CpCo1-mediated Diels-Alder reaction forming dimerie 1,3-dithiol-2-one derivative with spiro structure and successive formation of novel cobalt dithiolene complex

Article abstract of DOI:10.1246/cl.2008.1032

4,5-Bis(bromomethyl)-1,3-dithiol-2-one (1) reacts with CpCo(CO)₂ (2) under thermal condition to undergo a debromi-nation of 1 and to form dimerie 1,3-dithiol-2-one derivative having a spiro structure 3 by the [4 + 2] Diels-Alder reaction, and the resulted 3 further reacts with 2 to afford new CpCo-(dithiolene) complex 4. Copyright

Full text of DOI:10.1246/cl.2008.1032

1032
Chemistry Letters Vol.37, No.10 (2008)
CpCoI-mediated Diels–Alder Reaction Forming Dimeric 1,3-Dithiol-2-one Derivative
with Spiro Structure and Successive Formation of Novel Cobalt Dithiolene Complex
Tatsuya Masui, Mitsushiro Nomura,ꢀ Yusuke Kobayashi, Kosuke Terada,
Chikako Fujita-Takayama, Toru Sugiyama, and Masatsugu Kajitaniꢀ
Department of Materials and Life Sciences, Faculty of Science and Technology,
Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554
(Received July 3, 2008; CL-080658; E-mail: m-nomura@sophia.ac.jp, kajita-m@sophia.ac.jp)
CH2Br
S
S
S
S
4,5-Bis(bromomethyl)-1,3-dithiol-2-one (1) reacts with
NEt4I
O
O
CpCo(CO)2 (2) under thermal condition to undergo a debromi-
nation of 1 and to form dimeric 1,3-dithiol-2-one derivative
having a spiro structure 3 by the [4 + 2] Diels–Alder reaction,
and the resulted 3 further reacts with 2 to afford new CpCo-
(dithiolene) complex 4.
∆
CH2Br
1
Scheme 1.
S
S
S
S
CH2Br
CH2Br
S
S
O
+
Co
S
O
O
S
S
Metalladithiolene rings, which incorporate one metal, two
sulfurs, and two unsaturated carbons, are an interesting five-
membered metallacycles. The dithiolene metal complexes have
been thoroughly investigated from the viewpoint of optical,1
magnetic,2 and conductive studies.3 Some recent topics in dithio-
lene complexes are their photo catalyses for generating molecu-
lar hydrogen from water4 and selective olefin binding on the
dithiolene ligand.5
S
O
1
4
benzene
reflux
3
18%
+
9%
CO
S
Co
S
CH2Br
CH2Br
Co
S
Co
S
S
CO
Co
S
(3 equiv)
2
Not obtained
Not obtained
Scheme 2.
Synthetic procedures for dithiolene complexes have been
well developed. Among them, useful dithiolene sources are
mostly classified into five categories: (1) 1,2-dithiolate dianion
formed from the treatment of 1,3-dithiol-2-one, S-protected
dithiolene ligand by PhCH2, PhCO, and NC(CH2)2 groups, or
1,2-dithiol derivative in the presence of a strong base,6 (2) 1,2-
dithioketone or 1,2-dithiete generated by photolysis and ther-
molysis of 1,3-dithiol-2-one, or by the reaction of ꢀ-diketone
with Lawesson’s reagent,7 (3) thiophosphoric esters formed
from the reaction of benzoin analogues with diphosphorus
pentasulfide or Lawesson’s reagent,8 (4) zinc, titanium, or tin
dithiolate as a precursor,6 (5) stable 1,2-dithiolate salt such as
Na2(mnt) (mnt = maleonitrile-1,2-dithiolate), and (6) metal sul-
fide while reacted with an alkyne.6 Among them, using 1,3-di-
thiol-2-one derivative is the widely useful method to prepare
many kinds of dithiolene complex, and as is well-known, this
is also a useful precursor for tetrathiafulvalene (TTF) deriva-
tives.9
To prepare typical 1,3-dithiol-2-one derivatives, we can
usually use substitution of sulfur at the S=C group in 1,3-di-
thiol-2-thione by treatment with Hg(OAc)2,10 the reactions of
[Cp2Ti(dithiolene)] or [Zn(dithiolene)Ln] with triphosgene,11
and cyclization of xanthogenate by treatment with an acid.12
Furthermore, a direct introduction of 1,3-dithiol-2-one fragment
using the [4 + 2] Diels–Alder reaction13 can be useful but is
not well-known. This reaction involves double debromination
of 4,5-bis(bromomethyl)-1,3-dithiol-2-one (1) while treatment
with tetraethylammonium iodide generating the 1,3-diene
intermediate shown in Scheme 1. This transient diene itself
further undergoes the [4 + 2] Diels–Alder reaction to afford di-
meric 1,3-dithiol-2-one compound (3, see Scheme 2) or other
[4 + 2] adducts in the presence of a dienophile such as p-benzo-
quinone,13 acrolein,14 or fullerene.15 This paper reports on the
generation of the 1,3-diene intermediate from the reaction of 1
with CpCo(CO)2 (2), but without iodide. In addition, the succes-
sive formation of new CpCo(dithiolene) complex 4 derived from
precursor 3 is described.
