Fine electronic state tuning of cobaltadithiolene complexes by substituent groups on the benzene ring

Article abstract of DOI:10.1016/j.poly.2016.05.062

A series of 3,6- and 4,5-dihalogen-substituted 1,2-benzenedithiol (H₂bdt) ligands, (3,6-X¹₂-4,5-X²₂-1,2-H₂bdt) (X² = H, X¹ = F (1a), Cl (1b), Br (1c); X¹ = H, X² = Cl (4)), and their cobalt complexes, [Cp^?Co(3,6-X¹₂-4,5-X²₂-1,2-bdt)] (X² = H, X¹ = F (2a), Cl (2b), Br (2c); X¹ = H, X² = Cl (5)), were synthesized by a modified selective thiolation reaction. The 1,2-diphenyl-substituted cobaltadithiolene complex (2d) was also synthesized. The molecular structures of all cobaltadithiolene complexes were determined by single crystal X-ray diffraction analysis. Compounds 2a, 5 and 12 showed unique packing structures with intermolecular interactions that confirmed them as the first examples of half-sandwich-type metalladithiolene complexes with a Cp^? ligand. The effects of the benzene substituent type and position on the metalladithiolene ring were investigated using UV-vis spectroscopy measurements and cyclic voltammetry. The results indicate that substitution of halogen atoms at the 3 and 6 position of the benzene ring had a larger effect on the dithiolene ring than substitution at the 4 and 5 positions.

Full text of DOI:10.1016/j.poly.2016.05.062

Polyhedron 117 (2016) 265–272
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Fine electronic state tuning of cobaltadithiolene complexes by
substituent groups on the benzene ring
⇑
Satoru Tsukada , Masataka Kondo, Hironobu Sato, Takahiro Gunji
Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda-shi, Chiba 278-8510, Japan
a r t i c l e i n f o
a b s t r a c t
1
2
Article history:
2 2 2
A series of 3,6- and 4,5-dihalogen-substituted 1,2-benzenedithiol (H bdt) ligands, (3,6-X -4,5-X -1,2-
Received 25 February 2016
Accepted 25 May 2016
Available online 2 June 2016
bdt) (X = H, X1 = F (1a), Cl (1b), Br (1c); X = H, X2 = Cl (4)), and their cobalt complexes, [Cp Co(3,6-X
2
1
⁄
1
H
2
2
-
2
-1,2-bdt)] (X2 = H, X = F (2a), Cl (2b), Br (2c); X = H, X2 = Cl (5)), were synthesized by a modified
1
1
4,5-X
2
selective thiolation reaction. The 1,2-diphenyl-substituted cobaltadithiolene complex (2d) was also synthe-
sized. The molecular structures of all cobaltadithiolene complexes were determined by single crystal X-ray
diffraction analysis. Compounds 2a, 5 and 12 showed unique packing structures with intermolecular inter-
actions that confirmed them as the first examples of half-sandwich-type metalladithiolene complexes with
Keywords:
Metalladithiolene complex
Electronic state
Packing structure
Cobalt
⁄
a Cp ligand. The effects of the benzene substituent type and position on the metalladithiolene ring were
investigated using UV–vis spectroscopy measurements and cyclic voltammetry. The results indicate that
substitution of halogen atoms at the 3 and 6 position of the benzene ring had a larger effect on the dithi-
olene ring than substitution at the 4 and 5 positions.
Halogen
Ó 2016 Elsevier Ltd. All rights reserved.
1
. Introduction
The electronic state of the central metal ion in metal complexes
tuted benzenedithiolate ligands and their complexes have been
reported [21–30]. However, the effect of the substitution position
and halogen type have not been investigated in a systematic way
because the synthesis of halogen-substituted dithiol ligands is dif-
ficult due to the high reactivity of halogens. Therefore, the develop-
is one of the main factors determining the nature of the complex.
The electronic state is also effected by ligands and ligand sub-
stituents. Alteration of the substituents often drastically changes
the properties of a complex, such as photophysical [1–8] and cat-
alytic abilities [9–14].
Metalladithiolene complexes have been studied in a wide range
of fields because of their unique properties, such as reversible
redox activity, magnetic properties and catalytic abilities [15–
ment of
a facile synthetic method for halogen-substituted
benzenedithiolate ligands is desirable.
Here, we report the synthesis of 3,6-dihalo and 4,5-dichloro-
1,2-benzenedithiols and their incorporation as ligands in cobalta-
dithiolene complexes. 3,6-Diphenyl-1,2-benzenedithiol and its
cobaltadithiolene complex are also synthesized. Their properties
are investigated using single crystal X-ray diffraction, UV–vis spec-
troscopy and electrochemical measurements.
