Organometallic dithiolene complexes of benzenedithiolate analogues with π-coordinating and π-interacting Cp* ligand

Article abstract of DOI:10.1016/j.jorganchem.2009.05.022

Organometallic dithiolene complexes, which were formulated as [Cp*M(dcbdt)] and [Cp*M(dcdmp)] (M = Co, Rh, Ir; Cp* = η⁵-pentamethylcyclopentadienyl, dcbdt = 4,5-dicyanobenzene-1,2-dithiolate, dcdmp = 2,3-dicyano-5,6-dimercaptopyrazine) were pre

Full text of DOI:10.1016/j.jorganchem.2009.05.022

Journal of Organometallic Chemistry 694 (2009) 3116–3124
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Organometallic dithiolene complexes of benzenedithiolate analogues
with
p
-coordinating and p-interacting Cp* ligand
Mitsushiro Nomura , Eriko Tsukano, Chikako Fujita-Takayama, 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:
Received 21 April 2009
Received in revised form 15 May 2009
Accepted 19 May 2009
Available online 23 May 2009
Organometallic dithiolene complexes, which were formulated as [Cp*M(dcbdt)] and [Cp*M(dcdmp)]
5
(
M = Co, Rh, Ir; Cp* =
g
-pentamethylcyclopentadienyl, dcbdt = 4,5-dicyanobenzene-1,2-dithiolate,
I
dcdmp = 2,3-dicyano-5,6-dimercaptopyrazine) were prepared from a low valent Cp*Co or high valent
III
III
III
III
III
Cp*M species (M = Co , Rh , Ir ). The UV–Vis absorption spectral and electrochemical data of them
were obtained. The lowest absorption (HOMO–LUMO) energies of them became redshift in order of
the Co > Rh > Ir complexes. The reduction potentials suggested that the central metal modifies their
LUMO levels. The molecular and crystal structures of [Cp*Co(dcbdt)] (3a), [Cp*Co(dcdmp)] (4a) and
Keywords:
Dithiolene
Cp* ligand
Crystal structure
p–p stacking
Monomer
Dimer
[Cp*Rh(dcdmp)] (4b) were determined by X-ray diffraction studies. The cobalt complexes 3a and 4a were
monomeric, formally 16-electron complexes and have two-legged piano-stool geometries. The crystal
structure of 3a indicated some plane-to-plane intermolecular interactions such as benzeneÁ Á Ábenzene
interaction on the dcbdt ligand and two Cp*Á Á Ábenzene
p–p stackings. 4a showed plane-to-plane inter-
action with a pseudo-4-fold-symmetry arrangement between the pyrazine moieties on the dcdmp ligand.
The rhodium complex 4b was dimeric in the crystal to form a criss-cross arrangement and had a three-
legged piano-stool geometry, but it was monomerized in solution. The dimer of 3b was observed in the
oxidation process of the cyclic voltammogram.
Ó 2009 Elsevier B.V. All rights reserved.
1
. Introduction
have been reported. (3) Organometallic dithiolene complex [10],
which incorporates dithiolene ligand and some organic ligands to
Metal dithiolene complexes are widely investigated in chemis-
try, physics, optics and biology as well, because of their interesting
-electron system such as the -electron delocalization [1], -elec-
tron magnetic interaction [2], -electron-induced electrical
conductivity [3], and also biochemically reactive central metal
make metal–carbon bonds. Their typical examples are formulated
5
as [CpM(dithiolene)] [10] (Cp =
g -cyclopentadienyl) whose Cp/
p
p
p
dithiolene ratio is often 1:1 (M = Co, Rh, Ir, Ni) [11,12], 1:2
(M = Mo) [13], or 2:1 (M = Ti, Mo, W) [14,15]. Among them, the
Cp/dithiolene 1:1 complexes have been relatively classical, but re-
cently the preparation and properties of new organometallic radi-
p
[
[
4]. Since the first dithiolene complex has been reported in ‘60s
5], enormous examples of them have been synthesized and
III
Å
cal complexes [CpNi (dithiolene)] (S = 1/2) have been intensively
developed.
To our knowledge, metal dithiolene complexes are classified
studied [12]. These studies have really indicated that the Cp ligand
is not only a p-coordinating ligand but also a p-interacting ligand
into three main categories as follows. (1) Homoleptic dithiolene
complex whose coordinating ligands are dithiolene only [6]. For
example, bisdithiolene complexes with square–planar or tetrahe-
dral geometry and trisdithiolene complexes with trigonal pris-
matic geometry are well known. (2) Heteroleptic dithiolene
complex which has dithiolene and some other inorganic ligands
to make intermolecular magnetic interactions through CpÁ Á Ádithio-
lene [16], CpÁ Á ÁS@C [12,17], and CpÁ Á ÁCp as well [16,18].
III
On the other hand, Cp/dithiolene 1:1 complexes of Co have
been developed since ‘60s [19]. Interestingly, some recent papers
III
Å
have described that the paramagnetic [CpNi (dithiolene)] com-
III
plexes are isostructural to the diamagnetic [CpCo (dithiolene)]
[
[
7]. In general, luminescent [(N^N)M(dithiolene)] (N^N = diimine)
8] and [(P^P)M(dithiolene)] (P^P = diphosphine) [9] complexes
with the same dithiolene ligand [18,20]. Namely, the isostructural
CpCo complexes most probably have the similar intermolecular
interaction based on the Cp ligand. Needless to say, Cp* ligand
5
(
Cp* =
g
-pentamethylcyclopentadienyl) is also supposed to be an
-interacting ligand. Recently, [Cp*Co(dithiolene)]
*
Corresponding authors. Present address: Condensed Molecular Materials Lab-
attractive
p
oratory, RIKEN, 2-1, Hirosawa, Wako-shi, Saitama 351-0198, Japan (M. Nomura).
Tel.: +81 48 467 9412; fax: +81 48 462 4661.
E-mail addresses: m-nomura@sophia.ac.jp, mitsushiro@riken.jp (M. Nomura),
kajita-m@sophia.ac.jp (M. Kajitani).
incorporating benzene-1,2-dithiolate (bdt) [21], benzene-1,2,4,5-
tetrathiolate [21], benzene-hexathiolate complexes [22] have
been structurally characterized. Those crystal structures have
0
022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.05.022

M. Nomura et al. / Journal of Organometallic Chemistry 694 (2009) 3116–3124
3117
Chart 1.
