Formation and reaction of three-membered cobaltathiaziridine ring in (η5-cyclopentadienyl)(substituted imido-κN-thio-κS-ethene-2-thiolato-κS)cobalt(III). Ring opening and closure and transfer of imido group

Article abstract of DOI:10.1016/S0022-328X(00)00408-3

Three-membered cobaltathiaziridine rings are formed in the reactions of [CpCo{S₂C₂(COOMe)₂)₂}] either with some azides (RN₃: p-toluenesulfonyl azide (TsN₃), methanesulfonyl azide (MsN₃), and ethyl azidoformate (EtOOCN₃)) or with N-(phenyliodonio)-p-toluenesulfonamidate (PhI = NTs) to afford imido-bridged complexes, [CpCo{S₂C₂(COOMe)₂}(NR)]. The ring undergoes unique ring opening and reforming reactions. Hydrogen chloride brings about the cleavage of the Co-N bond to give S-iminodithiolatocobalt(III) complexes [Cp(Cl)Co{S(NR)-C(COOMe)-C(COOMe)-S)}], which very easily regenerates the cobaltathiaziridine ring on treatment with bases, such as pyridine and even with the very weak base, water. The reaction with triphenylphosphine at room temperature results in the ring opening to give an ylide. The heating of a benzene solution of the ylide at 80°C (under reflux) gives a product in which a sulfonylimido moiety migrates to a carbon atom of the cyclopentadienyl ring. The reduction halfwave potential values of the imido-bridged complexes depend on the substituent of bridging moiety. The CV of sulfonylimido-bridged complex shows one-electron two-step reduction processes. We found that the reductant of the original complex is regenerated not by the first reduction, but by the second reduction according to CV and OTTLE measurements.

Full text of DOI:10.1016/S0022-328X(00)00408-3

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 611 (2000) 376–385
Formation and reaction of three-membered cobaltathiaziridine ring
in (h5-cyclopentadienyl)(substituted imido-kN-thio-kS-
ethene-2-thiolato-kS)cobalt(III). Ring opening and closure and
transfer of imido group
Mitsushiro Nomura, Takayoshi Yagisawa, Chikako Takayama, Toru Sugiyama,
Yasuo Yokoyama, Kunio Shimizu, Akira Sugimori, Masatsugu Kajitani *
Department of Chemistry, Faculty of Science and Technology, Sophia Uni6ersity, Kioi-cho 7-1, Chiyoda-ku, Tokyo 102-8554, Japan
Received 3 March 2000; received in revised form 12 April 2000; accepted 12 April 2000
Abstract
Three-membered cobaltathiaziridine rings are formed in the reactions of [CpCo{S2C2(COOMe)2}] either with some azides (RN3:
p-toluenesulfonyl azide (TsN3), methanesulfonyl azide (MsN3), and ethyl azidoformate (EtOOCN3)) or with N-(phenyliodonio)-p-
toluenesulfonamidate (PhI=NTs) to afford imido-bridged complexes, [CpCo{S2C2(COOMe)2}(NR)]. The ring undergoes unique
ring opening and reforming reactions. Hydrogen chloride brings about the cleavage of the CoꢀN bond to give S-iminodithiolato-
cobalt(III) complexes [Cp(Cl)Co{S(NR)ꢀC(COOMe)ꢀC(COOMe)ꢀS)}], which very easily regenerates the cobaltathiaziridine ring
on treatment with bases, such as pyridine and even with the very weak base, water. The reaction with triphenylphosphine at room
temperature results in the ring opening to give an ylide. The heating of a benzene solution of the ylide at 80°C (under reflux) gives
a product in which a sulfonylimido moiety migrates to a carbon atom of the cyclopentadienyl ring. The reduction halfwave
potential values of the imido-bridged complexes depend on the substituent of bridging moiety. The CV of sulfonylimido-bridged
complex shows one-electron two-step reduction processes. We found that the reductant of the original complex is regenerated not
by the first reduction, but by the second reduction according to CV and OTTLE measurements. © 2000 Elsevier Science S.A. All
rights reserved.
Keywords: Cobaltathiaziridine; Cobaltadithiolene; Sulfonyl azide; N-(phenyliodonio)-p-toluenesulfonamidate; Ring opening; Migration
The alkylidene adducts further undergo various types
of bond cleavage. UV-irradiation causes the elimination
1. Introduction
of alkylidene group to give free cobaltadithiolene com-
plexes [3]. In the cases of the norbornadiene adducts,
the adducts are photocleaved to afford free cobalta-
dithiolene complexes and norbornadiene [5,6].
A metalladithiolene ring is a very interesting metal
chelate ring [1]. It is a conjugated ring with six p
electrons. In some cases, the ring behaves as an aro-
matic ring and undergoes substitution reactions [2],
while, under other conditions, the ring undergoes addi-
The attack of hydrogen halide to the three-membered
cobaltathiirane ring of alkylidene adducts gives rise to
tion reactions due to unsaturation.
the cleavage of CoꢀC bond [7]. The halide atom is
bonded to the cobalt atom and the hydrogen atom is
bonded to the bridging alkylidene carbon to give three-
component-adducts among cobaltadithiolene, alkyli-
dene, and hydrogen halide [3d].
The addition of phosphines or phosphites to the
cobalt atom in alkylidene adducts causes the cleavage
of either CoꢀC or CoꢀS bond depending on the elec-
A typical addition reaction is the bridging between
Co and S by alkylidene groups in the reaction with
diazo compounds [3]. Similar addition reactions occur
with dimethyl acetylenedicarboxylate [4] or with
quadricyclane [5].
* Corresponding author. Fax:+81-3-2383361.
E-mail address: kajita-m@hoffman.cc.sophia.ac.jp (M. Kajitani).
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(00)00408-3