1 reacted with 3 equiv of 2 in refluxing benzene for 24 h to
obtain the dimeric 1,3-dithiol-2-one with a spiro structure 3 and
the new CpCo(dithiolene) complex 4 in 18% and 9% yields, re-
spectively (Scheme 2). This reaction also occurred at room tem-
perature to form 3 in 21% yield but formed only trace amount of
4. For a comparison, a previous paper has reported that the reac-
tion of 1 with tetraethylammonium iodide (3 equiv) gives 3 in
30% yield under thermal conditions in acetonitrile.13 Unexpect-
edly, CpCo(dithiolene) complex having two bromomethyl
groups, [CpCo(S2C2(CH2Br)2)], was not obtained at all
(Scheme 2). To explain this reason, a bromine abstraction by
CpCoI is proposed, and then the 1,3-diene intermediate noted
in Scheme 1 should be formed. Accordingly, slight excess 2 (3
equiv) is necessary to obtain 4.
Furthermore, isolated compound 3 directly reacted with 2
for 24 h to form complex 4 in 4% yield under refluxing benzene,
in 19% yield under refluxing toluene and in 34% yield under re-
fluxing xylene. These results indicate that higher temperature ac-
celerates decarbonylation of 3 to generate 1,2-dithioketone or
1,2-dithiete intermediate.7 No formation of a dinuclear CpCo(di-
thiolene) complex in Scheme 2 suggests that only one of two 1,3-
dithiol-2-one fragments is thermally activated for decarbonyla-
tion.
The reaction of 1 with tetraethylammonium iodide (3 equiv)
for 3 h in the presence of N-phenylmaleimide in refluxing
acetonitrile was carried out, and this reaction resulted in 3 in
5% yield and the Diels–Alder cycloadduct 5 in 75% yield,
respectively. This result indicates that N-phenylmaleimide is
Copyright Ó 2008 The Chemical Society of Japan

Chemistry Letters Vol.37, No.10 (2008)
1033
close to the bond length of the vinylene moiety at C8–C9
˚
(1.316 A). These results show the C1–C2 bond becomes olefinic
by lack of aromaticity. Interestingly, while comparing 3 and 4,
the 1,3-dithiol-2-one fragments containing S3 and S4 are
located contrarily to each other (Figures 1 and S1 in Supporting
Information).
This paper reported a CpCoI-mediated a debromination of 1
to form 1,3-diene intermediate without the conventional use of
iodide and eventually underwent [4 + 2] Diels–Alder reactions.
The resulting 1,3-dithiol-2-one derivative is generally useful for
syntheses of TTF derivatives and metal dithiolene complexes
as well. An important point in this work is that CpCoI species
facilitates the Diels–Alder reaction and successively forms
CpCo(dithiolene) complex. Finally, the target CpCo(dithiolene)
complex 4 or 6 can be obtained in one-step reaction of 1 with 2
or in the presence of N-phenylmaleimide.
