Pd-catalyzed boronations and cross-coupling reactions of aromatic cobaltadithiolene complexes with aryl halides

Article abstract of DOI:10.1016/j.jorganchem.2011.04.014

The Pd-catalyzed reaction of [CpCo(S2C2(Ph)(Bpin))] (1, Bpin = 4,4,5,5-tetramethyl-1,3,2-dioxaboronate) with 1-iodonaphthalene or 2-bromothiophene gave the cross-coupling product [CpCo(S2C2(Ph)(Ar))] (Ar = 1-Np (4) or 2-Th (5)), although an early paper de

Full text of DOI:10.1016/j.jorganchem.2011.04.014

Journal of Organometallic Chemistry 696 (2011) 2720e2727
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Pd-catalyzed boronations and cross-coupling reactions of aromatic
cobaltadithiolene complexes with aryl halides
*
Mitsushiro Nomura , Kosuke Terada, Akihide Onozawa, Yoshiro Mitome, Toru Sugiyama,
**
Masatsugu Kajitani
Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
The Pd-catalyzed reaction of [CpCo(S2C2(Ph)(Bpin))] (1, Bpin ¼ 4,4,5,5-tetramethyl-1,3,2-dioxaboronate)
with 1-iodonaphthalene or 2-bromothiophene gave the cross-coupling product [CpCo(S2C2(Ph)(Ar))]
(Ar ¼ 1-Np (4) or 2-Th (5)), although an early paper described the reaction of 1 with 3-bromopyridine or
9-bromoanthracene (Ar ¼ 3-Py (2) or 9-Anth (3)). The boronation of the brominated precursor
[CpCo(S2C2(p-C6H4Br)(H))] (7) with Bpin-H in the presence of Pd catalyst gave the expected boronated
product [CpCo(S2C2(p-C6H4Bpin)(H))] (8) but also underwent an unexpected direct boronation on the
Received 20 January 2011
Received in revised form
5 April 2011
Accepted 13 April 2011
Keywords:
Dithiolene
dithiolene carbon to form [CpCo(S2C2(p-C6H4Br)(Bpin))] (9). The brominated complex
7 or
[CpCo(S2C2(Ph)(p-C6H4Br))] (10) was synthesized by thermal reaction and the microwave-enhanced
reaction relatively gave better yield with shorter reaction time than that of the conventional heating
reaction. The cross-coupling reactions of the boronated or [CpCo(S2C2(Ph)(p-C6H4Bpin))] (11) with aryl
halides successfully produced the corresponding cross-coupling products such as [CpCo(S2C2(p-
C6H4Py)(H))] (12) or [CpCo(S2C2(p-C6H4Anth)(H))] (13) from 8 and [CpCo(S2C2(Ph)(p-C6H4Py))] (14)
from 11. The structures of 7, 9, 11, 12, 13 and 14 were determined by X-ray diffraction studies. Electronic
absorption maxima (lmax) due to dithiolene LMCT in dichloromethane solution can be modified in the
range of 574e602 nm by a substituent effect on the dithiolene ring. Redox potentials obtained from CV
measurement were also reported.
Cross-coupling
SuzukieMiyaura reaction
Boronation
Molecular structure
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
[5]. Addition reactions are observed on the CoeS bond in the cobal-
tadithiolene ring [6]. The formed cobaltadithiolene adducts can be
Metallabenzenes and metallabenzenoids (M ¼ Os, Ir, Pt and Ta)
behave as aromatic metallacycles and they show some electrophilic
substitution reactions on the ring [1]. Furthermore, the five-
membered metalladithiolene ring (MS2C2) which has: one metal,
two sulfur atoms and two unsaturated carbon atoms; involves
dissociated by thermal [7], photochemical [8] and other chemical
reactions [9] toward rearomatized cobaltadithiolene complexes.
On the other hand, we have observed substitution reactions on
the dithiolene carbon when there is a CeH bond on the cobalta-
dithiolene ring ([CpCo(S2C2(R)(H))] complex). The ring undergoes
electrophilic substitution reactions (Friedel-Crafts type) [10],
carbon-centered [10,11], sulfur-centered and nitrogen-centered
radical substitution reactions [12]. Recently, we focused on some
coupling reactions of the cobaltadithiolene ring, because it is one
representative reactivity of an aryl group. The treatments of
[CpCo(S2C2(R)(H))] (R ¼ Me, Ph, 9-phenanthryl) with a protic acid
or Lewis acid give dithioleneedithiolene homo-coupling products
(Chart 1) [13]. Nishihara et al. reported the homo-coupling reaction
of [CpCo(S2C2H2)] with HX acid to afford the trinuclear complex
[CpCo(S2C2)]3 (Chart 1) [14]. In addition, we have reported the
formations of similar homo-coupling products by the reactions of
[CpCo(S2C2(R)(H))] with N-halosuccinimides (NXS) although the
unexpected imidation products [CpCo(S2C2(R)(N-succinimide))]
are mainly formed [13].
conjugated 6p electrons, thus this is also one aromatic metallacycle
due to Hückel’s rule [2]. Also a pseudo aromaticity of the metal-
ladithiolene ring has been proposed so far based on the ring current
effect during the NMR measurement [3] and theoretical DFT calcu-
lation [4]. On the basis of our research background, a cyclo-
pentadienyl cobalt dithiolene complex, which is usually formulated
as [CpCo(dithiolene)] (Cp ¼
h
5-cyclopentadienyl), shows unique
reactivities based on the coexistence of aromaticity and unsaturation
* Corresponding author. Present address: Condensed Molecular Materials Labo-
ratory, RIKEN 2-1, Hirosawa, Wako-shi, Saitama 351-0198, Japan. Tel.: þ81 48 467
9412; fax: þ81 48 462 4661.
