Light-induced synthesis of π-extended tetrathiafulvalenes incorporating ferrocenes: An efficient route for the synthesis of electron-donor materials

Article abstract of DOI:10.1055/s-0028-1087974

A new method for the synthesis of π-extended tetrathiafulvalenes was developed. The protocol is based on the exposure of 1,4-dithiafulvenes to sunlight or UV light at ambient temperature. In the resulting chalcogenofulvalenes the 1,3-dithiole ring systems are separated by conjugated spacers. Extended TTF analogues are obtained by insertion of linear π-conjugated spacers (C=C-C=C) of increasing dimensions between the two 1,4-dithiafulvenyl moieties. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-0028-1087974

1000
PAPER
Light-Induced Synthesis of p-Extended Tetrathiafulvalenes Incorporating
Ferrocenes: An Efficient Route for the Synthesis of Electron-Donor Materials
L
a
ight-Induced Syn
b
thesis of
p
-E
d
xtended
T
etr
e
athiafulval
l
enes In
w
corporating Ferroc
a
ene
s
reth A. O. Sarhan,*a,b Carsten Bolma
Institute of Organic Chemistry, RWTH Aachen University, 52056 Aachen, Germany
Chemistry Department, Faculty of Science, Assiut University, Assiut 71516, Egypt
E-mail: elwareth@aun.edu.eg; E-mail: Carsten.Bolm@RWTH-Aachen.de
b
Received 6 October 2008; revised 20 October 2008
properties revealed that the extended tetrathiafulvalenes
are strong electron donors, which exhibit small on-site
Coulomb repulsion owing to the extended p-conjugation.7
Furthermore, vinylogous TTFs with bulky groups at the
Abstract: A new method for the synthesis of p-extended tetrathia-
fulvalenes was developed. The protocol is based on the exposure of
1,4-dithiafulvenes to sunlight or UV light at ambient temperature.
In the resulting chalcogenofulvalenes the 1,3-dithiole ring systems
are separated by conjugated spacers. Extended TTF analogues are vinylic positions afforded conductors with uncommon
obtained by insertion of linear p-conjugated spacers (C=C–C=C) of
multidimensional structures and, due to the Coulomb re-
pulsion in the dicationic states as a result of the extended
p-conjugation, stable dication salts with unusual crystal
structures were obtained.8
increasing dimensions between the two 1,4-dithiafulvenyl moieties.
Key words: Wittig–Horner reaction, 1,4-dithiafulvenes, ferrocene,
oxidative dimerization, sunlight, p-extended tetrathiafulvalenes, or-
ganic conductors, electrochemical properties, charge-transfer com-
plex
Ueno and co-workers synthesized the first ferrocene-
containing tetrathiafulvalene and its vinylogues 3.9 Their
charge-transfer complexes with TCNQ and DDQ were
also described. Since then a few more reports have ap-
peared, which deal with the electrochemical properties
and charge-transfer complexes of tetrathiafulvalenes
bearing ferrocene moieties.10
After the discovery that tetrathiafulvalene (TTF, 1a) can
act as a molecular conductor,1 modifications of TTF in-
volving the replacement of the four hydrogen atoms at po-
sitions 4,5 and 4¢,5¢ have been extensively studied
(Figure 1).2 With the finding of the metallic behavior of
the TTF–TCNQ complex, synthetic approaches towards
tetrathiafulvalenes and tetraselenafulvalenes gained sig-
nificant attention and various electrically (super)conduct-
ing salts and charge-transfer (CT) complexes were
prepared. Furthermore, the charge-transfer process from
tetrathiafulvalene to tetracyanoquinodimethane (TCNQ)
between adjacent stacks has been extensively investigat-
ed.3
R
S
R
S
S
R
S
R
2 (ETTH)
R
Me
S
S
R
Fe
R
R1
R2
R3
R4
S
X
X
X
X
S
Me
3 [R = H, Me, (CH=CH)2]
R
X = S, Se
Figure 1 Tetrathiafulvalenes [for 1a (TTF), X = S and R1–R4 = H]
and tetraselenafulvalenes (1b, X = Se)
Figure 2 p-Extended tetrathiafulvalenes
Here, we describe an environmentally benign approach
towards the synthesis of new electron-donor tetrathiaful-
valene vinylogues using 1,4-dithiafulvenes as building
blocks.
Various TTF derivatives can be prepared in a single step
in low to moderate yields.4 The replacement of the central
ethylenic linkage (C=C) by larger conjugated spacers
(C=C–C=C)n leads to extended TTFs such as ETTH (2)
with enhanced intra- and interchain contacts (Figure 2),
due to the lowering of their charge density and increased
p-interactions.5 Also from these extended derivatives,
conducting salts have been prepared.6 Studies of their
Starting point for the synthesis of the tetrachalcogenoful-
valene derivatives was a Wittig–Horner reaction with
dimethyl 1,3-benzodithiol-2-ylphosphonate (4), which
was prepared following the previously reported method.11
After deprotonation of 4 with butyllithium at –78 °C in an-
hydrous tetrahydrofuran under argon, the resulting anion
was allowed to react with aldehydes 5a–e to give the cor-
responding 1,4-dithiafulvenes 6a–e (Scheme 1).12
SYNTHESIS 2009, No. 6, pp 1000–1006
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Advanced online publication: 24.02.2009
DOI: 10.1055/s-0028-1087974; Art ID: Z22608SS
© Georg Thieme Verlag Stuttgart · New York

PAPER
Light-Induced Synthesis of p-Extended Tetrathiafulvalenes Incorporating Ferrocenes
1001
H
S
spectroscopy showed that 6c had unexpectedly dimerized
S
n-BuLi, THF, –78 °C
H
to form the extended tetrathiafulvalene 7c. Encouraged by
this result the behavior of the other 1,4-dithiafulvenes was
studied (Table 1). As noticed also by Bryce and co-work-
ers,12 only the ferrocenyl-substituted substrates underwent
rapid dimerization, and thus, 7c (50%) and 7d (23%) were
obtained in conversions of 6c and 6d, respectively. Oxida-
tion of 6d with iodine in dichloromethane13 followed by
the reduction of the resulting dication with sodium thio-
sulfate (Na2S2O4) afforded 7d in 60% yield. The aryl-sub-
stituted dithiafulvenes 6a, 6b, and 6e were more stable.