Scheme 1. Method 1 for [Cp*Co(dcbdt)] (X = CH) and [Cp*Co(dcdmp)] (X = N)
complexes.
commonly resulted in the intermolecular Cp*Á Á Ábenzene plane-to-
plane interactions [21,22]. As noted above, probably a dithiolene li-
gand incorporating the benzene core is one of important keys to
make those plane-to-plane interactions.
In this work, we focused on the [Cp*M(dithiolene)] (M = Co, Rh,
Ir) bearing slightly modified benzenedithiolate (bdt) ligand such as
ate(2À) source, and the other is the reaction of Cp*Co(I) species
with 1,2-dithioketone(0) or 1,2-dithiete(0). The latter reaction in-
2
volves electron-transfer from Cp*Co(I) to S ligand, but eventually
we can obtain the same product using both ways. In conclusion,
the method 1 generates either 1,2-dithioketone(0) or 1,2-dithie-
4
,5-dicyanobenzene-1,2-dithiolate (dcbdt, Chart 1). In addition, the
2 2
te(0) as an intermediate from (PhCH ) (dcbdt) by homolysis of
Cp*M complexes of 2,3-dicyano-5,6-dimercaptopyrazine (dcdmp,
Chart 1) ligand whose six-membered core contains two nitrogen
atoms (pyrazine core), were prepared for sake of comparison. A
family of [Cp*Ni (bdt)] may be also interesting because of its
magnetic behavior. However, there is a synthetic difficulty using
the C–S bond.
For preparations of [Cp*Rh(dcbdt)] (3b) and [Cp*Ir(dcbdt)] (3c)
complexes, the method 2 is plausibly better way, because low va-
III
Å
I
I
lent Cp*Rh and Cp*Ir species are relatively difficult to prepare due
to their air-sensitivity and multistep preparations [28]. On the
other hand, probable Cp*Rh and Cp*Ir precursors are well
III
III
2
the precursor [Cp* Ni]. Almeida et al. have reported a rich family
III
of square–planar or tetrahedral bisdithiolene complexes (M = Fe,
Co, Ni, Pd, Pt, Cu, Au and Zn) based on the dcbdt [23,24] and the
dcdmp ligands [25,26] and their structural, magnetic and electrical
conductive properties have been studied as well [23–26]. Further-
more, Ueda et al. have reported the oxo-vanadium bisdithiolene
known as the dimeric chloride-bridged [Cp*M (Cl)(
plexes [29] and they are quantitatively obtained by the reaction
of commercially available MCl O with Cp*H in MeOH [29].
Accordingly, 3b and 3c were obtained by the method 2 in 48%
and 47% yields, respectively (Scheme 2). The method 1 for prepara-
tion of [Cp*Co(dcdmp)] (4a) resulted in 67% yield from
2
l-Cl)] com-
3
ÁnH
2
2
complex of the dcbdt, [O@V(dcbdt) ] [27]. Although the dithiolene
complexes of dcbdt and dcdmp have been intensively reported as
introduced above, no organometallic dithiolene complexes of
them, which are classified into the third category, have been
known yet. Here we report on the synthetic procedure of
(
PhCH
the method 2 using 5,6-dichloropyrazine-2,3-dicarbonitrile re-
sulted in 31% for 4a (M = Co) from [Cp*Co(CO)I ], 34% for 4b
M = Rh), or 34% yield for 4c (M = Ir) from [Cp*M(Cl)( -Cl)]
2 2 2
) (dcdmp) (2) and [Cp*Co(CO) ] (Scheme 1). In addition,
2
(
l
2
,
[
Cp*M(dcbdt)] (or dcdmp), their spectral, electrochemical charac-
respectively. The all products 3a–3c and 4a–4c were characterized
by spectroscopies and elemental analyses.
terizations, and crystal structure determinations, considering
plane-to-plane interactions as well.
1
13
The H NMR and C NMR spectra of 3a–3c and 4a–4c in CDCl
3
indicated that the all complexes were monomeric in their solu-
1
2
. Results and discussion
tions. If complexes are dimeric as shown in Fig. 7, those H NMR
1
3
signals on the dcbdt ligand or C NMR signals on the both dcbdt
and dcdmp have to be inequivalent. However, only equivalent sig-
nals were commonly found (e.g. H NMR for 3b, d = 8.14 ppm (sin-
2.1. Preparations and characterizations of [Cp*M(dcbdt)] and
1
[Cp*M(dcdmp)] complexes (M = Co, Rh, Ir)
glet, 2H, benzene)). As explained by X-ray data, 4b was dimeric at
solid state (Fig. 7), but the NMR result indicated the monomeriza-
tion of 4b while solubilized in a solvent. Accordingly, we had as-
sumed that the following UV–Vis spectra and CV data had been
obtained from monomeric species (Figs. 1–4).
Almeida et al. have already reported the preparation of dithio-
lene precursor, which has been the dcbdt2 ligand protected by
À
two benzyl groups (PhCH
with a strong base to isolate H
dcbdt has reacted with a metal source in the presence of a base
2
)
2
(dcbdt) (1), and then 1 has treated
2
dcbdt [24]. Furthermore, the
H
2
The UV–Vis spectra of them in dichloromethane solution
showed electronic absorption at 546 (3a), 520 (4a), 468 (3b), 448
(4b), 405 (3c), and 407 nm (4c) as lowest energy absorption max-
ima (Figs. 1 and 2). Early works have described that these absorp-
tion are attributed to LMCT [30]. These results indicate that the
absorption energy becomes lower in order of the Co > Rh > Ir com-
plexes. This fact is consistent while compared with early data (e.g.
