Preparation of new tetrathiafulvalene (TTF) derivatives with two functional groups at symmetrical positions: 2,6-diiodo-3,7-diphenyl-TTF, 2,6- bis[2-(trimethylsilyl)-ethynyl]-3,7-diphenyl-TTF, and 2,6-diethynyl-3,7- diphenyl-TTF

Article abstract of DOI:10.1055/s-1998-2033

Lithiation of diphenyltetrathiafulvalene (diphenyl-TTF) followed by treatment with perfluorohexyl iodide selectively gives a symmetrically diiodized product, 2,6-diiodo-3,7-diphenyl-TTF, from which 2,6-bis[2- (trimethylsilyl)ethynyl]-3,7-diphenyl-TTF and

Full text of DOI:10.1055/s-1998-2033

March 1998
SYNTHESIS
259
Preparation of New Tetrathiafulvalene (TTF) Derivatives with Two Functional Groups
at Symmetrical Positions: 2,6-Diiodo-3,7-diphenyl-TTF, 2,6-Bis[2-(trimethylsilyl)-
ethynyl]-3,7-diphenyl-TTF, and 2,6-Diethynyl-3,7-diphenyl-TTF
Takahisa Shimizu, Take-aki Koizumi, Isao Yamaguchi, Kohtaro Osakada, Takakazu Yamamoto*
Research Laboratory of Resources Utilization, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226, Japan
Fax +81(45)924-5276
Received 18 June 1997; revised 9 September 1997
Abstract: Lithiation of diphenyltetrathiafulvalene (diphenyl-
TTF) followed by treatment with perfluorohexyl iodide selectively
gives a symmetrically diiodized product, 2,6-diiodo-3,7-diphenyl-
TTF, from which 2,6-bis[2-(trimethylsilyl)ethynyl]-3,7-diphenyl-
TTF and 2,6-diethynyl-3,7-diphenyl-TTF are derived.
Key words: tetrathiafulvalene, symmetrical diiodide, diacetylenic
compounds, bis(trimethylsilyl)ethynyl, diethynyl
Scheme 1
tempts have so far not been successful (presumably due to
competitive lithiation of the methyl group).
Tetrathiafulvalene (TTF) and its derivatives are the sub-
ject of recent interest. They have highly electron-donating
properties1 and form electrically conducting adducts with
electron acceptors. In order to develop the chemistry of
TTF and its derivatives, introduction of various reactive
functional group(s) is desirable. Especially, introduction
of two functional groups (preferably at symmetrical posi-
tions and with a functional group in each 5-membered
ring) is desirable to obtain starting materials for various
purposes (e.g., for polycondensation and molecular
architecture2). However, examples of introduction of two
functionalgroupstoTTFatsymmetricalpositionshavebeen
limited.3 Forexample,althoughBernstein,Becker,andtheir
co-workers as well as Kato and his co-workers have reported
diiodization of TTF,3a, 3d, 3e isolation (e. g., by column chro-
matography) of isomers of the diiodized TTF with iodine in
each five-membered ring is difficult. Here we report prepara-
tion and isolation of newTTF derivatives with two iodo and
acetylenic groups at the symmetrical positions.
The reaction of 1 with trimethylsilylacetylene (3.4 mol/1)
in the presence of Pd(PPh3)4 (5 mol%/1), CuI (5 mol%/1),
and NEt3 (excess) in THF gives symmetrical 2,6-bis[2-
(trimethylsilyl)ethynyl]-3,7-diphenyltetrathiafulvalene
(2) in 70% yield. Treatment of 2 with 1 M aqueous KOH
easily generates 3. The molecular structure of 2 deter-
mined by X-ray crystallography is shown in Figure 2.
Treatment of diphenyltetrathiafulvalene4 (diphenyl-TTF)
with LDA (2.7 mol/diphenyl-TTF) followed by addition
of perfluorohexyl iodide (PFHI; 3.5 mol/diphenyl-TTF)
and work-up including recrystallization from toluene
gives trans-2,6-diiodo-3,7-diphenyltetrathiafulvalene 1 in
62% yield. The HPLC trace of the product 1 obtained after
the recrystallization gives only one peak, whereas the fil-
trate obtained in the recrystallization gives an additional
one peak (relative peak area to that of 1 = about 1/3) as-
signed to a cis-isomer of 1. The diphenyl- TTF used are
considered to be a mixture of cis- and trans-isomers,4 and
the trans product 1 is formed as the major product and iso-
lated as crystal.1H- and13C-NMR spectra of a product
(product 1¢) obtained by drying up the filtrate show no ob-
servable difference from those of isolated 1, indicating that
1 and the cis-isomer give rise to essentially the same NMR
data. NMR spectra of the product 1¢ exhibit no peaks as-
signabletootherproductslikeamono-iodizedproduct.The
trans-product 1 gives a melting point of 220–222°C,
whereas the product 1¢ shows a melting point of 212–
215 °C. The trans structure of 1 is unequivocally estab-
lished by X-ray crystallography as shown in Figure 1.
Scheme 1
Compounds 2 and 3 are not so stable in solutions, and
their isolation requires rapid treatment of the solution (cf.
experimental part).
Thus, new symmetrical TTF derivatives 1–3 with the
functional groups and the well-defined trans structure
have been obtained. Since iodo and the –CºCH group
have high reactivity in organic reactions, 1 and 3, which
contain these two functional groups, are expected to serve
as starting materials to prepare various TTF derivatives.
For example, it is known that polycondensation based on
C–C coupling6, 7 between ArX and Ar¢C–CH can be car-
ried out by using Pd-catalyst and bifunctional aromatic
compounds to yield (Ar–CºC-Ar¢-CºC)n type polymers;
¯
¯
n X–Ar–X + n HCºC–Ar¢ CºCH ® (Ar–C–C-Ar¢–
¯
CºC)n.8 For obtaining such polymers with the TTF unit,
¯
TTF derivatives with the two functional groups are neces-
sitated, and our preliminary investigation indicates that
such polycondensation proceeds smoothly between 1 and
3; the results will be reported elsewhere. Although intro-
We have tried similar diiodization of 2,6-dimethyltetra-
thiafulvalene under various conditions. However, the at-