Thus, neither stirring them in chloroform or dichlo-
romethane solutions in a reactor under UV light at room
temperature for 4–12 hours nor treating them with hydro-
gen chloride (as oxidizing agent) in anhydrous diethyl
ether12a or using the iodine/dichloromethane method13 led
to significant amounts of the corresponding dimers. At
best, only traces of 7b could be identified by mass spec-
trometry {[M]+ 542 (12%)} upon boiling 1,4-dithiaful-
vene 6b in an iodine/dichloromethane mixture.
then ArCHO (5a–e),
S
S
PO(OMe)2
Ar
r.t., 12–18 h
6a–e
4
a: Ar = Ph
b: Ar = 4-MeOC6H4
c: Ar = Fc
d: Ar = 4-(Fc)C6H4
e: Ar = 4-BrC6H4
Fc =
Fe
Scheme 1 Synthesis of thiafulvenes 6a–e
Attempts to synthesize extended TTFs 7 from 6a–e using
either electrochemical oxidation or treatment with hydro-
gen chloride and/or hydrogen bromide in an organic sol-
vent followed by reduction with zinc to dimerize the
intermediately formed radical cation of 6 led to low yields
of 7 and decomposition of the 1,4-dithiafulvenes.11d Un-
expected nitrofulvene 8 was obtained (as yellow crystals)
in considerable amounts when the oxidation was tried
with a mixture of acetic acid and nitric acid (Figure 3).
The molecular ion peak in the mass spectra of 8 ([M – 1],
286) confirmed its structures. Refluxing 6a in acetic acid
in the presence of concentrated sulfuric acid gave no prod-
uct and only the starting material was recovered.
Table 1 Syntheses of p-Extended Tetrathiafulvalenes 7 by Induced
Dimerizations
Ar
S
S
method
a, b, c, or d
H
S
S
S
S
Ar
S
S
Ar
NO2
S
S
Ar
S
S
7a–d
6a–d
Ar
Product
7a
Ara
Ph
Yield (%)
Methodb
a–d
a, c
7
8
–
Figure 3 p-Extended tetrathiafulvalenes and nitrofulvene 8
7b
4-MeOC6H4
Fc
trace
50
7c
a
Consequently, the strategy for the preparation of extended
tetrathiafulvalenes had to be changed. Formylation of
dithiafulvenes 6a–e according to the reported procedure13
using oxalyl chloride in anhydrous N,N-dimethylform-
amide at 0 °C and subsequent alkaline hydrolysis afforded
the corresponding products 9a–e in high yields. Wittig–
Horner-type reactions of 9a–e with phosphonate ester 4
gave the extended tetrathiafulvalene 10a–e in excellent
yields (Scheme 2).
7d
4-(Fc)C6H4
4-BrC6H4
23/60
–
a/c
7e
a, c
a Fc = ferrocenyl.
b Method a: sunlight; b: UV light; c: I2, CH2Cl2; d: HCl, Et2O.
Following the same strategy established for the dimeriza-
tions of 1,4-dithiafulvenes 6a–e, the conversions of
tetrathiafulvalenes 10a–e were attempted. Those com-
pounds possessed highly active CH protons on the conju-
gated system [>C=C(Ar)–CH=C<], and their dimer
formation was expected to lead to chalcogenofulvalenes
11a–e (Table 2). Confirming this hypothesis, dimers 11b–
d were formed upon exposure to sunlight albeit the yields
remained moderate ranging from 37% to 45%. Use of UV
light led to substrate decomposition and from the complex
product mixtures none of the targeted compounds could
be isolated. Oxidative dimerization of 10d using iodine/
dichloromethane gave 11d in 28% yield.
Ar
S
S
(COCl)2, DMF, 0 °C
6a–e
then NaOH, H2O,
r.t., 16 h
CHO
9a–e
Ar
S
S
n-BuLi, THF, –78 °C
4
S
then 9a–e, 25 °C,
12–18 h
S
10a–e
Scheme 2 Synthesis of extended tetrathiafulvalenes 10a–e
In conclusion, we prepared various ferrocene-containing
p-extended tetrathiafulvalenes by dimerization of thiaful-
venes using a simple protocol involving sunlight. The
electrochemical properties and conductivity measure-
Upon standing a darkening of the red color of 1,4-dithia-
fulvene 6c was noticed and H NMR spectroscopy re-
1
vealed that the ethylenic CH proton disappeared with
time. To our delight, mass spectrometry and 13C NMR
Synthesis 2009, No. 6, 1000–1006 © Thieme Stuttgart · New York

1002
A. A. O. Sarhan, C. Bolm
PAPER
Table 2 Syntheses of p-Extended Tetrathiafulvalenes 11 by Induced Dimerizations
Ar
Ar
S
S
S
method
a, b, c, or d
S
S
S
S
S
S
S
10a–d
S
Ar
S
11a–d
Product
Ara
Yield (%)
trace
Methodb
11a
Ph
a–d
11b
4-MeOC6H4
Fc
39
a
11c
37
a
11d
4-(Fc)C6H4
4-BrC6H4
45/0/28/0
trace
a/b/c/d
a, c
11e
a Fc = ferrocenyl.
b Method a: sunlight; b: UV light; c: I2, CH2Cl2; d: HCl, Et2O.
13C NMR (CDCl3): d = 137.6, 136.2, 128.3, 126.4, 126.1, 122.3,
121.6 (Carom, CHarom, thiafulvalene-C=CH), 112.7 (thiafulvalene-
C=CH), 83.4 (Cferrocene), 69.8, 69.0, 68.1 (CHferrocene).
ments are now being investigated and those results will be
published in due course.
MS (FAB): m/z (%) = 350 ([M]+, 90).
