Synthesis, electronic properties, and reactivity of phospholes and 1,1/-biphospholes bearing 2-or 3-thienyl C-substituents

Article abstract of DOI:10.1002/chem.200802677

Two series of phospholes and i,i'biphospholes bearing either 2-or 3-thienyl substituents at the C atoms are prepared by using the Fagan-Nugent route. Their optical (UV/Vis absorption, fluorescence spectra) and electrochemical properties are systematically

Full text of DOI:10.1002/chem.200802677

DOI: 10.1002/chem.200802677
Synthesis, Electronic Properties, and Reactivity of Phospholes and
1,1’-Biphospholes Bearing 2- or 3-Thienyl C-Substituents
Omrane Fadhel,[a] Dꢀnes Szieberth,[b] Valꢀrie Deborde,[a] Christophe Lescop,[a]
Lꢁszlꢂ Nyulꢁszi,*[b] Muriel Hissler,*[a] and Rꢀgis Rꢀau*[a]
Abstract: Two series of phospholes and
1,1’-biphospholes bearing either 2- or
3-thienyl substituents at the C atoms
are prepared by using the Fagan–
Nugent route. Their optical (UV/Vis
absorption, fluorescence spectra) and
electrochemical properties are system-
atically evaluated. Of particular inter-
est, the first ever reported 3-thienyl-
substituted phospholes exhibit higher
LUMO levels than their 2-thienyl ana-
logues, and show accordingly different
physical properties. This study also re-
veals that the 1,1’-biphospholes exhibit
s–p conjugation. The phosphole and
1,1’-biphosphole derivatives bearing 3-
thienyl substituents are characterized
by X-ray diffraction study. The struc-
ture–property relationship established
following the experimental data are
fully supported by theoretical studies
including
spectra.
time-dependent(TD)-DFT
photocyclization reaction
A
performed on the thioxo- and oxo-
phospholes having 3-thienyl substitu-
ents affords a novel ring-fused phosp-
hole–thiophene derivative, which was
characterized by an X-ray diffraction
study. The structure and electronic
properties of this novel dithienophos-
AHCTUNGTRENNUNG
Keywords: density functional calcu-
lations · phospholes · photocycliza-
tion · thiophenes · pi interactions
Introduction
unique properties.[1,2] First, it is possible to readily tune the
electronic properties of phosphole-based p-conjugated sys-
tems by chemical modifications of the reactive P atoms.[1,4,5]
Second, these heteroles exhibit a high electron affinity due
to an effective s*(PR)–p*(1,3-diene) orbital interaction.[5c,6]
This hyperconjugation is especially effective in 1,1’-biphos-
Phospholes are the most widely investigated P-heterocycles
due to their easy accessibility, substitution pattern variabili-
ty, and versatile reactivity.[1] Beside intensive studies devoted
to the elucidation of their electronic structure,[1,2] these het-
eroles have been extensively used as building blocks for the
tailoring of ligands for homogeneous catalysis,[3] as precur-
sors for other P-heterocycles,[1] and as subunits for the tailor-
ing of p-conjugated systems.[4] In this last domain, phos-
AHCTUNGTREGpNNUN hole derivatives A leading to a further reduction of
ACHTUNGTRENNUNGpholes are very appealing building blocks due to a set of
[a] Dr. O. Fadhel, V. Deborde, Dr. C. Lescop, Prof. M. Hissler,
Prof. R. Rꢀau
Sciences Chimiques de Rennes
UMR 6226 CNRS-Universitꢀ de Rennes 1
Campus de beaulieu, 35042 Rennes Cedex (France)
Fax : (+33)2-23-23-69-39
E-mail: muriel.hissler@univ-rennes1.fr
regis.reau@univ-rennes1.fr
[b] Dr. D. Szieberth, Prof. L. Nyulꢁszi
Department of Inorganic and Analytical Chemistry
Budapest University of Technology and Economics
Gellꢀrt tꢀr 4, 1111 Budapest (Hungary)
E-mail: nyulaszi@mail.bme.hu
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200802677.
4914
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Chem. Eur. J. 2009, 15, 4914 – 4924

FULL PAPER
HOMO–LUMO gaps.[7] Lastly, the quite high thermal stabil-
ity of phosphole-based conjugated oligomers such as B1
allows the use of these P-derivatives as materials in opto-
the 3,3’-bithiophene was found to be the largest among the
three possible bithiophenes.[12] These results clearly indicate
that varying the nature of the thienyl building blocks (2-
versus 3-) can be used for fine tuning the properties of p-
conjugated systems.
Herein, we describe the synthesis of these novel mixed
phosphole- and 1,1’-biphosphole-thiophene p-conjugated
systems (see Scheme 1) and the elucidation of their elec-
tronic properties by both experimental (UV/Vis spectrosco-
py, electrochemical behavior) and theoretical means. A com-
parative study of the influence of the substitution pattern of
the thienyl substituent (2- versus 3-) on their electronic
properties is also given. Furthermore, the preparation of a
A
devices
(organic
light-emitting
diodes
(OLEDs)).[4a,8] There is therefore a growing interest in the
design of p-conjugated materials containing phosphole subu-
nits. For example, the synthesis of novel P-based p-conjugat-
ed systems is the subject of intensive research as illustrated
by the work of Chujo and co-workers on polymers of type
[4f,g]
B3
and of Mathey and co-workers on mixed phosphole–
thiophene oligomers C.[4k] Quite recently, fused phosphole–
thiophene systems have also been reported to exhibit very
appealing functions. For example, Baumgartner and co-
workers have developed highly fluorescent dithieno-
previously
unknown
di(bithiophene)-fused
benzo-
[b,d]phospholes D,[4h] and Matano and co-workers have re-
ACHTUNGTREN[NUGN b,d]phosphole by a photocyclization process involving 3-
ported bithiophene-fused benzo[c]phospholes E,[4d,e] which
exhibit a high electron-transporting ability due to their low-
lying LUMOs. It is noteworthy that mixed phosphole–thio-
phene derivatives are the most widely investigated phosp-
hole-based p-conjugated systems,[4a–e,h–k] since i) this hetero-
leꢃs combination allows one to obtain derivatives with a low
HOMO–-LUMO gap due to maximized orbital interactions,
and ii) it is possible to exploit the rich chemistry of thio-
phene to readily obtain novel derivatives by Pd-catalyzed
thienyl substituents, an unprecedented reaction in phosphole
chemistry, is reported. The electronic properties of this
novel fused mixed phosphole–thiophene derivative are dis-
cussed on the basis of experimental and theoretical results.
Results and Discussion
Synthesis and characterization of 2,3,4,5-(2-thienyl)- and
2,3,4,5-(3-thienyl)phosphole derivatives: The target s3-
phospholes 2a,b were prepared according to the Fagan–
Nugent route.[13] The intramolecular oxidative coupling of
1,2-di(2-thienyl)ethyne (1a)[14a] and 1,2-di(3-thienyl)ethyne
(1b)[14b,c] with ꢄzirconocenesꢃ provided the in situ generated
zirconacyclopentadienes, which were allowed to react with
PhPBr2 to afford phospholes 2a and 2b, respectively
(Scheme 1). These mixed phosphole–thiophene compounds
were isolated in medium yields (2a, 46%; 2b, 60%) as air-
stable solids after purification by flash column chromatogra-
phy. They were characterized by high-resolution mass spec-
trometry, elemental analysis, and multinuclear NMR spec-
troscopy. Their 31P{1H} NMR spectra display a singlet at
classical chemical shifts for 1-phenylphosphole derivatives
(2a, d=+14.1 ppm; 2b, d=+13.9 ppm).[1] The 1H and
13C NMR spectra of these compounds are very simple with
ꢀ
C C coupling reactions or electropolymerization (see B2).
Considering the appealing functions of mixed phosphole–
thiophene derivatives, there is a great interest in developing
original structures to gain more insight into the structure–
property relationship and to making further use of thio-
phene chemistry to prepare unprecedented conjugated P,S
skeletons. The first phosphole and 1,1’-biphosphole to be
prepared were obtained as fully phenyl-substituted com-
pounds F[9a] and G,[9b,c] respectively and it is surprising to
1
two sets of H and 13C NMR signals assignable to the thienyl
substituents (2- or 3-) at the C2,5 and C3,4 atoms of the
phosphole rings, respectively. Moreover the 13C{1H} NMR
data of the phosphole moiety of 2a,b are very similar, the
PCa signals being shielded by about 2 ppm in 2b compared
to 2a.