M. Nomura et al. / Journal of Organometallic Chemistry 611 (2000) 376–385
377
2. Results and discussion
2.1. Formation of imido-bridged complexes 2a, 2b, and
2c
Sulfonyl azides (RN3, 3a: R=p-toluenesulfonyl and
Scheme 1.
3b: R=methanesulfonyl) and ethyl azidoformate (3c:
EtOOCN3) react with (h5-cyclopentadienyl)(1,2-
dimethoxycarbonyl-1,2-ethenedithiolato)cobalt(III) (1)
affording (h5-cyclopentadienyl)(sulfonylimido-kN-thio-
kS-ethene-2-thiolato-kS)cobalt(III) (2a and 2b) and the
corresponding ethoxycarbonylimido-bridged complex
(2c) in reasonable yields, respectively (Chart 2). The
reactions proceeds in boiling benzene. The mechanism
of the imido-bridging should be similar to that of the
alkylidene-bridging by diazo compounds, in which the
initial step is the attack of the negative center (N atom)
of an azide to the positive center (Co atom) of the
cobaltadithiolene ring and the succeeding process is the
attack of a negatively charged S atom to the positively
charged N of azide moiety to cause SN2-type elimina-
tion of N2 (Scheme 1).
tronic structure of the bridging alkylidene groups to
give S-ylide complexes or ring expansion complexes
having a six-membered dihydro-1,2,5-cobaltadithiine
ring [8,9]. Upon UV-irradiation, the dihydro-1,2,5-
cobaltadithiine complex regenerates the three-mem-
bered cobaltathiirane ring [3b].
On the other hand, organic azides [10] react with the
cobaltadithiolenes in two fashions. One is the replace-
ment of sulfur by imido group. Phenyl azide brings
about this type of reaction, in which nitrenes act as
reactants [11b]. The other type reaction is the bridging
between Co and S by imido group. This type reaction is
similar to the reaction of diazo compounds with cobal-
tadithiolene complexes and is caused by 1,3-dipolar
addition of sulfonyl azides to a CoꢀS bond. The latter
type reaction has been reported preliminarily [11a].
Similar to the diazo compounds, some organic azides
react with cobaltadithiolene complexes to give imido-
bridged compounds (Chart 1).
Chart 2.
N-(Phenyliodonio)-p-toluenesulfonamidate (4a) gives
also 2a in the reaction with 1. N-(Phenyliodonio)-p-
toluenesulfonamidate (4a) has been reported as good
nitrene precursor which generates nitrene under the
catalysis of copper complexes at elevated temperatures
[12]. However, even at room temperature and without
any catalyst the complex 2a is formed in good yield
(Chart 3).
Chart 1.
We report here the formation of substituted imido-
bridged cobaltadithiolene complexes [CpCo{S2C2-
(COOMe)2}(NR)] in the reactions of [CpCo{S2C2-
(COOMe)2}] either with some azides (RN3: p-tolylsul-
fonyl azide (TsN3), methanesulfonyl azide (MsN3), and
ethyl azidoformate (EtOOCN3)) or with N-
(phenyliodonio)-p-toluenesulfonamidate (PhI=NTs).
Reactivities of three-membered cobaltathiaziridine rings
in imido-bridged complexes were investigated in the
reactions with hydrogen chloride and triphenylphos-
phine. The comparison of the chemical and electro-
chemical behavior of the imido-bridged cobalta-
dithiolenes with that of alkylidene-bridged cobaltadithi-
olenes is of interest in the chemistry of this type
of bridged complexes. Sulfonylimido-bridged cobalta-
dithiolene complexes show remarkable reactions
which are different from those of alkylidene-bridged
complexes.
Chart 3.
In the reaction between equimolar 1 and 4a, the
yields of 2a and the recovery of 1 (in parentheses) are as
follows: in the presence of 1/20 molar CuI, 21% (70%);
in the presence of 1/20 molar [Cu(OTf)2], 27% (71%); in
the presence of 1/20 molar [Cu(acac)2], 24% (70%); and
in the absence of catalyst, 27% (64%). This fact indi-
cates that nitrene species does not participate in the
formation of the imido-bridged compound. Thus, the
bridging reaction by 4a should proceed in an ionic
reaction via dipolar addition similar to the process for