2
0]. Many types of dithiolene ligand have been synthesized with
different substituents in order to study their effects on the metal
center in metalladithiolene rings. In particular, 1,2-benzenedithio-
late (bdt ) is one of the most common ligands in metalladithi-
olene chemistry. Different substituents on the benzene dithiolate
ligand elicit changes in the properties of its complexes, especially
catalytic [21–26], magnetic [27] and electrochemical properties
2À
2
. Experimental
2.1. General information
[
28,29]. Fine control of the electronic state by substitution on the
benzene dithiolate ligand is important in order to develop remark-
able properties. Systematic halogen exchange on the benzenedithi-
olate ligand is a conceivable way to exert precise changes on the
metal center. Several examples of the synthesis of halogen-substi-
Commercially available reagents were used without further
purification. Solvents were purified before use according to
reported methods. Reactions were carried out under an argon
atmosphere unless stated otherwise. Tetrahydrofuran (THF) was
freshly distilled from sodium/benzophenone ketyl under N
2
. Col-
umn chromatography was performed using Wakogel C-200 (Silica
Gel, 75–150 m).
Ò
⇑
Corresponding author.
E-mail address: tsukada@rs.tus.ac.jp (S. Tsukada).
l
http://dx.doi.org/10.1016/j.poly.2016.05.062
277-5387/Ó 2016 Elsevier Ltd. All rights reserved.
0

2
66
S. Tsukada et al. / Polyhedron 117 (2016) 265–272
1H NMR (300 or 500 MHz) and 13C{ H} NMR (75 or 126 MHz)
1
2.4. Synthesis of 3,6-dichloro-1,2-benzenedithiol (1b)
spectra were measured using tetramethylsilane as an external
1
9
standard. F NMR (376 MHz) spectra were measured using triflu-
oroacetic acid as an external standard. All melting points are
uncorrected.
The general procedure was performed using 1,2,3,4-tetra-
chlorobenzene 3b (0.43 g, 2 mmol) to obtain 1b as a dark green
solid (0.13 g, 13%).
1
For structural determinations, crystal data were collected using
a Bruker AXS SMART APEX CCD X-ray diffractometer equipped
H NMR (300 MHz, CDCl
3
) d, ppm: 7.17 (2H, s, Ar–H), 4.62 (2H,
À1
s, SH); IR (KBr,
m
/cm ): 3057 (CH), 2563 (SH).
with
a
rotating-anode X-ray generator emitting graphite-
radiation (0.7107 Å). Empirical absorption
monochromatic Mo K
a
2.5. Synthesis of 3,6-dibromo-1,2-benzenedithiol (1c)
corrections using equivalent reflections and Lorentzian polariza-
tion corrections were performed using the SADABS program [31].
All data were collected with SMART and Bruker SAINTPLUS (Ver-
sion 6.45) software packages. The structures were solved using
the SHELXS-97 [32] program and refined against F2 by using
SHELEXL-97 [33].
The general procedure was performed using 1,2,3,4-tetrabro-
mobenzene 3c (9.4 g, 24 mmol) to obtain 1c as a brown viscous
solid (0.69 g, 23%).
1
H NMR (300 MHz, CDCl
3
) d, ppm: 7.25 (2H, s, Ar–H), 4.85 (2H,
) d, ppm: 131.9 (s), 134.1 (s),
1
3
1
s, SH); C{ H} NMR (75 MHz, CDCl
122.5 (s); HR-MS (HR-FAB) m/z calc. for C
[MÀH] , found: 298.8055; IR (KBr,
3
7
9
81
Electrochemical data were recorded with an ALS 650E electro-
6
À1
H
3
Br BrS
2
: 298.8022
À
chemical analyzer. Bu
which was recrystallized from EtOH, and dried under vacuum for
4 h. A series of measurements were carried out under an argon
4
NClO
4
used as a supporting electrolyte,
m/cm ) 2920 (CH), 2543 (SH).
⁄
2
2.6. Synthesis of Cp CoF
2
bdt (2a)
atmosphere in a three-electrode cell (BAS Inc.), using 3 mm-diam-
eter glassy carbon as a working electrode (BAS Inc.), a platinum
A
solution of 3,6-difluoro-1,2-benzenedithiol 1a (0.18 g,
⁄
wire as a counter electrode and Ag/AgClO
0.01 M AgClO in 0.1 M Bu NClO /acetonitrile, BAS Inc.). After
each measurement, ferrocene was added as an internal standard.
Caution; Bu NClO is a potentially explosive chemical.
