N-aryl pyrrolo-tetrathiafulvalene based ligands: Synthesis and metal coordination

Article abstract of DOI:10.1021/jo902529e

(Figure Presented) A straightforward general synthetic access to N-aryl-1,3-dithiolo[4,5-c]pyrrole-2-thione derivatives 6 from acetylenedicarbaldehyde monoacetal is depicted. In addition to their potentiality as precursors to dithioalkyl-pyrrole derivatives, thiones 6 are key building blocks to N-aryl monopyrrolotetrathiafulvalene (MPTTF) derivatives 10. X-ray structures of four of these thiones intermediates, reminiscent of the corresponding MPTTF derivatives, are provided. When the aryl group is a binding pyridyl unit, the MPTTF derivative 10a can coordinate M(II) salts (M = Pt, Pd). The first examples of metal-directed orthogonal MPTTF-based dimers 11-14, obtained through coordination of 10a to cis-blocked square planar Pt or Pd complexes are described. Studies on the parameters influencing the dimer construction are presented, as well as first recognition properties of the resulting electronrich clip for C₆₀.

Full text of DOI:10.1021/jo902529e

pubs.acs.org/joc
N-Aryl Pyrrolo-tetrathiafulvalene Based Ligands: Synthesis
and Metal Coordination
ꢀ
Jean-Yves Balandier, Marcos Chas, Paul I. Dron, Sebastien Goeb, David Canevet,
ꢀ
Ahmed Belyasmine, Magali Allain, and Marc Salle*
ꢀ
Institut des Sciences et Technologies Moleculaires d’Angers, MOLTECH ANJOU, UMR CNRS 6200,
Universiteꢀ d’Angers, 2 Bd Lavoisier, 49045 Angers Cedex, France
marc.salle@univ-angers.fr
Received December 3, 2009
A straightforward general synthetic access to N-aryl-1,3-dithiolo[4,5-c]pyrrole-2-thione derivatives 6
from acetylenedicarbaldehyde monoacetal is depicted. In addition to their potentiality as precursors
to dithioalkyl-pyrrole derivatives, thiones 6 are key building blocks to N-aryl monopyrrolo-
tetrathiafulvalene (MPTTF) derivatives 10. X-ray structures of four of these thiones intermediates,
reminiscent of the corresponding MPTTF derivatives, are provided. When the aryl group is a binding
pyridyl unit, the MPTTF derivative 10a can coordinate M(II) salts (M = Pt, Pd). The first examples
of metal-directed orthogonal MPTTF-based dimers 11-14, obtained through coordination of 10a to
cis-blocked square planar Pt or Pd complexes are described. Studies on the parameters influencing
the dimer construction are presented, as well as first recognition properties of the resulting electron-
rich clip for C60.
Introduction
reviewed.3 Interest for this π-electron donor results from a
conjunction of remarkable electronic properties and a ver-
satile chemistry, allowing functionalization for a broad
range of applications.2,3 For instance, efforts have been
produced for linking binding units to the redox-active TTF
moiety, in order to (i) prepare TTF-based redox-switchable
receptors able to electrochemically detect a metal cation
guest3 and (ii) obtain hybrid organic-inorganic materials
endowed with rich solid-state physical properties.4 In those
two cases, several examples of TTF-based systems involving
a binding pyridyl unit have been described.3,4 A significant
breakthrough in the use of TTF-based systems comes
from the synthesis some years ago of the more extended
monopyrrolo- and bispyrrolo-tetrathiafulvalene deriva-
tives (MPTTF and BPTTF, respectively, Scheme 1).5,6 These
Tetrathiafulvalene (TTF) and its derivatives have been the
subject of intense interest for nearly four decades. The initial
observation of remarkable conducting metallic behavior for
some of the corresponding salts1 has continuously stimu-
lated very active research regarding transport properties of
this π-electron-donating molecule in the solid state.2 More-
over, due to their electron-donating properties and the
possibility of reversible stepwise oxidation forming stable
radical cation and dication species, tetrathiafulvalene deri-
vatives have found use as redox switches in a myriad of recent
molecular and supramolecular architectures that we recently
(1) (a) Wudl, F.; Wobschall, D.; Hufnagel, E. J. J. Am. Chem. Soc. 1972,
94, 670–672. (b) Ferraris, J.; Cowan, D. O.; Walatka, V., Jr; Perlstein, J. H.
J. Am. Chem. Soc. 1973, 95, 948–949. (c) Coleman, L. B.; Cohen, M. J.;
Sandman, D. J.; Yamagishi, F. G.; Garito, A. F.; Heeger, A. J. Solid State
Commun. 1973, 12, 1125–1132.
ꢀ
(4) For a recent review, see: Lorcy, D.; Bellec, N.; Fourmigue, M.;
Avarvari, N. Coord. Chem. Rev. 2009, 253, 1398–1438.
(2) For recent reviews on this topic, see special issue on molecular
conductors : Batail, P., Guest Editor. Chem. Rev. 2004, 11.
ꢀ
(3) For a recent review, see: Canevet, D.; Salle, M.; Zhang, G.; Zhang, D.;
Zhu, D. Chem. Commun. 2009, 2245–2269.
(5) Jeppesen, J. O.; Becher, J. Eur. J. Org. Chem. 2003, 17, 3245–3266.
(6) (a) Jeppesen, J. O.; Takimiya, K.; Jensen, F.; Brimert, T.; Nielsen, K.;
Thorup, N.; Becher, J. J. Org. Chem. 2000, 65, 5794–5805. (b) Balandier,
ꢀ
J.-Y.; Belyasmine, A.; Salle, M. Synthesis 2006, 17, 2815–2817.
DOI: 10.1021/jo902529e
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Published on Web 02/09/2010
J. Org. Chem. 2010, 75, 1589–1599 1589
2010 American Chemical Society

Balandier et al.
JOCArticle
SCHEME 1
between 4-amino pyridine and the bromomethyl electro-
philic group. We have therefore developed a new access
to N-aryl (including N-pyridyl) 1,3-dithiolo[4,5-c]pyrrole-2-
thione A.12
The synthesis of thiones 6a-f is described in Scheme 2.
The starting key compound is the commercially available
mono(diethyl)acetal of acetylene dicarbaldehyde 1.13 This
electrophilic alkyne cycloadds onto ethylenetrithiocarbo-
nate to produce 1,3-dithiol-2-thione derivative 2.14 Imine
3a could be obtained by condensation of 2 with 4-aminopyr-
idine/piperidine in presence of molecular sieves or P2O5 in
refluxing toluene, which invariably results in low yields
(<18%). The most efficient route involves instead an aza-
Wittig reaction between 2 and iminophosphorane 4;15 in
this case, imino derivative intermediate 3a is not isolated
and is directly reduced with sodium borohydride to
produce amino-acetal 5a in 70% yield from 2. The key
point in this strategy corresponds to synthesis of final thione
6a, obtained in 79% yield through a single reaction, by
treatment of 5a with Amberlyst A15. Actually, this reac-
tion corresponds to three successive chemical steps:
acetal deprotection, intramolecular cyclization, and des-
hydration.
The generalization of this method to other aromatic
N-arylated 1,3-dithiolo[4,5-c]pyrrole-2-thiones 6b-f was
operated using various aromatic amines that are condensed
with aldehyde 2 (Scheme 2 and Table 1). The general route
involves the preparation of imine derivatives 3, reduction
with NaBH4, and then treatment with Amberlyst A15.
