-
pholes can be further tuned through addition of Lewis
acids and the effects on the absorption and/or emission
features depend on the degree of conjugation within the
(extended) dithienophosphole scaffolds. A similar behav-
iour was recently also reported for somewhat related,
2,1,3-benzothiadiazole-functionalized extended dithieno-
siloles [13].
1
the more extended
p-system with the addition of the
thiophene moiety of 3 (Fig. 4). The trend in the energy gaps
(Eg) of compounds 1, 2 and 3, i.e., Eg = 3.91, 3.60 and
3.50 eV, respectively, correlates well with the decreasing
trend observed in the optical energy gap (Eopt) extracted
from the lmax of absorption, i.e., Eopt = 3.44, 3.26 and
3.16 eV, respectively, possibly due to the increasing extent
of conjugation [1]. The relative values differ likely due to

T.J. Gordon et al. / C. R. Chimie 13 (2010) 971–979
977
Fig. 4. Isodensity plots for compounds 1, 2 and 3 and their associated HOMO and LUMO energy levels calculated at the B3LYP/6-31G(d) level of theory.
the level of the basis set employed, as well as the fact that
the molecules were not modeled in solvent.
crystalline properties and will be discussed in a future
publication.
3. Conclusions
4. Experimental
In conclusion, we have demonstrated that Friedel-
Crafts acylation conditions provide an easy and efficient
way to synthesize 2-mono-functionalized dithienophos-
pholes, which are otherwise very difficult to obtain.
Acylation of the main scaffold was found to provide
All the reactions were carried out under nitrogen
atmosphere using standard Schlenk techniques. Unless
otherwise specified, reagents were used as received. The
detailed preparation of compound 1 has been reported
elsewhere [3]. 1H NMR, 13C{1H} NMR, and 31P{1H} NMR
spectra were recorded on Bruker DRY-400, and Bruker
UGI-400 spectrometers. Mass spectrometry was per-
formed using a Finnigan SSQ700 or Bruker Daltonics
AutoFlex III system. Optical spectroscopy experiments
were recorded in dichloromethane solution using a UV-
vis-NIR Cary 5000 spectrophotometer and Edinburgh
Instruments Ltd FLS920P fluorescence spectrometer
equipped with an integrating sphere. Solutions were
degassed with N2 prior to measuring photoluminescence.
Lewis-acid complexation studies were performed by the
initial addition of 2.5 ꢂ 10ꢁ7 mol boron trifluoride diethyl
etherate to a solution of compounds 1, 2, or 3 in degassed
dichloromethane solution followed by the addition of a
large excess of boron trifluoride diethyl etherate
extended
p-conjugated systems with red-shifted photo-
physical properties, when compared to the dithienophos-
phole core. Acylation further induced a significant increase
in the absorption features, and also allows for additional
tuning of the photophysical properties through interaction
with Lewis acids, likely involving the P O group. The
mono-acylated species can further be functionalized with
a
bromo-substituent in the 6-position that permits
subsequent cross-coupling reactions to afford bis(dithie-
nophosphole) oligomers with strongly red-shifted photo-
physical properties and an enhanced absorption profile. It
is believed that the addition of alkylated thiophene-2-
carbonyl chlorides to the phosphole would yield more
soluble derivatives that may possess interesting liquid

978
T.J. Gordon et al. / C. R. Chimie 13 (2010) 971–979
(1.27 ꢂ 10ꢁ4 mol) to ensure full complexation of the Lewis-
acid to the phosphole. Additional aliquots of boron
trifluoride diethyl etherate were added; following the
excess addition, however, changes in absorption or
photoluminescence were not observed. Diffraction data
1H, J = 3.6, J = 1.2 Hz), 7.77–7.70 (m br, 3H), 7.59–7.54 (m
br, 1H), 7.49–7.43 (m br, 3H), 7.24–7.22 (dd, 1H, J = 4.8,
J = 2.4 Hz), 7.19–7.17 (dd, 1H, J = 4.8, J = 3.6 Hz) ppm; 13C-
NMR (CDCl3, 100 MHz):
d = 177.94 (s), 152.14 (d,
J = 22.1 Hz), 146.64 (d, J = 12.3 Hz), 144.95 (d, J = 23.0 Hz),
141.74 (d, J = 11.1 Hz), 140.52 (d, J = 53.5 Hz), 138.89 (s),
133.95 (d, J = 50.7 Hz), 132.86 (d, J = 2.9 Hz), 131.52 (d,
J = 14.9 Hz), 131.19 (d, J = 13.8 Hz), 130.85 (d, J = 11.3 Hz),
129.14 (d, J = 13.2 Hz), 129.06 (s), 128.14 (s), 127.97 (s),
126.47 (d, J = 14.3) ppm; MS (EI): m/z (%): 397.69 (100)
was collected on a Nonius Kappa CCD diffractometer using
˚
monochromated Mo Ka radiation (l = 0.71073 A). The
datasets were corrected for Lorentz and polarization
effects and absorption correction was applied to the net
intensities (Table 3). The structure was solved by direct
methods and refined using SHELX [14]. After full-matrix
least-square refinement of the nonhydrogen atoms with
anisotropic thermal parameters, the hydrogen atoms were
placed in calculated positions using a riding model.