All Wittig–Horner reactions were carried out under argon using
standard Schlenk techniques. THF was distilled from Na/benzophe-
none ketyl radical. Hexane, CH2Cl2, and CHCl3 for column chroma-
Anal. Calcd for C18H14FeS2 (350.2756): C, 61.72; H, 4.03; S, 18.31.
Found: C, 61.51; H, 4.22; S, 18.61.
1
tography were distilled before use. H and 13C NMR spectra were
2-[4-(Ferrocenyl)benzylidene]-1,3-benzodithiole (6d)
Orange crystals; yield: 85%; mp (dec).
recorded on a Varian Gemini 300 spectrometer (300 MHz and 75
MHz respectively) and on a Varian Inova 400 spectrometer (400
MHz and 100 MHz respectively); TMS was used as an internal stan-
dard. Phosphonate ester 4 was prepared according to the method
previously reported in literature.11 Except 4-(ferrocenyl)benzalde-
hyde, which was synthesized following a previously reported meth-
od,14 all aldehydes were commercially available and used without
further purification. The analytical data for compounds 6a and 6b
were in agreement with those previously reported.11
IR (KBr): 3093 (m), 3050 (w), 2987 (w), 1604 (m), 1575 (s), 1546
(s), 1521 (s), 1448 (s), 1284 (s), 1083 (s), 1033 (s), 1002 (m), 935
(s), 887 (s), 844 (s), 819 (s), 744 cm–1 (s).
1H NMR (CDCl3): d = 7.48 (d, J = 8.5 Hz, 2 Harom), 7.26 (d, J = 8.5
Hz, 4 Harom), 7.12–7.10 (m, 2 Harom), 6.54 (s, 1 H, CH=C), 4.65 (t,
J = 2 Hz, 2 Hferrocene), 4.32 (t, J = 2 Hz, 2 Hferrocene), 4.04 (s,
5 Hferrocene).
1,4-Dithiafulvenes 6a–e; General Procedure
13C NMR (CDCl3): d = 137.1, 136.5, 134.8, 134.2, 131.3, 127.0,
A sample of the 1,3-benzdithiol-2-ylphosphonate 4 (0.786 g, 3
mmol) was stirred in anhyd THF (50 mL) under a stream of argon
at –78 °C. A soln 1.6 M of BuLi (2.3 mL) was added portionwise
and the mixture was stirred for 15 min. A soln of the aldehyde 5 (3
mmol) in anhyd THF (50 mL) was added portionwise over 15 min.
The temperature of the reaction was raised to r.t., and the mixture
was stirred overnight. Then the solvent was removed under vacuum
and the residue washed with H2O and extracted with CHCl3. The ex-
tracts were dried (MgSO4) and the crude product was chromato-
graphed (silica gel, CHCl3–hexane, 1:2) to give the corresponding
product 6a–e in high yields. The analytical data for compounds 6a
and 6b were in satisfactory agreement with those reported in the lit-
erature.11d
126.1, 126.0, 125.6, 121.7, 120.9, 114.7, 114.7 (Carom, CHarom,
thiafulvalene-C=CH), 85.0 (Cferrocene), 69.6, 69.0, 66.4 (CHferrocene).
MS (EI): m/z (%) = 425 ([M – 1], 100), 426 ([M]+, 41).
Anal. Calcd for C24H18FeS2 (426.2756): C, 67.61; H, 4.26. Found:
C, 67.49; H, 4.15.
2-(4-Bromobenzylidene)-1,3-benzodithiole (6e)
Colorless crystals (EtOH); yield: 70%; mp 189.5–190 °C.
IR (KBr): 3050 (m), 2982 (w), 2918 (w), 1643 (s), 1549 (s), 1478
(s), 1431 (s), 1387 (s), 1332 (w), 1260 (w), 1187 (m), 1117 (s), 1068
(m), 931 (m), 831 (s), 738 (s), 670 cm–1 (m).
1H NMR (CDCl3): d = 7.47 (d, J = 8.5 Hz, 2 Harom), 7.27–7.18 (m,
4 Harom), 7.13–7.11 (m, 2 Harom), 6.48 (s, 1 H, CH=C).
13C NMR (CDCl3): d = 135.4, 131.5, 128.4, 126.1, 125.7, 121.7,
121.0, 119.4, 113.2 (Carom, CHarom, thiafulvalene-C=CH).
MS (EI): m/z (%) = 321 ([M]+, 100).
2-(Ferrocenylmethylene)-1,3-benzodithiole (6c)
Orange red crystals; yield: 71%; mp 154–155 °C.
IR (KBr): 3091 (m), 2994 (w), 1589 (s), 1448 (s), 1430 (s), 1407 (s),
1292 (m), 1259 (m), 1124 (m), 1101 (m), 1049 (m), 1029 (m), 998
(s), 809 (s), 744 cm–1 (s).
1H NMR (CDCl3): d = 7.24 (m, 1 Harom), 7.17 (m, 1 Harom), 7.08 (m,
2 Harom), 6.16 (s, 1 H, CH=C), 4.42 (t, J = 2 Hz, 2 Hferrocene), 4.23 (t,
J = 2 Hz, 2 Hferrocene), 4.17 (s, 5 Hferrocene).
Anal. Calcd for C14H9BrS2 (321.2553): C, 52.34; H, 2.82. Found: C,
52.06; H, 2.85.
Synthesis 2009, No. 6, 1000–1006 © Thieme Stuttgart · New York

PAPER
Light-Induced Synthesis of p-Extended Tetrathiafulvalenes Incorporating Ferrocenes
1003
2-[Nitro(phenyl)methylene]-1,3-benzodithiole (8)
2-(1,3-Benzodithiol-2-ylidene)-2-(ferrocenyl)acetaldehyde (9c)
Red crystals; yield: 71%; mp 147–148 °C.