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M. Nomura et al. / Journal of Organometallic Chemistry 611 (2000) 376–385
the formation of methylene-bridged complexes in the
reaction of 1 with diazo compounds (Scheme 2).
2.2. X-ray structures of imido-bridged complexes
The structures of the imido-bridged complexes 2a
and 2b were determined by single-crystal X-ray diffrac-
tion. The ORTEP drawings are shown in Figs. 1 and 2,
together with selected bond lengths and angles.
Scheme 2.
The structure of the imido-bridged complex is similar
to that of the alkylidene-bridged complex. These ad-
ducts are coordinatively saturated six-coordinate spe-
cies. The almost planar five-membered cobalta-
dithiolene rings are retained and the three-membered
cobaltathiaziridine rings are almost perpendicular to
the dithiolene rings in the these complexes (2a: 89.89;
2b: 91.37°). The imido-bridged complexes, 2a and 2b,
have a shape based on the 111.9 and 111.88° angles
formed by the Cp rings and the dithiolene rings, respec-
tively. These CoꢀS bond lengths in the imido-bridged
complexes become longer than those of the original
,
complex (CoꢀS, 2.108(2) and 2.104(2) A), resulting
from the formation of a bridging structure (2a: CoꢀS1,
2.176(1), CoꢀS2, 2.230(1); 2b: CoꢀS(1), 2.196(1),
,
CoꢀS(2), 2.220(1) A). Their CꢀC bond lengths in cobal-
tadithiolene rings are shorter than normal CꢀC bonds
and longer than normal CꢁC bonds; the bond length of
the original complex is 1.369(6) [3e].
Fig. 1. ORTEP drawing of [(Cp)Co(S2C2(COOMe)2)(NTs)] (2a). Se-
,
lected bond lengths (A): CoꢀS1 2.176(1), CoꢀS2 2.230(1), CoꢀN1
1.961(4), S1ꢀN1 1.714(4), S1ꢀC1 1.750(5), S2ꢀC2 1.704(5), C1ꢀC2
1.365(7). Selected bond angles (°): S1ꢀCoꢀS2 90.74(5), CoꢀS1ꢀC1
105.0(2), CoꢀS2ꢀC2 102.2(2), S1ꢀC1ꢀC2 117.4(4), S2ꢀC2ꢀC1
124.2(4), S1ꢀCoꢀN1 48.6(1), CoꢀS1ꢀN1 59.1(1), CoꢀN1ꢀS1 72.3(1).
Plane angles (°): Cp ring/dithiolene ring 110.9(3), plane of CoꢀS1ꢀS2/
plane of CoꢀS1ꢀN1 89.89.
2.3. Reacti6ities of imido-bridged complexes
2.3.1. Thermolysis
The imido-bridged complex 2a underwent thermal
dissociation in the solid state at 177–178°C to yield the
original dithiolene complex 1 (88%) and p-toluenesul-
fonamide (43%). The imido-bridged complex 2c under-
went also thermal dissociation in the solid state at
160°C to afford the original complex 1, but the corre-
sponding amine (urethane) did not appear. The thermal
reactions of the complexes 2a and 2c in cyclohexene did
not give any nitrene-trapping products (7-azanorcarane
and methylcyclohexene) [13].
On the other hand, the alkylidene-bridged complexes
dissociate thermally to give quantitatively the original
dithiolene complexes. Pyrolysis of the methylene-
bridged complexes in cyclohexene yielded the corre-
sponding original dithiolene complexes and cyclohexene
derivatives. This result gives some evidence for the
generation of methylene from the adducts; the alkyli-
dene-bridged complexes are regarded as precursors for
free carbene species [3b].
Fig. 2. ORTEP drawing of [(Cp)Co(S2C2(COOMe)2)(NMs)] (2b). Se-
,
lected bond lengths (A): CoꢀS1 2.196(1), CoꢀS2 2.220(1), CoꢀN1
1.959(3), S1ꢀN1 1.720(3), S1ꢀC1 1.754(4), S2ꢀC2 1.708(4), C1ꢀC2
1.346(5). Selected bond angles (°): S1ꢀCoꢀS2 90.75(6), CoꢀS1ꢀC1
104.4(1), CoꢀS2ꢀC2 102.2(1), S1ꢀC1ꢀC2 117.8(3), S2ꢀC2ꢀC1
124.7(3), S1ꢀCoꢀN1 48.51(6), CoꢀS1ꢀN1 58.6(2), CoꢀN1ꢀS1 72.9(1).
Plane angles (°): Cp ring/dithiolene ring 111.88, dithiolene ring/plane
of CoꢀS1ꢀN1 91.37.
2.3.2. Clea6age of the cobaltathiaziridine ring with HCl
and its reformation in the reaction of the resulting
three-component adduct with bases
A unique reaction of the cobaltathiaziridine ring was
found in the reaction with HCl: the cleavage of CoꢀN