4
as a reference electrode
1.0 mmol) and Cp CoI
2
(CO) (0.48 g, 1.0 mmol, 1 equiv.) in THF
(
4
4
4
(5 mL) was stirred for 2 h at room temperature. The reaction mix-
ture was then evaporated, and the crude product was purified by
column chromatography on silica gel using dichloromethane/hex-
ane (2:8) as the eluent. The purple first fraction was collected and
4
4
Elemental analyses were performed using a PerkinElmer 2400II
CHNS analyzer. Satisfactory elemental analyses for compounds
evaporated to yield 2a as a dark purple solid (0.23 g, 59%).
1
1
a–1c, 2a, 2c, 2d, 4, 5 and 7 could not be obtained, but high
H NMR (500 MHz, CDCl
3
) d, ppm: 6.77 (2H, t, J = 6.3 Hz, Ar–H),
); C{ H} NMR (126 MHz, CDCl ) d, ppm: 155.8
(dd, J = 243, 4.4 Hz), 143.8 (dd, J = 15, 9.6 Hz), 107.9 (dd, J = 20,
1
3
1
resolution mass spectra for 1a–1c, 2a, 2c, 2d, 4, 5 and 7 are in
accord with the formulations.
1.97 (15H, s, CH
3
3
1
9
1
,2,3,4-Tetrabromobenzene (3c) [34] and 1,2-difluoro-3,6-
13 Hz), 92.7 (s), 11.0 (s); F NMR (470 MHz, CDCl
3
) d, ppm:
CoS Na:
diiodobenzene (11) [35] were prepared according to the methods
described in the literature.
À117.62 (s); HR-MS (HR-ESI-TOF) m/z calc. for C16
H
18
F
2
2
+
392.99694 [M+Na] , found: 392.99682.
⁄
2
.7. Synthesis of Cp CoCl
2
bdt (2b)
2
.2. General procedure for the synthesis of 3,6-dihalo-1,2-
The method described above for the preparation of 2a was per-
formed using 1b (0.21 g, 1.0 mmol). The reaction mixture was
benzenedithiol
refluxed for 2 h to obtain 2b as a dark purple solid (0.59 g, 92%).
1
,2,3,4-Tetrahalobenzene (10 mmol), iron powder (0.89 equiv.),
1
H NMR (300 MHz, CDCl
3
) d, ppm: 7.32 (2H, s, Ar–H), 1.91 (15H,
); C{ H} NMR (75 MHz, CDCl ) d, ppm: 154.5 (s), 126.9 (s),
22.5 (s), 93.4 (s), 11.0 (s); Anal. Calc. for C16 CoCl : C, 47.22;
sulfur (0.66 equiv.) and NaSHÁnH
2
O (4.0 equiv.) were added to dry
1
3
1
s, CH
3
3
N,N-dimethylformamide (32 equiv.). The mixture was heated to
1
H
17
S
2
2
1
40 °C for 16 h. The reaction mixture was cooled to room temper-
ature and added to water (50 mL). The mixture was filtered and
H, 4.14. Found: C, 47.54; H, 4.49%.
air-dried to afford a black solid. The black solid was then added
⁄
2
.8. Synthesis of Cp CoBr
2
bdt (2c)
to
6.5 equiv.) and water (20 mL), and allowed to reflux for 2 h. After
cooling to room temperature, the mixture was filtered with Celite.
The filtrate was added to 2 M H SO and then extracted with
dichloromethane. The organic phase was washed with brine and
dried with MgSO . After filtration, evaporation and drying, the cor-
responding 3,6-dihalo-1,2-benzenedithiol was afforded as a solid.
a solution of methanol (20 mL), ZnO (1.2 equiv.), NaOH
(
The method described above for the preparation of 2a was per-
formed using 3c (0.096 mg, 0.32 mmol) to obtain 2c as a black-pur-
ple solid (110 mg, 73%).
2
4
1
2 2
H NMR (500 MHz, CD Cl ) d, ppm: 7.27 (2H, s, Ar–H), 1.95
4
1
3
1
(
15H, s, CH
3
2 2
); C{ H} NMR (126 MHz, CD Cl ) d, ppm: 154.5 (s),
1
H
22.5 (s), 93.4 (s), 11.0 (s); HR-MS (HR-APCI-TOF) m/z calc. for C16
: 490.85487 [M+H] , found: 490.85411; IR (KBr,
cm ) 2984 (CH), 2912 (CH).