** Corresponding author.
E-mail address: mitsushiro@riken.jp (M. Nomura).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.04.014

M. Nomura et al. / Journal of Organometallic Chemistry 696 (2011) 2720e2727
2721
instead of Na2CO3, one can well inhibit the formation of 6 (Entries 2
and 4). These results suggest that use of a strong base undergoes
deprotection of the Bpin group from 1 and can not ensure effective
formation of the cross-coupling product. In fact, the treatment of 1
with Na2CO3 in THF gave the hydrogenated product 6 in 30% yield
[15]. In this work, the cross-coupling reaction of 1 with 1-iodo-
naphthalene or 2-bromothiophene in the presence of triethylamine
gave [CpCo(S2C2(Ph)(1-Np))] (4, 4% yield) or [CpCo(S2C2(Ph)(2-
Th))] (5, 2% yield) as shown in Scheme 1 and Table 1 (Entries 5 and
6). The hydrogenated complex 6 was also obtained in 6e7% yields.
Unfortunately, we could not obtain a good yield of the cross-
coupling product, although all the starting boronated complex 1
reacted. The resulted reaction mixture contained some unidentified
products and these could not be collected by column chromatog-
raphy. One reason for the poor efficiency of the reaction may be due
to the pseudo aromaticity of the metalladithiolene ring.
R
S
Co
R
H
S
Co
HX, AlCl3 or NXS
S
S
S
Co
S
R
Co
H
H
S
S
S
S
HX
Co
S
Co
S
Co
S
S
Chart 1. Dithioleneedithiolene homo-coupling reaction.
2.2. Boronation of p-bromophenyl group substituted on the
dithiolene ring
Furthermore, dithiolene-aryl cross-coupling reactions can be also
an attractive work for us because one can introduce some aryl-
based functional groups to the dithiolene ring. According to an
early communication paper by our research group, the cobaltadi-
thiolene complex having a boronated ester group, which is
formulated as [CpCo(S2C2(Ph)(Bpin))] (1, Bpin ¼ 4,4,5,5-tetra-
methyl-1,3,2-dioxaboronate), shows dithiolene-aryl cross-coupling
reactions in the presence of Pd catalyst (Scheme 1) [15]. This has
been the first case of SuzukieMiyaura cross-coupling reaction [16]
to a pseudo aromatic metallacycle.
In this work, we studied more applications of the cross-coupling
reaction with naphthyl group or thienyl group, because the
previous paper only described dithiolene-pyridyl or dithiolene-
anthryl cross-coupling reaction. These reactions can produce
dithiolene-fused polyaryl units such as an aryl-dithiolene-aryl
compound, but a dithiolene-aryl-aryl formation is one other
possibility in this work. Namely, we can introduce a Bpin group on
the Ph group to form [CpCo(S2C2(peC6H4eBpin)(H))] (8) and it can
undergo cross-coupling reactions with aryl halides. Although one
straightforward synthetic method of 8 may be a boronation of the
brominated precursor [CpCo(S2C2(peC6H4eBr)(H))] (7), we found
an unexpected direct boronation on the dithiolene ring as well.
The brominated complex [CpCo(S2C2(p-C6H4Br)(H))] (7) was
prepared by the thermal reaction of [CpCo(CO)2] with 4-(p-bro-
mophenyl)-1,3-dithiol-2-one under conventional heating in
refluxing benzene (33% yield) for 18 h or under microwave irradi-
ation (264 W) in refluxing ethylene glycol (62% yield) for 10 min.
The microwave-enhanced reaction can produce almost twice
greater yield with very short reaction time compared with that of
the conventional heating reaction. The higher yield of 7 (86% yield)
was found by the ligand exchange reaction of [CpCo(CO)I2] with
1,2-dithiolate dianion, followed by the activation of 4-(p-bromo-
phenyl)-1,3-dithiol-2-one with sodium methoxide (see Section 4).
The boronation of 7 with 4,4,5,5-tetramethyl-1,3,2-dioxabor-
olane (Bpin-H) in the presence of [PdCl2(PPh3)2] gave the corre-
sponding boronated complex [CpCo(S2C2(p-C6H4Bpin)(H))] (8) in
17% yield (Scheme 2). During precise separation of the reaction
mixture by HPLC, we found another boronated complex (9) in trace
yield. However, a large scale reaction of 7 (5 mmol scale) gave
enough amount of 9 (ca. 10 mg) for some spectral and analytical
data. The 1H NMR spectrum of 8 indicated the presence of
a dithiolene proton at 9.06 ppm, which is similar to that of 7
(8.97 ppm). On the other hand, the 1H NMR spectrum of 9 showed
absence of the dithiolene proton, and presence of bromine atom
was indicated by the mass spectrum. Elemental analysis and X-ray
structure determination (Fig. 3) of 9 eventually prove that the Bpin
group is directly substituted on the dithiolene carbon and the
bromine atom is left on the para-position of phenyl group.
2. Results and discussion
2.1. Cross-coupling reaction of boronated dithiolene ring with aryl
halides
Probably this reaction can be explained by a hydroboration of the
dithiolene C]C moiety and it may be oxidized during workup
process in air atmosphere or dehydrogenated by thermolysis. In fact,
some other research groups reported that the oxidation (dehydro-
genation) of saturated dithiolane complex to the corresponding
unsaturated dithiolene complex by treatment with O2 or thermolysis
[17]. In addition, we reported one-pot reaction of [CpCo(CO)2],
elemental sulfur and alkene to form [CpCo(dithiolene)] complexes
upon dehydrogenation involved by thermolysis [18]. On the other
hand, the non-brominated complex 6 did not form the boronated
complex by Bpin-H. We assume that the bromine atom in 7 activates
the dithiolene carbon atoms. Actually, the difference of reduction
potentials between 6 (ꢀ1.30 V) and 7 (ꢀ1.23 V) explains an electron-
withdrawing effect of the bromine atom (Table 2).