[Cp*Co(dmit)] (677 nm) [21], [Cp*Rh(dmit)] (600 nm) [31],
[Cp*Ir(dmit)] (477 nm)[32], dmit = 1,3-dithiol-2-thione-4,5-dithi-
olate). The reduction potentials taken from CV measurement well
explain difference of these LUMO levels between Co, Rh and Ir
complexes (Figs. 3 and 4). There are large differences of reduction
potentials as follows: À1.19 V (3a, M = Co), À1.48 V (3b, M = Rh),
and À1.97 V (3c, M = Ir) for the dcbdt complexes, and À0.97 V
(4a, M = Co), À1.31 V (4b, M = Rh), and À1.63 V (4c, M = Ir) for
the dcdmp complexes. However, no remarkable difference of the
oxidation potential was found in the all complexes except for the
oxidation process of 3b (Table 1).
again to give the corresponding M(dcbdt) complexes [23,24]. For
preparations of some dcdmp complexes, they have used a direct
generation of the dcdmp2 from 5,6-dichloropyrazine-2,3-dicarbo-
nitrile and sodium sulfide [26]. The latter synthetic way is sup-
posed to be better because isolation of an intermediate is not
required.
À
On the other hand, we found more convenient way for
[
Cp*Co(dcbdt)] (3a) without generation of dcbdt2À. One synthetic
procedure was the direct reaction of [Cp*Co(CO)
ing toluene without any other treatment to obtain 3a in 74% yield
Scheme 1, described as method 1). One other procedure was the
2
] with 1 in reflux-
(
one-pot synthesis of 3a without preparation of 1, which is similar
to the Almeida’s method noted above [26]. Namely, 4,5-dichlor-
ophthalonitrile treated with sodium sulfide in acetone to form
2
À
dcbdt , and successive addition of [Cp*Co(CO)I
2
] afforded 3a in
5
0% yield (Scheme 2, method 2). The method 1 requires a low va-
I
III
lent Cp*Co species. In contrast, the method 2 requires a Cp*Co
species. Normally, there are two different synthetic methods to
prepare [Cp*Co (dithiolene)] complexes. One is a simple ligand
exchange reaction between Cp*Co(III) species and 1,2-dithiol-
3b showed two oxidation waves at +0.39 and +0.92 V (Fig. 3).
The first oxidation potential is quite lower than those of the other
complexes (+0.68 V À +0.89 V, Table 1). This result probably
III

3
118
M. Nomura et al. / Journal of Organometallic Chemistry 694 (2009) 3116–3124
Scheme 2. Method 2 for [Cp*M(dcbdt)] (X = CH) and [Cp*M(dcdmp)] (X = N) complexes.
Fig. 1. UV–Vis spectra of [Cp*M(dcbdt)] (M = Co (3a), Rh (3b), Ir (3c)) in
À5
À3
dichloromethane solution (c = c.a. 5.0 Â 10 mol dm ).
Fig. 3. Cyclic voltammograms of [Cp*M(dcbdt)] (M = Co (3a), Rh (3b), Ir (3c)) series
in dichloromethane solution containing 0.1 M TBAP.
Fig. 2. UV–Vis spectra of [Cp*M(dcdmp)] (M = Co (4a), Rh (4b), Ir (4c)) in
À5
À3
dichloromethane solution (c = c.a. 5.0 Â 10 mol dm ).
explains an existence of equilibrium between the monomer and di-
mer of 3b in solution. The dimer can be precedently oxidized at a
lower potential compared with the monomer, because the formal
1
8-electron dimer is more electron-rich than the 16-electron
monomer. Namely, the second oxidation wave at +0.92 V corre-
sponds to the oxidation of the monomer. In contrast, the monomer
can be precedently reduced than the dimer. After that, the mono-
mer–dimer equilibrium rapidly shifts and then the dimer becomes
very poor amount. In fact, the reduction wave of the dimer couldn’t
be found. A previous work have already evidenced the dimer–
Fig. 4. Cyclic voltammograms of [Cp*M(dcdmp)] (M = Co (4a), Rh (4b), Ir (4c))
series in dichloromethane solution containing 0.1 M TBAP.

M. Nomura et al. / Journal of Organometallic Chemistry 694 (2009) 3116–3124
3119
Table 1
Redox potentials (vs Fc/Fc ) and electronic absorption maxima (kmax/nm).
monoclinic, space group P2
/n with two crystallographically inde-
1
+
pendent molecules in general positions in the unit cell. 4a crystal-
lized in the orthorhombic, space group Pbcn with one independent
molecule. On the other hand, 4b is dimeric and has three-legged
piano-stool geometry (Fig. 7). 4b crystallized in the monoclinic,
space group C2/c. The dimeric structure is perfectly symmetric
and lies on a crystallographic inversion center. Namely, the half
molecule of 4b is crystallographically unique (Fig. 7b).
E1/2(red)/V
E
1/2(ox)/V
kmax/nm
[Cp*Co(dcbdt)] (3a)
[Cp*Rh(dcbdt)] (3b)
[Cp*Ir(dcbdt)] (3c)
[Cp*Co(dcdmp)] (4a)
[Cp*Rh(dcdmp)] (4b)
[Cp*Ir(dcdmp)] (4c)
À1.19(r)
À1.48(r)
À1.97(r)
À0.97(r)
À1.31(r)
À1.63(r)
+0.79(ir)
+0.39(r), +0.92(ir)
+0.89(ir)
+0.81(ir)
+0.68(r)
546
468
405
520
448
407
+0.82(ir)
The Cp*/CoS
shown in Table 2, but the Cp*/RhS
b. These results evidence the difference of those piano-stool
2
dihedral angles in 3a and 4a are almost 90° as
(
r) Reversible wave. (ir) Irreversible wave.
2
dihedral angle is 55.933° for
4
monomer equilibrium of [( 6
g
-C
6
geometries. Although the Co-dithiolene rings of 3a and 4a are al-
most planar, the Rh-dithiolene ring for 4b is folded at the SÁ Á ÁS
hinge, whose dithiolene folding angle is 13.585°. Formally, the
6
R )Ru(dithiolene)] complexes, and
those electrochemical behavior have been investigated [33]. As
noted above, no NMR signals attributed to the dimer were ob-
served in solution, even if the solution was almost saturated. How-
ever, we assume that the dimer–monomer equilibrium rate is too
fast to detect both species.