Because of the instability of some intermediate compounds,
the sequence from 2 to 6 is followed without isolation of
imines 3 (except 3b) or amine intermediates 5.
systems have been extensively incorporated in a great variety
of molecular and supramolecular architectures.5,7 Never-
theless, in comparison to the parent TTF unit, the study of
their synthetic versatility has been less developed. In parti-
cular, only few examples of MPTTF or BPTTF derivatives
incorporating binding units have been described.5,8 In the
course of our studies, related to metal-directed self-assembly
of electron-rich polygons,9 we have been interested in intro-
ducing aromatic binding units (such as 4-pyridyl or 4-cyano
phenyl groups) at the periphery of the pyrroloTTF frame-
work, which to the best of our knowledge has not been
described yet. Beyond these units, there is a need for a general
synthetic route to N-aryl pyrroloTTF precursors. We pro-
pose here a new general access to N-aryl-1,3-dithiolo[4,5-
c]pyrrole-2-thione derivatives, key building blocks to N-aryl
MPTTF and BPTTF derivatives, and we develop their
application in the first examples of metal-directed orthogo-
nal MPTTF-based dimers, through their coordination to cis-
blocked square planar Pt or Pd complexes.
Results and Discussion
Conversion of 1,3-dithiolo[4,5-c]pyrrole-2-thione A (X=
S) to the corresponding dithiocarbonate (X=O) provides an
efficient entry to dithioalkyl pyrrole derivatives, as shown
recently16 in the case of R=H (Scheme 1). Accordingly, we
converted thioxo compounds 6a and 6b to their oxo deriva-
tives 60a and 60b, respectively, by treatment with mercuric
acetate in glacial acetic acid. Yields were remarkably low
(60a, 10%; 60b, 54%), which we assign to a competitive
binding of Hg(II) by the pyridyl moiety along the reaction.
We therefore modified the procedure, by operating the
transchalcogenation step prior to introduction of the pyridyl
substituent (Scheme 3). Oxo derivative 20 was quantitatively
produced in this case.14 A similar synthetic path as for the
preparation of 6a was then followed for the preparation of
60a (imine formation, reduction, intramolecular cyclization
with aromatization).
A synthetic access to key intermediates A has already been
described (with R = Ts, Scheme 1), through a route invol-
ving the synthesis of 4,5-bis(bromomethyl)-1,3-dithiole-2-
thione and subsequent annelation with tosylamide.6a
Noteworthy, only few examples of N-arylated derivatives
of A are described. They are obtained by modifying the
above-described strategy, through reaction of an aromatic
amine/K2CO310,11 (instead of tosylamide) along the cycliza-
tion step with 4,5-bis(bromomethyl)-1,3-dithiole-2-thione.
Nevertheless, such strategy cannot be applied in the case of
insertion of a pyridyl group, because of undesired reactivity
(7) See for instance: (a) Nielsen, K. A.; Cho, W. S.; Jeppesen, J. O.;
Lynch, V. M.; Becher, J.; Sessler, J. L. J. Am. Chem. Soc. 2004, 126, 16296–
16297. (b) Nielsen, K. A.; Cho, W. S.; Sarova, G. H.; Petersen, B. M.; Bond,
A. D.; Becher, J.; Jensen, F.; Guldi, D. M.; Sessler, J. L.; Jeppesen, J. O.
Angew. Chem., Int. Ed. 2006, 45, 6848–6853.
ꢀ
ꢀ
(8) Trippe, G.; Levillain, E.; Le Derf, F.; Gorgues, A.; Salle, M.;
Jeppesen, J. O.; Nielsen, K.; Becher, J. Org. Lett. 2002, 4, 2461–2464.
(9) Balandier, J.-Y.; Chas, M.; Goeb, S.; Dron, P. I.; Rondeau, D.;
In order to further extend the linear extension of the
corresponding BPTTF derivative, a Sonogashira coupling
was carried out between thione 6e and 4-pyridyl acetylene 7,
prepared in two steps from 4-bromopyridine,17 to produce
thione 8 in 45% yield (Scheme 4).
ꢀ
Belyasmine, A.; Gallego, N.; Salle, M. Submitted for publication.
(10) Nygaard, S.; Leung, K. C. F.; Aprahamian, I.; Ikeda, T.; Saha, S.;
Laursen, B. W.; Kim, S. Y.; Hansen, S. W.; Stein, P. C.; Flood, A. H.;
Stoddart, J. F.; Jeppesen, J. O. J. Am. Chem. Soc. 2007, 129, 960–970.
(11) Bingzhu, Y.; Yonghua, Y.; Zhiqi, C.; Kimiaki, I. Heterocycles 2004,
63, 1577.
(12) Though we could efficiently (>65% yield) operate
a
model
(13) Gorgues, A.; Stephan, D.; Belyasmine, A.; Khanous, A.; Le Coq, A.
Tetrahedron 1990, 46, 2817.
N-arylation of the naked pyrrole heterocycle to produce N-p-pyridyl pyrrole,
by reaction of 4-chloropyridine with pyrryl potassium or by copper-catalysed
coupling of pyrrole with 4-iodopyridine, all of our attempts to direct
N-arylation of A (R = H) according to the same procedures failed. Also,
an example of N-arylation on a preformed MPTTF, using the Buchwald
copper catalyst system, has been described but failed in our attempts to
introduce the pyridyl unit: Li, H.; Lambert, C. Chem.;Eur. J. 2006, 12,
1144–1155.
ꢀ
(14) Salle, M.; Gorgues, A.; Jubault, M.; Boubekeur, K.; Batail, P.
Tetrahedron 1992, 48, 3081–3090.
ꢀ
(15) Balandier, J.-Y.; Belyasmine, A.; Salle, M. Eur. J. Org. Chem. 2008,
269–276.
(16) (a) Li, H.; Lambert, C. J. Mater. Chem. 2005, 15, 1235. (b) Li, H.;
Lambert, C.; Stahl, R. Macromolecules 2006, 39, 2049–2055.
(17) Yu, L.; Lindsey, J. S. J. Org. Chem. 2001, 66, 7402.
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SCHEME 2
SCHEME 3
TABLE 1. Synthesis of Thiones 6a-e from 2 and Various Aryl Amines
between thiones 60a (or 60b) and 1,3-dithiole-2-thione 9
in refluxing trimethylphosphite (Scheme 5) to afford 10a
(respectively 10b).
Thiones 5a and 6a-c could be grown as single crystals,
and corresponding X-ray structures were solved by X-ray
diffraction. Crystallographic data are gathered in Table SI-1
in Supporting Information, and corresponding molecular
structures are shown in Figure 1.
Thione 5a crystallizes as yellow needles in the monoclinic
space group P21/n. Mean planes of both heterocycles of 5a
are nearly perpendicular (82.55(5)°), which of course is not
the case for thiones 6a-c. N-Substituted 1,3-dithiolo[4,5-c]-
pyrrole-2-thiones 6a-c present molecular structures
whose basic fragments prefigure the structure of the corres-
ponding MPTTF or BPTTF derivatives. Some structural
distinctions can be found between thiones 6a-c, in particular
the rotation angle around the N(pyrrole)-C(Ar) bond, between
both aromatic rings. In the case of 6b, mean planes defined
by (N01C05C02S02C01S03C03C04) and (C06C07C08C09C10C11)
deviate by only 8.17(8)°. The corresponding rotation angle
around the N(pyrrole)-C(Ar) bond reaches a value of 33.1(1)°
and 39.0(1)° for 6a and 6c, respectively.
DFT calculations (Gaussian 2003, (Becke3LYP (B3LYP))18
have been carried out on 10a,b. These calculations were led
with atomic bases 6-31G(d,p) on all atoms. Frontier orbitals
of TTF derivatives 10a,b are shown in Table 2. For both of
them, the electronic density in the HOMO is located on the
central donating skeleton and on the lateral pyrrole motifs,
illustrating the strong π-delocalization in BPTTF derivatives
aIsolated product. bAza-Wittig reaction from 4.
An evident interest of thiones intermediates 6a,b, relies
on the preparation of new MPTTF and BPTTF derivatives
N-substituted with coordinating units. Monotopic MPTTF
derivatives could be reached through a cross-coupling reaction
(18) Becke, D. J. Chem. Phys. 1993, 98, 5648.