An early communication paper described the cross-coupling
reaction of 1 with 3-bromopyridine or 9-bromoanthracene in the
presence of [Pd(PPh3)4] to form [CpCo(S2C2(Ph)(3-Py))] (2) or
[CpCo(S2C2(Ph)(9-Anth))] (3), respectively [15]. The Pd-catalyzed
reactions of 1 with aryl halides are summarized in Table 1. While
Na2CO3 is used as a base, quite higher yield of [CpCo(S2C2(Ph)(H))]
(6, 49% yield) has been obtained than those of cross-coupling
products (Entries 1 and 3). However, when triethylamine is used
Ar-X, base
[Pd(PPh3)4]
S
S
S
S
S
S
Co
Co
Co
+
O
B
Ar
H
In order to inhibit the boronation on the dithiolene carbon, we
used the diarylated complex [CpCo(S2C2(Ph)(p-C6H4Br))] (10)
where no hydrogen atom is located on the dithiolene carbon. 10
was synthesized by the one-pot reaction of [CpCo(CO)2], elemental
sulfur and 1-bromo-4-(phenylethynyl)benzene and produced in 4%
O
6
Ar = 3-Py (2)
9-Anth (3)
1-Np (4)
1
2-Th (5)
Scheme 1. Pd-catalyzed dithiolene-aryl cross-coupling reactions.

2722
M. Nomura et al. / Journal of Organometallic Chemistry 696 (2011) 2720e2727
Table 1
Cross-coupling reactions of boronated dithiolene complexes with aryl halides.
Entry
Boronated complex
ArBr
Base
Solvent
Temp.
Time/h
Yield/%
Yield/% (6)
Ref.
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
8
8
3-PyBr
3-PyBr
Na2CO3
NEt3
Na2CO3
NEt3
NEt3
NEt3
Na2CO3
Na2CO3
Na2CO3
THF
1,4-dioxane
THF
reflux
reflux
reflux
reflux
reflux
reflux
reflux
reflux
reflux
3
24
4
30
24
24
4
trace (2)
6 (2)
49
13
49
12
7
6
0
0
e
[15]
[15]
[15]
[15]
This work
This work
This work
This work
This work
9-AnthBr
9-AnthBr
1-NpI
2-ThBr
2-PyBr
9 (3)
9 (3)
4 (4)
2 (5)
24 (12)
10 (13)
30 (14)
THF
1,4-dioxane
1,4-dioxane
THF
THF
THF
9-AnthBr
2-PyBr
4
2
11
yield by conventional heating or in 15% yield by microwave irra-
diation. The boronation of 10 with Bpin-H in the presence of
[PdCl2(PPh3)2] gave better yield of the boronated complex
[CpCo(S2C2(Ph)(p-C6H4Bpin))] (11) in 35% yield compared with the
boronation of 7 (17% yield, Scheme 3).
measurement (v ¼ 100 mV sꢀ1) indicating CoIII/CoII redox couple
[20], but oxidation waves are irreversible due to a following
chemical reaction of the oxidized species (Fig. 2). As described in
some previous papers [21,22], the oxidized species dimerizes by the
formation of an additional MeS bond.
The structures of 7, 9, 11, 12 and 13 were determined by X-ray
diffraction studies. Among them, unfortunately the crystal quality
of 9 was not good and then we obtained large R1 factor (0.0935 by 2
sigma cut off) and low data completeness (89.5%) (Table 4), but the
data may be enough for a brief structure determination. The ORTEP
drawings of them are displayed in Fig. 3. They have two-legged
piano-stool geometries, because the dihedral angles of Cp/CoS2
planes are almost 90ꢁ. The CoeS bond lengths are in the range of
2.08e2.11 Å which are shorter than those of typical CoIIIeSR bonds
2.3. Cross-coupling reaction boronated phenyl group substituted on
the dithiolene ring
The cross-coupling reaction of 8 with 2-bromopyridine or 9-
bromoanthracene was performed in the presence of [Pd(PPh3)4] as
a catalyst and Na2CO3 aq as a base. The reaction was monitored by
TLC and performed until no more starting complex was detected.
Each reaction gave the cross-coupling product [CpCo(S2C2(p-
C6H4Py)(H))] (12, 24% yield) or [CpCo(S2C2(p-C6H4Anth)(H))] (13,
10% yield), respectively as shown in Scheme 4 and Table 1 (Entries
7 and 8). No hydrogenated complex 6 was obtained from 8,
although 1 was well hydrogenated by the treatment with Na2CO3
aq (Entries 1 and 3). Moreover, the cross-coupling reaction of 11
with 2-bromopyridine was also carried out (Scheme 4) and then
[CpCo(S2C2(Ph)(p-C6H4Py))] (14) was obtained in 30% yield
(Table 1, Entry 9). In 12 and 13, those 1H NMR spectra indicated
dithiolene protons at 9.18 and 9.13 ppm by ring current effect of
cobaltadithiolene.
(2.25e2.48 Å) [23], because there is a p-donation from sulfur to the
central metal in the dithiolene ring [24]. In addition, the C1eC2
bond lengths (1.34e1.37 Å) in the metallacycle are between single
and double carbonecarbon bond lengths. Therefore, these metal-
lacycles are
p-electron delocalized (aromatized) cobaltadithiolene
rings. In fact, the cobaltadithiolene rings of them are extremely
planar because the largest deviations of the perfect planes are
0.0103e0.0303 Å (Table 3). All bond angles in the metallacycle are
also summarized in Table 3. They are comparable with those of
early [CpCo(dithiolene)] complexes [25]. The BeC(dithiolene) bond
length in 9 (1.562(13) Å) and the BeC(aryl) bond length in 11
(1.550(4) Å) are similar to that of 1 (1.566(5) Å) [15].