To a sample of dithiafulvene 6a (60 mg, 0.25 mmol) in stirred hot
AcOH (10 mL), concd HNO3 (32 mg, 0.5 mmol) was added, and the
mixture kept at ca. 100 °C for 5–10 min. The color turned to orange
red and the mixture was stirred for an additional 10 min at r.t. and
monitored (TLC). After 10 min no starting material was left in the
mixture. H2O (25 mL) was added, and the yellow precipitate thus
formed was collected by filtration and chromatographed (CH2Cl2)
to give the product as yellow crystals; yield: 35%.
IR (KBr): 3094 (m), 3010 (s), 2920 (s), 2847 (m), 1632 (s), 1493 (s),
1426 (s), 1378 (s), 1272 (s), 1213 (s), 1164 (w), 1112 (s), 1048 (s),
999 (m), 931 (m), 824 (s), 752 (s), 665 cm–1 (m).
1H NMR (CDCl3): d = 9.96 (s, 1 H, CHO), 7.58–7.57 (m, 1 Harom),
7.51–7.49 (m, 1 Harom), 7.31–7.28 (m, 2 Harom), 4.55 (t, J = 1.5 Hz,
2 Hferrocene), 4.36 (t, J = 1.5 Hz, 2 Hferrocene), 4.21 (s, 5 Hferrocene).
13C NMR (CDCl3): d = 186.3 (CHO), 154.8, 138.5 (C=CS2), 132.9,
126.5, 126.4, 122.6, 121.6, 118.0 (Carom, CH), 84.2 (Cferrocene), 69.3,
68.3, 67.6 (CHferrocene).
1H NMR (CDCl3): d = 7.68–7.65 (m, 1 Harom), 7.58–7.50 (m, 4
H
arom), 7.45–7.30 (m, 4 Harom).
13C NMR (CDCl3): d = 130.4 (thiafulvalene, >C=C), 130.3, 129.6
(Carom), 128.8, 127.2, 127.1, 123.1 (CHarom), 121.9 (>C=CNO2).
MS (DIP): m/z (%) = 378 ([M]+, 100).
Anal. Calcd for C19H14FeOS2 (378.2889): C, 60.33; H, 3.73. Found:
C, 60.44; H, 3.89.
MS (EI): m/z (%) = 286 ([M – 1], 87), 288 ([M + 1], 14), 240 (M –
NO2], 100).
Anal. Calcd for C14H9NO2S2 (287.3568): C, 58.52; H, 3.16; N, 4.87.
Found: C, 59.06; H, 3.67, N; 4.02.
2-(1,3-Benzodithiol-2-ylidene)-2-[4-(ferrocenyl)phenyl]acetal-
dehyde (9d)
Red crystals; yield: 51%; mp 188.5–189 °C.
2-Aryl-2-(1,3-benzodithiol-2-ylidene)acetaldehydes 9a–e; Gen-
eral Procedure
IR (KBr): 3057 (w), 2925 (m), 2815 (m), 1526 (s), 1458 (s), 1382
(s), 1264 (s), 1101 (s), 937 (m), 819 (s), 738 cm–1 (s).
1H NMR (CDCl3): d = 9.5 (d, J = 3 Hz, 1 H, CHO), 7.61–7.60 (dd,
J = 3, 5.5 Hz, 1 Harom), 7.55–7.54 (d, J = 7.5 Hz, 2 Harom), 7.46–7.45
(d, J = 7.5 Hz, 1 Harom), 7.36–7.25 (m, 4 Harom), 4.75 (s, 2 Hferrocene),
4.42 (s, 2 Hferrocene), 4.14 (s, 5 Hferrocene).
13C NMR (CDCl3): d = 184.8 (CHO), 158.9, 139.7 (C=CS2), 138.4,
134.9, 132.5 (Carom), 128.7, 126.9, 126.7, 126.5, 122.8, 122.8, 121.6
(CHarom), 78.8 (Cferrocene), 70.3, 69.9, 67.0 (CHferrocene).
To anhyd DMF (25 mL) under stream of argon at 0 °C was added
dropwise oxalyl chloride (0.3 mL, 3.45 mmol) and the mixture
stirred for 15 min. After this time, 6 (2.28 mmol) was added and the
mixture warmed to 20 °C and stirred overnight. The mixture was
quenched with aq 1 M NaOH (75 mL), precipitating a deep yellow
to red solid. This product was collected by filtration and washed
with H2O (50 mL). The solid product was dissolved in CH2Cl2,
washed with H2O; the organic phase was separated, dried (MgSO4),
and evaporated under reduced pressure. The residue was chromato-
graphed (silica gel, CH2Cl2) to afford products 9a–e.
MS (EI): m/z (%) = 454 ([M]+, 100).
Anal. Calcd for C25H18FeOS2 (454.3848): C, 66.08; H, 3.99. Found:
C, 65.23; H, 4.01.
2-(1,3-Benzodithiol-2-ylidene)-2-phenylacetaldehyde (9a)
Yellow crystals (EtOH); yield: 76%; mp 97–98 °C.
2-(1,3-Benzodithiol-2-ylidene)-2-(4-bromophenyl)acetalde-
hyde (9e)
Dark yellow crystals; yield: 97%; mp 173–173.5 °C.
IR (KBr): 3058 (s), 2928 (s), 2830 (s), 1695 (s), 1627 (s), 1558 (s),
1499 (s), 1459 (s), 1424 (s), 1382 (s), 1251 (s), 1096 (s), 926 (m),
854 (m), 745 (s), 701 cm–1 (s).
1H NMR (CDCl3): d = 9.45 (s, 1 H, CHO), 7.61–7.60 (m, 1 Harom),
IR (KBr): 3055 (m), 2920 (m), 2808 (s), 1694 (s), 1638 (s), 1556 (s),
1495 (s), 1438 (s), 1380 (s), 1268 (s), 1176 (m), 1074 (s), 1008 (m),
934 (m), 869 (s), 816 (s), 741 (s), 670 cm–1 (s).
7.58–7.56 (m, 1 Harom), 7.52–7.38 (m, 5 Harom), 7.33–7.24 (m, 2
Harom).