-
7
9
81
+
18 Br BrCoS
2
m
/
À1
2.3. Synthesis of 3,6-difluoro-1,2-benzenedithiol (1a)
2.9. Synthesis of 1,2-dichloro-4,5-diiodobenzene (6)
The general procedure was performed using 1,2,3,4-tetrafluo-
robenzene 3a (1.5 g, 10 mmol) and NaSHÁnH
.2 equiv.). The reaction mixture was stirred for 24 h at 140 °C in
a sealed tube to obtain 1a as a dark green solid (0.37 g, 21%).
2
O (1.9 g, 22 mmol,
A slightly modified reported literature method was used to syn-
2
thesize 6 in 80% yield, using 1,2-dichlorobenzene instead of 1,2-
dibromobenzene [36]. Spectral data for the product was in agree-
ment with the previous report [37].
1
H NMR (500 MHz, CDCl
3
) d, ppm: 6.87 (2H, t, J = 6.5 Hz, Ar–H),
.93 (2H, s, SH); C{ H} NMR (126 MHz, CDCl ) d, ppm: 155.0 (dd,
J = 242, 3.8 Hz), 120.2 (dd, J = 16, 9.6 Hz), 112.4 (dd, J = 21, 13 Hz);
1
3
1
3
3
2.10. Synthesis of 4,5-dichloro-1,2-benzenedithiol (4)
1
9
3
F NMR (470 MHz, CDCl ) d, ppm: À110.95 (t, J = 5.9 Hz); HR-MS
À
(
HR-ESI-TOF) m/z calc. for C
76.96448.
H
6 3
F
2
S
2
: 176.96497 [MÀH] , found:
The general procedure was performed using 1a (4.0 g, 10 mmol)
to obtain 4 as a gray-green solid (0.9 g, 43%).
1

S. Tsukada et al. / Polyhedron 117 (2016) 265–272
267
1
H NMR (500 MHz, CDCl
3
) d, ppm: 7.46 (2H, s, Ar–H), 3.76 (2H,
s, SH); C{ H} NMR (126 MHz, CDCl ) d, ppm: 131.9 (s), 131.4 (s),
30.5 (s); HR-MS (HR-APCI-TOF) m/z calc. for C Cl : 208.90532
(1:3, 5 mL) was added Pd(PPh
mixture was stirred for 40 h at 80 °C, then extracted with ethyl
acetate. The organic layer was dried with MgSO , filtered and evap-
orated. The crude product was purified by column chromatography
on silica gel with chloroform/hexane (1:1) as the eluent. The pale
yellow second fraction was collected and evaporated to yield a pale
3
)
4
(69 mg, 60
l
mol). The reaction
1
3
1
3
1
6
H
3
S
2 2
4
À
[
MÀH] , found: 208.90532.
⁄
2
.11. Synthesis of Cp CobdtCl
2
(5)
yellow solid (0.12 g, 60%).
1
The method described above for the preparation of 2b was per-
formed using 4 (106 mg, 0.5 mmol) instead of 1b to obtain 5 as a
6
H NMR (300 MHz, Acetone-d ) d, ppm: 7.51–7.30 (12H, m,
1
3
1
Ar–H), 2.09 (6H, s, CH
d, ppm: 147.0 (s), 141.6 (s), 131.1 (s), 130.1 (s), 128.8 (s), 128.0
(s), 20.2 (s); HR-MS (HR-APCI-TOF) m/z calc. for C20 Na:
: C,
3
);
6
C{ H} NMR (75 MHz, Acetone-d )
black-purple solid (121 mg, 60%)
1
H NMR (500 MHz, CDCl
3
) d, ppm: 7.86 (2H, s, Ar–H), 1.93 (15H,
); C{ H} NMR (126 MHz, CDCl ) d, ppm: 154.4 (s), 129.9 (s),
26.2 (s), 92.3 (s), 11.0 (s); HR-MS (HR-APCI-TOF) m/z calc. for C16
H
18
S
2
1
3
1
+
s, CH
3
3
345.0748 [M+Na] , found: 345.0754; Anal. Calc. for C20
H
18
S
2
1
H
-
74.49; H, 5.63. Found: C, 73.78; H, 5.44%.
+
18Cl
2
1 2
Co S : 402.95590 [M+H] , found: 402.95536.
⁄
2
.16. Synthesis of Cp CoPh
2
bdt (2d)
2
.12. Synthesis of 10
A
solution of
8
(97 mg, 0.30 mmol) and MeSNa (42 mg,
n-BuLi (3.7 mL, 6.0 mmol) and diisopropylamine (0.88 mL,
.4 mmol) were added to anhydrous THF (10 mL) at À78 °C and
0
.60 mmol) in DMF (3 mL) was stirred for 40 h at 160 °C.