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FIGURE 1. X-ray structures of 1,3-dithiol-2-thione 5a (a) and 1,3-dithiolo[4,5-c]pyrrole-2-thiones 6a (b), 6b (c), and 6c (d) (H atoms omitted).
SCHEME 4
SCHEME 5
compared to the parent TTF framework.5 On the other
hand, the LUMO is essentially distributed on pyrrole and
pyridyl heterocycles (10a) or p-cyanophenyl units (10b). The
corresponding energies are very similar to that of unsubsti-
tuted BPTTF, anticipating a comparable high π-donating
ability.
These rigid monotopic ligands are suitable candidates
for construction of metalla-assembled structures of con-
trolled geometries, by association with chosen metal
complexes. cis-Blocked square planar Pt(II) or Pd(II) salts
(such as dpppM(OTf)2 or enM(NO3)2 with M = Pt or Pd)
present two orthogonal positions for binding ligands,
typically pyridine derivatives. Based on such metal-
directed assembly, various exotic supramolecular structures
(e.g., polygons and polyhedron) have been reached in a
straightforward way,19 architectures that are otherwise
very challenging to synthesize using classical covalent chem-
istry.
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TABLE 2. HOMO and LUMO of MPTTF Derivatives 10a,b
SCHEME 6
On this ground, a metal-assembled dimer presenting two
orthogonal MPTTF-based ligands and one metal corner
constitutes therefore a base elemental unit regarding their
correponding self-assembled polyhedra and may provide
useful information on their self-assembly process. In addi-
tion, such angular TTF dimers correspond to a class of
derivatives that have been the focus of a continuous interest,
for two reasons: (i) electrical conducting properties of TTF-
based organic salts often suffer from their anisotropic orga-
nization in the crystal; among the solutions proposed to
increase their dimensionality, important efforts have been
developed by synthetic chemists to design two or three-
dimensionnal architectures, including orthogonal TTF di-
mers;20,21 (ii) such orthogonal dimers can be assimilated to
electron-rich clips that potentially present a good affinity for
electron-poor units. For instance, these interactions have
been recently used to bind C60 within a clip involving two
π-donating extended TTF units.22
Dimers 11, 12, and 13 (Scheme 6) were prepared through
reaction between bis(triflate) complexes dpppM(OTf)2 (M = Pd,
ꢀ
(20) (a) Gomez, R.; Segura, J. L.; Martın, N. J. Org. Chem. 2000, 65, 7566.
´
(b) Tatemitsu, H.; Nishikawa, E.; Sakata, H.; Misumi, S. Synth. Met. 1987,
19, 565. (c) Ueda, K.; Yamanoha, M.; Sugimoto, T.; Fujita, H.; Ugawa, A.;
Yakushi, K.; Kano, K. Chem. Lett. 1997, 461.
(19) For recent reviews, see: (a) Li, S. S.; Northrop, B. H.; Yuan, Q. H.;
Wan, L. J.; Stang, P. J. Acc. Chem. Res. 2009, 42, 249. (b) Stang, P. J. J. Org.
Chem. 2009, 74, 2. (c) Northrop, B. H.; Chercka, D.; Stang, P. J. Tetrahedron
2008, 64, 11495. (d) Northrop, B. H.; Yang, H. B.; Stang, P. J. Chem.
Commun. 2008, 5896. (e) Zangrando, E.; Casanova, M.; Alessio, E. Chem.
Rev. 2008, 108, 4979. (f) Fujita, M.; Tominaga, M.; Hori, A.; Therrien, B.
Acc. Chem. Res. 2005, 38, 369. (g) Fiedler, D.; Leung, D. H.; Bergman, R. G.;
Raymond, K. N. Acc. Chem. Res. 2005, 38, 349. (h) Kaiser, A.; Bauerle, P.
(21) An example of
a TTF dimer involving a conformationnally
flexible TTF-based unit and dpppM(OTf)2 (M = Pt, Pd) has recently
been described: Devic, T.; Avarvari, N.; Batail, P. Chem.;Eur. J. 2004,
10, 3697.
ꢀ
ꢀ
(22) (a) Perez, E. M.; Sierra, M.; Sanchez, L.; Torres, M. R; Viruela, R.;
Viruela, P. M.; Ortı, E.; Martın, N. Angew. Chem., Int. Ed. 2007, 46, 1847. (b)
´
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€
€
Top. Curr. Chem. 2005, 127. (i) Wurthner, F.; You, C. C.; Saha-Moller, C. R.
Chem. Soc. Rev. 2004, 33, 133.
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Perez, E. M.; Sanchez, L.; Fernandez, G.; Martın, N. J. Am. Chem. Soc. 2006,
128, 7172.
ꢀ
´
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TABLE 3. Chemical Shifts (CD2Cl2) for Complexes 11-13 and Corresponding Starting Complexesa
1H NMR δ (ppm)
complex
31P NMR δ (ppm)
19F NMR δ (ppm)
HR
Hβ
dpppPt(OTf)2
11
dpppPd(OTf)2
12
cis-(PEt3)2Pt(OTf)2
13
-9.8
-14.7
17.7
6.8
9.4
-2.5
-79.3
-79
79.2
-79
-79.4
-79
8.87
8.83
9.10
6.87
6.85
7.40
aNB: compound 10a δ(HR) = 8.56 ppm and δ(Hβ) = 7.46 ppm in DMSO-d6 (insoluble in CD2Cl2).
FIGURE 2. 1H, 31P, and 19F NMR spectra of 13 (5 ꢀ 10-3 mol L-1) in CD2Cl2.
Pt) (or cis-(PEt3)2Pt(OTf)2) with an excess of 10a in dichloro-
methane at rt (>80% yields).
moiety.24 Only one signal is observed in the 31P NMR
spectra, accompanied in the case of 11 and 13 by Pt satellite
peaks from the spin-spin 195Pt-31P coupling. Signals in 11
and 12 are shifted by ca. 5 and 11 ppm, respectively, related
to corresponding starting metallic salts (dpppM(OTf)2 (M =
Pd, Pt)), whereas the shift reaches 12 ppm for 13. These
values are comparable with those described for self-as-
sembled systems based on 4,40-bipyridyle ligands and the
same metal(II) triflates.25 The 19F NMR exhibits a single
signal at -79 ppm in all cases, which associated to vibration
bands at 1160 and 1130 cm-1 in the IR spectrum, are usual
values for triflate counterion.26
Complexes 11-13 have been characterized by multinuc-
lear NMR (1H, 31P, 19F) analyses in CD2Cl2. Chemical shifts
are gathered in Table 3, and NMR spectra of 13 (illustrative
example) are shown in Figure 2 (see also Figures SI-1 and SI-
2 in Supporting Information for 11 and 12). As expected for
symmetrical structures, only a simple set of signals is detected
in the 1H NMR spectra; in particular three signals are
observed for protons of the pyridine (HR and Hβ) and the
pyrrole moieties. HR and more particularly Hβ appear sig-
nificantly upfield shifted in 13 related to dppp complexes 11
and 12;23 this difference is ascribed to the shielding effect
provided by the dppp phenyl groups that sit over the pyridine
Ligand 10a can also react with enPd(NO3)2 in DMSO-d6,
to generate complex 14 (Scheme 7). Only 15 min are required
in this case. This complex shows a good solubility in DMSO,
(23) Ligand 10a, being insoluble in CD2Cl2, no direct comparison has
been possible between the free ligand and the corresponding complexes.
(24) Stang, P. J.; Cao, D. H.; Saito, S.; Arif, A. M. J. Am. Chem. Soc.
1995, 117, 6273.
(25) Stang, P. J.; Cao, D. H. J. Am. Chem. Soc. 1994, 116, 4981.
(26) Lawrence, G. A. Chem. Rev. 1986, 86, 17.