Phosphole 2b bearing 3-thienyl substituents was charac-
terized by an X-ray diffraction study (Figure 1, Table 1). The
angles and bond lengths of this compound are classical and
compare well with those observed for other phosphole de-
rivatives.[4,5] For example, the P atom has a strong pyramidal
note that they are still the only fully aryl-substituted phos-
phole derivatives known to date. Considering the rarity of
these structures and the intriguing electronic properties of
mixed phosphole–thiophene derivatives, we decided to in-
vestigate phospholes and 1,1’-biphospholes bearing 2- or 3-
thienyl substituents at their C atoms (see Scheme 1). 2-
Thienyl building blocks are widely used for tailoring p-con-
jugated systems; in contrast 3-thienyl moieties have been
scarcely employed for such a purpose. In fact, investigation
of 3-thienyl building blocks is usually limited to the oligo-
thiophene family due to the complicated derivatization of
the ring at the b-position.[10] Interestingly, the conjugation
energy of 3,3’-bithiophene was found to be slightly lower
than for its 2,2’-isomer,[11] whereas the rotational barrier in
ꢀ
character (ꢀPang =302.88) and the endocyclic P C bond
ꢀ
lengths (1.801(2)–1.804(3) ꢅ, Table 2) approach that of a P
ꢀ
C single bond (1.84 ꢅ). The lengths of the C C links be-
tween the heteroles are in the range expected for Csp2–Csp2
single bonds (1.463(6)–1.485(3) ꢅ, Table 2) and are slightly
shorter for the thienyl rings at the 2- and 5-positions com-
Chem. Eur. J. 2009, 15, 4914 – 4924
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4915

L. Nyulꢁszi, M. Hissler, and R. Rꢀau et al.
70%; Figure 1). The twist angles between the phosphole and
the 3-thienyl rings at C3,4-atoms are rather high (67.28 and
75.98) presumably to avoid the steric encumbrance. In
marked contrast, the angles between the 3-thienyl moieties
at the C2,5-atoms and the P ring are much smaller (18.78 and
19.18; Figure 1) allowing an electronic interaction between
these subunits to take place.
The presence of an extended p-conjugation in compounds
2a,b was confirmed by the presence of absorption bands, as-
signed to p–p* transitions (vide supra), in the visible part of
the absorption spectra (Figure 2). The absorption maximum
Figure 2. Absorption spectra of 2a,b in CH2Cl2, and TD-DFT simulated
spectra (vertical lines) of 2a (continuous line) and 2b (dashed line).
of 2-thienyl-substituted 2a (lmax =420 nm) compares with
that
AHCTUNGTRENNUNG
observed
for
related
2,5-di(2-thienyl)-3,4-di-
(alkyl)phosphole derivatives.[5c] These data suggest that the
p-conjugated pathway in 2a mainly involves the phosphole
ring and its 2,5-substituents. It is noteworthy that 3-thienyl-
substituted 2b (lmax =375 nm) exhibits an absorption maxi-
mum that is notably blue-shifted compared to that of 2a
(Figure 2). Therefore, as expected,[11] the electronic interac-
tion of the phosphole p-system is more efficient with 2-
thienyl than with 3-thienyl substituents. Cyclic voltammetry
(CV) performed at 200 mVsꢀ1 revealed that the redox pro-
cesses observed for 2a,b are irreversible, behavior that is
typical for s3-phosphole-containing p-conjugated systems.[5]
These two compounds exhibit similar oxidation potentials
but derivative 2a is more easily reduced than compound 2b
(Table 3). Note that phospholes 2a,b are emissive deriva-
tives (lem. =2a, 515 nm; 3b, 484 nm) but with low quantum
yields (ca 0.2%).
Scheme 1. Synthesis of thienyl-capped phosphole and 1,1’-biphosphole
derivatives.
Figure 1. Molecular structures of phospholes 2b and 3b in the solid state.
Hydrogen atoms are omitted for clarity.
To get more insight into the electronic interactions be-
tween the phosphole ring and the 2- or 3-thienyl substitu-
ents, density functional calculations (B3LYP/6-31G*) have
been performed on compounds 2a and 2b. It is worth
noting that the computed structural data for 2b are very
similar to those obtained from the X-ray diffraction study
pared to the 3- and 4-positions (Table 2). As already ob-
served for linear oligomers bearing terminal thiophene
rings[15] and other mixed phosphole–thiophene deriva-
tives,[5b,c] the thienyl rings of 2b exhibit a statistical disorder.
Note that this statistical disorder prevents an accurate deter-
mination of certain bond lengths within the thienyl ring
(vide supra). The sulfur atoms of the thienyl substituents in
2,5-positions have a cis-arrangement with respect to the cen-
tral phosphorus atom in the prevailing conformation (ca.
ꢀ
(Table 2), with the exception of the C40 C42 bond length.
This is probably due to the statistical disorder of the thienyl
substituents (vide supra). Remarkably, these calculations re-
vealed that compounds 2a,b exhibit a similar gross struc-
4916
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Chem. Eur. J. 2009, 15, 4914 – 4924

Phospholes and 1,1’-Biphospholes Bearing 2- or 3-Thienyl C-Substituents
Table 1. Crystal data and structure refinement for 2b, 3b, 5b, and 6b.
FULL PAPER
the HOMOꢀ1 level of 2a and
2b, since the phospholeꢃs
HOMOꢀ1 has a node at the
2b
3b
6b
5b
molecular formula
CCDC number
Mr
C26H17PS4
713600
488.61
C26H17PS5
713601
520.67
C32H19PS5
713602
594.74
C40H15.12P2S8
713603
814.06
100(2)
monoclinic
P21/c
13.446(2)
13.836(1)
21.006(3)
90
108.303(5)
90
3710.0(8)
4
1.457
connecting
C
atom. The
HOMOs, however, are consid-
erably destabilized with respect
to the original phosphole orbi-
tals. This destabilization is sim-
ilar for 2a and 2b, owing to
the small difference of the C2
and C3 coefficients in the thio-
pheneꢃs HOMO (Figure 3).
The LUMO, which is a bond-
ing combination of the phosp-
T [K]
100(2)
100(2)
100(2)
crystal system
space group
a [ꢅ]
b [ꢅ]
c [ꢅ]
monoclinic
P21/c
15.783(2)
6.008(1)
24.761(5)
90
94.972(6)
90
2339.0(7)
4
monoclinic
P21/c
11.843(5)
17.398(5)
12.615(5)
90
114.136(5)
90
2372.0(15)
4
triclinic
P1
¯
9.592(2)
10.098(2)
15.683(3)
71.535(1)
79.969(2)
69.163(2)
1343.4(5)
2
a [8]
b [8]
g [8]
V [ꢅ3]
Z
1calcd (gcmꢀ3
)
1.387
1.458
1.470
holeꢃs
and
thiopheneꢃs
wavelength MoKa [ꢅ]
crystal size [mm]
0.71073
0.6ꢆ0.3ꢆ0.2
0.487
0.71073
0.04ꢆ0.03ꢆ0.01
0.570
0.71073
0.04ꢆ0.04ꢆ0.01
0.514
0.71073
0.06ꢆ0.04ꢆ0.02
0.598
LUMOs, is stabilized in both
cases (Figure 3). However
since the thiopheneꢃs LUMO
has a significantly larger coeffi-
cient at C2 than at C3, the
LUMO of compound 2a is
more stabilized leading to a
lower HOMO–LUMO separa-
tion by about 0.4 eV for 2a
compared to 2b. This conclu-
sion is also supported by the
TD-DFT simulated spectra,
which show an intense transi-
m [mmꢀ1
(000)
]
F
A
1008
1072
612
1652
q limit [8]
index ranges hkl
2.95–27.48
ꢀ20ꢁhꢁ20,
ꢀ7ꢁkꢁ6,
ꢀ32ꢁlꢁ32
9711
3.01 ꢀ27.48
ꢀ15ꢁhꢁ15,
ꢀ22ꢁkꢁ22,
ꢀ16ꢁlꢁ16
10639
2.94–27.54
ꢀ12ꢁhꢁ12,
ꢀ13ꢁkꢁ13,
ꢀ20ꢁlꢁ20
11089
1.60–24.54
ꢀ15ꢁhꢁ15,
ꢀ16ꢁkꢁ16,
ꢀ24ꢁlꢁ24
59870
reflections collected
independent reflections
reflections [I>2s(I)]
data/restraints/parameters
goodness-of-fit on F2
Final R indices [I>2s(I)]
5346
3203
16116
5428
6126
5174
6207
4755
5346/0/279
1.044
R1=0.0523
wR2=0.1374
R1=0.0966
wR2=0.1595
5428/0/299
1.053
R1=0.0421
wR2=0.1145
R1=0.0494
wR2=0.1212
6126/0/343
0.916
R1=0.0337
wR2=0.0829
R1=0.0437
wR2=0.0898
6207/0/459
1.119
R1=0.0502
wR2=0.1557
R1=0.0715
wR2=0.1879
R indices (all data)
!