[M+], 320.70 (46) [M+
C
C
–
C6H5], 110.87 (35) [M+
14H8S2PO]; HR-MS (TOF MS CI+): calculated for
19H11O2S3P m/z: 397.9659 [M+], found m/z: 397.9641,
–
mp: 210 – 2118.
4.1. Compounds (2) and (3) were prepared using a similar
4.2. Compounds 4 and 5
procedure
In a typical bromination reaction, 0.19 g (0.47 mmol) of
1.72 g (11.7 mmol) of AlCl3 was dissolved in dry DCM.
0.390 g (2.67 mmol) of thiophene-2-carbonyl chloride (in
the preparation of 3) was added into the flask. 0.310 g
(1.07 mmol) of the phosphole oxide 1 was dissolved in dry
DCM and added into the flask containing the AlCl3 and acyl
chloride. The reaction was stirred overnight at room
temperature. The fluorescence changed from yellow-green
to yellow-orange during the course of the reaction. The
solution was quenched over sodium bicarbonate water and
the organic layer separated. The compounds were
extracted from the aqueous layer with DCM three times,
followed by washing with aqueous sodium bicarbonate,
water, and lastly saturated NaCl. The organic layer was
dried with MgSO4, filtered, and evaporated yielding a
yellow powder (2) or orange oil (3). Compound 2 was
further purified on a silica column using ethyl acetate as an
eluent followed by recrystallization from acetone. Analysis
of column fractions yielded a minor amount of the di-
reacted product 2x for which the crystal structure was
determined. Compound 3 was further purified on a silica
column with 4:1 ethyl acetate:hexane as the eluent and
recrystallized from ethanol yielding yellow crystals.
(2) Yield: 0.359 g, 1.13 mmol, 71.6%; 31P-NMR (CD2Cl2,
the keto-phosphole oxide, 2 or 3, was dissolved in
chloroform and acetic acid (1:2) mixture. N-bromosuccin-
imide, 0.092 g (0.51 mmol), was added and stirred for 24 h.
The solution was then quenched with NaOH solution and
extracted with CHCl3 (3 ꢂ 25 mL) and subsequently
washed with (3 ꢂ 25 mL) with aqueous NaOH. The
combined organic layers were dried with MgSO4, filtered
and reduced to a yellow powder.
(4) Yield: 0.289 g, 0.710 mmol, 64.7%; 31P-NMR (CD2Cl2,
162 MHz):
400 MHz):
d
= 18.67 (s, 1P) ppm; 1H-NMR (CD2Cl2,
d
= 7.74–7.68 (m br, 3H), 7.62–7.58 (tdt, 1H,
J = 7.2, J = 1.8 Hz), 7.50–7.45 (m br, 2H), 7.23–7.22 (d, 1H,
J = 2.4 Hz), 2.50 (s, 3H) ppm; 13C-NMR (CD2Cl2, 100 MHz):
d
= 190.67 (s), 151.86 (s), 148.78 (d, J = 8.5 Hz), 145.61 (d,
J = 22.9 Hz), 141.82 (d, J = 106.8 Hz), 139.14 (d, J = 110 Hz),
133.55 (d, J = 3.1 Hz), 131.40 (d, J = 11.3 Hz), 131.07 (d,
J = 13.6 Hz), 129.82 (d, J = 108.6 Hz), 129.75 (d, J = 13.1 Hz),
129.34 (d, J = 13.7 Hz), 26.90 (s); HR-MS (TOF MS EI+):
calculated for C16H10O2PS2Br m/z: 409.9023 [M+], found
m/z: 409.9029, mp: 212 – 215 8C.