⁄
6
Cp CoI
2
(CO) (0.21 g, 0.45 mmol) was then added at room tempera-
stirred for 30 min. Compound 9 (0.49 mL, 5.0 mmol) was then
added to the reaction mixture at À78 °C and stirred for 1 h. A
ture, followed by stirring for 2 h at 80 °C. The reaction mixture was
extracted with diethyl ether and the organic layer was washed
with brine, dried with MgSO , filtered and evaporated. The crude
4
2
pre-cooled solution of I (1.28 g, 5.0 mmol) in THF (5 mL) was then
added and stirred for a further 3 h, allowing the reaction to return
from À78 °C to room temperature. After adding Na (10 mg,
.3 mmol) and stirring for a further 1 h, the reaction mixture was
extracted with diethyl ether. The organic layer was dried with
NaSO , filtered and evaporated. The crude product was purified
product was purified by column chromatography on silica gel
using dichloromethane/hexane (8:2) as the eluent. The purple sec-
ond fraction was collected and evaporated to yield a black-purple
2 2 3
S O
8
solid (90 mg, 62%).
1
4
2 2
H NMR (500 MHz, CD Cl ) d, ppm: 7.65 (4H, d, J = 7.5 Hz), 7.51
by column chromatography on silica gel using hexane as the elu-
ent. The colorless fraction was collected and evaporated to yield
(
4H, t, J = 7.5 Hz), 7.44 (2H, t, J = 7.5 Hz), 7.13 (2H, s), 1.88 (15H, s);
1
3
1
C{ H} NMR (125 MHz, CD
2 2
Cl ) d, ppm: 154.1 (s), 142.6 (s), 141.9
white needle crystals (0.81 g, 72%).
(
(
s), 130.5 (s), 128.4 (s), 127.5 (s), 124.1 (s), 92.5 (s), 10.9 (s); HR-MS
HR-APCI-TOF) m/z calc. for C28H28CoS Na: 487.0964 [M+Na] ,
2
1
+
3
H NMR (300 MHz, CDCl ) d, ppm: 7.50–7.46 (1H, m, Ar–H),
7
.18–7.09 (1H, m, Ar–H), 6.89–6.81 (1H, m, Ar–H).
found: 487.0961.
2.13. Synthesis of 12
3
. Results and discussion
The general procedure was performed using 11 (1.5 g, 10 mmol)
The 3,6-dihalo-1,2-benzenedithiols 1a–1c were prepared from
,2,3,4-tetrahalobenzenes using a modification of a literature
and NaSHÁnH
2
O (1.1 equiv.). The reaction mixture was stirred for
h at 140 °C. The crude product was obtained as a dark green solid.
1
7
method reported for the synthesis of tetra- or trichloro-1,2-ben-
zenedithiols [25,28]. This reaction required heating at 140 °C in
the initial step. However, the boiling point of 1,2,3,4-tetrafluo-
robenzene is 95 °C. Therefore, the synthesis of 1a was carried out
in a sealed tube to allow heating temperatures above the boiling
The crude product was then used in the method described above
for 2b. After recrystallization from chloroform, 12 was obtained
as a black-purple solid.
2
.14. Synthesis of 7
point. The dihalo-substituted cobaltadithiolene complexes 2a–2c
⁄
were synthesized from 1a to 1c and Cp CoI
2
(CO) in good yield
A 1 M KOH ethanolic solution (3.2 mL, 3.2 mmol) was added
dropwise to a stirred solution of 3,6-dibromo-1,2-benzenedithiol
0.49 g, 1.6 mmol) in THF/EtOH (3 mL/3 mL). THF (3 mL) was then
added to the solution and the mixture was stirred for 30 min at
room temperature. After the solution changed to a brown suspen-
sion, the reaction was cooled to 0 °C and iodomethane (1.2 g,
.5 mmol) was added. The reaction mixture was then stirred for
7 h at 40 °C, before extracting with diethyl ether. The organic
4
layer was washed with brine, dried with MgSO , filtered and evap-
(
Scheme 1). The 4,5-dichloro-substituted cobaltadithiolene 5 was
synthesized in the same manner as 2b, through a nucleophilic aro-
matic substitution reaction selective for iodine substituents on 6,
and following a complexation reaction of 4 (Scheme 2).
Unfortunately, the 3,6-diiodo-substituted benzenedithiol and
cobaltdithiolene compounds were not obtained using the above
method. Therefore, we attempted to synthesize the 3,6-diiodo-sub-
stituted benzenedithiol and the corresponding cobalt complex
using 1,2-difluoro-3,6-diiodobenzene 11 instead of 1,2,3,4-
tetraiodobenzene. Nucleophilic aromatic substitution reactions
(
8
1
orated. The crude product was purified by column chromatography
on silica gel using dichloromethane/hexane (1:3) as the eluent. The
colorless third fraction was collected and evaporated to yield a
white solid (0.39 g, 72%).