tion (LUMO HOMO) at
largest diff peak and hole [eꢅꢀ3
]
0.335 and ꢀ0.323 0.651 and ꢀ0.725 0.388 and ꢀ0.386 0.701 and ꢀ0.482
438 nm and 393 nm for phosp-
holes 2a and 2b, respectively
(Figure 2). They are in good
ture; the thienyl rings at the 2,5-positions are coplanar with
the central phosphole moiety, whereas the thienyl rings at
the 3,4-positions are almost perpendicular to the phosphole
ring (Figure 3). Note that the calculated rotational barriers
between the phosphole and the thiophene units at the 2,5-
agreement with the experimental ones (2a, 420 nm; 2b,
375 nm), reproducing the changes attributable to the nature
of thienyl building blocks used as substituents. In summary,
this theoretical study fits nicely with the experimental data
(UV/Vis sprectroscopy, electrochemical behavior, Table 3),
which shows that 2a possesses a lower LUMO level and
lower HOMO–LUMO separation than 2b.
positions are smaller (2a, 1.1 kcalmolꢀ1
;
2b, and
0.9 kcalmolꢀ1) than that reported (3.7 kcalmolꢀ1)[5c] for 2,5-
bis(2-thienyl)phosphole having a fused saturated six-mem-
bered carbocycle at the 3,4-positions. The lowering of this
rotational barrier, however, is not indicative of a diminished
conjugative interaction between the phosphole and the thio-
phene substituents at C2,5-atoms in 2a,b. In the transition
structure of this rotation process, the 2,5-thienyl substituents
are perpendicular to the phosphole ring allowing the 3,4-
thienyl substituents to be coplanar with the phosphole ring.
This coplanarity allows a conjugative stabilization between
the phosphole ring and the 3,4-thienyl groups, compensating
somewhat for the loss of the conjugative stabilization with
the thienyl moieties at the 2,5-positions. The frontier MOs
of compounds 2a and 2b have been analyzed to rationalize
their different spectroscopic and electrochemical behavior.
The HOMOꢀ1 and HOMO of these derivatives are the an-
tibonding combination of the phospholeꢃs HOMOꢀ1 and
HOMO with the HOMOs of the thiophene rings, respective-
ly (Figure 3). There is no significant interaction in case of
One key property of phosphole-based p-conjugated sys-
tems is that chemical modifications of the P atom result in a
fine-tuning of their electronic property.[4] To check whether
this property is retained within these novel mixed phos-
phole–thiophene series, derivatives 2a,b were oxidized with
elemental sulfur and sodium periodate (Scheme 1). The cor-
responding phosphole derivatives 3a,b and 4a,b were isolat-
ed in high yields (85–90%) as air-stable derivatives. The
multinuclear NMR spectroscopic data of the isolated phos-
AHCTUNGTRENNUNG
pholes are typical[1] and support the proposed structures as
do the high-resolution mass spectra and elemental analysis.
In comparison with the s3-phospholes 2a,b, the Cb of the
corresponding s4-phosphole sulfides 3a,b and oxides 4a,b
are slightly deshielded (Dd, 3a/2a, 1.7 ppm; 3b/2b,
1.2 ppm), whereas the Ca resonances are considerably more
shielded (Dd, 3a/2a, 9.3 ppm; 3b/2b, 5.5 ppm). It is note-
worthy that these effects are more pronounced for the series
of compounds incorporating the 2-thienyl subtituents (i.e.
Chem. Eur. J. 2009, 15, 4914 – 4924
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4917

L. Nyulꢁszi, M. Hissler, and R. Rꢀau et al.
Table 2. Selected bond lengths [ꢅ] and angles [8] and the corresponding
calculated values (in brackets) for compounds 2b, 3b, 5b, and 6b.
Table 3. 31P{1H} NMR, optical, and electrochemical data for phosphole
and 1,1’-biphosphole derivatives.
[b]
[c]
[c]
Derivatives
d
Yield lmax/lonset
loge
Epa
Epc
31P{1H}[a] [%]
AHCTUNGTERG[NNUN ppm]
[nm]
[V]
[V]
2a
2b
3a
3b
4a
4b
5a
+14.1
+13.9
+52.4
+53.2
+41.1
+43.4
46
60
85
80
90
95
55
420/488
375/435
454/538
413/485
456/530
411/484
375–452/
570
343–423/
500
391/520
389/525
3.71
3.95
3.75
3.48
3.83
3.83
4.31–
3.94
4.31–
3.78
3.56
3.63
+0.62
+0.64
+0.81
+0.97
+0.82
+0.98
+0.60
ꢀ2.22
ꢀ2.53
ꢀ1.70[d]
ꢀ1.93[d]
ꢀ1.72[d]
ꢀ1.91[d]
ꢀ1.65
2b
3b
5b
6b
ꢀ
P1 C1
1.804(3)
T
1.816(2)
T
1.808(3)–11(3)
[1.818–1.827]
1.357(5)–1.367(5)
[1.375–1.376]
1.455(5)–1.460(5)
[1.474–1.476]
1.370(5)–1.369(5)
[1.376–1.376]
1.804(3)–06(3)
[1.817–1.825]
1.474(5)–68(5)
[1.465-1.467]
1.406(5)–00(5)
[1.443–1.444][a]
1.377(6)–91(5)
[1.381–1.384]
1.7971(18)
ACHTUNGTRENNUNG
ꢀ
C1 C2
ꢀ0.8
N
N
ACHTUNGTRENNUNG
ꢀ
C2 C3
5b
ꢀ5.9
50
+0.69
ꢀ1.90
R
R
ACHTUNGTRENNUNG
ꢀ
C3 C4
6b
7b
+41.6
+33.6
10
26
+1.00[d] ꢀ2.13[d]
E
E
ACHTUNGTRENNUNG
+1.15
ꢀ2.15[d]
ꢀ
C4 P1
[a] In CDCl3. [b] Measured in CH2Cl2. [c] All potentials were obtained
during cyclic voltametric investigations in 0.2m Bu4NPF6 in CH2Cl2. Plati-
num electrode diameter 1 mm, sweep rate : 200 mVsꢀ1. All reported po-
tentials are referenced to the reversible formal potential of the ferro-
cene/ferrocenium couple. [d] Reversible processes, E8ox and E8red values
provided.
E
E
ACHTUNGTRENNUNG
ꢀ
C1 C10
E
E
ACHTUNGTRENNUNG
ꢀ
C10 C11
G
G
ACHTUNGTRENNUNG
ꢀ
C10 C12
A
A
ACHTUNGTRENNUNG
ꢀ
C2 C20
1.488(5)–87(5)
[1.484–1.488]
G
N
ACHTUNGTRENNUNG
tion of the P center has an impact on their optical and elec-
trochemical properties, and ii) oxo and thiooxo derivatives
exhibit similar properties. The oxidation of the P atom of
2a,b induces a bathochromic shift of the lmax (ca. 30 nm,
Table 3, Figure 4) as well as an increase of the first oxidation
and reduction potentials (2a!3a,4a; 2b!3b,4b, Table 3).
It is worth noting that the increase of the oxidation potential
is more pronounced for the 3-thienyl than for the 2-thienyl
series, whereas an opposite trend is observed for the reduc-
tion potentials. Nevertheless, the electrochemical HOMO–
LUMO gap for the 2-thienyl series (Table 3) remains even
smaller than for the 3-thienyl series.
ꢀ
C3 C30
1.490(5)–80(5)
[1.489–1.483]
1.472(5)–78(5)
[1.466–1.465]
1.399(5)–1.386(5)
[1.383–1.382]
1.384(5)–1.405(5)
[1.444-1.443][a]
129.3(3)–126.9(3)
[128.7–129.3]
128.6(3)–129.3(3)
[128.9–128.5]
125.3(3)–124.2(3)
[123.9–124.4]
124.9(3)–124.5(3)
[124.3–123.4]
G
G
ACHTUNGTRENNUNG
ꢀ
C4 C40
E
ACHTUNGTRENNUNG
ꢀ
C40 C41
N
ACHTUNGTRENNUNG
ꢀ
C40 C42
R
ACHTUNGTRENNUNG
C2-C1-C10
C3-C4-C40
C1-C2-C20
C4-C3-C30
N
ACHTUNGTRENNUNG
E
ACHTUNGTRENNUNG
G
ACHTUNGTRENNUNG
The impact of the chemical modifications of the s3,l3-
phosphorus atom have also been investigated by theoretical
calculations. The calculated structural data of thiooxophos-
A
ACHTUNGTRENNUNG
[a] Discrepancy attributed to the statistical disorder of the thienyl sub-
stituents in the solid state.