III
III
16-electron CpM (or Cp*M ) dithiolene complexes are coordin-
atively unsaturated [34]. However, a strong -electron donation
from the sulfur to metal can stabilize the electron poor metal cen-
p
ter [35]. In fact, the only dimeric CpCo dithiolene complex has been
2.2. Crystal structure determination by X-ray diffraction study
2
reported for the formal 18-electron dimer, [CpCo(bdt)] in the crys-
tal at room temperature, with a single crystal-to-single crystal
The structures of the cobalt complexes 3a and 4a, and the rho-
phase transition at 150 °C to the monomeric form [36]. The iso-
dium complex 4b were determined by single crystal X-ray struc-
ture analyses. The ORTEP drawings and crystal packing diagrams
are displayed in Figs. 5–7. In addition, the selected bond lengths,
bond angles and dihedral angles are summarized in Table 2. The
both cobalt complexes 3a and 4a are monomeric and have two-leg-
ged piano-stool geometries (Figs. 5a and 6a). 3a crystallized in the
2
structural selenium complex [CpCo(bds)] (bds = benzene-1,2-
diselenolate) has been dimeric as well [37]. Those dimers can be
monomerized in solution, or monomer/dimer equilibria have been
observed [30a,33,37]. In contrast, the [Cp*Rh(dithiolene)] com-
plexes are relatively easy to dimerize. Actually, the dimeric Rh
2
complexes have been well known as follows: [Cp*Rh(bdt)] [38],
Fig. 5. (a) ORTEP drawing of 3a. One of two independent molecules is shown. The thermal ellipsoid is drawn at 30% probability level. All hydrogen atoms are omitted for
simplicity. (b) Packing diagram of 3a showing benzeneÁ Á Ábenzene (A) and Cp*Á Á Ábenzene interactions (B and C). (c) Overlap pattern of A interaction. (d,e) Overlap patterns of B
and C interactions.

3
120
M. Nomura et al. / Journal of Organometallic Chemistry 694 (2009) 3116–3124
Fig. 6. (a) ORTEP drawing of 4a. The thermal ellipsoid is drawn at 30% probability level. (b) Projection view along the c axis of 4a showing intermolecular pyrazineÁ Á Ápyrazine
interaction, giving rise to a pseudo-4-fold symmetry arrangement within the c axis column. (c) Projection view along the b axis of 4a.
Fig. 7. (a) ORTEP drawing of 4b. The thermal ellipsoid is drawn at 30% probability level. (b) Side view of 4b showing the folded dithiolene ring. The half molecule of 4b is
shown.
[
Cp*Rh(dmit)]
2
[31], and [Cp*Rh(mnt)]
2
(mnt = maleonitrile-1,2-
in the dimeric 4b are longer than those of the monomeric
dithiolate) [39]. According to our literature survey, there are two
geometrically different [Cp(or Cp*)M(dithiolene)] dimers (M = Co,
Rh). One is an inversion-centered dimer (Fig. 8a), which has been ob-
served in the dimeric [CpM(dichalcogenolene)] complexes, and
2
the other is a criss-cross dimer (Fig. 8b) whose two molecules are
shifted at almost 90°. The latter example involves the dimeric
[CpRh(dmit)] (Rh–S = 2.241, 2.242 Å) [31]. These facts explain a
strong
p-electron donation from the sulfur to metal center to
shorten the M–S bond in these electron poor monomeric com-
plexes. In the dimer 4b, the S2 atom is tripodal, because it is coor-
dinating to another rhodium atom (Rh1*). The Rh1*–S2 bond
length is 2.423 Å, which is slightly longer than those of the Rh1–
S1 and Rh1–S2 in the dithiolene ring (Table 2). Accordingly, the
Rh1*–S2 is supposed to be a weaker bond compared with the oth-
ers. In fact, such dimeric species monomerize again in solution, fol-
lowed by the Rh1*–S2 bond cleavage.
[
2
Cp*M(dichalcogenolene)] complexes and also 4b in this work
as well.
The Co–S bond lengths in the monomeric 3a and 4a are c.a.
2
.12–2.14 Å (Table 2). These results are similar to those of typical
monomeric [CpCo(dithiolene)] complexes [40], but shorter than
those of the dimeric [CpCo(bdt)] complex (Co–S = 2.230,
.246 Å) [36]. Similarly, the Rh–S (2.347, 2.359 Å) bond lengths
In the crystal structure of 3a, some plane-to-plane interactions
were observed within one layer. One is an intermolecular ben-
zeneÁ Á Ábenzene interaction at the dcbdt ligand (A = c.a. 3.7 Å)
2
2

M. Nomura et al. / Journal of Organometallic Chemistry 694 (2009) 3116–3124
3121
Table 2
of the dcbdt (3a) had both benzeneÁ Á Ábenzene and Cp*Á Á Ábenzene
Selected bond lengths (Å), bond angles (°) and dihedral angles (°).
interactions within one plane (two dimensional). However, the di-
3
aa
4a
4b
2
meric [Cp*Rh(dcbdt)] complex did not result in no remarkable
plane-to-plane interactions, because probably one side of the
dithiolene ligand was hidden by dimerization. As described in
Bond length
M1–S1
M1–S2
S1–C1
S2–C2
C1–C2
2.1362(7)
2.1214(10)
1.737(3)
1.734(2)
1.407(4)
–
2.1299(11)
2.1463(13)
1.722(3)
1.727(3)
1.419(5)
–
2.359(2)
2.347(2)
1.715(9)
1.760(8)
1.444(11)
2.423(2)
the introduction of this paper, the complexes of non-substituted
5
g
-cyclopentadienyl ligand (Cp) have shown the intermolecular
CpÁ Á ÁCp [16,18] and CpÁ Á Ádithiolene interactions [16]. Especially,
III
while the complex has paramagnetic Ni (S = 1/2), those p–p inter-
M1*–S2
actions make strong magnetic interactions [16–18], because there
Bond angles
S1–M1–S2
M1–S1–C1
M1–S2–C2
S1–C1–C2
S2–C2–C1
are some spin densities on the Cp ligand. We believe that the Cp*/
93.04(3)
104.21(8)
104.22(12)
118.5(2)
119.5(2)
93.68(4)
86.85(7)
104.8(2)
104.2(2)
121.8(6)
120.2(6)
III
103.71(12)
103.50(14)
119.9(2)
bdt complexes of Ni will be interesting compounds because the
III
III
Ni complexes could be isostructural to the complexes of Co as
previously reported [20], although there is a synthetic difficulty
119.2(3)
III
Å
for [Cp*Ni (dithiolene)] complexes. Therefore, two dimensionally
magnetic interaction based on plane-to-plane interactions such as
benzeneÁ Á Ábenzene and Cp*Á Á Ábenzene, will be expected by using
Dihedral angles
Cp*/MS
MS /S C
2 2 2
2
92.888
7.113
92.861
1.949
55.933
13.585
b
the
p-interacting Cp* ligand.
a
Data taken from one of two independent molecules.