O
2
+
1
+
N Ph
benzene
reflux
(3 equiv)
O
(2 equiv)
O
O
S
S
S
S
3
+
4
+
+
Co
N Ph
O
N Ph
O
O
5
16%
6
38%
12%
1%
Scheme 3.
an effective dienophile. Moreover, the reaction shown in
Scheme 2 in the presence of N-phenylmaleimide was performed
(Scheme 3), and produced 3 in 12% yield, 4 in 1% yield, 5 in
16% yield, and new dithiolene complex 6 in 38% yield. Lower
yields of 3 and 4 were found than those in Scheme 2 upon the
absence of any dienophiles. This result proves that the dieno-
phile effectively combines with the 1,3-diene intermediate to
avoid the formation of dimeric cycloadduct 3. Therefore, the
formation of 5 reveals that CpCoI can mediate the [4 + 2]
Diels–Alder reaction with 3 and the resulting 5 successively
reacts with 2 to form 6 under thermal conditions.
Some new compounds 4–6 were identified with spectro-
scopic data and elemental analysis (Supporting Information).18
Single crystals of 3 and 4 were obtained by recrystallization from
dichloromethane/n-hexane.16,17 Analytical data for 3 has been
reported previously,13 but has been not structurally characterized
yet. The ORTEP drawings of 4 is shown in Figure 1 together
with selected bond lengths and angles, respectively. The ORTEP
of 3 is shown in Supporting Information.18
References and Notes
1
2
3
4
5
a) S. D. Cummings, R. Eisenberg, Prog. Inorg. Chem. 2003, 52, 315.
b) H. Kisch, Coord. Chem. Rev. 1993, 125, 155.
´
a) M. Fourmigue, Acc. Chem. Res. 2004, 37, 179. b) C. Faulmann,
P. Cassoux, Prog. Inorg. Chem. 2003, 52, 399.
a) R. Kato, Chem. Rev. 2004, 104, 5319. b) A. Kobayashi, E.
Fujiwara, H. Kobayashi, Chem. Rev. 2004, 104, 5243.
J. Zhang, P. Du, J. Schneider, P. Jarosz, R. Eisenberg, J. Am. Chem.
Soc. 2007, 129, 7726.
a) K. Wang, E. I. Stiefel, Science 2001, 291, 106. b) Y. Fan, M. B.
Hall, J. Am. Chem. Soc. 2002, 124, 12076. c) D. J. Harrison, N.
Nguyen, A. J. Lough, U. Fekl, J. Am. Chem. Soc. 2006, 128,
11026. d) D. J. Harrison, A. J. Lough, N. Nguyen, U. Fekl, Angew.
Chem., Int. Ed. 2007, 46, 7644.
6
7
T. B. Rauchfuss, Prog. Inorg. Chem. 2003, 52, 1.
a) A. Sugimori, T. Akiyama, M. Kajitani, T. Sugiyama, Bull. Chem.
Soc. Jpn. 1999, 72, 879. b) R. Schulz, A. Schweig, K. Hartke,
J. Koester, J. Am. Chem. Soc. 1983, 105, 4519.
In complex 4, the Cp plane is located at an almost perpen-
dicular position with respect to the cobaltadithiolene plane
because the dihedral angle of Cp/cobaltadithiolene is equal to
83.972ꢁ. This result suggests a typical two-legged piano-stool
geometry. The dihedral angle between the C3–C4–C5 and S3–
C4–C8 is almost 90ꢁ indicating a general spiro structure. The
8
9
T. Ozturk, E. Ertas, O. Mert, Chem. Rev. 2007, 107, 5210.
M. Bendikov, F. Wudl, D. F. Perepichka, Chem. Rev. 2004, 104,
4891.
10 F. Challenger, E. A. Mason, E. C. Holdsworth, R. Emmott, J. Chem.
Soc. 1953, 292.
˚
11 a) R. Kato, H. Kobayashi, A. Kobayashi, Synth. Met. 1991, 42,
2093. b) T. Imakubo, H. Sawa, R. Kato, Synth. Met. 1997, 86,
1883. c) R. J. Pafford, J.-H. Chou, T. B. Rauchfuss, Inorg. Chem.
1999, 38, 3779.