AHCTUNGTREGpNNNU hole derivative 3b are very similar to those recorded by an
X-ray diffraction study (Table 2). The HOMO of 3b is a p-
orbital mainly localized on the carbon framework (see the
Supporting Information, Figure S1), and its energy is stabi-
lized in comparison with that of 2b. It is surprising that the
stabilization is less pronounced in the case of the LUMO,
resulting in a slight increase of the calculated HOMO–
LUMO gap. This is unusual, since the generally observed
red shift of the phosphole derivatives upon oxidation was
shown to be attributable mainly to the stabilization of the
LUMO.[5c] Despite the increase of the calculated HOMO–
LUMO gap of 3b, the TD-DFT simulated spectrum (shown
as vertical lines in Figure 4) has reproduced the experimen-
tal observations showing a red shift in the vertical absorp-
tion energy upon oxidation. These experimental and theo-
retical studies show that the fine-tuning of phosphole-based
p-conjugated systems upon P modifications is effective
whatever the nature (2-thienyl or 3-thienyl) of the substitu-
ent of the phosphole ring.
2a and 3a). These modifications of the NMR spectroscopic
data suggest that the dienic moiety of the phosphole ring is
perturbed by the chemical modifications involving the P
atom.
Derivative 3b was characterized by an X-ray diffraction
study (Figure 1, Table 1). As observed for 2b, a statistical
disorder of the thienyl ring was observed for 3b. The gross
structure of this thiooxophosphole is very similar to that of
its s3-precursor 2b, with two rather small and large twist
angles (Table 2) between the phosphole ring and the 3-
thienyl substituents at the C2,5- and C3,4-positions, respective-
ly. The oxidation of the phosphorus atom results in an in-
ꢀ
crease in the C C bond length alternation within the phos-
phole ring (2b versus 3b, Table 2), indicating a decrease of
the aromatic character on going from s3- to the s4-deriva-
tive. This is a classical behavior for phosphole-based p-con-
jugated systems.[6d] As classically observed for mixed thio-
phene–phosphole derivatives,[4a,5] i) the chemical modifica-
4918
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Chem. Eur. J. 2009, 15, 4914 – 4924

Phospholes and 1,1’-Biphospholes Bearing 2- or 3-Thienyl C-Substituents
FULL PAPER
(Scheme 1). Their 1H and
13C NMR data are very similar
to those of the corresponding
phospholes 2a,b and their
31P{1H} NMR spectra display a
singlet at usual chemical shifts
for 1,1’-biphospholes.[7] To
complete the series of deriva-
tives bearing 3-thienyl substitu-
ents (i.e. 2b and 3b, Scheme 1)
and enable comparisons, 1,1’-
biphosphole 5b was subjected
to an X-ray diffraction study
(Figure 5, Table 1). As also ob-
served for the two other 1,1’-
biphospholes characterized by
X-ray diffraction study,[7,9c] the
two substituted phosphole moi-
eties adopt a gauche conforma-
ꢀ
tion. The P P (2.2141(13) ꢅ)
ꢀ
and P C (1.804(3)–1.808(3)/
1.806(3)–1.811(3) ꢅ) distances
are in the range expected for
single bonds. The bond lengths
and valence angles within the
P ring are comparable to those
Figure 3. Frontier orbitals of thiophene, phosphole, and compounds 2a,b.
Figure 5. Molecular structure of 5b in the solid state. Hydrogen atoms
are omitted for clarity.
observed for 2b (Table 2, see note [a]) and the P atoms are
strongly pyramidalized (ꢀPang
, 305.138) (Figure 5), with
Figure 4. Electronic spectra of compounds 2b, 3b, 5b, and 6b in CH2Cl2,
and TD-DFT simulated spectra (vertical lines) of 2b (doted line) and 3b
(continuous line).
rather acute C-P-P angles (101,428(11)–108.338(11)). The
twist angles between the phosphole rings and their 2,2’- and
5,5’-thienyl subtituents range from 4.38 to 40.58. The corre-
sponding angles involving the 3,3’- and 4,4’-thienyl subtitu-
ents are much higher (>708). This tendency was already ob-
served with phosphole 2b and its thiooxo derivative 3b
(Figure 1), and thus seems to have a general character.
It was observed that while the absorption spectra of
phosphole 2a,b show only one absorption above 350 nm
due to a p–p* transition (Figure 2), several bands are re-
Synthesis and characterization of fully substituted (2-thien-
yl)- and (3-thienyl)-1,1’-biphosphole derivatives: 1,1’-Bi-
ACHTUNGTRENNUNGphospholes bearing aromatic rings at the 2,2’- and 5,5’-posi-
tions are unique derivatives in which two p-systems com-
posed of the phosphole butadienic moiety and its 2,5-sub-
ꢀ
stituents are in electronic interaction via a P P bound (s–p
conjugation).[7] However, these types of derivative are still
rare and only two of them have been structurally character-
ized to date.[7,9] The novel derivatives 5a,b were readily ob-
tained by an efficient synthetic route[7] involving the reac-
tion of intermediate zirconacyclopentadienes with PBr3
corded for 5a,b with one red-shifted broad shoulder (lonset =
5a, 570 nm; 5b, 500 nm) (Figure 4). It is noteworthy that
1,1’-biphospholes 5a,b are more easily reduced than com-
pounds 2a,b, whereas the oxidation potentials of these two
types of derivatives are essentially the same (Table 3). These
Chem. Eur. J. 2009, 15, 4914 – 4924
ꢂ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4919

L. Nyulꢁszi, M. Hissler, and R. Rꢀau et al.
experimental data clearly indicate that i) the HOMO–
LUMO separation of 1,1’-biphospholes 5a,b is smaller than
that of the corresponding P-aryl phospholes 2a,b, and
ii) 1,1’-biphospholes 5a,b possess a higher density of states
than phospholes 2a,b. Theoretical calculations on the pres-
ent system confirmed both features, and the analysis of the
orbitals has clearly shown the interaction of the sPP and s*PP
orbital with both diACTHNUTRGNEUNG(thienyl)phospholeꢃs p-systems. For ex-
ample, the LUMO and the LUMO+1 of 5b (shown as Fig-
ure S2 in the Supporting information) are the antibonding
and the bonding combinations of the p-systems. This behav-
ior is characteristic for through-bond coupling of two p-sys-
tems over an odd number of s-bonds.[16] Since the through-
bond interaction involves the occupied sPP and the unoccu-
pied bonding combination of the LUMOs (p-type) of the di-
Scheme 2. Synthesis of fused phosphole-thiophene derivatives 6b and 7b.
Molecular structure of 6b in the solid state. Hydrogen atoms are omitted
for clarity.
ACHTUNGTRENNUNG(thienyl)phosphole units (see the LUMO+1 orbital of 5b in
Figure S2 in the Supporting Information), some stabilization
is expected as a result of this interaction. Indeed, the isodes-
mic reaction (1) revealed that assembly 5b is stabilized by
3.6 kcalmolꢀ1, in spite of the apparently increased steric en-
cumbrance (see Figure 3) in comparision with a simple di-
the best of our knowledge, this is the first time that a photo-
cyclization on phosphole-based derivatives is reported.
Fused derivatives 6b and 7b exhibit 31P NMR chemical
shifts that are slightly shifted to higher field compared to
1
ꢀ
phosphine Me2P PMe2.
those of their precursors 3b and 4b (Table 3). The H and
13C NMR data of both fused phosphole–thiophene com-
pounds are very similar and fully consistent with the pro-
posed structures. The transformation of the compounds 3b
and 4b into the corresponding fused derivatives 6b and 7b
perturbs the phosphole ring as shown by the shielding of the
13C NMR P-Ca signal (3b/6b, d=128.9 ppm/125.9 ppm; 4b/
7b, d=129.1 ppm/124.2 ppm). An X-ray diffraction study of
6b (Table 1) revealed that the P atom adopts a distorted tet-
rahedral geometry and that the p-system has a helicoidal
structure (helical curvature, ca. 388; Scheme 2). This helicoi-
dal structure is due to the o,o’-substitution pattern of the
newly formed six-membered rings, which cause a steric re-
pulsion of the two H atoms on the C31 and C22 atoms, re-
spectively (Scheme 2). Note that theoretical calculations re-
vealed that the inversion barrier of this helicoidal moiety is
8.5 kcalmolꢀ1 only. These six-membered rings are almost
planar (maximum deviation from the mean plane, 0.056 ꢅ
5 bþ2 PhPMe2 ! 2 2 bþMe2PꢀPMe2
ð1Þ
Note that theoretical calculations have also shown that
s,p-conjugation in 1,1’-biphospholes results in a narrowing
of the HOMO–LUMO gap and an increased density of
states compared to the corresponding 1-phenylphospholes.