1
H NMR (300 MHz, CDCl
3
) d, ppm: 7.25 (2H, s, Ar–H), 2.51 (6H,
); C{ H} NMR (75 MHz, CDCl ) d, ppm: 144.8 (s), 134.3 (s),
30.7 (s), 20.6 (s); HR-MS (HR-APCI-TOF) m/z calc. for C
1
3
1
Co
s, CH
3
3
1
) NaSH·nH
Fe, S
2
O,
7
9-
X
X
HS
SH
S
S
1
H
8 9
2
Cp*CoI (CO)
8
1
+
Br BrS
2
: 326.85124 [M+H] , found: 326.85186.
X
X
X
X
X
X
2
) NaOH, ZnO
) H SO
3
2
4
3
a: X = F
3b: X = Cl
c: X = Br
1a: X = F
2a: X = F
2.15. Synthesis of 8
1b: X = Cl
1c: X = Br
2b: X = Cl
2c: X = Br
3
To a suspension of 7 (0.20 g, 0.60 mmol), PhB(OH)
.3 mmol) and t-BuOK (0.17 g, 1.5 mmol) in deionized water/THF
2
(0.16 g,
Scheme 1. Synthesis of 3,6-dihalo-1,2-benzenedithiols 1a–1c and their cobalta-
dithiolene complexes 2a–2c.
1

2
68
S. Tsukada et al. / Polyhedron 117 (2016) 265–272
at the fluorine positions in 11. The synthesis of 3,6-diiodo-substi-
tuted benzenedithiol was attempted with 11 under similar condi-
Co
tions to the synthesis of 2b, using 1.1 equivalents of NaSHÁnH
2
O
I
I
1) NaSH·nH O, HS
Fe, S
SH
Cl
2
S
S
Cp*CoI2(CO)
and refluxing for 7 h. However, the products of this reaction were
difficult to isolate. Therefore, the subsequent complexation was
carried out using the crude product. A single crystal was obtained
by recrystallization from chloroform. Surprisingly, this single crys-
tal was not 3,6-diiodo-substituted cobaltadithiolene, but 12
2) NaOH, ZnO
Cl
Cl 3) H2SO4
Cl
Cl
Cl
6
4
5
Scheme 2. Synthesis of 4,5-dichloro-1,2-benzenedithiols 4 and its cobaltadithi-
olene complex 5.
(
Scheme 3), indicating that the substitution with thiolate ions
had occurred at both the fluoro and iodo positions. In other words,
the substitution reaction seemed to have low selectivity under
these conditions.
1
) NaSH·nH
Fe, S
2
O,
The diphenyl-substituted cobaltadithiolene complex 2d was
obtained via a three-step reaction of 1c (Scheme 4). The thiol
groups in 1c had to be protected with methyl groups for the syn-
thesis of 8 using the Suzuki–Miyaura coupling reaction. Because
of low stability, 3,6-diphenyl-1,2-benzenedithiol could not be iso-
lated. Therefore, 2d was synthesized by deprotecting 8, followed
by a one-pot complex-forming reaction with dithiolate ions.
The molecular structures of 2a–2d, 5 and 12 were successfully
determined by single crystal X-ray diffraction analysis (Fig. 1–4,
Table 1). The structural features of the metalladithiolene rings in
1
) n-BuLi,
i-Pr NH
) I
1) n-BuLi,
i-Pr NH
2) I
2) NaOH, ZnO
3) H SO
2
4) Cp*CoI (CO)
Co
2
2
2
4
F
F
F
F
F
F
S
S
I
2
2
2
I
I
I
F
9
10
11
12
Scheme 3. Synthesis of 12.
⁄
these complexes resembled those of Cp Cobdt 2e [39]. The pla-
narity of the metalladithiolene ring in 2a–2d, 5 and 12 increased
compared to 2e. The dihedral angles between the S–Co–S and
S–C–C–S planes of 2a–2d, 5, 12 and 2e were 0.87°, 3.83°, 2.92°,
PhB(OH)
t-BuOK,
Pd(PPh )
2
,
Co
1
2
) KOH
1) MeSNa
2) Cp*CoI (CO)
S
S
S
S
S
S
) CH
3
I
3
4
2
1c
Br
Br
Ph
Ph
Ph
Ph
0
.74°, 4.04°, 2.00° and 6.93°, respectively.