1H NMR (CDCl3): d = 9.42 (s, 1 H, CHO), 7.65–7.60 (m, 3 Harom),
13C NMR (CDCl3): d = 184.7 (CHO), 159.3, 138.3, 137.4 (C=CS2),
132.4, 129.3, 128.8, 128.4, 126.6, 126.5, 122.9, 122.8, 121.6 (Carom
CH).
7.47–7.44 (m, 1 Harom), 7.36–7.27 (m, 4 Harom).
,
13C NMR (CDCl3): d = 184.1 (CO), 138.2, 136.2 (C=CS2), 132.5,
130.5, 126.8 (Carom), 126.7, 122.9, 122.4, 121.7.
MS (EI): m/z (%) = 269 ([M – 1], 100), 271 ([M + 1], 23).
MS (EI): m/z (%) = 349 ([M]+, 100).
Anal. Calcd for C15H10OS2 (270.3693): C, 66.63; H, 3.73. Found: C,
66.43; H, 4.09.
Anal. Calcd for C15H9BrOS2 (349.2654): C, 51.58; H, 2.60. Found:
C, 51.36; H, 2.70.
2-(1,3-Benzodithiol-2-ylidene)-2-(4-methoxyphenyl)acetalde-
hyde (9b)
Yellow crystals; yield: 91%; mp 123.5–124.5 °C.
p-Extended Tetrathiafulvalenes 10a–e; General Procedure
To a stirred soln of the Wittig–Horner reagent 4 (1.0 mmol) in an-
hyd THF (50 mL) under argon atmosphere 1.6 M BuLi in hexane
was added at –78 °C and the reaction allowed to stir at this temper-
ature for 30 min. A soln of aldehyde 9 (1.0 mmol) in anhyd THF
was then added dropwise and the reaction allowed to warm to 20 °C
and stirred overnight. The solvent was evaporated under vacuum
and the residue was washed with H2O, extracted with CH2Cl2, and
the organic phase was separated, washed with H2O, dried (MgSO4),
and evaporated. The solid residue was chromatographed (silica gel,
CH2Cl2–hexane, 1:3) to give the targeted p-extended tetrathiaful-
valenes 10a–e.
IR (KBr): 3093 (m), 2848 (m), 1635 (s), 1562 (s), 1492 (s), 1452 (s),
1427 (s), 1376 (s), 1265 (s), 1114 (s), 1047 (s), 1002 (s), 831 (s), 802
(s), 736 cm–1 (s).
1H NMR (CDCl3): d = 9.43 (s, 1 H, CHO), 7.58 (dd, J = 3, 8 Hz, 1
Harom), 7.43–7.41 (m, 1 Harom), 7.37–7.34 (m, 2 Harom), 7.32–7.27
(m, 2 Harom), 7.03–7.01 (m, 2 Harom), 3.86 (s, 3 H, OCH3).
13C NMR (CDCl3): d = 184.9 (CHO), 159.6, 158.9, 136.4, 132.4,
130.2 (Carom, C=CS2), 129.7, 126.6, 126.5, 122.8, 122.6, 121.6,
114.7 (Carom), 55.4 (OCH3).
MS: m/z (%) = 300 (M+, 100).
2,2¢-(1-Phenylethane-1,2-diylidene)bis(1,3-benzodithiole) (10a)
Yellow crystals; yield: 68%; mp 185.5–186 °C.
Anal. Calcd for C16H12O2S2 (300.3953): C, 63.97; H, 4.03. Found:
C, 63.38; H, 4.12.
Synthesis 2009, No. 6, 1000–1006 © Thieme Stuttgart · New York

1004
A. A. O. Sarhan, C. Bolm
PAPER
IR (KBr): 3104 (m), 3051 (w), 2961 (w), 2924 (m), 2842 (w), 1641
(s), 1558 (s), 1505 (s), 1432 (s), 1383 (s), 1320 (s), 1253 (s), 1154
(s), 1112 (s), 1062 (s), 926 (s), 807 (s), 739 (s), 691 cm–1 (s).
1H NMR (CDCl3): d = 7.47–7.35 (m, 4 Harom), 7.23 (m, 1 Harom),
7.22–7.19 (m, 4 Harom), 7.13–6.89 (m, 4 Harom), 6.21 (s, 1 H, CH=C).
13C NMR (CDCl3): d = 137.6, 137.6 (C2, C2¢, C=CS2), 136.4,
136.0, 134.6, 132.7, 131.3, 125.3 (Carom, C=CH), 129.9, 129.1,
MS (EI): m/z (%) = 590 ([M]+, 100).
Anal. Calcd for C32H22FeS4 (590.6221): C, 65.07; H, 3.75. Found:
C, 64.97; H, 3.96.
2,2¢-[1-(4-Bromophenyl)ethane-1,2-diylidene]bis(1,3-ben-
zodithiole) (10e)
Yellow crystals; yield: 66%; mp 206.5–207.5 °C.
128.3, 125.7, 125.5, 124.7, 121.5, 121.4, 121.4, 120.8 (CHarom
CH=C), 112.5 (CH).
MS (EI): m/z (%) = 406 ([M]+, 100).
,
IR (KBr): 3058 (s), 2928 (s), 2804 (m), 1652 (s), 1557 (s), 1507 (s),
1472 (s), 1433 (s), 1387 (s), 1258 (m), 1161 (m), 1116 (s), 1063 (s),
1009 (s), 927 (s), 819 (s), 740 (s), 675 (m), 603 cm–1 (s).
1H NMR (CDCl3): d = 7.59–7.55 (m, 2 Harom), 7.29–7.21 (m, 3
Anal. Calcd for C22H14S4 (406.6066): C, 64.99; H, 3.47. Found: C,
64.64; H, 3.52.
Harom), 7.16–6.97 (m, 7 Harom), 6.17 (s, 1 H, CH=C).
13C NMR (CDCl3): d = 136.5, 136.2, 134.6, 133.3 (C2, C2¢, C=CS2,
arom), 132.3, 131.6 (CHarom), 127.7, 125.9, 125.7, 125.6, 125.4,
2,2¢-[1-(4-Methoxyphenyl)ethane-1,2-diylidene]bis(1,3-ben-
zodithiole) (10b)
C
122.3, 121.6, 120.9, 112.1 (CHarom, CH=C).