260
Short Papers
SYNTHESIS
for 1 h and at r.t. for 1 h. After quenching with water, the powder
formed was washed with water (3 ´) and Et2O (3 ´). Crystallization
from toluene gave red needles of 1; yield: 0.743 g (62%).
1H NMR: d = 7.40–7.50 (m, 10H, -Ph)
MS: m/z = 608 (M+).
Anal. Found: C, 35.45; H, 1.70. Calcd.: C, 35.54; H, 1.66.
2,6-Bis[2-(trimethylsilyl)ethynyl]-3,7-diphenyltetrathiafulvalene
(2):
1 (0.600 g, 0.986 mmol) was dissolved in anhyd THF (20 mL). CuI
(5 mol%; 9.37 mg, 0.0494 mmol), Pd(PPh3)4 (5 mol%; 57.0 mg,
0.0494 mmol) and NEt3 (20 mL) were added, and then the mixture
was stirred for a few minutes. Trimethylsilylacetylene (0.331 g,
3.35 mmol) was added dropwise to the mixture. The mixture was
stirred for 12 h at 60 °C. Flash column chromatography (silica gel, tol-
uene) and crystallization (toluene) gave red plates of 2; yield: 0.142 g
(27%).
1H NMR: d = 7.31–7.80 (m, 10H, -Ph), 0.18 (s, 18H, Si–CH3).
Figure 1. Molecular structure of 1. Selected structural parameters
(Å, °): I1-C2 2.076(5), S1-C1 1.746(6), S1-C2 1.752(6), S2-C1
1.775(6), S2-C3 1.782(6), C1-C1 1.32(1), C2-C3 1.310(7), C3-C4
l.472(7), C1-S1-C2 95.3(3), C1-S2-C3 95.7(3), S1-C1-S2 113.7(3),
S1-C1-C1 124.8(6), S2-C1-C1 121.5(6), I1-C2-S1 113.2(3), I1-C2-
C3 126.9(4), S1-C2-C3 119.9(4), S2-C3-C2 115.4(4), S2-C3-C4
113.9(4), C2-C3-C4 130.6(5).
IR: n = 2136 (CºC), 1248, 844 cm–1 (Si–CH3).
Anal. Found: C, 60.87; H, 4.95. Calcd.: C, 61.26; H, 5.14.
2,6-Diethynyl-3,7-diphenyltetrathiafulvalene (3):
2 (0.142 g, 0.259 mmol) was dissolved in Et2O (45 mL) and MeOH
(30 mL). 1 M aq KOH (15 mL) was added to the solution. The mix-
ture was stirred for 1 h and washed with water repeatedly. Purification
on a silica gel column (hexane/toluene 3:1) gave an orange powder of
3; yield: 0.221 g (47.5%).
1H NMR: d = 7.35–7.70 (m, 10H, –Ph), 3.34 (s, 2H, CºC–H).
IR: n = 3282 (CºC–H), 2090 cm–1 (CºC).
MS: m/z = 404 (M+), isotope pattern agreed.
HPLC Analysis:
A recycle-type preparative HPLC Type LC-908 made by Japan Ana-
lytic Industry Co. Ltd. was used with two columns (JAI GEL H-1 and
H-2) set in series; eluent was CHCl3.
Crystal Structure Determination of 1:
Crystal of 1 suitable for crystallography was obtained by recrystalli-
zation from toluene. The crystal was mounted in a glass capillary
tube. The unit cell parameters were obtained by least-squares refine-
ment of 2 q values of 20 reflections with 5≤2 q<55°. Intensities were
collected on Rigaku AFC-5R automated fourcycle diffractometer by
using Mo-Ka radiation (l = 0.71069 Å) and the w-2q method.
Calculations were carried out by using a program package TEXSAN
on a DEC Micro VAX-II computer. Atomic scattering factors were
obtained from the literature. A full matrix least-squares refinement