These data nicely corroborate and rationalize the experi-
mental UV/Vis spectra (Figure 4).
Synthesis and characterization of fused phosphole–thio-
phene derivatives: An appealing property of mixed phos-
phole–thiophene derivatives is that the chemistry of the thio-
phene rings can be exploited towards the synthesis of origi-
nal mixed p-conjugted P,S skeletons. This possibility was in-
vestigated by using 3-thienylphosphole derivatives with the
aim to obtain novel fused phosphole–thiophene frameworks.
DithienoACHTUNGTRENNUNG[b,d]phospholes and bithiophene-fused benzo[c]-
ꢀ
phospholes have been receiving growing interest since they
possess rigid and extented p-systems.[4] As recently noted by
Matano et al., “the number of ring-fused phosphole-based
systems is quite limited and their potential in optoelectro-
chemical applications has not been fully addressed.”[4d] The
synthesis of phosphole derivatives 3b and 4b gave us the
opportunity to investigate the synthesis of ring-fused phos-
phole-based systems with an unprecedented structure using
a photocyclization reaction.[17] The aerobic irradiation at
320–400 nm in a Rayonet apparatus of a dilute toluene solu-
tion of 3b and 4b containing a catalytic amount of iodine af-
forded the air-stable derivatives 6b and 7b, respectively
(Scheme 2). These compounds are the sole products of the
reaction. However, as usually observed in this type of photo-
cyclization process, they are obtained in low yields (ca. 15–
20%, reaction time of 12 h). Note that this reaction cannot
be conducted with the s3-phosphole 2b due to fast decom-
position of this derivative under the reaction conditions. To
and 0.047 ꢅ) and the C C bond lengths vary from 1.403 ꢅ
ꢀ
ꢀ
to 1.428 ꢅ. The C2 C20 and C3 C30 bonds are much
ꢀ
longer than the other C C distances (Table 2), probably due
to the steric repulsion between the helix CH moieties
(Scheme 2). However, the fact that these six-membered
rings are planar and that the average C C distance (1.41ꢂ
ꢀ
0.2 ꢅ) is close to that of benzene clearly shows that they ex-
hibit a high aromatic character. The aromaticity of the cen-
tral five-membered ring, however, is somewhat less in the
presence of the fused aromatic systems (NICS(0): 6b, d=
+3.9 ppm; 3b d=+0.4 ppm). In the same vein, the NICS(0)
data for different dithieno[3,2-b:2’,3’-d]phosphole oxides are
between d=+3.9 and +5.5 ppm,[4h] while for 2,5-bis(2-thie-
nyl)phosphole oxide a value of d=ꢀ1.7 ppm was report-
ed.[18] Interestingly, similar changes can be seen when
NICS(0) values of cyclopentadiene and fluorene (d=
ꢀ4.2 ppm and + 0.5 ppm) are compared at the HF/6-31G*//
B3LYP/6-31G* level.[19] Although all the above-mentioned
4920
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Chem. Eur. J. 2009, 15, 4914 – 4924

Phospholes and 1,1’-Biphospholes Bearing 2- or 3-Thienyl C-Substituents
FULL PAPER
(Centre de Diffractomꢀtrie, Universitꢀ de Rennes 1, France) with MoKa
radiation (l=0.71073 ꢅ). Reflections were indexed, Lorentz-polarization
corrected, and integrated by the DENZO program of the KappaCCD
software package. The data merging process was performed by using the
SCALEPACK program.[21] Structure determinations were performed by
direct methods with the program SIR97,[22] which revealed all the non-hy-
drogen atoms. The SHELXL program[23] was used to refine the structures
by full-matrix least-squares based on F2. All non-hydrogen atoms were
refined with anisotropic displacement parameters. Hydrogen atoms were
included in idealized positions and refined with isotropic displacement
parameters.
changes are small, they show a similar trend: the conjuga-
tion within the central five-membered ring system decreases
upon formation of fused rings.[20] The competitive electronic
delocalization within the fused “thiophene” and “benzene”
ꢀ
moieties in 6b is illustrated by the fact the C C bond of the
thiophene fragments is more localized in 6b than in deriva-
tive 3b (Scheme 2, Table 2). Likewise, the C=C bond length
of the phosphole ring considerably increases on going from
3b (1.360ꢂ0.1 ꢅ) to 6b (1.404ꢂ0.1 ꢅ). It can be concluded
from these solid-state data that 6b has a considerable diben-
zophosphole character. This conclusion is further supported
by the optical and electrochemical behavior of compounds
6b and 7b. Compared to their respective precursors 3a,b,
fused derivatives exhibit blue-shifted absorption maxima,
higher oxidation, and lower reduction values (3b/6b; 4b/7b,
Table 3, Scheme 1). These experimental data indicate a less
efficient electron p-delocalization over the sp2-C atoms of
the fused carbon framework (i.e. an increased localization of
the p-electron within the subunits), behavior that is typical
for dibenzophosphole derivatives. Note that compounds 6b
and 7b are emissive derivatives (lem.: 6b, 475 nm; 7b,
477 nm) but with low quantum yields (ca. 1%).
In the case of the derivatives 2b and 5b, all the thienyl moieties were
found disordered over two superposed orientations. This disorder was
treated for each thienyl ring with a partition of these two orientations.
For each of these orientations, the relative population was refined. In the
case of the derivative 3b, only one of the thienyl rings presented a similar
disorder, which was treated according to the same procedure.
Atomic scattering factors for all atoms were taken from International
Tables for X-ray Crystallography.[24] Details of crystal data and structural
refinements are given in Table 1. CCDC-713600 (2b), CCDC-713601
(3b), CCDC-713602 (5b), and CCDC-713603 (6b) 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
Computations: Density functional calculations were carried out at the
B3LYP/6-31G* level[25] of theory by using the Gaussian 03 suite of pro-
grams.[26] This level of the theory has provided satisfactory results for the
phosphole–thiophene oligomers before.[4c,h,5d,7] The geometries were fully
optimized, and for the resulting structures, second derivatives were calcu-
lated, which revealed only positive eigenvalues of the Hessian matrix.
The vertical excitation energies were calculated for the optimized struc-
tures by the time-dependent density functional (TD-DFT) method, using
the B3LYP functional and the 6-31G* basis set. NICS(0) values[27] were
calculated at the geometrical center of each ring. The MOLDEN pro-
gram[28] was used for the visualization of the MOs.
Conclusions
The study of these novel series of mixed phosphole–thio-
phene derivatives revealed that varying the nature of the
thienyl substituents (2-thienyl versus 3-thienyl) is an effi-
cient means to tune the electronic properties of these heter-
oatomic p-conjugated systems. Theoretical calculations, in
accordance with experimental data, revealed that this fine-
tuning is mainly due to a destabilization of the LUMO level
on going from 2-thienyl- to 3-thienyl substituents. The
family of 1,1’-diphospholes exhibiting s,p-conjugation has
been extended and the stabilization due to this hyperconju-
gation was evaluated by studying an isodesmic reaction. A
novel type of fused thiophene–dibenzophosphole skeleton
was synthesized by a photocyclization reaction. Although
the yield of this reaction is quite modest, its high selectivity
makes it a novel and valuable synthetic tool for preparing
dibenzophosphole derivatives. The electronic properties of
this unprecedented fused framework are intriguing since
both experimental and theoretical data suggest that the cen-
tral P ring exhibits slight antiaromatic character, reducing
the extent of the delocalization of the p-system over the
entire molecule. This work opens further possibilities to
tune the electronic properties of conjugated p-systems by
fully exploiting the chemistry of both P- and S-heteroles.