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FIGURE 3. (a) Stepwise formation of 11 monitored by UV-vis spectroscopy (mixture of 10a (5 ꢀ 10-5 mol L-1) in CH3CN with 0.5 equiv of
dpppPt(OTf)2). (b) Formation of the monosubstituted complex (mixture of 10a (5 ꢀ 10-5 mol L-1) in CH3CN with dpppPt(OTf)2 (0-1.2
equiv)).
SCHEME 7
and formation of 14 can be monitored by NMR (DMSO-d6)
(Figure SI-3 and Table SI-2 in Supporting Information).
Pyridine protons are significantly shifted in 14 (HR = 8.68
ppm ; Hβ = 7.79 ppm) relatively to free ligand 10a (HR =
8.56 ppm ; Hβ = 7.46 ppm). On the contrary, it is worth
noting that after heating enPt(NO3)2 with an excess of 10a at
100 °C in DMSO-d6 for 3 days, only a mixture of mono- and
disubstituted complexes could be obtained.
UV-vis spectroscopy has been used to probe the forma-
tion of complexes 11-13. Two cases can be identified. Direct
formation of the Pd complex 12 is observed upon addition of
0.5 equiv of dpppPd(OTf)2 to 10a (Figure SI-4 in Support-
ing Information). The absorption band at λmax = 334 nm
corresponding to free ligand 10a decreases progressively to
the benefit of a new one at 421 nm corresponding to complex
12. A different behavior is observed upon formation of the
Pt analogue 11 (Figure 3). Addition of 0.5 equiv of dpppPt-
(OTf)2 to ligand 10a is accompanied by decrease of the
band at 334 nm and the concomitent progressive appearance
of a new one at 397 nm. This band is attributed to the
displacement of only one triflate by a pyridine ligand on the
metal center. This band progressively red-shifts with time to
a new value at 421 nm (Figure 3a), assigned to complex 11.
An isosbestic point at 412 nm illustrates existence of only two
species in equilibrium in the solution, i.e., the monosubsti-
tuted complex (397 nm) and the target dimer 11 (421 nm).
This assignement is confirmed by an additional experiment:
when quick addition of dpppPt(OTf)2 (0-1.2 equiv) is car-
ried out on a solution of 10a, only one band appears, at 397
nm, which does not evolve anymore for more than 1 equiv
introduced, confirming the 1:1 stoichiometry (Figure 3b).
Therefore, whereas no intermediate could be observed at rt
upon formation of the Pd complex 12, the monosubstituted
intermediate could be observed for the Pt analogue 11. This
difference is directly correlated to the more energetically
demanding Pt-N bond related to the more labile Pd-N one.
In the case of the cis-(PEt3)2Pt(OTf)2, we observe the rapid
formation of the bis substituted complex 13 at 423 nm
(Figure SI-5 in Supporting Information); in addition, no
evolution of the spectrum is observed for more than 0.5 equiv
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FIGURE 4. Deconvoluted CV of (a) 11 (5 ꢀ 10-4 mol L-1); NBu4PF6 (10-1 mol L-1), v = 100 mV s-1, vs AgCl/Ag, CH3CN/CH2Cl2 (1/1), Pt;
(b) 10a (2.5 ꢀ 10-4 mol L-1) and 14 (4.5 ꢀ 10-4 mol L-1), NBu4PF6 (10-1 mol L-1), v = 100 mV s-1, DMF, Pt, Fc/Fcþ = 478 mV.
of cis-(PEt3)2Pt(OTf)2 (Figure SI-6 in Supporting Informa-
tion), which confirms the rapid formation of the 2:1 (10a/Pt)
complex.
one-electron oxidations of the two (MeS)2MPTTF into a
bis(cation-radical) and a bis(dication) successively. In the
case of 14, the CV could be run in DMF, a solvent in which
ligand 10a is also soluble. Deconvoluted voltammograms of
the free ligand and the complex are superimposed in
Figure 4b. In both cases, two reversible redox waves are
observed as expected (Table SI-4 in Supporting Information).
Similarity of both CV shapes illustrates the lack of any
detectable electrochemical interactions between MPTTF
units in the complex. A positive shift of E1ox and E2ox by
þ35 mV is observed for the complex compared to the free
ligand, accounting for a more difficult oxidation of the redox
unit once it is bound to the metal center. This behavior is
well-known in the field of redox-responsive ligands and has
been extensively illustrated with various types of TTF-based
ligands designed for electrochemical detection of cations.3
The fact that a positive shift is also observed for E2ox is an
indication that the metal is still bound at this potential,30
confirming the robustness of the complex and its ability to
generate an electrochemically stable hexacationic species.
Taking advantage of the robustness of the complexes, we
probed their ability to act as C60 receptors since electron-rich
receptors, such as those based on TTF derivatives, appear
attractive and several recent works depict complexation of
electron-poor fullerene by molecular architectures incorpor-
ating two or more electron-rich TTF analogues.22,31 In
We could not characterize any complex formation using
the p-cyanophenyl MPTTF derivative 10b. No reaction
occurs with dpppPd(OTf)2, whereas the solution instanta-
neously turns green upon addition of Pt(II) complexes
(dpppPt(OTf)2, cis-(PEt3)Pt(OTf)2), a color that is charac-
teristic of MPTTF oxidation. This is confirmed by a UV-vis
titration study, for which very similar spectra are observed
upon a progressive treatment of 10b with cis-(PEt3)2Pt(OTf)2
or with the NOSbF6 oxidizing agent (Figure SI-7 in Support-
ing Information).
It has been shown that metalla-assembled structures in-
volving dpppM(OTf)2 (M = Pt, Pd) are stable in a large
window of potentials.27,28 The three complexes 11-13 pre-
sent analogous cyclic voltammograms, which are character-
ized by occurrence of two well-defined reversible redox
systems (Figure 4a, Figure SI-8 and Table SI-3 in Supporting
Information). For each complex, no appearance of any
interaction between both electroactive units can be observed
from the deconvoluted CV. The two redox systems are well
resolved, indicating that both redox units are electrochemi-
cally independent.
Coulometric measurements have been performed on 13 by
thin layer cyclic voltammetry (TLCV), with ferrocene as
internal redox reference (Figure SI-9 in Supporting Informa-
tion). This technique has shown its efficiency for determining
coulometric data with TTF derivatives.29 Contrary to con-
ventional cyclic voltammetry, in TLCV the current is not
limited by the kinetics of mass transfer to the electrode, and
all of the material confined within the thin layer is involved in
the electrode reaction. Compound 13 shows the expected
well-defined two redox waves, indicating that both MPTTF
units behave independently. Importantly, comparison of
both MPTTF redox waves area with the one of ferrocene
used as an internal redox reference shows that two electrons
are exchanged at each redox processes. Therefore, the first
and second redox waves correspond to two simultaneous
particular, Martın et al. have described the synthesis of a
´
tweezer incorporating two large extended-TTF units, which
shows a good affinity for C60 (K = ca. 3 ꢀ 103 mol L-1 in
chlorobenzene).22b
The binding affinity of 13 for C60 was studied by UV-vi-
sible titration. Increasing amounts of C60 were added to a
solution of 13 in dichloromethane (Figure 5).
ꢀ
(30) (a) Dolder, S.; Liu, S. X.; Le Derf, F.; Salle, M.; Neels, A; Decurtins,
S. Org. Lett. 2007, 9, 3753–3756. (b) Balandier, J.-Y.; Belyasmine, A.; Salle,
ꢀ
M. Eur. J. Org. Chem. 2008, 269. (c) Benhaoua, C.; Mazari, M.; Mercier, N.;
ꢀ
Le Derf, F.; Salle, M. New J. Chem. 2008, 32, 913–916.