Yellow crystals; yield: 89%; mp 187–187.5 °C.
MS (EI): m/z (%) = 485 ([M]+, 100).
IR (KBr): 3047 (m), 2947 (m), 2828 (m), 1603 (s), 1565 (s), 1513
(s), 1440 (s), 1383 (s), 1320 (s), 1293 (s), 1246 (s), 1171 (s), 1115
(s), 1027 (s), 927 (s), 828 (s), 739 (s), 674 (s), 606 cm–1 (s).
Anal. Calcd for C22H13BrS4 (485.5026): C, 54.43; H, 2.70. Found:
C, 54.14; H, 2.76%
1H NMR (CDCl3): d = 7.33–7.23 (m, 4 Harom), 7.23–7.06 (m, 4
Harom), 7.05–6.96 (m, 4 Harom), 6.23 (s, 1 H, CH=C), 3.90 (s, 3 H,
OCH3).
1,2-Diaryl-1,2-bis(1,3-benzodithiol-2-ylidene)ethanes 7c,d and
2,2¢,2¢¢,2¢¢¢-(1,4-diarylbutane-1,2,3,4-tetraylidene)tetrakis(1,3-
benzodithioles) 11b–d; General Procedures
Method a: A sample of the dithiafulvene 6 (0.1 mmol) in CHCl3 (20
mL) was stirred at r.t. under sunlight for 3–18 h. The soln was con-
centrated under vacuum and the residue was chromatographed (sil-
ica gel, hexane–CH2Cl2) to give the corresponding p-extended
tetrathiafulvalenes (Tables 1 and 2).
13C NMR (CDCl3): d = 159.65 (Carom–O), 137.9, 136.6, 136.3,
134.7, 131.5, 125.9, 125.7 (C2, C2¢, C=CS2, Carom), 125.6, 125.5,
121.6, 121.5, 121.0, 114.6 (CHarom, CH=C), 55.5 (OCH3).
MS (EI): m/z (%) = 406 (M+, 100).
Anal. Calcd for C23H16OS4 (436.6325): C, 63.27; H, 3.69. Found: C,
63.20; H, 3.73.
Method b: A sample of the dithiafulvene 6 or 10 (0.1 mmol) in
CH2Cl2 (20 mL) was stirred in a UV reactor at r.t. under UV irradi-
ation for 3–18 h. The soln was concentrated under vacuum and the
residue was chromatographed (silica gel, hexane–CH2Cl2) to afford
the corresponding p-extended tetrathiafulvalenes (Tables 1 and 2).
2,2¢-[1-(Ferrocenyl)ethane-1,2-diylidene]bis(1,3-benzodithiole)
(10c)
Red crystals; yield: 61%; mp 94–95 °C.
Method c: To a soln of the dithiafulvene 6a,b,d,e, 10a,d,e (100 mg)
in CH2Cl2 (20 mL) under a stream of argon, I2 (3 mmol) was added
and the mixture was heated to reflux for 8 h. Then, excess Na2S2O4
(0.5 g) was added. The mixture was refluxed overnight and allowed
to reach r.t. After filtration of the suspension, the filtrate was
washed with H2O (2 × 50 mL) and dried (MgSO4); the solvent was
removed under vacuum and the extended TTFs 7b,d and 11a,d,e
were purified by column chromatography (silica gel, hexane–
CH2Cl2).
IR (KBr): 3056 (s), 2923 (s), 2851 (m), 1642 (s), 1539 (s), 1441 (s),
1383 (s), 1262 (s), 1187 (m), 116 (s), 1031 (s), 997 (s), 814 (s), 738
(s), 675 cm–1 (s).
1H NMR (CDCl3): d = 7.30–7.28 (m, 1 Harom), 7.24–7.20 (m, 2
Harom), 7.15–7.13 (m, 1 Harom), 7.10–7.03 (m, 4 Harom), 6.18 (s, 1 H,
CH=C), 4.56 (t, J = 2 Hz, 2 Hferrocene), 4.27 (t, J = 2 Hz, 2 Hferrocene),
4.23 (s, 5 Hferrocene).
13C NMR (CDCl3): d = 137.2, 136.8, 136.2, 136.3, 135.5, 128.5,
125.5 (C2, C2¢, C=CS2, Carom), 125.5, 125.5, 125.3, 121.7, 121.5,
121.3, 121.2, 119.5, 114.7 (CHarom, CH=C), 83.8 (Cferrocene), 69.2,
68.3, 67.4 (CHferrocene).
Method d: To a stirred soln of the dithiafulvene (0.10 mmol) in an-
hyd Et2O (25 mL) under argon at r.t. was added anhyd HCl (0.1 mL
in anhyd Et2O) and the mixture was stirred for 24 h. The solvent was
evaporated and the residue chromatographed (silica gel, hexane–
CH2Cl2) to afford the corresponding chalcogenofulvalenes 7 and 11
(Tables 1 and 2).
MS (EI): m/z (%) = 513 ([M – 1], 100), 514 ([M]+, 49).
Anal. Calcd for C26H18FeS4 (514.5261): C, 60.69; H, 3.53. Found:
C, 60.46; H, 3.70.
1,2-Bis(1,3-benzodithiol-2-ylidene)-1,2-bis(ferrocenyl)ethane
(7c)
Dark red crystals; yield: 50% (method a); mp (dec).
2,2¢-{1-[4-(Ferrocenyl)phenyl]ethane-1,2-diylidene}bis(1,3-
benzodithiole) (10d)
Orange crystals; yield: 96%; mp (dec).
IR (KBr): 3055 (w), 2968 (w), 2814 (w), 1636 (s), 1534 (s), 1440
(s), 1383 (s), 1253 (s), 1159 (m), 1108 (s), 1043 (m), 999 (m), 924
(s), 821 (s), 734 (s), 676 cm–1 (m).