Syntheses
General information: All experiments were performed under an atmos-
phere of dry argon using standard Schlenk techniques. Column chroma-
tography was performed in air, unless stated in the text. Solvents were
freshly distilled under argon from sodium/benzophenone (tetrahydro-
furan, diethyl ether) or from phosphorus pentoxide (pentane, dichloro-
methane). [Cp2ZrCl2] was obtained from Alfa Aesar Chem. Co. nBuLi,
CuI, and S8 were obtained from Acros Chem. Co. 2-Bromothiophene, 3-
bromothiophene, [PdCl2ACHTUNTRGNNEUG(PPh3)2], 1,8-diazabicycloHCATUNGTREN[NGUN 5.4.0]undec-7-ene, tri-
methylsilylacetylene, and elemental sulfur were obtained from Aldrich
Chem. Co. All compounds were used as received without further purifi-
cation. PPhBr2,[29] 1,2-di(2-thienyl)ethyne (1a),[14a] and 1,2-di(3-thienyl)-
ethyne (1b)[14b,c] were prepared as described in the literature. Preparative
separations were performed by gravity column chromatography on basic
alumina (Aldrich, Type 5016 A, 150 mesh, 58 ꢅ) or silica gel (Merck Ge-
duran 60, 0.063–0.200 mm) in 3.5–20 cm columns. Irradiation reactions
1
were conducted by using a Heraeus TQ 150 mercury vapor lamp. H, 13C,
and 31P NMR spectra were recorded on Bruker AM300 or DPX200. 1H
and 13C NMR chemical shifts were reported in parts per million (ppm)
relative to SiACTHNUTRGNEUNG
(CH3)4 as an external standard. 31P NMR downfield chemical
shifts were expressed with a positive sign, in ppm, relative to external
85% H3PO4. Assignment of the proton atoms was based on a COSY ex-
periment. Assignment of the carbon atoms was based on HMBC,
HMQC, and DEPT-135 experiments. High-resolution mass spectra were
obtained on a Varian MAT 311 or ZabSpec TOF Micromass instrument
at CRMPO, University of Rennes 1. Elemental analyses were performed
by the CRMPO, University of Rennes 1.
Experimental Section
Determination of optical data: UV/Vis spectra were recorded at room
temperature on a UVIKON 942 spectrophotometer, and luminescence
spectra were recorded in freshly distilled solvents at room temperature
with a PTI spectrofluorimeter (PTI-814 PDS, MD 5020, LPS 220B) using
a xenon lamp. Quantum yields were calculated relative to fluorescein
(F=0.90 in 0.1n NaOH).[30]
Details of the X-ray crystallography studies: Single crystals suitable for
X-ray crystal analysis were obtained by slow diffusion of vapors of pen-
tane into a dichloromethane solution of 2b, 3b, or 5b or by slow evapo-
ration of a benzene solution of 6b at room temperature. Single-crystal
data collection was performed at 100 K with an APEX II Bruker-AXS
Chem. Eur. J. 2009, 15, 4914 – 4924
ꢂ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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4921

L. Nyulꢁszi, M. Hissler, and R. Rꢀau et al.
Cyclic voltammetry measurements: The electrochemical studies were car-
ried out under argon using an Eco Chemie Autolab PGSTAT 30 poten-
tiostat for cyclic voltammetry with a three-electrode configuration: the
working electrode was a platinum disk, the reference electrode a saturat-
ed calomel electrode, and the counter-electrode a platinum wire. All po-
tentials were internally referenced to the ferrocene/ferrocenium couple.
For the measurements, concentrations of 10ꢀ3 m of the electroactive spe-
cies were used in freshly distilled and degassed dichloromethane (Lichro-
solv, Merck) and 0.2m tetrabutylammonium hexafluorophosphate
(TBAHFP, Fluka), which was twice recrystallized from ethanol and dried
under vacuum prior to use.
CD2Cl2): d=126.7 (s, CHthienyl), 127.5 (s, CHthienyl), 128.6 (s, CHthienyl),
128.8 (s, CHthienyl), 128.7 (d, J
90.2 Hz, Ca), 129.3 (d, J(P,C)=12.7 Hz, CHmeta,phenyl), 129.6 (d, J
5.2 Hz, CHthienyl), 129.8 (s, CHthienyl), 130.5 (d, (P,C)=11.7 Hz,
CHortho,phenyl), 132.6 (d, J(P,C)=3.1 Hz, CHpara,phenyl), 134.4 (d, J(P,C)=
15.8 Hz, Cthienyl), 134.6 (d, J(P,C)=17.5 Hz, Cthienyl), 140.2 ppm (d, J(P,C)=
A
ACHTUNGTRENNUNG(P,C)=
A
ACHTUNGTRENNUNG
JACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
23.3 Hz, Cb); 31P{1H} NMR (CDCl3, 121.5 MHz): d=+52.4 ppm (s); HR-
MS (EI) : m/z: 519.9682 [M]+; C26H17PS5 calcd: 519.96715; elemental
analysis calcd (%) for C26H17PS5 (520.718): C 59.97, H 3.29, S 30.79;
found: C 60.01, H 3.38, S 30.95.
1-Phenyl-2,3,4,5-tetra(3-thienyl)thiooxophosphole (3b): An excess of ele-
mental sulfur was added at room temperature to a solution of 1-phenyl-
2,3,4,5-tetra(3-thienyl)phosphole (2b; 0.350 g, 0.77 mmol) in CH2Cl2
(10 mL). This mixture was stirred overnight at room temperature, and
then all the volatile materials were removed under vacuo. The precipitate
was washed with pentane (4ꢆ10 mL) and 1-phenyl-2,3,4,5-tetra(3-thie-
nyl)thiooxophosphole (3b) was obtained as an air-stable orange solid
(0.320 g, 80% yield). 1H NMR (300 MHz, CD2Cl2): d=6.67 (d, 2H; 3J-
1-Phenyl-2,3,4,5-tetra(2-thienyl)phosphole (2a): A solution of BuLi in
hexanes (2.5m, 0,38 mL; 0.95 mmol) was added dropwise at ꢀ788C to a
solution of [Cp2ZrCl2] (0.132 g, 0.45 mmol) and 1,2-di(2-thienyl)ethyne
(1a; 0.172 g, 0.9 mmol) in THF (10 mL). After stirring overnight, the so-
lution turned deep red and neat PhPBr2 (0.102 mL, 0.5 mmol) was added
at ꢀ788C. The solution was stirred for an additional 5 h and filtered
through basic alumina (THF, Rf =0.8). All the volatile materials were re-
moved under vacuum. 1-Phenyl-2,3,4,5-tetra(2-thienyl)phosphole (2a)
was washed several times with pentane and isolated as an orange solid
3
4
N
N
ACHTUNGTREN(NUNG H,H)=1.1 Hz,
A
ACHTUNGTRENNUNG
(0.10 g, yield 46%).1H NMR (200 MHz, CDCl3):
d
=6.82 (m, 2H;
thienyl), 6.96–7.10 (m, 8H; Hthienyl), 7.30–7.40 (m, 5H; Hthienyl, Hmeta, and
para,phenyl), 7.62 ppm (m, 2H;
ortho,phenyl); 13C{1H} NMR (75.46 MHz,
(P,C)=1.9 Hz, CHthienyl), 126.7 (s, CHthienyl), 126.9
(P,C)=10.4 Hz, CHthienyl), 127.0 (s, CHthienyl), 127.3 (s, CHthienyl), 129.0
(d, J(P,C)=8.9 Hz, CHmeta,phenyl), 129.2 (d, J(P,C)=1.9 Hz, CHthienyl), 130.4
(d, (P,C)=1.7 Hz, CHpara,phenyl), 131.6 (d, J(P,C)=10.9 Hz, ipso,phenyl),
(P,C)=20.7 Hz, CHortho,phenyl), 137.0 (d, J(P,C)=2.1 Hz, Cthienyl),
(P,C)=20.8 Hz, Ca), 139.6 (d, (P,C)=8.6 Hz, Cthienyl),
(P,C)=3.9 Hz, Cb); 31P{1H} NMR (CDCl3, 121.5 MHz):
A
ACHTUNGTRENNUNG
3
H
H
H
A
R
ACHTUNGTRENNUNG
CD2Cl2): d=126.5 (d, J
(d, J
N
H
U
ACHTUNGTRENNUNG
A
U
ACHTUNGTRENNUNG
J
N
U
C
J
N
JACHTUNGTRENNUNG
134.1 (d, J
N
U
A
ACHTUNGTRENNUNG
138.5 (d,
J
N
J
U
A
ACHTUNGTRENNUNG
141.3 ppm (d, J
A
JACHTUNGTRENNUNG
d=+14.1 ppm (s); HR-MS (EI): m/z: 487.9960 [M]+; C26H17PS4 calcd
487.99508; elemental analysis calcd (%) for C26H17PS4 (488.654): C 63.91,
H 3.51, S 26.25; found: C 63.73, H 3.74, S 26.15.
:
C26H17PS5 calcd: 519.96715; elemental analysis calcd (%) for C26H17PS5
(520.718): C 59.97, H 3.29, S 30.79; found: C 59.71, H 3.13, S 30.85.