(31) (a) Nielsen, K. A.; Cho, W. S.; Sarova, G. H.; Petersen, B. M.; Bond,
A. D.; Becher, J.; Jensen, F.; Guldi, D. M.; Sessler, J. L.; Jeppesen, J. O.
Angew. Chem., Int. Ed. 2006, 45, 6848–6853. (b) Nielsen, K. A.; Martꢀın-
Gomis, L.; Sarova, G. H.; Sanguinet, L.; Gross, D. E.; Fernandez-Lazaro,
F.; Stein, P. C.; Levillain, E.; Sessler, J. L.; Guldi, D. M.; Sastre-Santos, A.;
€
(27) Wurthner, F.; Sautter, A.; Schmid, D.; Weber, P. J. A. Chem.;Eur.
J. 2001, 7, 894.
€
ꢀ ꢀ
Jeppesen, J. O. Tetrahedron 2008, 64, 8449–8463. (c) Fernandez, G.; Perez,
ꢀ
E. M.; Sanchez, L.; Martꢀın, N. Angew. Chem., Int. Ed. 2008, 47, 1094–1097.
ꢀ
(d) Perez, E. M.; Martꢀın, N. Chem. Soc. Rev. 2008, 37, 1512–1519.
(28) You, C. C.; Wurthner, F. J. Am. Chem. Soc. 2003, 125, 9716.
ꢀ
ꢁ
(29) Carlier, R.; Frere, P.; Salle, M.; Roncali, J.; Jubault, M.; Tallec, A.;
Gorgues, A. Adv. Mater. 1993, 5, 445.
1596 J. Org. Chem. Vol. 75, No. 5, 2010

Balandier et al.
JOCArticle
dimers. In the latter, the redox-active units behave as their
individual MPTTF components, without any detectable
intramolecular interaction by CV and TLCV studies. One
dimer presents a good affinity for electron-accepting C60.
This finding, obtained from a basic assembly (two perpendi-
cular electron-rich ligands linked to a metal corner), offers
appealing perspectives. First, these simple systems constitute
an interesting model, useful for a better understanding of the
self-assembly process occurring along the construction of
higher symmetry metalla-assembled systems (polygons and
polyhedra). Then, the recognition properties obtained with
these angular systems for C60 predict a good affinity of their
higher electron-rich homologues for fullerene derivatives.
The metal-assisted construction of self-assembled TTF-
based polygons and polyhedra is in due course.
FIGURE 5. (a) UV-vis titration of 13 (5 ꢀ 10-5 mol L-1, CH2Cl2)
with C60 (5 ꢀ 10-3 mol L-1, CS2).
Experimental Section
4-(Diethoxymethyl)-5-((cyanophen-4-ylimino)methyl)-1,3-dithiol-
2-thione 3b. To a solution of 4-formyl-5-(diethoxymethyl)-1,3-
dithiole-2-thione 2 (2.70 g, 10.2 mmol) in 200 mL of dry toluene
was added an excess of 4-aminobenzonitrile (3.62 g, 30.7 mmol),
and the medium was refluxed for 3 h with molecular sieves (4 A)
(reaction monitored by TLC CH2Cl2/cyclohexane 8/2 v/v). After
cooling, the medium was filtered, the molecular sieves were washed
with toluene, and the filtrate was concentrated under vacuum.
Purification by column chromatography over silica gel (CH2Cl2/
cyclohexane 8/2 v/v þ 1% triethylamine) afforded imine 3b (3.52 g,
9.69 mmol) as a yellow solid (yield = 95%). Mp = 153-156 °C. 1H
NMR (acetone-d6): 8.77 (s, 1H), 7.85 (d, 2H, J = 8.7 Hz), 7.41 (d,
2H, J= 8.7 Hz), 6.15 (s, 1H), 3.76 (m, 4H), 1.22 (t, 6H, J=7.2Hz).
13C NMR (acetone-d6): 212.2, 153.6, 152.8, 151.7, 139.5, 133.5,
122.1, 118.2, 110.2, 96.4, 61.9, 14.4. C16H16N2O2S3: MALDI-TOF:
Upon addition of C60, a decrease of the absorption band at
421 nm corresponding to 13 is observed and is accompanied
by a progressive increase of a new band at 575 nm assigned to
complex 13-C60. An isosbestic point at 475 nm indicates the
existence of two species in equilibrium in the solution, i.e.,
free ligand 13 and complex 13-C60. From the Benesi-
Hildebrand curve (Figure SI-10 in Supporting Information),
a 1:1 stoichiometry is found and an association constant of
log K = 3.15 is determined. At this stage, it is worth noting
that, though incorporating donor units devoid of any con-
cave fragments and presenting a smaller π-extension than ex-
TTF analogues,22b compound 13 exhibits a good affinity for
the spherical electron-poor C60. Such result partially diverges
from recent observations made with a tweezer incorporating
two parent TTF units (instead of MPTTF in 13), for which a
poor affinity was found for C60.32 Therefore, beside a favor-
able spatial distribution of the two orthogonal electron-rich
moieties that compensates for the lack of conformational
flexibility within the tweezer, additional recognition ele-
ments must be considered in 13 compared to the TTF
analogue.32 They presumably result from a combination of
(i) a greater π-extension involving heteroaromatic rings of
the MPTTF moieties and (ii) the presence of a metal ion
whose effect cannot be excluded, since it is known to
potentially have a strong influence on the binding ability of
the receptor, as demonstrated for instance with porphyrin-
based tweezers.33 To address this point, work is in due course
for designing new MPTTF-based tweezers devoid of any
assembling metal ion.
MHþ 365.05. IR (KBr): 2224, 1576, 1067 cm-1
.
4-(Diethoxymethyl)-5-((amino-4-pyridyl)methyl)-1,3-dithiol-
2-thione 5a. A solution of 4-formyl-5-(diethoxymethyl)-1,3-
dithiole-2-thione 2 (542 mg, 1.53 mmol) and iminophosphor-
ane 4 (404 mg, 1.53 mmol) in 150 mL of dry toluene was
refluxed under nitrogen for 12 h (until total consumption of
starting thione 2, TLC AcOEt/1% triethylamine). After cool-
ing, toluene was removed under vacuum, and the residue was
filtered over silica gel to procure a brown oil containing imine
3a and triphenylphosphine oxide. The mixture was then solu-
bilized in 300 mL of dry methanol, and NaBH4 (75 mg, 2.00
mmol) was added at room temperature. The medium was then
stirred for 15 min, and the solvent was evaporated. The residue
was dissolved in 300 mL of CH2Cl2 and washed with water. The
organic layer was dried over MgSO4, filtered, and concentrated
under vacuum. Purification of the residual oil by column
chromatography on silica gel (CH2Cl2/methanol 9/1 v/v þ
1% triethylamine) afforded amine 5a (366 mg, 1.07 mmol) as
a yellow solid (70% yield from 2). Mp = 154-156 °C. 1H NMR
(acetone-d6): 8.15 (dd, 2H, J = 1.6 Hz, J = 4.8 Hz), 6.65 (dd,
2H, J = 1.6 Hz, J = 4.8 Hz), 6.50 (t, 1H, J = 6.0 Hz), 5.84 (s,
1H), 4.56 (d, 2H, J = 6.0 Hz), 3.72 (m, 4H, J = 7.2 Hz), 1.23 (t,
6H, J = 7.2 Hz). 13C NMR (acetone-d6): 213.2, 153.7, 150.7,
145.0, 140.3, 108.6, 97.3, 62.6, 41.5, 15.3. C14H18N2O2S3:
MALDI TOF: Mþ• 342.00. IR (KBr): 1606, 1533, 1505,
Conclusion
A new general synthetic strategy to N-aryl-substituted
MPTTF derivatives is presented, including the case of in-
troduction of a metal-binding pyridyl group. Coordination
ability of the corresponding ligand is shown with cis-blocked
Pd(II) and Pt(II) salts, giving rise to the first examples of
self-assembled rigid and orthogonal electron-rich MPTTF
1324, 1044 cm-1
.