1H NMR (CDCl3): d = 7.34 (m, 2 Harom), 7.22–7.20 (m, 2 Harom),
7.13–7.09 (m, 4 Harom), 4.55 (m, 2 Hferrocene), 4.45 (m, 2 Hferrocene),
4.28 (s, 10 Hferrocene), 4.21 (m, 4 Hferrocene).
13C NMR (CDCl3): d = 137.5, 136.4, 130.7, 123.6 (C1, C2, 2
C=CS2, Carom), 125.5, 125.1, 122.5, 121.2 (CHarom), 83.9 (Cferrocene),
69.4, 68.0, 67.9, 67.7, 65.9 (CHferrocene).
MS (EI): m/z (%) = 698 ([M]+, 100).
MS (FAB): m/z (%) = 698 ([M]+, 100).
IR (KBr): 3052 (s), 2926 (m), 2859 (m), 1633 (s), 1566 (s), 1522 (s),
1441 (s), 1383 (s), 1278 (s), 1159 (s), 1113 (s), 1060 (s), 1007 (s),
925 (s), 881 (m), 815 (s), 739 (s), 676 (m), 608 cm–1 (s).
1H NMR (CDCl3): d = 7.57–7.54 (m, 2 Harom), 7.30–7.24 (m, 4
Harom), 7.15–7.10 (m, 4 Harom), 7.09–6.89 (m, 2 Harom), 6.25 (s, 1 H,
CH=C), 4.75 (t, J = 2 Hz, 2 Hferrocene), 4.37 (t, J = 2 Hz, 2 Hferrocene),
4.04 (s, 5 Hferrocene).
13C NMR (CDCl3): d = 139.5, 137.7, 136.6, 136.1, 134.8, 134.6,
132.5, 130.5, 130.1 (C2, C2¢, C=CS2, Carom), 126.3, 125.7, 125.5,
125.4, 124.7, 122.8, 121.5, 121.4, 121.3, 120.8, 112.5 (CHarom
,
CH=C), 84.1 (Cferrocene), 70.0, 69.4, 66.4 (CHferrocene).
Synthesis 2009, No. 6, 1000–1006 © Thieme Stuttgart · New York

PAPER
Light-Induced Synthesis of p-Extended Tetrathiafulvalenes Incorporating Ferrocenes
1005
Anal. Calcd for C36H26Fe2S4 (698.5314): C, 61.90; H, 3.75. Found:
C, 62.60; H, 4.60%
MS (EI): m/z (%) = 648 ([M – 530], 28), 590 ([M – 589], 100).
Anal. Calcd for C64H42Fe2S8 (1179.2283): C, 65.19; H, 3.59. Found:
C, 65.35; H, 3.27.
1,2-Bis(1,3-benzodithiol-2-ylidene)-1,2-bis[4-(ferrocenyl)phe-
nyl)]ethane (7d)
Chromatography (silica gel, hexane–CHCl3, 1:1) gave orange crys-
tals; yield: 23% (method a), 60% (method c).
Acknowledgment
We thank the Fonds der Chemischen Industrie and gratefully
acknowledge the Alexander von Humboldt Stiftung for supporting
this work by a Georg-Forster fellowship for A.A.O.S.
IR (CHCl3): 3091 (m), 3013 (m), 2924 (m), 2854 (m), 1603 (w),
1571 (m), 1528 (s), 1441 (s), 1383 (m), 1281w (s), 1215 (s), 1107
(s), 1073 (s), 927 (w), 887 (w), 823 (s), 756 cm–1 (s).
1H NMR (CDCl3): d = 7.49 (m, 8 Harom), 7.24–7.17 (m, 4 Harom),
7.12–7.06 (m, 4 Harom), 4.61 (s, 4 Hferrocene), 4.30 (s, 4 Hferrocene), 4.05
(s, 10 Hferrocene).
13C NMR (CDCl3): d = 139.6, 138.1, 136.7, 136.3, 126.3 (C1, C2, 2
C=CS2, Carom), 128.3, 126.9, 125.7, 125.5, 121.6, 121.2 (CHarom),
85.3 (Cferrocene), 69.7, 69.0, 66.5 (CHferrocene).
References
(1) (a) Wudl, F.; Smith, G. M.; Hufnagel, E. G. J. Chem. Soc.,
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Lett. 1970, 11, 2633. (c) Sarhan, A. A. O.; Murakami, M.;
Izumi, T. J. Heterocycl. Chem. 2002, 39, 1.
MS (FAB): m/z (%) = 850 ([M]+, 8).
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Fänghanel, E. Sulfur Rep. 1993, 14, 245. (c) Sarhan, A. A.
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Yamagishi, F. G.; Garito, A. F.; Heeger, A. J. Solid State
Commun. 1973, 12, 1125.
Anal. Calcd for C48H34Fe2S4 (850.7336): C, 67.77; H, 4.03. Found:
C, 66.98; H, 4.12.
2,2¢,2¢¢,2¢¢¢-[1,4-Bis(4-methoxyphenyl)butane-1,2,3,4-tetraylid-
ene]tetrakis(1,3-benzodithiole) (11b)
Chromatography (silica gel, hexane–CH2Cl2, 1:1); yellow crystals;
yield: 40% (method a); mp >300 °C.
(4) (a) Coustumer, G.; Moller, Y. J. Chem. Soc., Chem.
Commun. 1980, 38. (b) Yoshida, Z.; Kawase, T.; Awaji, H.;
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1983, 24, 3469. (c) Khanous, A.; Gorgues, A.; Jubault, M.
Synth. Met. 1991, 41-43, 2327.
IR (KBr): 3051 (m), 2923 (m), 2838 (w), 1602 (s), 1566 (m), 1506
(s), 1453 (s), 1385 (s), 1297 (m), 1245 (s), 1175 (s), 1118, 1026 (s),
908 (s), 826 (s), 734 (s), 676 cm–1 (m).