1-Phenyl-2,3,4,5-tetra(3-thienyl)phosphole (2b): A solution of BuLi in
hexanes (1.6m, 0,656 mL; 1.05 mmol) was added dropwise at ꢀ788C to a
solution of [Cp2ZrCl2] (0.146 g, 0.5 mmol) and 1,2-di(3-thienyl)ethyne
(1b; 0.190 g, 1 mmol) in THF (10 mL). After stirring overnight, the solu-
tion turned deep red and neat PhPBr2 (0.103 mL, 0.5 mmol) was added
at ꢀ788C. The solution was stirred for an additional 5 h and filtered
through basic alumina (THF, Rf =0.8). All the volatile materials were re-
moved under vacuum. 1-Phenyl-2,3,4,5-tetra(3-thienyl)phosphole (2b)
was washed several times with pentane and isolated as an orange solid
(0.145 g, yield 60%). 1H NMR (300 MHz, CD2Cl2): d=6.69 (d, 2H; 3J-
1-Phenyl-2,3,4,5-tetra(2-thienyl)oxophosphole (4a): An excess of sodium
periodate in aqueous solution (10 mL) was added to a solution of 1-
phenyl-2,3,4,5-tetra(2-thienyl) phosphole 2a (0.100 g, 0.2 mmol) in
CH2Cl2 (10 mL). This mixture was stirred for 30 min at room tempera-
ture. The aqueous layer was extracted with CH2Cl2 (4ꢆ10 mL) and then
dried under MgSO4. Then all the volatiles materials were removed under
vacuo. The precipitate was washed with pentane (2ꢆ10 mL), and 1-
phenyl-2,3,4,5-tetra(2-thienyl)oxophosphole (4a) was obtained as an air-
stable brownish solid (0.93 g, 90% yield). 1H NMR (300 MHz, CD2Cl3):
d=6.91 (dd, 2H; 3J
2H; 3J(H,H)=3.9 Hz, 4J
5.1 Hz, 3J(H,H)=3.6 Hz, Hthienyl), 7.20 (d, 2H; 3J
7.44 (d, 2H; J
(H,H)=1.2 Hz, Hthienyl), 7.58 (m, 3H; Hmeta,phenyl and Hpara,phenyl), 8.00 ppm
(ddd, 2H; 3J(H,H)=8.0 Hz, 4J
(H,H)=1.4 Hz, (P,H)=12.6 Hz,
ortho,phenyl); 13C{1H} NMR (75.46 MHz, CD2Cl2): d=126.9 (s, CHthienyl),
127.5 (s, CHthienyl), 128.6 (s, CHthienyl), 128.8 (s, CHthienyl), 128.7 (d, J(P,C)=
96.4 Hz, Cipso,phenyl), 128.9 (d, J(P,C)=92.8 Hz, Ca), 129.4 (d, J(P,C)=
12.4 Hz, CHmeta,phenyl), 129.6 (s, CHthienyl), 129.7 (d, (P,H)=4.5 Hz,
CHthienyl), 130.5 (d, (P,C)=10.7 Hz, CHortho phenyl), 132.7 (d, (P,C)=
2.8 Hz, CHpara,phenyl), 134.2 (d, J(P,C)=18.3 Hz, Cthienyl), 135.0 (d, J(P,C)=
15.0 Hz, Cthienyl), 140.1 ppm (d,
(P,C)=26.7 Hz, Cb); 31P{1H} NMR
A
ACHTUNGTRENNUNG
A
R
A
R
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
3
3
4
H
H
ACHTUNGTRNE(UNG H,H)=3.6 Hz, Hthienyl), 7.50 (dd, 2H; JACHTUNGTNER(NUGN H,H)=5.1 Hz, J-
N
ACHTUNGTRENNUNG
R
A
R
JACHTUNGTRENNUNG
A
U
H
J
J
N
R
ACHTUNGTRENNUNG
U
A
ACHTUNGTRENNUNG
(d,
J
N
J
U
JACHTUNGTRENNUNG
C
J
U
J
G
,
JACHTUNGTRENNUNG
121.5 MHz): d=+13.9 ppm (s); HR-MS (EI): m/z: 487.9966 [M]+;
C26H17PS4 calcd 487.99508; elemental analysis calcd (%) for C26H17PS4
(488.654): C 63.91, H 3.51, S 26.25; found: C 63.61, H 3.86, S 26.31.
A
ACHTUNGTRENNUNG
JACHTUNGTRENNUNG
(CD2Cl2, 121.5 MHz): d=+41.1 ppm (s); HR-MS (EI) : m/z: 505.0007
[M+H]+; C26H17POS4+H+ calcd: 504.99782; elemental analysis calcd
(%) for C26H17POS4 (504.653): C 61.88, H 3.40, S 25.42; found: C 61.78,
H 3.53, S 25.47.
1-Phenyl-2,3,4,5-tetra(2-thienyl)thiooxophosphole (3a): An excess of ele-
mental sulfur was added at room temperature to a solution of 1-phenyl-
2,3,4,5-tetra(2-thienyl)phosphole 2a (0.150 g, 0.31 mmol) in CH2Cl2
(10 mL). The reaction mixture was stirred for two days, filtered, and the
solvent was removed in vacuo. After purification on silica gel (heptane/
CH2Cl2, 20:80, v/v), 3a was obtained an air-stable orange solid (yield:
0.136 g, 0.26 mmol, 85%). 1H NMR (300 MHz, CD2Cl2): d=6.88 (dd,
1-Phenyl-2,3,4,5-tetra(3-thienyl)oxophosphole (4b): An excess of sodium
periodate in aqueous solution (10 mL) was added to a solution of 1-
phenyl-2,3,4,5-tetra(3-thienyl)phosphole (2b; 0.510 g, 1.10 mmol) in
CH2Cl2 (10 mL). This mixture was stirred for 30 min at room tempera-
ture. The aqueous layer was extracted with CH2Cl2 (4ꢆ10 mL) and then
dried under MgSO4. Then all the volatiles materials were removed under
vacuo. The precipitate was washed with pentane (2ꢆ10 mL), and 1-
phenyl-2,3,4,5-tetra(3-thienyl)oxophosphole (4b) was obtained as an air-
stable brownish solid (0.49 g, 95% yield). 1H NMR (300 MHz, CDCl3):
2H; 3J
7.22 (d, 2H; 3J
thienyl), 7.51 (dd, 2H; 3J
(m, 3H; Hmeta,phenyl, Hpara,phenyl), 8.11 ppm (ddd, 2H; 3J
(H,H)=1.9 Hz, J
(P,H)=14.2 Hz, Hortho,phenyl); 13C{1H} NMR (75.46 MHz,
A
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
H
N
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
A
ACHTUNGTRENNUNG
4922
www.chemeurj.org
ꢂ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 4914 – 4924

Phospholes and 1,1’-Biphospholes Bearing 2- or 3-Thienyl C-Substituents
FULL PAPER
d=6.66 (d, 2H; 3J
5.1 Hz, 4J
(H,H)=1.1 Hz, Hthienyl), 6.95 (dd, 2H;
(H,H)=1.1 Hz,
thienyl), 7.06 (ddd, 2H; 3J(H,H)=5.1 Hz, 4J
1.0 Hz, J (H,H)=5.1 Hz, J
(P,H)=2.9 Hz, Hthienyl), 7.26 (dd, 2H; 3J
2.9 Hz, thienyl), 7.38 (m, 2H; Hthienyl), 7.50 (m, 3H; Hmeta,phenyl and
para phenyl), 7.95 ppm (ddd, 2H; 3J(H,H)=8.1 Hz, 4J
(H,H)=1.4 Hz, J-
(P,H)=12.3 Hz, Hortho,phenyl);13C{1H} NMR (75.46 MHz, CDCl3): d=125.1
(s, CHthienyl), 125.2 (s, CHthienyl), 125.7 (d, J(P,H)=5.9 Hz, CHthienyl), 125.9
(s, CHthienyl), 126.9 (d, (P,H)=6.6 Hz, CHthienyl), 127.6 (d, (P,C)=
95.0 Hz, ipso,phenyl), 128.1 (s, CHthienyl), 129.1 (d, (P,C)=12.0 Hz,
CHmeta,phenyl), 129.1 (d, J(P,C)=94.0 Hz, Ca), 130.6 (d, J(P,C)=10.4 Hz,
CHortho,phenyl), 132.3 (d, J(P,C)=2.9 Hz, CHpara,phenyl), 132.8 (d, J(P,C)=
11.4 Hz, Cthienyl), 135.4 (d, J(P,C)=17.7 Hz, Cthienyl), 143.4 ppm (d, J(P,C)=
G
G
G
G
ACHTUNGTREN(NUNG P,H)=14.5 Hz,
H
ACHTUNGTRENNUNG
G
JACHTUNGTRENNUNG
JACHTUNGTRENNUNG
G
H
N
AHCTUNGTRENNUNG
A
E
AHCTUNGTRENNUNG
H
,
J
A
JACHTUNGTRENNUNG
H
ACHTUNGTRENNUNG
G
ACHTUNGTRENNUNG
G
ACHTUNGTRENNUNG
G
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
N
ACHTUNGTRENNUNG
J
N
C
JACHTUNGTRENNUNG
ACHTUNGTRENNUNG
G
G
27.2 Hz, Cb); 31P{1H} NMR (CDCl3, 121.5 MHz): d=+43.4 ppm (s); HR-
MS (EI) : m/z: 503.9820 [M]+; C26H17POS4 calcd: 503.98999; elemental
analysis calcd (%) for C26H17POS4 (504.653): C 61.88, H 3.40, S 25.41;
found: C 61.78, H 3.63, S 25.67.