was used for non-hydrogen atoms with anisotropic thermal parame-
ters. The hydrogens were located by assuming ideal positions (d (C–
H)=0.95 Å) and included in the structure calculation without further
refinement of the parameters.
Figure 2. Molecular structure of 2. Selected structural parameters
(Å, °): S1-C1 1.767(4), S1-C2 1.758(4), S2-C1 1.750(4), S2-C3
1.767(4), Si1-C5 1.832(4), C1-C1 1.307(7), C2-C31.349(5), C2-C4
1.423(5), C4-C5 1.203(5), C1-S1-C295.3(2), C1-S2-C397.3(2), S1-
C1-S2 113.1(2), S1-C1-C1 122.2(4), S2-C1-C1 124.7(4), S1-C2-C3
118.9(3), S1-C2-C4 114.0(3), C3-C2-C4 127.1(4), S2-C3-C2
114.6(3), S2-C3-C9 117.0(3), C2-C3-C9 128.4(3), C2-C4-C5
174.7(4), Sil-C5-C4 173.7(4).
The compound crystallizes in monoclinic space group P21/c (14) a =
4.137 (4), b = 12.99 (1), c = 17.937 (9) Å. V = 961 (1) Å3, Z = 4, and
b = 93.96 (7)°. The calculated density and the total number of elec-
trons in the cell amount to 2.10 g cm–3 and F(000) = 576. R = 3.2%.
Rw = 3.2%.
Crystal Structure Determination of 2:
duction of one –C–CSiMe3 or –CºCH group to TTF has
been reported,9 preparation of the TTF derivative with the
–C–CSiMe3 or –CºCH group in each 5-membered ring
has no precedent to our knowledge.
Crystal of 2 suitable for crystallography was obtained by recrystalli-
zation from toluene. The crystals was mounted in a glass capillary
tube. The unit cell parameters were obtained by least-squares refine-
ment of 2 q values of 20 reflections with 5≤2 q<55°. Intensities were
collected on Rigaku AFC-5R automated fourcycle diffractometer by
using Mo-Ka radiation (l = 0.71069 A) and the w-2q method.
Calculations were carried out in a manner similar to those applied for
the crystal structure determination of 1.
2,6-Diiodo-3,7-diphenyltetrathiafulvaleue (1):
2,6(7)-Diphenyltetrathiafulvalene (diphenyl-TTF purchased from Al-
drich Chemical Co. Inc.4; 0.700 g, 1.96 mmol) in anhyd THF (25 mL)
was lithiated at –78 °C with LDA (2.7 mol/diphenyl-TTF). After stir-
ring for 1 h, perfluorohexyl iodide (PFHI; 3.5 mol/diphenyl-TTF) was
added dropwise to the suspension. The mixture was stirred at –60°C
The compound crystallizes in monoclinic space group P21/n (14) a =
14.308 (6), b = 6.051 (2), c = 17.100 (6) Å. V = 1480.4 (9) Å3, Z = 4,
and b = 90.55 (3)°. The calculated density and the total number of
electrons in the cell amount to 1.231 g cm–3 and F(000) = 576. R =
5.7%. Rw = 5.5%.

March 1998
SYNTHESIS
261
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2047.
(4) Purchased from Aldrich Chemical Co. Inc. The figure in the
catalogue shows a cis structure for diphenyl-TTF. However, the
response from Aldrich Chemical Co. Inc. says that it may be a
mixture of cis- and trans-diphenyl-TTF and their separation has
not been carried out.