1H NMR (CDCl3): d = 7.35 (m, 4 Harom), 7.25 (m, 8 Harom), 7.10 (m,
8 Harom), 6.78 (m, 4 Harom), 3.79 (s, 6 H, OCH3).
(5) (a) Bryce, M. R.; Fleckenstein, E.; Hünig, S. J. Chem. Soc.,
Perkin Trans. 2 1990, 1777. (b) Sallè, M.; Belyasmine, A.;
Gorgues, A.; Jubault, M.; Soya, N. Tetrahedron Lett. 1991,
32, 2897. (c) Sugimoto, T.; Awaji, H.; Sugimoto, I.; Misaki,
Y.; Kawase, T.; Yoncda, S.; Yoshida, Z. Chem. Mater. 1989,
1, 535. (d) Hansen, T. K.; Lakshmikantham, M. V.; Cava, U.
P.; Becher, J. J. Chem. Soc., Perkin Trans. 2 1991, 2873.
(e) Belyasmine, A.; Gorgues, A.; Jubault, M.; Duguay, G.
Synth. Met. 1991, 42, 2323. (f) Sallè, M.; Gorgues, A.;
Jubault, M.; Gouriou, Y. Synth. Met. 1991, 42, 2575.
(g) Benahmed, A. S.; Frère, P.; Belyasmine, A.; Malik, K.
M. A.; Hursthouse, M. B.; Moore, A. J.; Bryce, M. R.;
Jubault, M.; Gorgues, A. Tetrahedron Lett. 1993, 34, 2131.
(6) (a) Balavoine, G. G. A.; Dosneau, G.; Fillebeen-Khan, T. J.
Organomet. Chem. 1991, 412, 381. (b) Rinehart, K. L. Jr.;
Motz, K. L.; Moon, S. J. Am. Chem. Soc. 1957, 79, 2749.
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(d) Woodward, R. B.; Rosenblum, M.; Whiting, M. C. J. Am.
Chem. Soc. 1952, 74, 3458.
13C NMR (CDCl3): d = 137.7, 128.7, 125.8, 125.7, 121.8, 121.3,
120.8, 114.4, 114.1 (C1, C2, 2 C=CS2, Carom, CHarom), 55.4 (OCH3).
MS (EI): m/z (%) = 870 ([M]+, dec.).
MS (FAB): m/z (%) = 870 ([M]+, 12).
Anal. Calcd for C46H30O2S8 (871.2492): C, 63.41; H, 3.47. Found:
C, 63.22; H, 3.99.
2,2¢,2¢¢,2¢¢¢-[1,4-Bis(ferrocenyl)butane-1,2,3,4-tetraylidene]tet-
rakis(1,3-benzodithiole) (11c)
Chromatography (silica gel, hexane–CHCl3, 2:1); dark red crystals;
yield: 37% (method a); mp (dec).
IR (CHCl3): 3021 (m), 2922 (m), 2854 (w), 1542 (m), 1437 (s),
1384 (s), 1262 (w), 1215 (s), 1091 (s), 923 (w), 756 (s), 670 cm–1 (s).
1H NMR (CDCl3): d = 7.61–7.56 (m, 4 Harom), 7.36–7.30 (m, 4
Harom), 7.24 (m, 4 Harom), 7.04 (m, 4 Harom), 4.89 (m, 2 Hferrocene), 4.77
(m, 4 Hferrocene), 4.50 (t, 2 Hferrocene), 4.26 (s, 10 Hferrocene).
(7) Roncoli, J. J. Mater. Chem. 1997, 7, 2307.
(8) Yamashita, Y.; Tomura, M. J. Solid State Chem. 2002, 168,
MS (ESI): m/z (%) = 1094 ([M + 67], 6), 566 ([M – 461], 100).
Anal. Calcd for C52H34Fe2S8 (1027.0364): C, 60.81; H, 3.34. Found:
C, 60.46; H, 3.52.
427.
(9) Ueno, Y.; Sano, H.; Okawara, M. J. Chem. Soc., Chem.
Commun. 1980, 28.
2,2¢,2¢¢,2¢¢¢-{1,4-Bis[4-(ferrocenyl)phenyl]butane-1,2,3,4-tetra-
ylidene}tetrakis(1,3-benzodithiole) (11d)
Chromatography (silica gel, hexane–CH2Cl2, 3:1); dark red crys-
tals; yield: 45% (method a), 0% (method b); 28% (method c); mp
164–165 °C.
(10) (a) Togni, A.; Hobi, M.; Rihs, G.; Rist, G.; Albinati, A.;
Zanello, P.; Zech, D.; Keller, H. Organometallics 1994, 13,
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Fujiwara, K.; Hoshino, M. Chem. Lett. 1975, 1099.
(d) Akiba, K.; Ishikawa, K.; Inamoto, N. Bull. Chem. Soc.
Jpn. 1978, 51, 2674.
IR (KBr): 3060 (m), 3011 (s), 2997 (s), 2858 (s), 1670 (s), 1574 (m),
1527 (m), 1444 (s), 1381 (m), 1262 (m), 1215 (s), 1116 (s), 1013 (s),
925 (m), 872 (s), 823 (s), 755 (s), 670 cm–1 (m).
1H NMR (CDCl3): d = 7.55 (m, 4 Harom), 7.30 (m, 8 Harom), 7.20–6.9
(m, 12 Harom), 4.74 (t, J = 3 Hz, 4 Hferrocene), 4.39 (t, J = 3 Hz,
4 Hferrocene), 4.06 (s, 10 Hferrocene).
Synthesis 2009, No. 6, 1000–1006 © Thieme Stuttgart · New York

1006
A. A. O. Sarhan, C. Bolm
PAPER
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S.; Goldenberg, L. M.; Howard, J. A. K. J. Chem. Soc.,
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P.; Lorcy, D. J. Org. Chem. 2007, 72, 4655.
(14) Misaki, Y.; Matsumura, Y.; Sugimoto, T.; Yoshida, Z.-I.
Tetrahedron Lett. 1989, 30, 5289.
Synthesis 2009, No. 6, 1000–1006 © Thieme Stuttgart · New York