4-(Diethoxymethyl)-5-((amino-4-pyridyl)methyl)-1,3-dithiol-
2-one 50a. A solution of 4-formyl-5-(diethoxymethyl)-1,3-
dithiole-2-one 20 (1.80 g, 7.26 mmol) and iminophosphorane
4 (2.65 g, 7.5 mmol) in 150 mL of dry toluene was refluxed for 5
h under nitrogen. After cooling, the solvent was removed, and
the residual oil was chromatographied over silica gel (AcOEt/
1% de triethylamine) to give a brown oil containing imine 30a
ꢀ
ꢀ
ꢀ
(32) Perez, E. M.; Capodilupo, A. L.; Fernandez, G.; Sanchez, L.;
Viruela, P. M.; Viruela, R.; Ortı, E.; Bietti, M.; Martın, N. Chem. Commun.
2008, 4567–4569.
´
´
(33) (a) Yanagisawa, M.; Tashiro, K.; Yamasaki, M.; Aida, T. J. Am.
Chem. Soc. 2007, 129, 11912–11913. (b) Tashiro, K.; Aida, T. Chem. Soc.
Rev. 2007, 36, 189–197. (c) Sun, D.; Tham, F. S.; Reed, C. A.; Chaker, L.;
Boyd, P. D. W. J. Am. Chem. Soc. 2002, 124, 6604–6612.
J. Org. Chem. Vol. 75, No. 5, 2010 1597

Balandier et al.
JOCArticle
and triphenylphosphine oxide. This mixture was solubilized in
250 mL of dry methanol, and NaBH4 (303 mg, 8 mmol)
was added at room temperature. The medium was stirred for
15 min, and the solvent was removed under vacuum. The crude
product was dissolved in 300 mL of CH2Cl2 and washed with
water. The organic layer was dried over MgSO4 and filtered,
and the solvent evaporated in vacuo. Purification by column
chromatography over silica gel (CH2Cl2/methanol 9/1 v/v þ
1% triethylamine) afforded amine 50a (1.55 g, 4.79 mmol) as a
creamy oil (yield 66% from 20) that is sensitive to light. 1H
NMR (acetone-d6): 8.14 (dd, 4H, J = 1.2 Hz, J = 4.8 Hz), 6.65
(dd, 4H, J = 1.2 Hz, J = 4.8 Hz), 6.67 (m, 1H), 5.83 (s, 1H),
4.53 (d, 2H, J = 6.0 Hz), 3.70 (m, 4H, J = 7.2 Hz), 1.22 (t, 6H,
J = 7.2 Hz). 13C NMR (acetone-d6): 191.2, 154.0, 150.5, 134.0,
130.0, 108.6, 97.5, 62.6, 41.7, 15.3.
5-(p-cyanophenyl)-5H-1,3-dithiolo[4,5-c]pyrrole-2-one 60b. To
solution of 5-p-cyanophenyl-1,3-dithiolo[4,5-c]pyrrole-2-
a
thione 6b (690 mg, 2.52 mmol) in a mixture of dichloromethane
(300 mL)/glacial acetic acid (12 mL) was added in one portion
Hg(OAc)2 (1.61 g, 5.04 mmol) (TLC CH2Cl2/cyclohexane 7/3 v/
v), and the medium was stirred at room temperature for 20 min.
After filtration over hyflosupercel, the filtrate was washed with a
saturated solution of sodium hydrogenocarbonate until pH =
7. The organic layer was dried over MgSO4 and filtered, and the
solvent was evaporated in vacuo. Purification by column chro-
matography on silica gel (CH2Cl2) procured the corresponding
one 60b (350 mg, 1.36 mmol) as a white solid (yield = 54%).
1
Mp = 243-244 °C. H NMR (CD2Cl2): 7.76 (d, 2H, J = 9.1
Hz), 7.49 (d, 2H, J = 9.1 Hz), 7.22 (s, 2H). 13C NMR (CD2Cl2):
194.9, 142.6, 134.0, 120.3, 118.0, 116.8, 112.0, 109.9. C12H6N2O-
S2 (DSQ): Mþ• 257.90. IR (KBr): 2225, 1701, 1636, 1604, 1517,
N-(4-Pyridyl)-5H-1,3-dithiolo[4,5-c]pyrrole-2-thione 6a. To a
solution of amine 5a (270 mg, 0.79 mmol) in 250 mL of CH2Cl2
was added 20.0 g of dry Amberlyst A15 resin. The medium was
stirred vigorously at room temperature under nitrogen (reaction
monitored by TLC CH2Cl2/methanol 9/1 v/v; the reaction is
finished when the medium becomes colorless). Triethylamine
(30 mL) was added to desorb the desired compound from the
resin (pH must be basic). Afterward, the resin was removed by
filtration and washed with CH2Cl2, and the filtrate was con-
centrated. Cold methanol (30 mL) was then added to the brown
residue. Thione 6a was isolated by filtration and washed with
additional cold methanol (20 mL). After being dried, thione 6a
(156 mg, 0.63 mmol) was produced as a gold solid (yield =
79%). Mp = 248-250 °C (decomp). 1H NMR (DMSO-d6): 8.65
(dd, 2H, J = 1.6 Hz, J = 4.8 Hz), 7.92 (s, 1H), 7.68 (dd, 2H, J =
1.6 Hz, J = 4.8 Hz). 13C NMR (DMSO-d6): 219.8, 151.5, 145.0,
125.7, 113.3, 111.1. C10H6N2S3: Mþ (calcd) 249.96931; Mþ•
1389, 1311 cm-1
.
5-(p-Bromophenyl)-5H-1,3-dithiolo[4,5-c]pyrrole-2-thione 6c.
To a solution of thione 2 (800 mg, 3.03 mmol) in 100 mL of
dry toluene were added an excess of 4-bromoaniline (626 mg,
3.64 mmol) and 2 g of molecular sieves (4 A). The medium was
refluxed for 2 h (reaction monitored by TLC CH2Cl2/cyclohex-
ane 1/1 v/v). After cooling, the solvent was removed under
vacuum. The residue was dissolved in 100 mL of dry methanol,
and 114 mg (3.01 mmol) of NaBH4 were added (reduction
monitored by TLC CH2Cl2/cyclohexane 1/1 v/v). The medium
was stirred during 1 h at room temperature, and then methanol
was removed under vacuum. After dissolution of the residue in
200 mL of dichloromethane, the organic layer was washed three
times with water, dried over MgSO4, and filtered. Amberlyst
A15 dry resin (30 g) was added to the filtrate, and the mixture
was stirred for 20 min (TLC CH2Cl2/cyclohexane 1/1 v/v). The
resin was then removed by filtration and washed with 250 mL of
CH2Cl2, and the solvent was evaporated. Purification by col-
umn chromatography on silica gel (CH2Cl2/cyclohexane 1/1
v/v) provided thione 6c (370 mg, 1.13 mmol) as a yellow solid
(yield = 37%). Mp = 244-245 °C. 1H NMR (DMSO-d6): 7.71
(d, 2H, J = 8.7 Hz), 7.69 (s, 2H), 7.57 (d, 2H, J = 8.7 Hz). 13C
NMR (DMSO-d6): 219.9, 138.9, 133.2, 124.9, 122.5, 119.7,
112.2. C11H6NBrS3: Mþ• (calcd) 326.8846, Mþ• (found) 326.8835.
(found) 249.9687. IR (KBr): 1594, 1503, 1313, 1063 cm-1
.