Dithiolene folding angles at the SÁ Á ÁS hinge.
b
4
. Experimental
between two independent molecules shown as the Co1 and Co2
molecules (Fig. 5b). The others are intermolecular Cp*Á Á Ábenzene
interactions in the two Co1 molecules (B = c.a. 3.6 Å) and the two
Co2 molecules (C = c.a. 3.6 Å). These face-to-face dihedral angles
4.1. Materials and instrumentation
All reactions were carried out under an argon atmosphere by
means of standard Schlenk techniques. All solvents were dried
and distilled by Na-benzophenone (for benzene and toluene),
(
h) are very small to indicate their parallels (h
A
= 1.868°,
h
B
= 3.244°, and h = 2.263°). Fig. 5c displays the overlap pattern
C
2
molecular sieve (for acetone) or CaH (for methanol) before use.
of A, and Fig. 5d and e exhibit the overlap patterns of B and C,
respectively. A–C lie on two dimensional columns along the
Cp*H (1,2,3,4,5-pentamethylcyclopentadiene), 4,5-dichloropht-
halonitrile, and 5,6-dichloropyrazine-2,3-dicarbonitrile were ob-
(
b + c) axis in the crystal (Fig. 5b). In the crystal structure of 4a,
the molecules interact at the pyrazine moiety each other (c.a.
.5 Å). The face-to-face dihedral angle is 11.658°. This intermolec-
tained from Wako Pure Chemicals Industries, Ltd. RhCl
and IrCl O were obtained from STREM Chemicals. [Cp*Co(-
ÁnH
CO) ] [41], [Cp*Co(CO)I ] [42], [Cp*M(Cl)( -Cl)] (M = Rh, Ir) [29],
(PhCH (dcbdt) (1) [24], and (PhCH (dcdmp) (2) [43] were pre-
pared by literature methods. Mass and IR spectra were recorded
on a JEOL JMS-D300 and a Shimadzu Model FTIR 8600PC instru-
ments, respectively. UV–Vis spectra were recorded on a Hitachi
Model UV-2500PC spectrometer. Elemental analyses were deter-
mined by using a Shimadzu PE2400-II instrument.
3
Á3H
2
O
3
2
3
2
2
l
2
ular interaction lies on one dimensional column along the c axis.
Fig. 6b and c indicated that the pyrazine moieties interacted at
van der Waals contact to afford this one dimensional chain struc-
ture, with a pseudo-4-fold-symmetry arrangement. However, no
plane-to-plane interaction based on Cp* ligand was observed in
2
)
2
2 2
)
4
a. One reason might be due to an introduction of some nitrogen
atoms at the benzene core.
4.2. CV measurements
3
. Conclusion
All electrochemical measurements were performed under an
In this work, we studied on the organometallic Co, Rh and Ir
complexes of mixed Cp*/dcbdt and Cp*/dcdmp ligands. Among
them, the Co complex of the dcdmp (4a) showed one dimensional
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 inter-
p–
p
interaction based on its pyrazine moiety, but no Cp*Á Á Ápyra-
+
zine interaction was observed. On the other hand, the Co complex
nally to the ferrocene/ferrocenium (Fc/Fc ) couple. A stationary
2
Fig. 8. (a) Criss-cross dimeric structure of 4b from the top view. (b) Inversion-centered dimer of [CpCo(bds)] .[37]

3
122
M. Nomura et al. / Journal of Organometallic Chemistry 694 (2009) 3116–3124
platinum disk (1.6 mm in diameter) was used as a working elec-
trode. The Model CV-50 W instrument from BAS Co. was used for
was obtained as a purple solid in 74% (29.5 mg) yield. A benzene
2
solution (80 ml) of [Cp*Co(CO) ] and 1 was refluxed for 42 h to give
cyclic voltammetry (CV) measurements. CVs were measured in
3a in 67% yield.
À3
1
0
mmol dm dichloromethane solutions of complexes containing
.1 mol dm tetra-n-butylammonium perchlorate (TBAP) at 25 °C.
À3
4.5. Synthesis of [Cp*Co(dcbdt)] (3a) by method 2
4.3. X-ray diffraction study
An acetone solution (20 ml) of 4,5-dichlorophthalonitrile
(
60 mg, 0.3 mmol) was added to acetone solution (30 ml) of
Na O (120 mg, 0.5 mmol) and stirred at room temperature
SÁ9H
for 4 h. An acetone solution (20 ml) of [Cp*Co(CO)I ] (190 mg,
Single crystals of complexes 3a, 4a and 4b were obtained by
2
2
recrystallization from the dichloromethane solutions and then va-
por diffusion of n-hexane into those solutions. Crystals were
mounted on the top of a thin glass fiber. The measurement was
made on a Rigaku MERCURY diffractometer with graphite-mono-
2
0.39 mmol) was further added to the reaction mixture and reacted
for 20 h. The solvent was removed under reduced pressure. Dichlo-
romethane was added to dissolve a product and dried with MgSO .
4
chromated Mo K
a
radiation (k = 0.71073 Å). Each structure was
Solid components were removed by filtration. The filtrate was con-
centrated and was moved to column chromatography on silica gel.
A purple product was separated with dichloromethane. The purple
product 3a was further purified by recrystallization from dichloro-
methane and hexanes (50% yield).
solved by direct methods and expanded Fourier techniques [44].
The non-hydrogen atoms were refined anisotropically. Hydrogen
atoms were introduced at calculated positions (riding model), in-
cluded in structure factor calculations, and these were not refined.
Absorption corrections were applied. Idealized positions of com-
plexes were used for the Crystal Structure crystallographic soft-
ware package of Molecular Structure Corp [45]. Crystallographic
data of complex 3a, 4a and 4b are summarized in Table 3.