2.4. Absorption spectra, electrochemical properties and molecular
structures
3. Conclusion
All products 4e14 synthesized in this work were characterized
by spectroscopic data, electrochemical data and six of them were
also determined by X-ray structure analyses. 1e3 have been char-
acterized by a previous work [15]. Table 2 summarizes electronic
absorption maxima (lmax/nm) obtained from UVevis spectra in
dichloromethane solution (Fig. 1) and redox potentials (E/V vs Fc/
Fcþ) taken from CV (Fig. 2). Electronic absorption in the range of
In this work, we carried out Pd-catalyzed boronations and cross-
coupling reactions of the aromatic cobaltadithiolene complexes. An
unexpected direct boronation on the dithiolene carbon could be
observed. One possible reaction mechanism is through a hydro-
boration of dithiolene carbons by Bpin-H. Furthermore, we can
574e602 nm (
e
¼ 5400e17,500 Mꢀ1 cmꢀ1) are due to LMCT in the
Table 2
CV and UVevis spectral data.
metallacycle [19], and can be modified by a substituent effect on the
dithiolene ring. For example, the substitutions of Bpin group by
other aryl groups (Fig. 1) or by hydrogen atom indicate remarkable
redshift of the LMCT absorption (e.g. 1 vs 2e6 and 15, 8 vs 7, 12 and
13), although 11 vs 13 is exceptional. The reduction potentials are
modified toward positive by an electron-withdrawing effect (e.g. Br
or Py). All reduction waves are reversible on the time scale of CV
Complex Substituents
E1/2
Ep
lmax
/
e
/
Ref.
(red)/Va (ox)/Va nm
M
ꢀ1 cmꢀ1
1
Ph
Bpin
3-Py
ꢀ1.33
ꢀ1.25
þ0.66 574
þ0.68 595
þ0.61 587
þ0.55 592
þ0.54 590
þ0.55 592
5600
8600
8000
6700
7800
6500
[15]
[15]
[15]
2
Ph
3
Ph
9-Anth ꢀ1.28
4
Ph
1-Np
2-Th
H
H
H
ꢀ1.29
ꢀ1.30
ꢀ1.30
ꢀ1.23
ꢀ1.27
ꢀ1.27
ꢀ1.26
ꢀ1.27
ꢀ1.25
ꢀ1.26
ꢀ1.25
This work
This work
This work
This work
This work
This work
This work
This work
This work
This work
This work
5
Ph
6
Ph
7
8
9
10
11
12
13
14
p-C6H4Br
p-C6H4Bpin
p-C6H4Br
p-C6H4Br
þ0.55 591 10,200
O
O
O
B
þ0.60 583
þ0.69 574
þ0.55 599
7900
9900
5400
Br
H
B
Br
O
Bpin
Ph
S
S
[PdCl2(PPh3)2]
S
S
S
S
Co
Co
Co
+
p-C6H4Bpin Ph
þ0.56 600 12,100
H
O
H
B
p-C6H4Py
p-C6H4Anth
p-C6H4Py
H
H
Ph
þ0.55 598 17,500
7
O
þ0.61 593
7000
8
9
þ0.57 602 10,900
a
Scheme 2. Pd-catalyzed boronation of 7.
E1/2 ¼ jEpc e Epaj/2: half-wave potential, Ep: peak potential.

M. Nomura et al. / Journal of Organometallic Chemistry 696 (2011) 2720e2727
2723
O
B
O
O
Br
H B
O
S
S
[PdCl2(PPh3)2]
S
Co
S
Co
10
11
Scheme 3. Pd-catalyzed boronation of 10.
introduce some aryl-based functional groups to the dithiolene
complex by dithiolene-aryl or arylearyl cross-coupling reactions,
although low efficiency of the reaction up to 30% yield (Table 1) is
a problem. Concerning one possible application of this reaction, the
complex with a phenyl-pyridyl group such as 12 or 14 may undergo
a cyclometallation toward a luminescent Ir or Pt complex [26,27]. In
addition, the boronated square-planar [M(dithiolene)2] complexes
may be also a promising precursor for a cross-coupling reaction
because of its aromatic character [2]. Also a cross-coupling reaction
between different metalladithiolene rings will be more challenging
work to develop an asymmetrical bis-metalladithiolene ring [28].
Fig. 1. UVevis spectra of 1 and 2 in dichloromethane solution at room temperature.
removed under vacuum. Two blue products [CpCo(S2C2(Ph)(1-
Np))] (4) and [CpCo(S2C2(Ph)(H))] (6) were separated by column
chromatography on alumina. 4 was further recrystallized from
dichloromethane/n-hexane (4% yield). 6 was obtained in 7% yield.
The cross-coupling reaction of 1 (0.48 mmol) with 2-bromo-
thiophene (4.8 mmol) was performed by the similar procedure to
that of 1 with 1-iodonaphthalene. The cross-coupling product
[CpCo(S2C2(Ph)(2-Th))] (5) or 6 was obtained in 2% or 6% yield,
respectively.
4. Experimental section
4.1. General remarks
All reactions were carried out under an argon atmosphere by
means of standard Schlenk techniques. Toluene, THF and 1,4-
dioxane were dried with Na-benzophenone and distilled before
use. Triethylamine, 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (Bpin-
H), 1-iodonaphthalene, 2-bromothiophene, 2-bromopyridine,
9-bromoanthracene and [PdCl2(PPh3)2] were obtained from Tokyo
Chemical Industry Co., Ltd. Silica gel (Wakogel C-300) was supplied
from Wako Pure Chemical Industries, Ltd. [Pd(PPh3)4] [29],
[CpCo(S2C2(Ph)(Bpin))] (1) [15], [CpCo(CO)2] [30], 1-bromo-4-
(phenylethynyl)benzene [31] and 4-(p-bromophenyl)-1,3-dithiol-
2-one [32] were prepared by literature methods. Mass spectra were
recorded on a JEOL JMS-D300 spectrometer. NMR spectra were
measured with a JEOL LA500 spectrometer. CDCl3 and acetone-d6
for NMR measurements were supplied from Aldrich Chemicals.