N-(4-Pyridyl)-5H-1,3-dithiolo[4,5-c]pyrrole-2-one 60a. To a
solution of amine 50a (1.30 g, 4.01 mmol) in 130 mL of CH2Cl2
was added 55.0 g of Amberlyst A15 dry resin. The reaction was
stirred at room temperature, and the course of the reaction
followed by TLC (CH2Cl2/methanol 9/1 v/v). Triethylamine (60
mL) was slowly added. The resin was removed by filtration and
washed with CH2Cl2. The filtrate was washed twice by water,
dried over MgSO4, filtered, and concentrated under vacuum.
Purification by column chromatography on silica gel (CH2Cl2/
methanol 9/1 v/v) provided N-pyridyl-1,3-dithiolo[4,5-c]pyr-
role-2-one 60a (374 mg, 1.6 mmol) as a creamy solid (yield =
40%). Mp = 198-199 °C. 1H NMR (DMSO-d6): 8.64 (dd, 2H,
J = 1.6 Hz, J = 4.8 Hz), 7.99 (s, 2H), 7.66 (dd, 2H, J = 1.6 Hz,
J = 4.8 Hz). 13C NMR (DMSO-d6): 195.3, 151.4, 144.8, 115.6,
112.8, 112.7. C10H6N2OS2 (EI): Mþ• 233.80. IR (KBr): 1720,
IR (KBr): 1494, 1037, 863, 821, 761 cm-1
5-Tolyl-5H-1,3-dithiolo[4,5-c]pyrrole-2-thione 6d. To a solu-
tion of 4-formyl-5-(diethoxymethyl)-1,3-dithiole-2-thione
.
2
(100 mg, 0.38 mmol) in 20 mL of dry toluene were added an
excess of p-toluidine (1.00 g, 9.33 mmol) and 2 g of molecular
sieves (4 A). The medium was refluxed for 4 days (TLC CH2Cl2).
After cooling, the solvent was removed. The residue was dis-
solved in a mixture CH2Cl2 (10 mL)/EtOH (30 mL), and 300 mg
of NaBH4 was added. The medium were then stirred for 4 h, and
solvents were removed under vacuum. The residue was dissolved
in 100 mL of dichloromethane, washed three times with water,
dried over magnesium sulfate, and filtered. To the filtrate was
added 1 g of Amberlyst A15 dry resin, and the medium was
stirred for 30 min (TLC CH2Cl2/cyclohexane 1/1 v/v). The resin
was removed by filtration and washed with 150 mL of dichlor-
omethane, and the filtrate was concentrated. Purification by
column chromatography over silica gel (CH2Cl2) afforded
thione 6d (65 mg, 0.25 mmol) as a yellow solid (yield = 66%).
Mp = 196-198 °C. 1H NMR (DMSO-d6): 7.63 (s, 2H), 7.46 (d,
2H, J = 8.7 Hz), 7.31 (d, 2H, J = 8.7 Hz), 2.33 (s, 3H). 13C
NMR (DMSO-d6): 219.8, 137.4, 136.8, 130.7, 124.2, 120.5, 20.8.
C12H9NS3: Mþ• (calcd) 262.9897, Mþ• (found) 262.9908. IR
1638, 1594, 1514, 1392, 1309 cm-1
.
5-(p-cyanophenyl)-5H-1,3-dithiolo[4,5-c]pyrrole-2-thione 6b.
To a solution of imine 3b (880 mg, 2.41 mmol) in 150 mL of a
THF/methanol mixture (1/1 v/v) was added 100 mg of NaBH4
at room temperature (TLC CH2Cl2/cyclohexane 8/2 v/v). After
20 min stirring, the solvent was evaporated, and the residue was
dissolved in 250 mL of CH2Cl2. The organic layer was washed
three times with 300 mL of water, dried over MgSO4, and
filtered. To this filtrate was added 45 g of Amberlyst A15 dry
resin, and the medium was stirred vigorously for 20 min
(TLC CH2Cl2/cyclohexane 6/4 v/v). The amberlyst resin was
removed by filtration and washed with 250 mL of dichlo-
romethane, and the filtrate was concentrated under vacuum.
Purification by column chromatography over silica gel (CH2Cl2/
cyclohexane 6/4 v/v) provided thione 6b (415 mg, 1.52 mmol) as a
yellow solid (yield = 63%). Mp = 290 °C (decomp). 1H NMR
(DMSO-d6): 8.00 (d, 2H, J = 8.7 Hz), 7.82 (d, 2H, J = 8.7 Hz),
7.83 (s, 2H). 13C NMR (DMSO-d6): 219.6, 142.2, 134.3, 125.4,
120.2, 118.4, 111.6, 108.9. C12H6N2S3: Mþ• (calcd) 273.9693 ; Mþ•
(KBr): 1511, 1480, 1036 cm-1
.
5-(p-Iodophenyl)-5H-1,3-dithiolo[4,5-c]pyrrole-2-thione 6e. To a
solution of 4-formyl-5-(diethoxymethyl)-1,3-dithiole-2-thione 2
(1.50 g, 5.68 mmol) in 250 mL of dry toluene were added an excess
of 4-iodoaniline (1.10 g, 6.00 mmol) and 4 g of molecular sieves
(4 A). The medium was refluxed for 4 h (TLC CH2Cl2/cyclohexane
(found) 273.9688. IR (KBr): 2225, 1605, 1517, 1314, 1058 cm-1
.
1598 J. Org. Chem. Vol. 75, No. 5, 2010

Balandier et al.
JOCArticle
1/1 v/v). After cooling, the solvent was removed. The residue was
dissolved in 100 mL of dry methanol, and 215 mg of NaBH4 was
added. The medium was then stirred for 15 min, and the solvent
was removed under vacuum. The residue was dissolved in 250 mL
of dichloromethane, washed three times with water, dried over
magnesium sulfate, and filtered. To the filtrate was added 40 g of
Amberlyst A15 dry resin, and the medium was stirred for 20 min
(TLC CH2Cl2/cyclohexane 1/1 v/v). The resin was removed by
filtration and washed with 250 mL of dichloromethane, and the
filtrate was evaporated to dryness. The solid residue was suspended
in 25 mL of acetonitrile, isolated by filtration and washed with
acetonitrile (150 mL) and diethyl ether (20 mL). Thione 6e was
obtained (737 mg, 1.96 mmol) as a yellow crystalline solid
(yield = 34%). Mp = 249-250 °C (decomp). 1H NMR
(DMSO-d6): 7.86 (d, 2H, J = 8.3 Hz), 7.69 (s, 2H), 7.43 (d, 2H,
J = 8.3 Hz). 13C NMR (DMSO-d6): 219.9, 139.3, 139.0, 124.9,
122.6, 112.0, 92.3. C11H6IN2S3 (DSQ): Mþ• 374.70. IR (KBr):
(110 mg, 0.25 mmol) was obtained as a yellow solid (yield =
25%). Mp > 260 °C. 1H NMR (DMSO-d6): 7.93 (d, 2H, J = 8.7
Hz), 7.73 (d, 2H, J = 8.7 Hz), 7.65 (s, 2H), 2.44 (s, 6H).
C17H12N2S6: Mþ• (calcd) 435.9325; Mþ• (found) 435.9314. IR
(KBr): 2223, 1604, 1518, 1385, 1314, 826, 749 cm-1
.
Complex [10a2Ptdppp]2þ 2(OTf)- 11. To a solution of
3
dpppPt(OTf)2 (15.8 mg, 17 μmol) in 6 mL of dichloromethane,
was added in one portion 10a (16 mg, 40 μmol). The medium was
stirred for 12 h. After filtration, to remove the excess of 10a
which did not react, the filtrate was concentrated in a vacuum
and the final complex 11 (25 mg, 14 μmol) was precipitated by
addition of petroleum ether and isolated by filtration (orange
1
solid, yield = 82%). Mp = 189-194 °C (decomp). H NMR
(CD2Cl2): 8.87 (d, 4H, J = 6.0 Hz), 7.67 (m, 8H), 7.36 (m, 12H),
6.87 (d, 4H, J = 6.0 Hz), 6.80 (s, 4H), 3.23 (m, 4H), 2.39 (bs,
12H), 2.24 (m, 2H). 31P NMR (CD2Cl2): -14.7 (JPt-P = 3084
Hz). 19F NMR (CD2Cl2): -79. C58H50F3N4O3P2PdS13: ESI-
FTICR (calcd) 1490.8721 [11 - OTf]þ; (found) 1490.8789. IR
(KBr): 3137, 2923, 2859, 1611, 1516, 1436, 1399, 1311, 1276,
1495, 1063, 756 cm-1
.