4.5.1. [Cp*Co(dcbdt)] (3a)
+
+
+
Mass (EI , 70 eV) m/z (rel. intensity) 384 (M , 100), 135 (Cp* ,
18). 1H NMR (CDCl
1.93 (s, 15H, Cp*). C NMR (CDCl
, vs TMS, 500 MHz) d 8.14 (s, 2H, benzene),
3
1
3
There is a level A alert in the CIF report for 4b, because of a large
3
, vs TMS, 125 MHz) d 160.0
3
void of 259 Å . This result suggests an existence of cocrystallized
(CN), 134.3, 116.8, 106.4 (benzene), 93.4 (Cp*), 10.9 (Me). UV–Vis
solvent. The solvent was supposed to be CH
mental analysis revealed the (4b) (CH Cl ) formula. Unfortunately,
we couldn’t determine the positions of those atoms. However,
structure of the main molecule [Cp*Rh(dcdmp)] was nicely re-
and GOF values were obtained without the
2
Cl
2
, because the ele-
(CH
2
Cl
2
) kmax/nm (
e
) 546 (10 000), 385 (14 400), 300 (50 600),
À1
2
2
2
264 (21 600). IR (KBr disk) 2222 cm
for C18 17CoN
56.14; H, 4.37; N, 7.34; S, 16.94%.
(mCN). Elemental Anal. Calc.
H
2
2
S : C, 56.24; H, 4.46; N, 7.29; S, 16.68. Found: C,
2
fined, and the fair R
1
solvent (Table 3).
4.6. Synthesis of [Cp*Co(dcdmp)] (4a) by method 1
4.4. Synthesis of [Cp*Co(dcbdt)] (3a) by method 1
2 2 2
[Cp*Co(CO) ] (61 mg, 0.25 mmol) and (PhCH ) (dcdmp) (75 mg,
0
.2 mmol) were reacted in refluxing toluene (30 ml) for 28 h. The
[
Cp*Co(CO) ] (40 mg, 0.16 mmol) and 1 (39 mg, 0.1 mmol) were
2
solvent was removed under reduced pressure, and the residue
was separated by column chromatography on silica gel (eluent:
dichloromethane). A dark red solid was isolated and the product
was further purified by recrystallization from dichloromethane
and hexanes. [Cp*Co(dcbdt)] (4a) was obtained as a dark red solid
in 67% yield.
reacted in refluxing toluene (15 ml) for 5 h. The solvent was re-
moved under reduced pressure, and the residue was separated
by column chromatography on silica gel (eluent: dichlorometh-
ane). A purple solid was isolated and the product was further puri-
fied by recrystallization from dichloromethane and hexanes. 3a
4.7. Synthesis of [Cp*Co(dcdmp)] (4a) by method 2
Table 3
Crystallographic data.
An acetone solution (20 ml) of 5,6-dichloropyrazine-2,3-dicar-
Compound
Formula
3a
4a
4b
bonitrile (60 mg, 0.3 mmol) was added to acetone solution
30 ml) of Na O (120 mg, 0.5 mmol) and stirred at room tem-
SÁ9H
perature for 2 h. An acetone solution (20 ml) of [Cp*Co(CO)I
58 mg, 0.12 mmol) was further added to the reaction mixture
C
18
H17CoN S
2 2
C
16
H
15CoN
S
4 2
32 30 8 2 4
C H N Rh S
860.69
Dark brown
Block
(
2
2
À1
FW (g mol
)
384.40
Purple
Prism
386.37
Purple
Block
2
]
Crystal color
Crystal shape
Crystal size (mm)
Crystal system
Space group
T (K)
(
0.23 Â 0.13 Â 0.07 0.13 Â 0.13 Â 0.10 0.30 Â 0.05 Â 0.05
and reacted for 2 h. The solvent was removed under reduced pres-
sure. The purple product 4a (31% yield) was purified and was crys-
tallized by the same procedure as method 2 for 3a.
Monoclinic
P2 /n (#14)
Orthorhombic
Pbcn (#60)
298.1
Monoclinic
C2/c (#15)
298.1
1
298.1
a (Å)
b (Å)
c (Å)
16.1544(9)
14.1443(5)
17.4177(9)
116.4909(5)
3562.0(3)
8
1.434
1.198
25 769
8071 (0.026)
19.803(5)
11.666(3)
15.319(3)
21.1256(15)
9.3084(5)
21.6226(15)
99.0146(10)
4199.5(5)
4
1.361
1.013
16 010
4797 (0.028)
4
.7.1. [Cp*Co(dcdmp)] (4a)
+
+
+
Mass (EI , 70 eV) m/z (rel. intensity) 386 (M , 100), 342 (M –SC,
b (°)3
+
1
1
1
0), 135 (Cp* , 10). H NMR (CDCl
3
, vs TMS, 500 MHz) d 1.86 (s,
, vs TMS, 125 MHz) d 114.4 (benzene),
V (Å )
3538.9(14)
8
1.450
1.209
20 306
3976 (0.031)
13
5H, Cp*). C NMR (CDCl
3
Z
1
3
À3
94.6 (Cp*), 10.7 (Me) but other C signals for CN group and ben-
zene ring were very weak. UV–Vis (CH Cl ) kmax/nm ( ) 520
(10 000), 399 (9800), 300 (40 300). IR (KBr disk) 2233 cm
Elemental Anal. Calc. for C16 15CoN : C, 49.74; H, 3.91; N,
4.50. Found: C, 49.58; H, 4.37; N, 14.47%.
Dcalc (g cm
)
À1
l
(mm
)
2
2
e
À1
Total refls.
Unique reflections
(R )
int
(mCN).
H
4 2
S
1
Unique reflections
I > 2 (I))
(I > 2 (I))
wR (I > 2 (I))
Goodness-of-fit
5552
2491
3856
(
r
r
R
1
0.0387
0.0987
0.981
0.0458
0.1171
1.047
0.0586
0.1003
1.194
4.8. [Cp*Rh(dcbdt)] (3b) and [Cp*Rh(dcdmp)] (4b) by method 2
2
r
An acetone solution (40 ml) of 4,5-dichlorophthalonitrile
(
GOF)
(
120 mg, 0.63 mmol) was added to acetone solution (40 ml) of
P||F
| À |F
||/P = [P
|F |; wR
w(F 2o À F ) / wF ]1/2.