7
8
2d
Using X-ray and neutron diffraction analysis, it was shown that
the two external phenyl groups of the p-terphenyl group were pla-
nar at room temperature, and twisted toward the central phenyl
ring by about 25° at 193 K (the phase transition temperature)
[40–42]. In contrast, both external phenyl groups in 2d became
highly twisted toward the central bdt ligand compared with p-ter-
phenyl (Fig. 1d). The twist angles in 2d were approximately 78°
Scheme 4. Synthesis of 1,2-diphenyl-substituted cobaltadithiolene complex 2d.
with thiolate ions are more facile at fluorine-substituted than
iodine-substituted positions [38]. Therefore, it was expected that
substitution reactions with thiolate ions would occur selectively
Fig. 1. ORTEP drawings of (a) 2a, (b) 2b, (c) 2c and (d) 2d, with thermal ellipsoids at the 50% probability level. Hydrogen atoms are omitted for clarity.

S. Tsukada et al. / Polyhedron 117 (2016) 265–272
269
Fig. 2. Packing structure of 2a.
Fig. 3. (a) ORTEP drawings of 5 with thermal ellipsoids at the 50% probability level. Hydrogen atoms are omitted for clarity. (b) Packing structure of 5.
Fig. 4. (a) ORTEP drawings of 12 (only one of the two independent molecules is shown) with thermal ellipsoids at the 50% probability level. Hydrogen atoms are omitted for
clarity. (b) Packing structure of 12.

2
70
S. Tsukada et al. / Polyhedron 117 (2016) 265–272
Table 1
Summary of crystal data.
trile-2,3-dithiolate; 3.381 Å) [44], which were the only previous
examples of face-to-face interactions of Cp–Cp in metalladithi-
⁄
2
a
2b
2c
olene complexes. These Cp ligands had a staggered conformation
in order to minimize steric repulsion.
p–p Stacking was also
Empirical formula
Formula weight
Crystal system
Space group
a (Å)
C
16
H
17CoF
2
S
2
C
16
H
17CoCl
403.25
orthorhombic orthorhombic
2
S
2
C
16
H
17CoBr
2 2
S
370.35
monoclinic
P21/c
10.3872(8)
10.8599(8)
14.0431(10)
90
492.17
observed between the phenyl rings in the bdt ligands, with a dis-
tance of 3.676 Å, giving rise to the opposite conformation. Mole-
cules of 2a were organized into a staircase pattern due to the
Pbca
Pbca
8.3712(14)
13.590(2)
29.439(5)
90
8.3890(13)
13.529(2)
30.435(5)
90
⁄
⁄
Cp –Cp face-to-face interactions and
p–p stacking of the bdt
b (Å)
c (Å)
ligands. Compound 5 also exhibited intermolecular interactions
(Fig. 3). The molecular organization of 5 was different from 2a, in
which a staircase pattern arose from the two interactions, orga-
nized by right angles at each step. Furthermore, a staircase pattern
was arranged in the same direction in 5.
a
(°)
b (°)
104.8130
90
90
(
10)
c
(°)
90
1531.5(2)
4
90
90
3454.2(9)
8
3
V (Å )
3349.1(10)
8
103
1.599
1.582
1648
16682
Z
The crystal structure of 12 displayed different types of packing
structure (Fig. 4). Two crystallographically independent molecules
T (K)
103
103
À3
Dcalc (g cm
)
1.606
1.403
760
7889
2784
(0.0210)
0.0262
0.0723
1.112
1.893
5.852
1936
20164
⁄
were identified. The Cp ring of one molecule was almost parallel
À1
l
(Mo K ) (mm
a
)
to the benzene ring of the bdt ligand of another molecule. This
F (000)
Reflection collected
Independent reflections
int
(R )
⁄
indicates that Cp -bdt intermolecular interactions are present,
3094 (0.0587) 4069 (0.0884)
leading to the formation of a tetrameric motif with four molecules
⁄
through four Cp -bdt interactions, with the shortest CCp⁄–Cbdt
R
1
(I > 2r
(I))
0.1266
0.3027
1.24
0.0785
0.156
1.16
intermolecular distances being 3.457 and 3.493 Å.