12 A. K. Bhattacharya, A. G. Hortmann, J. Org. Chem. 1974, 39, 95.
13 R. M. Renner, G. R. Burns, Tetrahedron Lett. 1994, 35, 269.
14 Y. Ishikawa, T. Miyamoto, A. Yoshida, Y. Kawada, J. Nakazaki, A.
Izuoka, T. Sugawara, Tetrahedron Lett. 1999, 40, 8819.
15 D. Kreher, M. Cariou, S.-G. Liu, E. Levillain, J. Veciana, C. Rovira,
A. Gorgues, P. Hudhomme, J. Mater. Chem. 2002, 12, 2137.
16 Crystal data for 4: (C14H13CoOS4): blue crystal, crystal size: 0:23 ꢂ
0:15 ꢂ 0:02 mm3, fw 384.45 gꢃmolꢄ1, monoclinic, space group
C1–C2 bond length in cobaltadithiolene is 1.353 A. This is
˚
intermediary between a typical C–C single bond (ca. 1.5 A)
˚
and C=C double bond (ca. 1.3 A) relating to an aromaticity of
the cobaltadithiolene ring.7a The cobaltadithiolene plane is
quite planar due to negligible mean deviation from the plane
˚
(0.0314 A). This fact also supports the aromaticity of the cobal-
tadithiolene ring. In compound 3, there is also a spiro structure
centered at the C4 carbon (Supporting Information).18 The
˚
C1–C2 bond length in the dithiolene ring is 1.333 A, which is
˚
˚
˚
Pa(#7), a ¼ 10:9508ð11Þ A, b ¼ 6:3141ð9Þ A, c ¼ 11:1090ð13Þ A,
ꢁ
3
˚
ꢀ ¼ 94:2048ð19Þ , V ¼ 766:06ð16Þ A , Z ¼ 2, T ¼ 298 K, Dcalc
¼
1:667 gꢃcmꢄ3, ꢁ(Mo Kꢂ) = 1.658 mmꢄ1, 5334 reflections meas-
ured, 2793 unique (Rint ¼ 0:023), RðI > 2ꢃðIÞÞ ¼ 0:0343 and
wR ¼ 0:0971, goodness-of-fit = 1.046, CCDC No. 693392.
17 Crystal data for 3: (C10H8O2S4): colorless crystal, crystal size:
0:42 ꢂ 0:12 ꢂ 0:10 mm3, fw 288.41 gꢃmolꢄ1, monoclinic, space
Figure 1. ORTEP drawing of 4 (thermal ellipsoids 30% proba-
˚
bility). Selected bond lengths (A): Co1–S1 2.1108(15), Co1–S2
˚
˚
group P21=n(#14), a ¼ 7:750ð2Þ A, b ¼ 15:616ð4Þ A, c ¼
ꢁ
3
˚
˚
9:586ð3Þ A, ꢀ ¼ 97:6871ð13Þ , V ¼ 1149:7ð5Þ A , Z ¼ 4, T ¼
298 K, Dcalc ¼ 1:666 gꢃcmꢄ3, ꢁ(Mo Kꢂ) = 0.804 mmꢄ1, 8764 re-
flections measured, 2594 unique (Rint ¼ 0:016), RðI > 2ꢃðIÞÞ ¼
0:0332 and wR ¼ 0:0978, goodness-of-fit = 1.052, CCDC No.
693393.
2.1150(17), S1–C1 1.720(4), S2–C2 1.721(4), C1–C2 1.353(5),
C8–C9 1.302(8), O1–C7 1.190(8). Selected bond angles (ꢁ):
S1–Co1–S2 91.07(7), Co1–S1–C1 105.61(15), Co1–S2–C2
105.39(14), S1–C1–C2 118.8(3), S2–C2–C1 119.0(3). Dihedral
angles: Cp/dithiolene = 83.972ꢁ, C3–C4–C5/S3–C4–C8 =
90.988ꢁ.
18 Supporting Information is available electronically on the CSJ-
Journal Web site, http://www.csj.jp/journals/chem-lett/index.html.
Published on the web (Advance View) August 30, 2008; doi:10.1246/cl.2008.1032