Elemental analyses were determined by using a Shimadzu PE2400-
II instrument. HPLC was performed using model LC-908 produced
by Japan Analytical Industry Co. UVeVis spectra were recorded on
a Hitachi model UV-2500PC.
4.2.1. Spectroscopic data of [CpCo(S2C2(Ph)(1-Np))] (4)
Mass (EIþ, 70 eV) m/z (rel. intensity) 416 ([Mþ], 53), 188
([CpCoS2þ], 100), 124 ([CpCoþ], 24). 1H NMR (CDCl3, 500 MHz, vs
TMS)
d
¼ 7.79 (d, J ¼ 8.3 Hz, 2H), 7.37 (t, J ¼ 8.6 Hz, 2H), 7.21e7.29
(m, 3H), 7.13e7.18 (m, 2H), 7.06 (t, J ¼ 7.6 Hz, 2H), 6.97 (t, J ¼ 7.6 Hz,
2H), 5.45 (s, 5H, Cp). UVevis (CH2Cl2) lmax/nm (e) 592 (6700), 294
(25400). HR-Mass (EIþ, 70 eV) Calcd. for C23H17CoS2: 416.0103,
Found: 416.0109.
4.2.2. Spectroscopic data of [CpCo(S2C2(Ph)(2-Th))] (5)
Mass (EIþ, 70 eV) m/z (rel. intensity) 372 ([Mþ], 61), 188
([CpCoS2þ], 100), 124 ([CpCoþ], 30). 1H NMR (CDCl3, 500 MHz, vs.
4.2. Cross-coupling reaction of 1 with 1-iodonaphthalene or
2-bromothiophene
1 (0.2051 g, 0.49 mmol), 1-iodonaphthalene (0.7 ml, 4.8 mmol),
[Pd(PPh3)4] (0.1954 g, 0.17 mmol), triethylamine (4.0 ml) were
reacted in refluxing 1,4-dioxane (40 ml) for 24 h. All volatiles were
O
Ar
B
O
Ar-X, Na2CO3
S
S
S
[Pd(PPh3)4]
Co
Co
S
R
R
R = H; Ar = 2-Py (12)
R = H; Ar = 9-Anth (13)
R = Ph; Ar = 2-Py (14)
R = H (8)
R = Ph (11)
Fig. 2. Cyclic voltammograms of (a) 11 and (b) 14 (c ¼ 1 mmol dmꢀ3, v ¼ 100 mV sꢀ1
)
in dichloromethane solution containing 0.1 mol dmꢀ3 tetra-n-butylammonium
Scheme 4. Pd-catalyzed arylearyl cross-coupling reactions by 8 or 11.
perchlorate (TBAP).

2724
M. Nomura et al. / Journal of Organometallic Chemistry 696 (2011) 2720e2727
Table 3
Selected bond lengths (Å), bond angles (ꢁ), dihedral angles (ꢁ) and largest deviations (Å) from the perfect CoS2C2 plane.
7
9
11
12
13
14
Bond length
Co1eS1
Co1eS2
S1eC1
S2eC2
2.1090(5)
2.0988(5)
1.7276(16)
1.7014(19)
1.354(2)
e
2.089(2)
2.081(2)
1.703(8)
1.712(9)
1.363(12)
1.562(13)
2.1123(9)
2.0881(9)
1.721(2)
1.706(3)
1.376(4)
1.550(4)
2.1064(15)
2.096(2)
1.719(5)
1.690(5)
1.347(7)
e
2.0952(19)
2.090(2)
1.723(6)
1.688(6)
1.365(10)
e
2.1027(9)
2.1151(10)
1.721(3)
1.729(3)
1.368(5)
e
C1eC2
CeB
Bond angles
S1eCo1eS2
Co1eS1eC1
Co1eS2eC2
S1eC1eC2
S2eC2eC1
Largest deviation from CoS2C2 plane
Cp/CoS2 dihedral angle
91.099(19)
105.98(5)
105.23(6)
116.62(13)
120.92(13)
0.0303
90.54(10)
106.6(3)
107.0(3)
118.5(6)
117.4(6)
0.0163
90.61(3)
106.04(10)
107.29(10)
118.1(2)
117.9(2)
0.0103
90.84(6)
105.96(18)
105.32(19)
116.8(3)
121.0(4)
0.0187
90.85(8)
107.0(2)
105.5(2)
115.1(4)
121.5(5)
0.0168
90.58(3)
106.55(13)
106.41(13)
118.6(2)
117.7(2)
0.0268
94.270
88.405
90.137
87.685
92.612
93.833
TMS)
d
¼ 7.21e7.36 (m, 2H), 6.76e6.82 (m, 2H), 5.40 (s, 5H, Cp).
chromatography on silica gel (eluent: dichloromethane/n-
hexane ¼ 1:2). 7 was obtained in 62% yield.
UVevis (CH2Cl2) lmax/nm (e) 590 (7800), 295 (22800). HR-Mass
(EIþ, 70 eV) Calcd. for C17H13CoS3: 371.9511, Found: 371.9518.
4.3.2. Preparation of 7 derived from [CpCo(CO)I2]
4-(p-bromophenyl)-1,3-dithiol-2-one (0.16 g, 0.6 mmol) was
treated with sodium methoxide (1.2 mmol) in methanol (15 ml) for
3 h. The initial colorless solution was changed to yellow. [CpCo(CO)
I2] (0.24 g, 0.6 mmol) was added into the reaction mixture and then
a dark blue solution was rapidly formed. The solution was stirred
for 2 h and then solvents were removed under reduced pressure.