(5) Yield: 0.19 g, 0.34 mmol, 85%; 31P-NMR (CDCl3,
162 MHz):
400 MHz):
d
= 19.06 (s, 1P) ppm; 1H-NMR (CDCl3,
= 7.89–7.88 (d, 1H, J = 2.8 Hz), 7.86–7.85 (dd,
d
162 MHz):
400 MHz):
d
d
= 17.88 (s, 1P) ppm; 1H-NMR (CD2Cl2,
= 7.74–7.68 (m br, 3H), 7.60–7.55 (m br,
1H, J = 3.6, J = 0.8 Hz), 7.76–7.70 (m br, 3H), 7.61–7.56 (tdt,
1H, J = 3.2, J = 1.6 Hz), 7.49–7.44 (m br, 2H), 7.20–7.17 (m
br, 2H) ppm; 13C-NMR (CDCl3, 100 MHz):
d = 177.90 (s),
1H), 7.52–7.50 (dd, 1H, J = 4.8, J = 3.2 Hz), 7.50–7.43 (m br,
2H), 7.22–7.20 (dd, 1H, J = 4.8, J = 2.4 Hz), 2.50 (s, 3H) ppm;
151.47 (d, J = 22.6 Hz), 147.12 (d, J = 12.4 Hz), 144.95 (d,
J = 21.7 Hz), 141.69 (d, J = 6.5 Hz), 138.86 (d, J = 110.5 Hz),
134.12 (d, J = 86.3 Hz), 133.15 (s), 131.05 (s), 130.88 (s),
130.77 (s), 129.31 (d, J = 13.4 Hz), 128.84 (d, J = 13.8),
128.52 (s), 128.21 (s), 127.43 (s), 118.40 (d, J = 18.0 Hz)
ppm; MS (EI): m/z (%): 477.84 (100) [M+], 400.15 (23) [M+ -
C6H5], 111.04 (47) [M+ - C14H7S2PO-Br]; HR-MS (TOF MS
EI+): calculated for C19H10O2S3PBr m/z: 477.8743 [M+],
found m/z: 477.8719, mp: 260 – 263 8C.
13C-NMR (CD2Cl3, 100 MHz):
d = 190.73 (s), 148.50 (d,
J = 11.6 Hz), 145.59 (d, J = 23.1 Hz), 142.61 (d, J = 109.6 Hz),
140.91 (d, J = 109.2 Hz), 139.38 (s), 133.30 (d, J = 2.9 Hz),
132.16 (d, J = 14.8 Hz), 131.40 (d, J = 11.1 Hz), 131.19 (d,
J = 13.2 Hz), 130.51 (d, J = 108.1 Hz), 129.64 (d, J = 13.0 Hz),
126.82 (d, J = 14.0 Hz), 26.88 (s) ppm; HR-MS (TOF MS EI+):
calculated for C16H11O2PS2 m/z: 329.9938 [M+], found m/z:
329.9948, mp: 192 – 195 8C.
(2x) 31P-NMR (CDCl3, 162 MHz):
1H-NMR (CDCl3, 400 MHz):
= 7.76–7.71 (m br, 2H), 7.69 (d,
d = 18.10 (s, 1P) ppm;
d
4.3. Compound 6 - Yamamoto coupling of 5
2H, J = 2.8 Hz), 7.63–7.58 (dtd, 1H, J = 7.2, J = 1.6 Hz), 7.51–
7.48 (m br, 2H), 2.54 (s, 6H) ppm; MS (EI): m/z (%): 371.88
(100) [M+], 356.88 (57) [M+ – CH3], 294.93 (20) [M+ – C6H5].