wR (all data)
2
2
UV–vis absorption spectra of 2a–2e and 5 were recorded in
dichloromethane solution (Fig. 5). The strong absorption peak at
Goodness of fit (GOF) on F
2
d
5
12
5
74 nm for 2e was attributed to a LMCT (ligand to metal charge
Empirical formula
Formula weight
Crystal system
Space group
a (Å)
C
28
H
27CoS
2
C
16
H
17CoCl
403.25
orthorhombic monoclinic
2
S
2
C
16
H
17CoFIS
2
transfer) transition from the S–C–C–S dithiolate ligand to the
cobalt atom, which is usually observed for half-sandwich-type
group 9 metalladithiolene complexes [30,45,46]. Therefore, the
absorption peaks at around 560 nm for these complexes were also
assigned to LMCT transitions. The spectral profiles of the com-
plexes are quite similar; the 3,6-dihalo-substituted cobaltadithi-
olene complexes showed a significant blue-shift compared to the
others, while 3,6-diphenyl substitution led to a small blue-shift
486.55
monoclinic
P21/n
9.1242(5)
14.7837(7)
17.2384(9)
90
94.3230(10)
90
478.25
Pnma
P21/n
9.3932(8)
24.538(2)
15.1135(13)
90
97.8980(10)
90
13.7760(4)
14.122485)
8.7571(3)
90
90
90
b (Å)
c (Å)
a
(°)
b (°)
(°)
c
3
V (Å )
2318.7(2)
4
1703.70(10)
4
3450.5(5)
8
(Table 2). The absorption peak of 5 was almost the same as the
Z
non-substituted complex 2e. Therefore, substitution at the 4 and
5 positions of the benzene ring had little effect on the dithiolene
ring compared with substitution at the 3 and 6 positions.
T (K)
103
1.394
0.934
1016
103
103
À3
Dcalc (g cm
)
1.572
12.976
824
1.841
3.026
1872
À1
l
(Mo K ) (mm
a
)
F (000)
Reflection collected
Independent reflections
12220
4252
12854
18185
1808 (0.0400) 6314 (0.0218)
(
R
int
)
r
(0.0159)
0.0268
0.0737
1.049
R
1
(I > 2
wR (all data)
Goodness of fit (GOF) on F
(I))
0.0568
0.1442
1.228
0.0388
0.115
1.118
2
2
and 82°, because of the electronic repulsion between the sulfur
lone pair and the ortho-proton of the external phenyl ring.
Unique packing structures were observed in 2a, 5 and 12. The
packing structure of 2a showed two intermolecular interactions
⁄
⁄
(
Fig. 2). Intermolecular Cp –Cp face-to-face interactions were
identified as having a distance of 3.688 Å. To the best of our knowl-
edge, this is the first example of a face-to-face-type interaction in a
metalladithiolene complex. This distance was slightly longer than
Å
that in CpNi(bdt) (3.32 Å) [43] and [CpNi(adt)] (adt = acryloni-
Fig. 5. UV–vis-near infrared absorption spectra of 2a–2e and 5 in dichloromethane.
Table 2
UV–vis spectra and electrochemical data of 2a–2e and 5.
/103
M
À1
cm
À1
k
e
/103
M
À1
cm
À1
Potential/V vs. Fc /Fc
+
k
1
/nm
e
1
2
/nm
2
E0’
DE
p
a
E
pc
E
pa
2
2
2
2
5
2
e
a
b
c
574
556
555
553
573
569
9.1
8.1
8.6
9.1
7.8
8.7
788
775
779
779
784
798
0.9
0.9
0.9
1
0.7
0.9
À1.36
À1.22
À1.21
À1.22
À1.26
À1.31
À1.29
À1.15
À1.15
À1.15
À1.17
À1.24
À1.33
À1.18
À1.18
À1.18
À1.22
À1.28
0.07
0.06
0.06
0.07
0.09
0.07
d
a
D
E
p
= Epa À Epc
.

S. Tsukada et al. / Polyhedron 117 (2016) 265–272
271
Acknowledgments
This work was supported by a Grant-in-Aid for Scientific
Research on Innovative Areas ‘‘New Polymeric Materials Based on
Element-Blocks (no. 2401)” (24102008A02) from The Ministry of
Education, Culture, Sports, Science, and Technology, Japan.
This work was supported by JSPS KAKENHI Grant Number
JP24102008A02.
Appendix A. Supplementary data
CCDC 1453538, 1453539, 1453540, 1453541, 1453542 and
1
453543 contains the supplementary crystallographic data for
2
a–2d, 5 and 12. These data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: (+44) 1223 336 033; or e-mail:
deposit@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at http://dx.doi.org/10.
Fig. 6. Cyclic voltammograms of (a) 2e, (b) 2a, (c) 2b, (d) 2c, (e) 5 and (f) 2d at
À1
0
.1 V s in 0.1 M n-Bu
4
NClO
4
-MeCN.
1
016/j.poly.2016.05.062.
Cyclic voltammograms of 2a–2e and 5 in 0.1 M n-Bu
4 4
NClO -
References
MeCN are shown in Fig. 6. All the complexes displayed one
0’
reversible redox wave in the range E = À1.18 to À1.33 V vs. the
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