The residue was purified by column chromatography on silica gel.
The dark blue product 7 was obtained in 86% yield.
4.3. Preparation of [CpCo(S2C2(p-C6H4Br)(H))] (7)
4.3.1. Preparation of 7 derived from [CpCo(CO)2]
[CpCo(CO)2] (0.7 ml, 5.0 mmol), 4-(p-bromophenyl)-1,3-dithiol-
2-one (0.8034 g, 2.9 mmol) were refluxed in benzene (40 ml) for
18 h. Solvents were removed under reduced pressure, and the
residue was separated by column chromatography on silica gel
(eluent: dichloromethane/n-hexane ¼ 1:2). The resulted blue
fraction was further purified by recrystallization with dichloro-
methane/n-hexane. 7 was obtained in 33% yield as a dark blue solid.
The reaction mixture of [CpCo(CO)2] and 4-(p-bromophenyl)-
1,3-dithiol-2-one was also reacted in ethylene glycol (40 ml) under
microwave irradiation (264 W) for 10 min. After the reaction,
ethylene glycol was separated by a short column chromatography
on silica gel. The resulted mixture was further purified by column
4.3.3. Spectroscopic data of [CpCo(S2C2(p-C6H4Br)(H))] (7)
Mass (EIþ, 70 eV) m/z (rel. intensity) 370 ([Mþ(81Br)], 53), 368
([Mþ(79Br)], 50), 188 ([CpCoS2þ], 100). 1H NMR (CDCl3, 500 MHz, vs.
TMS)
d
¼ 8.97 (s, 1H, dithiolene-H), 7.65 (d, 2H, J ¼ 8.6 Hz, Ar), 7.43
(d, 2H, J ¼ 8.6 Hz, Ar), 5.38 (s, 5H, Cp). UVevis (CH2Cl2) lmax/nm (
e)
591 (10200), 294 (10700). Anal. Calcd. for C13H10BrCoS2: C, 42.29; H,
2.73; S, 17.37. Found: C, 42.56; H, 2.57; S, 17.19.
Table 4
Crystallographic data.
Compound
7
9
11
12
13
14
Formula
C
13H10BrCoS2
C19H21BBrCoO2S2
495.14
Purple
C25H26BCoO2S2
492.34
Dark blue
Block
0.17 ꢂ 0.17 ꢂ 0.13
Monoclinic
P21/c (No. 14)
298
C18H14CoNS2
367.37
Dark blue
Chip
0.35 ꢂ 0.07 ꢂ 0.05
Orthorhombic
Pna21 (No. 33)
298
C27H19CoS2
466.50
Dark blue
Block
0.17 ꢂ 0.17 ꢂ 0.15
Monoclinic
P21/n (No. 14)
298
C24H18CoNS2
443.47
Dark blue
platelet
0.25 ꢂ 0.06 ꢂ 0.01
Monoclinic
P21/a (No. 14)
298
FW (g molꢀ1
Crystal color
)
369.18
Dark blue
Needle
0.15 ꢂ 0.15 ꢂ 0.06
Monoclinic
P21/n (No. 14)
298
Crystal shape
Crystal size (mm)
Crystal system
Space group
T (K)
Chip
0.50 ꢂ 0.10 ꢂ 0.10
Triclinic
Pꢀ1(No.2)
298
a (Å)
b (Å)
c (Å)
5.7785(4)
10.0873(5)
23.1028(14)
6.847(7)
9.291(9)
16.847(18)
87.84(3)
89.52(3)
76.04(3)
1039.4(18)
2
12.259(3)
11.539(3)
17.018(4)
8.7946(8)
17.8876(14)
10.0299(8)
12.700(4)
11.827(4)
14.426(5)
15.5592(15)
5.9610(5)
22.221(2)
a
b
g
(ꢁ)
(ꢁ)
(ꢁ)
91.4364(9)
96.6652(10)
102.8029(11)
104.1543(13)
V (Å3)
1346.23(14)
4
1.821
2391.0(10)
4
1.368
1577.8(2)
4
1.546
2112.9(12)
4
1.466
1998.4(3)
4
1.474
Z
Dcalc (g cmꢀ3
)
1.582
2.965
m
(mmꢀ1
)
4.535
0.912
1.346
1.022
1.077
Total refls.
Unique refls. (Rint
Unique refls. (I > 2
R1 (I > 2 (I))
wR2 (I > 2 (I))
10,063
3031 (0.031)
7793
0.0320
0.0891
1.047
7453
4251 (0.083)
3120
0.0935
0.1379
18,295
5468 (0.033)
3196
0.0428
0.1090
1.036
11,698
3602 (0.039)
2254
0.0437
0.1262
1.036
16,166
4837 (0.030)
2650
0.0725
0.2315
1.003
14,855
4562 (0.038)
3253
0.0494
0.1218
1.014
)
s(I))
s
s
Goodness-of-fit
1.335
P
P
P
P
R1
¼
jjFoj ꢀ jFcjj= jFoj; wR2
¼
½
ðwðFo2 ꢀ Fc2Þ2Þ= wðFo2Þ2ꢃ1=2
.