Compound 7b: A solution of 1-phenyl-2,3,4,5-tetra(3-thienyl)oxophos-
phole (4b; 0.105 g, 0.2 mmol) in toluene (240 mL) containing a catalytic
amount of iodine was stirred and irradiated overnight by using a Heraeus
TQ 150 mercury vapor lamp. Then all the volatile materials were re-
moved under vacuo and the resulting precipitate was chromatographed
on silica gel (ethyl acetate, Rf =0.5). Compound 7b was obtained as a
brownish solid (0.027 g, 26% yield). 1H NMR (300 MHz, CDCl3): d=
1,1’-[2,3,4,5-Tetra(2-thienyl)]bisphosphole (5a): A solution of BuLi in
hexanes (2.5m, 0.86 mL; 2.1 mmol) was added dropwise at ꢀ788C to a
solution of [Cp2ZrCl2] (0.301 g, 1.0 mmol) and 1,2-di(2-thienyl)ethyne
(1a; 0.391 g, 2 mmol) in THF (30 mL). After stirring overnight, the solu-
tion turned deep red and neat PBr3 (0.19 mL, 1 mmol) was added at
ꢀ788C. The solution was stirred for four days at room temperature and
turned light red. The solution was then filtered through basic alumina
(THF, Rf =0.8) and all volatile materials were removed under vacuum.
The precipitate was washed several times with n-heptane/ethyl acetate
7.36 (m, 3H; Hmeta,phenyl and Hpara,phenyl), 7.50 (d, 2H; 3J
Hthienyl), 7.62 (d, 2H; 3J(H,H)=5.3 Hz, Hthienyl), 7.64 (d, 2H; 3J
5.6 Hz, Hthienyl), 7.76 (ddd, 2H; (H,H)=1.5 Hz, (H,H)=6.9 Hz, J-
(P,H)=13.2 Hz, 2H; (H,H)=5.6 Hz,
ortho,phenyl), 8.01 ppm (d, 2H; 3J
Hthienyl); 13C{1H} NMR (CDCl3; 75.46 MHz): d=122.8 (d, J
(P,C)=2.8 Hz,
CHthienyl), 125.3 (s, CHthienyl), 124.2 (d, J(P,C)=106.6 Hz, Ca), 125.7 (s,
CHthienyl), 127.8 (s, CHthienyl), 128.9 (d, J(P,C)=12.6 Hz, CHmeta,phenyl), 129.3
(d, J(P,C)=76.0 Hz, Cipso,phenyl), 131.1 (d, J(P,C)=11.1 Hz, CHortho,phenyl),
131.7 (d, J(P,C)=12.1 Hz, Cthienyl), 132.3 (d, J(P,C)=2.9 Hz, CHpara,henyl),
135.1 (d, J(P,C)=11.5 Hz, Cthienyl), 136.3 (d, J(P,C)=10.6 Hz, Cthienyl),
137.3 (d, J(P,C)=22.5 Hz, Cthienyl), 140.4 ppm (d, J(P,C)=2.2 Hz, Cb);
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
J
N
JACHTUNGTRENNUNG
A
H
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
1
(8:2) (Rf =0.4) and isolated as a dark red powder (0.45 g, 55%). H NMR
A
ACHTUNGTRENNUNG
(300 MHz, CD2Cl2): d=6.56 (d, 4H; 3J
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
4H; 3J
7.09 (dd, 4H; J
(H,H)=5.1 Hz,
13C{1H} NMR (75.46 MHz, CDCl3): d=126.7 (s, CHthienyl), 126.8 (s,
CHthienyl), 127.0 (s, CHthienyl), 127.1 (s, CHthienyl), 127.4 (t-like, J(P,C)=
11.5 Hz and 11.5 Hz, CHthienyl), 129.2 (d, 1J
(P,C)=86.5 Hz, PCa), 129.5 (s,
CHthienyl), 136.6 (s, Cthienyl), 138.4 (t-like, J(P,C)=11.5 Hz and 11.5 Hz,
ACHTUNGTRENNUNG ACHTUNGTRENNUNG
(H,H)=3.5 Hz, 3J
A
ACHTUNGTRENNUNG
3
3
3
G
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
A
H
ACHTUNGTRENNUNG
31P{1H} NMR (CDCl3, 121.5 MHz): d=+33.6 (s); HR-MS (ESI): m/z:
500.9655 [M+H]+; C26H14POS4 calcd: 500.96652; elemental analysis
calcd (%) for C26H13POS4 (501.629): C 62.25, H 2.81, S 25.57; found: C
62.30, H 2.68, S 25.87.
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
C
thienyl), 139.8ppm (m, PCb); 31P{1H} NMR (CD2Cl2, 121.5 MHz): d=
ꢀ0.8 ppm (s); HR-MS (ESI) : m/z: 821.9112 [M]+; C40H24P2S8 calcd:
821.91190; elemental analysis calcd (%) for C40H24P2S8 (823.095): C
58.37, H 2.94, S 31.16; found: C 58.21, H 3.06, S 31.08.
Acknowledgements
This work is supported by the Ministꢇre de la Recherche et de l’En-
seignement Supꢀrieur, the Institut Universitaire de France, the CNRS,
the Rꢀgion Bretagne and the project ANR PSICO. Support from the Sci-
entific and Technological French-Hungarian Bilateral Cooperation (BA-
LATON program) is also acknowledged. The Alexander von Humbold
Foundation is also acknowledged (R.R).
1,1’-[2,3,4,5-Tetra(3-thienyl)]bisphosphole (5b): A solution of BuLi in
hexanes (1.6m, 0.656 mL; 1.05 mmol) was added dropwise at ꢀ788C to a
solution of [Cp2ZrCl2] (0.146 g, 0.5 mmol) and 1,2-di(thiophene-3-yl)-
ethyne (0.190 g, 1 mmol) in THF (10 mL). After stirring overnight, the
solution turned deep red and neat PBr3 (0.95 mL, 1 mmol) was added at
ꢀ788C. The solution was stirred for four days at room temperature and
turned light red. The solution was then filtered through basic alumina
(THF, Rf =0.8) and all volatile materials were removed under vacuum.
The precipitate was washed several times with pentane and isolated as a
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red solid (0.205 g, 50%). H NMR (300 MHz, CDCl3): d=6.48 (d, 4H; 3J-
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
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AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
144.5 ppm (m, Cb); 31P{1H} NMR (CD2Cl2, 121.5 MHz): d=ꢀ7.4 ppm (s);
HR-MS (mNBA, FAB) : m/z: 844.9031 [M+Na]+; C40H24P2S8+Na calcd:
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phosphole (3b; 0.150 g, 0.3 mmol) in toluene (500 mL) containing a cata-
lytic amount of iodine was stirred and irradiated overnight by using a
Heraeus TQ 150 mercury vapor lamp. Then all the volatile materials
were removed under vacuo and the resulting precipitate was chromato-
graphed on silica gel (CH2Cl2, Rf =0.7). Compound 6b was obtained as a
brownish solid (0.020 g, 10% yield). 1H NMR (500 MHz, CDCl3): d=
7.37 (m, 2H; Hmeta,phenyl), 7.48 (m, 1H; Hpara,phenyl), 7.54 (d, 2H; 3J
ACHTUNGTRENNUNG
5.3 Hz, Hthienyl), 7.67 (d, 2H; 3J
ACHTUNGTRENNUNG
Chem. Eur. J. 2009, 15, 4914 – 4924
ꢂ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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Received: December 18, 2008
Published online: March 19, 2009
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