P
2
c
2
4
o
R
1
=
o
c
o 2
Na O (350 mg, 1.44 mmol) and stirred at room temperature
2
SÁ9H
2

M. Nomura et al. / Journal of Organometallic Chemistry 694 (2009) 3116–3124
3123
for 4 h. A dichloromethane solution (30 ml) of [Cp*Rh(Cl)(
l
-Cl)]
2
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
(
190 mg, 0.31 mmol) was further added to the reaction mixture
and reacted for 20 h. The solvent was removed under reduced pres-
sure. The red product 3b (48% yield) was purified and was crystal-
lized by the same procedure as method 2 for 3a. The red product
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jorganchem.2009.05.022.
4
b was obtained in 34% yield by the same method 2 as 3b from
References
[
Cp*Rh(Cl)( -Cl)] (200 mg, 0.32 mmol), Na (370 mg,
l
2
2 2
SÁ9H O
1
0
.56 mmol) and 5,6-dichloropyrazine-2,3-dicarbonitrile (120 mg,
.61 mmol).
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[
2] (a) M. Fourmigué, Acc. Chem. Res. 37 (2004) 179;
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(
[
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(
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.8.1. [Cp*Rh(dcbdt)] (3b)
+
+
c) G. Matsubayashi, M. Nakano, H. Tamura, Cood. Chem. Rev. 226 (2002) 143.
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Mass (EI , 70 eV) m/z (rel. intensity) 428 (M , 100), 316
+
1
(
Cp*RhS
2
CH
2
, 15). H NMR (CDCl
3
, vs TMS, 500 MHz) d 8.14 (s,
Cl ) kmax/nm (
(
2
4
2
H, benzene), 2.04 (s, 15H, Cp*). UV–Vis (CH
2
2
e)
(
68 (6800), 347 (14 200), 282 (34 400), 253 (21 400). IR (KBr disk)
À1
219 cm
2 2 2 2
(mCN). Elemental Anal. Calc. for C18H17RhN S (CH Cl ):
(
C, 44.46; H, 3.73; N, 5.46. Found: C, 44.37; H, 3.41; N, 5.75%.
(
Eisenberg, Coord. Chem. Rev. 171 (1998) 125.
8] (a) J.A. Zuleta, J.M. Bevilacqua, R. Eisenberg, Coord. Chem. Rev. 111 (1991) 237;
4
.8.2. [Cp*Rh(dcdmp)]2. (4b)
[
+
+
+
Mass (EI , 70 eV) m/z (rel. intensity) 430 (M , 100), 386 (M –SC,
(
b) J.A. Zuleta, M.S. Burberry, R. Eisenberg, Coord. Chem. Rev. 97 (1990) 47.
+
1
3
1
2
2), 238 (Cp*Rh , 22). H NMR (CDCl
5H, Cp*). UV–Vis (CH Cl ) kmax/nm (
82 (24 700). IR (KBr disk) 2222 cm
Rh (CH Cl ): C, 41.91; H, 3.41; N, 11.85. Found: C,
1.67; H, 3.35; N, 11.95%.
3
, vs TMS, 500 MHz) d 1.93 (s,
e) 448 (10 300), 316 (26 100),
(mCN). Elemental Anal. Calc.
[9] (a) K.-S. Shin, Y.J. Jung, S.-K. Lee, M. Fourmigué, F. Barrière, J.-F. Bergamini, D.-
Y. Noh, Dalton Trans. (2008) 5869;
2
2
(
(
b) K.-S. Shin, K.-I. Son, J.I. Kim, C.S. Hong, M. Suh, D.-Y. Noh, Dalton Trans.
2009) 1767.
À1
for C32
4
H
30
N
8
S
2 4
2
2
[10] M. Fourmigué, Coord. Chem. Rev. 178 (1998) 823.
[
[
[
11] A. Sugimori, T. Akiyama, M. Kajitani, T. Sugiyama, Bull. Chem. Soc. Jpn. 72
1999) 879.
(
12] M. Fourmigué, T. Cauchy, M. Nomura, Cryst. Eng. Comm. (2009), in press,
doi:10.1039/b823200h.
13] (a) M. Fourmigué, C. Coulon, Adv. Mater. 6 (1994) 948;
4
.9. [Cp*Ir(dcbdt)] (3c) and [Cp*Ir(dcdmp)] (4c) by method 2
(
(
b) J.A. McCleverty, T.A. James, E.J. Wharton, Inorg. Chem. 8 (1969) 1340;
c) J. Locke, J.A. McCleverty, Inorg. Chem. 5 (1966) 1157;
An acetone solution (30 ml) of 4,5-dichlorophthalonitrile
(
130 mg, 0.65 mmol) was added to acetone solution (50 ml) of
Na O (430 mg, 1.77 mmol) and stirred at room temperature
SÁ9H
for 4 h. A dichloromethane solution (30 ml) of [Cp*Ir(Cl)( -Cl)]
280 mg, 0.35 mmol) was further added to the reaction mixture
(d) M.R. Churchill, J. Coake, J. Chem. Soc. A (1970) 2046.
[14] (a) R. Clerac, M. Fourmigué, C. Coulon, J. Solid State Chem. 159 (2001) 413;
b) R. Clerac, M. Fourmigué, J. Gaultier, Y. Barrans, P.A. Albouy, C. Coulon, Eur.
Phys. J. B9 (1999) 445;
c) B. Domercq, M. Fourmigué, Eur. J. Inorg. Chem. 6 (2001) 1625;
2
2
(
l
2
(
(
and reacted for 20 h. The solvent was removed under reduced pres-
sure. The red product 3c (47% yield) was purified and was crystal-
lized by the same procedure as method 2 for 3a. The red product 4c
was obtained in 34% yield by the same method 2 as 3c from
(d) M. Fourmigué, B. Domercq, I.V. Jourdain, P. Molinie, F. Guyon, J. Amaudrut,
Chem. Eur. J. 4 (1998) 1714;
(
(
e) M. Fourmigué, C. Lenoir, C. Coulon, F. Guyon, J. Amaudrut, Inorg. Chem. 34
1995) 4979;
(f) J.K. Hsu, C.J. Bonangelino, S.P. Kaiwar, C.M. Boggs, J.C. Fettinger, R.S. Pilato,
Inorg. Chem. 35 (1996) 4743.