M. Nomura et al. / Journal of Organometallic Chemistry 696 (2011) 2720e2727
2725
4.5.1. Spectroscopic data of [CpCo(S2C2(Ph)(p-C6H4Br))] (10)
Mass (EIþ, 70 eV) m/z (rel. intensity) 446 ([Mþ(81Br)], 15), 444
([Mþ(79Br)], 14), 188 ([CpCoS2þ], 100), 124 ([CpCoþ], 28). 1H NMR
(CDCl3, 500 MHz, vs. TMS)
J ¼ 2.4 Hz, 1H), 7.26e7.39 (m, 5H), 7.24 (t, J ¼ 2.4 Hz, 1H), 7.21 (t,
) 599
d
¼ 7.49 (t, J ¼ 2.4 Hz, 1H), 7.46 (t,
J ¼ 2.4 Hz, 1H), 5.64 (s, 5H, Cp). UVevis (CH2Cl2) lmax/nm (
e
(5400), 294 (22000). Anal. Calcd. for C19H14BrCoS2: C, 51.25; H, 3.17;
S, 14.40. Found: C, 51.71; H, 3.05; S, 14.35.
4.6. Preparation of boronated dithiolene complex
[CpCo(S2C2(Ph)(p-C6H4Bpin))] (11)
10 (0.0558 g, 0.13 mmol) and 4,4,5,5-tetramethyl-1,3,2-dioxa-
borolane (Bpin-H, 0.98 ml, 6.8 mmol) werereacted in the presence of
[PdCl2(PPh3)2] (0.0431 g, 0.061 mmol) in triethylamine (0.1 ml) and
toluene (40 ml). Thereaction mixturewasheatedat80 ꢁC for 24h. All
volatiles were removed under vacuum. The resulted mixture was
separated by HPLC and recrystallized by dichloromethane/n-hexane
solution. The dark blue product [CpCo(S2C2)(Ph)(p-C6H4Bpin))] (11)
was obtained in 35% yield.
Fig. 3. ORTEP drawings of 7, 9, 11, 12, 13 and 14. Thermal ellipsoids are drawn at 30%
probability level. All hydrogen atoms are omitted for simplicity.
4.4. Preparation of boronated dithiolene complex [CpCo(S2C2(p-
C6H4Bpin)(H))] (8)
7 (1.8568 g, 5.0 mmol) and 4,4,5,5-tetramethyl-1,3,2-dioxa-
borolane (Bpin-H, 2.2 ml, 15.2 mmol) were reacted in the pres-
ence of [PdCl2(PPh3)2] (1.0913 g, 1.6 mmol) in triethylamine
(42 ml) and 1,4-dioxane (40 ml). The reaction mixture was heated
at 80 ꢁC for 24 h. All volatiles were removed under vacuum. The
resulted mixture was separated by HPLC and the isolated prod-
ucts were recrystallized by dichloromethane/n-hexane solution.
The dark blue product [CpCo(S2C2(p-C6H4Bpin)(H))] (8) was
obtained in 17% yield. The other boronated complex
[CpCo(S2C2(p-C6H4Br)(Bpin))] (9) was also obtained as a purple
solid by HPLC separation (trace amount).
4.6.1. Spectroscopic data of [CpCo(S2C2(Ph)(p-C6H4Bpin))] (11)
Mass (EIþ, 70 eV) m/z (rel. intensity) 492 ([Mþ], 20), 188
([CpCoS2þ], 100), 124 ([CpCoþ], 23). 1H NMR (CDCl3, 500 MHz, vs.
TMS)
d
¼ 7.56 (d, J ¼ 8.3 Hz, 2H, Ar), 7.19e7.27 (m, 7H, Ar), 5.52 (s,
5H, Cp), 1.33 (s, 12H, Me). UVevis (CH2Cl2) lmax/nm (
e
) 600 (12100),
293 (49400). Anal. Calcd. for C25H26BCoO2S2: C, 60.99; H, 5.32.
Found: C, 60.06; H, 5.36.
4.7. Cross-coupling reaction of 8 with 2-bromopyridine or 9-
bromoanthracene
8 (0.0384 g, 0.092 mmol), 2-bromopyridine (0.45 ml, 4.7 mmol),
[Pd(PPh3)4] (0.0384 g, 0.030 mmol), Na2CO3 aq (5 ml,
c ¼ 5 mol dmꢀ3) were reacted in refluxing THF (40 ml) for 4 h. All
volatiles were removed under reduced pressure. The blue product
[CpCo(S2C2(p-C6H4Py)(H))] (12) was separated by HPLC. 12 was
obtained as a dark blue solid in 24% yield.
The cross-coupling reaction of 8 (0.037 mmol) with 9-bro-
moanthracene (0.75 mmol) and its purification were carried out by
the similar procedure to that of 8 with 2-bromopyridine. The cross-
coupling product [CpCo(S2C2(Ph)(p-C6H4Anth))] (13) was obtained
in 10% yield as a dark blue solid.
4.4.1. Spectroscopic data of [CpCo(S2C2(p-C6H4Bpin)(H))] (8)
Mass (EIþ, 70 eV) m/z (rel. intensity) 416 ([Mþ], 53), 188
([CpCoS2þ], 100). 1H NMR (CDCl3, 500 MHz, vs. TMS)
d
¼ 9.06 (s, 1H,
dithiolene-H), 7.80 (d, 2H, J ¼ 8.2 Hz, Ph), 7.75 (d, 2H, J ¼ 8.2 Hz, Ph),
5.38 (s, 5H, Cp), 1.34 (s, 12H, Me). UVevis (CH2Cl2) lmax/nm ( ) 583
e
(7900), 294 (31600). Anal. Calcd. for C19H22BCoO2S2: C, 54.82; H,
5.33; S, 15.41. Found: C, 54.60; H, 5.20; S, 15.39.
4.4.2. Spectroscopic data of [CpCo(S2C2(p-C6H4Br)(Bpin))] (9)
Mass (EIþ, 70 eV) m/z (rel. intensity) 496 ([Mþ(81Br)], 30), 494
([Mþ(79Br)], 27), 188 ([CpCoS2þ], 100). 1H NMR (CDCl3, 500 MHz, vs.