(3) Yield: 0.510 g, 1.27 mol, 83%; 31P-NMR (CDCl3,
0.035 g (0.13 mmol) of Ni(cod)2 was added to a flask
containing 0.10 g (0.21 mmol) of the brominated species
(5) and 0.034 g (0.13 mmol) of PPh3. 0.014 g (0.134 mmol)
of dry cod was added to the flask and was stirred at 60 8C
for 72 h. The solution was poured over HCl acidic methanol
162 MHz):
400 MHz):
d
= 18.81 (s, 1P) ppm; 1H-NMR (CDCl3,
= 7.90–7.89 (d, 1H, J = 2.8 Hz), 7.87–7.86 (dd,
d

T.J. Gordon et al. / C. R. Chimie 13 (2010) 971–979
979
[2] (a) F. Mathey, Angew. Chem. Int. Ed. 42 (2003) 1578 ;
(b) D.P. Gates, Top. Curr. Chem. 107 (2005) 250 ;
and filtered. The red precipitate was washed with HCl
acidic methanol, ethanol, hot toluene, hot aqueous EDTA
(pH = 4), hot aqueous EDTA (pH = 10) and then distilled
water (in this order) yielding 6 as a red powder.
(c) T. Baumgartner and R. Re´au, Chem. Rev. 2006, 106, 4681 (Correc-
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(e) Y. Matano, H. Imahori, Org. Biomol. Chem. 7 (2009) 1258 ;
Yield: 0.14 g, 0.18 mmol, 82%; 31P-NMR (CDCl3,
´
(f) J. Crassous, R. Reau, Dalton Trans. (2008) 6865 ;
162 MHz):
400 MHz):
d
= 18.85 (s, 1P) ppm; 1H-NMR (CDCl3,
= 7.91–7.90 (d, 2H, J = 3.2 Hz), 7.87–7.86 (dd,
(g) A. Fukazawa, Y. Ichihashi, Y. Kosaka, S. Yamaguchi, Chem. Asian J. 4
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d
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2H, J = 3.6 Hz), 7.80–7.75 (m br, 4H), 7.72–7.71 (d, 2H,
J = 4.8 Hz), 7.62–7.58 (m br, 2H), 7.52–7.47 (m br, 4H),
7.31–7.30 (d, 2H, J = 2.8 Hz), 7.19–7.17 (m br, 2H,) ppm; MS
(ESI): m/z: 794.82 [M+]; HR-MS (MALDI-TOF): calculated
for C38H21O4P2S6 m/z: 794.9234 [M + H]+, found m/z:
794.9262, mp: > 300 8C.
´
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(b) T. Baumgartner, W. Bergmans, T. Karpati, T. Neumann, M. Nieger, L.
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CCDC-763125 (3) & 763126 (2x) contain the supple-
mentary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request.cif.
[5] D.R. Bai, C. Romero-Nieto, T. Baumgartner, Dalton Trans. 39 (2010)
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Conflict of interest statement
[6] Y.-J. Cheng, T.-Y. Luh, J. Organomet. Chem. 689 (2004) 4137.
[7] C. Romero-Nieto, S. Merino, J. Rodrı´guez-Lo´pez, T. Baumgartner, Chem.
Eur. J. 15 (2009) 4135.
[8] R. Benassi, U. Folli, D. Iarossi, L. Schenetti, F. Taddei, A. Musatti, M.
Nardelli, J. Chem. Soc., Perkin Trans. 2 (1989) 1741.
We hereby certify that there is no conflict of interest
with this manuscript.
[9] Gaussian 03, Revision C.02, M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E.
Scuseria, M.A. Robb, J.R. Cheeseman, J.A. Montgomery, Jr., T. Vreven,
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M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T.
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Acknowledgements
Financial support by NSERC of Canada, the Canada
School of Energy and Environment, and by the Canada
Foundation for Innovation (CFI) is gratefully acknowledged.
We thank the University of Calgary for a PURE student
scholarship (LDS) and Alberta Ingenuity now part of Alberta
Innovates – Technology Futures for New Faculty Awards
(CPB and TB).
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