N-(4-(4-Pyridylethynyl)phenyl)-5H-1,3-dithiolo[4,5-c]pyrrole-
2-thione 8. To a solution of thione 6e (108 mg, 0.29 mmol) in
10 mL of freshly distilled THF were added 4-ethynylpyridyne 7
(39 mg, 0.38 mmol), 24 mg (0.13 mmol) of copper(I) iodide, and
69 mg (0.005 mmol) of Pd(PPh3)4. The medium was degassed for
30 min under nitrogen, and 0.42 mL of triethylamine was added.
Afterward, the reaction was heated at 60 °C overnight, under
nitrogen. After filtration, the solvent was removed, and the
residue was purified by column chromatography over silica gel
(CH2Cl2/AcOEt 1/1 v/v). The solvent was removed to dryness,
and the brown residue was dissolved in minimum of CH2Cl2.
Petroleum ether was then added to precipitate thione 8 (46 mg,
0.13 mmol) as a yellow solid (yield = 45%) which was isolated
by filtration. Mp = 235-238 °C (decomp). 1H NMR (DMSO-
d6): 8.64 (d, 2H, J = 4.3 Hz), 7.79 (s, 2H), 7.76 (d, 2H, J = 8.7
Hz), 7.74 (d, 2H, J = 8.7 Hz), 7.54 (d, 2H, J = 4.3 Hz). 13C
NMR (DMSO-d6): 219.6, 150.0, 139.6, 133.5, 130.0, 125.4,
124.8, 120.1, 119.3, 111.6, 92.8, 87.5. C18H10N2S3: Mþ• (calcd)
350.0006, Mþ• (found) 350.0006. IR (KBr): 3131, 3024, 2221,
1591, 1518, 1480, 1310, 1054 cm-1
2-[4,5-Bis(dimethylsulfanyl)-1,3-dithiol-2-ylidene]-N-(4-pyridyl)-
1,3-dithiolo[4,5-c]pyrrole 10a. A mixture of compound 60a (270 mg,
1.15 mmol) and thione 9 (261 mg, 1.15 mmol) suspended in 12 mL
of freshly distilled triethylphosphite was heated at 120 °C. After 30
min, an additional 1 equiv of thione 9 (261 mg, 1.15 mmol) was
added, and the medium was stirred for 4 h at 120 °C (precipitation
of a yellow solid). After cooling, 30 mL of methanol were added.
The solid in suspension was isolated by filtration and washed
successively with methanol, dichloromethane, acetone, and diethyl
ether. Compound 10a (128 mg, 0.31 mmol) was obtained as a gold
yellow solid (yield = 27%). Mp > 260 °C. 1H NMR (DMSO-d6):
8.56 (dd, 2H, J = 1.6 Hz, J = 4.8 Hz), 7.71 (s, 2H), 7.46 (dd, 2H,
J = 1.6 Hz, J = 4.8 Hz), 2.44 (s, 6H). C15H12N2S6: Mþ• (calcd)
411.9325; Mþ• (found) 411.9307. MHþ (calcd) 412.9403; MHþ
(found) 412.9405. Anal. Calcd: C, 43.66; H, 2.93; N, 6.79. Found:
C, 43.95; H, 2.83; N, 6.77.
1256, 1226, 1160, 1031 cm-1
.
Complex [10a2Pddppp]2þ 2(OTf)- 12. To a solution of
3
dpppPd(OTf)2 (17.3 mg, 21 μmol) in 6 mL of dichloromethane
was added in one portion 10a (20 mg, 47 μmol). The medium was
stirred for 12 h. After filtration, to remove the excess of 10a that
did not react, the filtrate was concentrated in a vacuum, and
complex 12 (33.4 mg, 20 μmol) was precipitated by addition of
petroleum ether and isolated by filtration (orange solid, yield =
96%). Mp = 195-201 °C (decomp). 1H NMR (CD2Cl2): 8.83
(d, 4H, J = 6.0 Hz), 7.63 (m, 8H), 7.35 (m, 12H), 6.85 (d, 4H,
J = 6.0 Hz), 6.80 (s, 4H), 3.13 (m, 4H), 2.39 (bs, 12H), 2.24 (m,
2H). 31P NMR (CD2Cl2): 6.83. 19F NMR (CD2Cl2): -79.
C58H50F3N4O3P2PdS13: ESI-FTICR [12
1579.9324; (found) 1579.9426. IR (KBr): 3137, 2929, 2859, 1614,
-
OTf]þ (calcd)
1518, 1437, 1402, 1311, 1257, 1161, 1031 cm-1
.
Complex [10a2Pt(PEt3)2]2þ 2(OTf-) 13. To a solution of cis-
3
(PEt3)2Pt(OTf)2 (21.8 mg, 30 μmol) in 6 mL of dichloromethane
was added in one portion 10a (27 mg, 66 μmol). The medium was
stirred of 12 h. After filtration, to remove the excess of 10a that
did not react, the filtrate was concentrated in a vacuum, and the
final complex13 (37.3 mg, 24 μmol) was precipitated by addition
of diethyl ether and isolated by filtration (orange solid, yield =
1
80%). Mp = 183-188 °C. H NMR (CD2Cl2): 9.10 (d, 4H,
J = 5.6 Hz), 7.40 (d, 4H, J = 5.6 Hz), 7.04 (s, 4H), 2.40 (bs,
12H), 1.78 (m, 12H), 1.31 (m, 18H). 31P NMR (CD2Cl2): -2.5
(JPt-P = 3103 Hz). 19F NMR (CD2Cl2): -79. C43H54F3N4O3-
P2PtS13Cl: ESI-FTICR [13 - OTf]þ Cl• (calcd) 1438.9366;
3
(found) 1438.9324. IR (KBr): 3137, 1613, 1516, 1402, 1311,
.
1259, 1159, 1032 cm-1
Acknowledgment. The authors gratefully acknowledge Dr.
C. Afonso (SM3P platform, Paris) and Pr. D. Rondeau
for their help duringESI-FTICRanalyses and Dr. E. Levillain
for his assistance in TLCV analyses. This work has
been financially supported by ANR-PNANO (TTF-Based
Nanomat).
2-[4,5-Bis(dimethylsulfanyl)-1,3-dithiol-2-ylidene]-N-p-cyano-
phenyl-1,3-dithiolo[4,5-c]pyrrole 10b. A mixture of 60b (253 mg,
0.98 mmol) and thione 9 (221.5 mg, 0.98 mmol) suspended in 10
mL of freshly distilled triethylphosphite was heated at 120 °C.
After 30 min, an additional 1 equiv of thione 9 (221.5 mg, 0.98
mmol) was added and the medium was stirred for 4 additionnal
hours at 120 °C (precipitation of a yellow solid). After cooling,
30 mL of methanol was added. The solid in suspension was then
isolated by filtration and washed successively with methanol,
dichloromethane, acetone and diethyl ether. Compound 10b
Supporting Information Available: Full spectroscopic data
for new compounds (UV-vis and 1H, 13C, 31P, and 19F NMR
spectra), as well as cyclic voltammograms related to the com-
pounds under study. X-ray data in CIF format for compounds
5a, 6a, 6b, and 6c. This material is available free of charge via the
Internet at http://pubs.acs.org.
J. Org. Chem. Vol. 75, No. 5, 2010 1599