TMS)
d
¼ 7.40 (d, 2H, J ¼ 8.2 Hz, Ph), 7.35 (d, 2H, J ¼ 8.2 Hz, Ph), 5.37
4.7.1. Spectroscopic data of [CpCo(S2C2(p-C6H4Py)(H))] (12)
Mass (EIþ, 70 eV) m/z (rel. intensity) 367 ([Mþ], 79), 188
([CpCoS2þ], 100), 124 ([CpCoþ], 47). 1H NMR (CDCl3, 500 MHz, vs.
(s, 5H, Cp), 1.23 (s, 12H, Me). UVevis (CH2Cl2) lmax/nm (
(9900), 293 (49100). Anal. Calcd. for C19H21BBrCoO2S2: C, 46.09; H,
4.27. Found: C, 46.34; H, 4.22.
e) 574
TMS)
d
¼ 9.18 (s,1H, dithiolene-H), 8.68 (ddd,1H, J ¼ 7.6, 2.7,1.0 Hz),
8.15 (t, 1H, J ¼ 2.1 Hz), 8.12 (t, 1H, J ¼ 2.1 Hz), 8.02 (t, 1H, J ¼ 2.1 Hz),
7.99 (t, 1H, J ¼ 2.1 Hz), 7.96 (t, 1H, J ¼ 1.3 Hz), 7.87 (dt, 1H, J ¼ 15.5,
2.1 Hz), 7.34 (ddd, 1H, J ¼ 7.6, 4.8, 1.0 Hz), 5.52 (s, 5H, Cp). UVevis
4.5. Preparation of [CpCo(S2C2(Ph)(p-C6H4Br))] (10) derived from
[CpCo(CO)2]
(CH2Cl2) lmax/nm (e) 598 (17500), 303 (48900). Anal. Calcd. for
One-pot reaction of [CpCo(CO)2] (1.4 ml, 10 mmol), elemental
sulfur (0.6453 g, 20 mmol) and 1-bromo-4-(phenylethynyl)
benzene (1.2880 g, 5.0 mmol) was performed in refluxing toluene
(40 ml) for 2 h. A blue fraction was separated by column chroma-
tography on silica gel with dichloromethane. The dark blue product
(10) was obtained in 4% yield.
The similar one-pot reaction was carried out under micro-
wave irradiation (264 W) in ethylene glycol (40 ml) for 10 min.
After the reaction, ethylene glycol was separated by a short
column chromatography on silica gel. Again 10 was precisely
separated by column chromatography with dichloromethane as
an eluent (15% yield).
C18H14CoNS2: C, 58.85; H, 3.84; N, 3.81; S, 17.46. Found: C, 58.54; H,
3.61; N, 3.84; S, 17.46.
4.7.2. Spectroscopic data of [CpCo(S2C2(p-C6H4Anth)(H))] (13)
Mass (EIþ, 70 eV) m/z (rel. intensity) 466 ([Mþ], 93), 278 ([Mþ
e
CpCoS2], 100), 188 ([CpCoS2þ], 21), 124 ([CpCoþ], 46). 1H NMR
(CDCl3, 500 MHz, vs. TMS)
d
¼ 9.13 (s, 1H, dithiolene-H), 8.50 (s, 1H,
Anth), 8.06 (d, 2H, J ¼ 1.4 Hz), 8.00 (dt, J ¼ 8.6, 2.1 Hz, 2H), 7.70 (dd,
J ¼ 8.9, 1.0 Hz, 2H), 7.45 (dt, J ¼ 15.1, 1.4 Hz, 2H), 7.30e7.40 (m, 4H),
5.42 (s, 5H, Cp). UVevis (CH2Cl2) lmax/nm (e) 593 (7000), 380
(9200), 294 (22300). HR-Mass (EIþ, 70 eV) Calcd. for C27H19CoS2:
466.0260, Found: 466.0258.

2726
M. Nomura et al. / Journal of Organometallic Chemistry 696 (2011) 2720e2727
4.8. Cross-coupling reaction of 11 with 2-bromopyridine
Supplementary material
11 (0.0298 g, 0.061 mmol), 2-bromopyridine (0.060 ml,
0.63 mmol), [Pd(PPh3)4] (0.0107 g, 0.0093 mmol), Na2CO3 aq (5 ml,
c ¼ 5 mol dmꢀ3) were reacted in refluxing THF (40 ml) for 2 h. All
volatiles were removed under reduced pressure. The blue product
[CpCo(S2C2(Ph)(p-C6H4Py))] (14) was separated by HPLC. 12 was
obtained as a dark blue solid in 30% yield.
CCDC 808149 (11), 808150 (12), 808151 (13), 808152 (14),
808153 (7), 808154 (9); contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via www.
ccdc.cam.ac.uk/data_request/cif.
References
4.8.1. Spectroscopic data of [CpCo(S2C2(Ph)(p-C6H4Py))] (14)
Mass (EIþ, 70 eV) m/z (rel. intensity) 443 ([Mþ], 96), 188
([CpCoS2þ], 100), 124 ([CpCoþ], 42). 1H NMR (acetone-d6, 500 MHz,
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d
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4.10. CV measurements
All electrochemical measurements were performed under an
argon atmosphere. Solvents for electrochemical measurements
were dried by molecular sieve 4A before use. A platinum wire
served as a counter electrode, and the reference electrode Ag/AgCl
was corrected for junction potentials by being referenced internally
to the ferrocene/ferrocenium (Fc/Fcþ) couple. A stationary plat-
inum disk (1.6 mm in diameter) was used as a working electrode.
The Model CV-50W instrument from BAS Co. was used for cyclic
voltammetry (CV) measurements. CVs were measured in
1 mmol dmꢀ3 dichloromethane solutions of complexes containing
0.1 mol dmꢀ3 tetra-n-butylammonium perchlorate (TBAP) at 25 ꢁC.
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