[
3
1
Cp*Ir(Cl)(
l
-Cl)]
2
(560 mg, 0.70 mmol), Na
2
SÁ9H
2
O
(790 mg,
[
15] (a) B. Domercq, C. Coulon, M. Fourmigué, Inorg. Chem. 40 (2001) 371;
.30 mmol) and 5,6-dichloropyrazine-2,3-dicarbonitrile (240 mg,
.22 mmol).
(
b) H. Köpf, Z. Naturforsch. B23 (1968) 1531;
(c) M.L.H. Green, W.E. Lindsell, J. Chem. Soc. A (1967) 1455;
(
(
(
d) J.R. Knox, C.K. Prout, J. Chem. Soc., Chem. Commun. (1967) 1277;
e) J.R. Knox, C.K. Prout, Acta Crystallogr. B25 (1969) 2013;
f) A. Kotuglu, H. Köpf, J. Organomet. Chem. 25 (1970) 455;
4
.9.1. [Cp*Ir(dcbdt)] (3c)
Mass (EI , 70 eV) m/z (rel. intensity) 518 (M , 100). 1H NMR
+
+
(g) M.L.H. Green, W.B. Heuer, G.C. Saunders, J. Chem. Soc., Dalton Trans. (1990)
789;
3
(
3
CDCl , vs TMS, 500 MHz) d 8.37 (s, 2H, benzene), 2.16 (s, 15H,
1
3
(h) R.S. Pilato, K.A. Eriksen, M.A. Greaney, E.I. Stiefel, S. Goswami, L. Kilpatrick,
T.G. Spiro, E.C. Taylor, A.L. Rheingold, J. Am. Chem. Soc. 113 (1991) 9372.
Cp*). C NMR (CDCl
16.5, 107.3 (benzene), 93.8 (Cp*), 10.5 (Me). UV–Vis (CH
3
, vs TMS, 125 MHz) d 159.9 (CN), 134.5,
1
2
Cl
2
)
[16] T. Cauchy, E. Ruiz, O. Jeannin, M. Nomura, M. Fourmigué, Chem. Eur. J. 13
(2007) 8858.
[17] M. Fourmigué, N. Avarvari, Dalton Trans. (2005) 1365.
18] (a) M. Nomura, T. Cauchy, M. Geoffroy, P. Adkine, M. Fourmigué, Inorg. Chem.
45 (2006) 8194;
k
max/nm (
e
) 405 (8100), 342 (36 500), 296 (25 400), 262 (8300).
À1
IR (KBr disk) 2218 cm
(mCN). Elemental Anal. Calc. for
[
C
18
2 2
H17IrN S : C, 41.76; H, 3.31; N, 5.41; S, 12.39. Found: C,
4
1.86; H, 3.59; N, 5.64; S, 12.61%.
(b) P. Grosshans, P. Adkine, H. Sidorenkova, M. Nomura, M. Fourmigué, M.
Geoffroy, J. Phys. Chem. A 112 (2008) 4067.
[
19] (a) J.M. Locke, J.A. McCleverty, Inorg. Chem. 5 (1966) 157;
4
.9.2. [Cp*Ir(dcdmp)] (4c)
(
b) R.B. King, J. Am. Chem. Soc. 85 (1963) 1587.
+
+
+
Mass (EI , 70 eV) m/z (rel. intensity) 520 (M , 100), 476 (M –SC,
[20] M. Nomura, M. Fourmigué, J. Organomet. Chem. 692 (2007) 2491.
[21] M. Nomura, M. Fourmigué, Inorg. Chem. 47 (2008) 1301.
[
[
1
, vs TMS, 500 MHz) d 1.77 (s, 15H, Cp*). 13
2
0). H NMR (CDCl
3
C
22] Y. Shibata, B. Zhu, S. Kume, H. Nishihara, Dalton Trans. (2009) 1939.
23] (a) H. Alves, D. Simao, I.C. Santos, V. Gama, R.T. Henriques, H. Novais, M.
Almeida, Eur. J. Inorg. Chem. (2004) 1318;
NMR (CDCl
Me) but other C signals for CN group and benzene ring were very
weak. UV–Vis (CH Cl ) kmax/nm ( ) 407 (9600), 334 (25 300). IR
CN). Elemental Anal. Calc. for C16 15IrN
C, 36.98; H, 2.91; N, 10.78; S, 12.34. Found: C, 37.09; H, 2.82; N,
0.64; S, 12.50%.
3
, vs TMS, 125 MHz) d 114.1 (benzene), 94.6 (Cp*), 9.9
1
3
(
(
b) L. Valade, J. Fraxedas, D. de Caro, J.-P. Savy, I. Malfant, C. Faulmann, M.
Almeida, J. Low Temp. Phys. 142 (2006) 141;
c) H. Alves, D. Simao, I.C. Santos, E.B. Lopes, H. Novais, R.T. Henriques, M.
Almeida, Synth. Met. 135–136 (2003) 543;
d) L.C.J. Pereira, A.M. Gulamhussen, J.C. Dias, I.C. Santos, M. Almeida, Inorg.
Chim. Acta 360 (2007) 3887;
e) D. de Caro, H. Alves, M. Almeida, S. Caillieux, M. Elgaddari, C. Faulmann, I.
2
À1
2
e
(
KBr disk) 2224 cm
(
m
H
4 2
S :
(
(
1
(
Malfant, F. Senocq, J. Fraxedas, A. Zwick, L. Valade, J. Mater. Chem. 14 (2004)
2801;
Appendix A. Supplementary material
(
f) H. Alves, I.C. Santos, E.B. Lopes, D. Belo, V. Gama, D. Simao, H. Novais, M.T.
Duarte, R.T. Henriques, M. Almeida, Synth. Met. 133–134 (2003) 397;
g) H. Alves, D. Simao, E.B. Lopes, D. Belo, V. Gama, M.T. Duarte, H. Novais, R.T.
Henriques, M. Almeida, Synth. Met. 120 (2001) 1011;
CCDC 724140, 724141 and 724142 contains the supplementary
crystallographic data for 3a, 4b and 4a. These data can be obtained
(

3
124
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