M. Nomura et al. / Journal of Organometallic Chemistry 611 (2000) 376–385
379
bond by hydrogen chloride and the reformation of the
cobaltathiaziridine ring by the action of a very weak
base such as water.
reformation of a strained three membered ring is a
characteristic reaction for this type of complex. The
reformation of the strained three-membered ring by a
very weak base such as water is a characteristic reaction
for the cobaltaziridine ring. Namely, a feature of ring
opening product 5 is its strong base. Similar behavior is
not observed in the three-component-adducts from
alkylidene-bridged adducts.
Similar to the methylene-adducts, the imido-bridged
complex reacts with hydrogen chloride[3d,7]. When the
imido adduct 2a was treated with an equal amount of
hydrogen chloride in a dichloromethane solution, the
color of the solution was rapidly changed from green to
brown and a product was obtained. The 1H-NMR
spectrum and elemental analysis show that the product
5a has an S-NHTs structure of (h5-cyclopentadi-
enyl)(chloro)(p-toluenesulfonylimidothio-kS-ethene-2-
thiolato-kS)cobalt(III) (5a), a three-component-adduct
consisting of cobaltadithiolene, p-toluenesulfonylimino
group, and hydrogen chloride. Other imido-bridged
complexes 2b and 2c reacted similarly. The proton may
either attack directly to the bridging nitrogen or may
attack to the basic sulfur atom first and then migrate to
the bridging nitrogen.
2.3.3. Clea6age of the cobaltathiaziridine ring with
PPh3
The addition of triphenylphosphine to a benzene
solution of 2 at room temperature results in the ring
opening to give quantitatively the three-component ad-
duct which has an S-ylide structure, 6 (Chart 5). The
formation of a six-membered ring complex as another
three-component adduct was denied by the results of
1H-NMR, UV–vis, and CV measurement, although in
the reactions of alkylidene-bridged complexes with
trimethylphosphine or trimethyl phosphite, we observed
ylide complexes along with six-membered ring com-
plexes, depending on the substituents at the bridging
carbon atom [9] (Chart 6).
Along with the ring opening, the elimination of the
bridging group also takes place by the action of excess
HCl. Free cobaltadithiolene complex 1 and p-toluene-
1
sulfonamide were identified by H-NMR spectral data.
Thus, complex 5 is not stable enough in an acidic
solution (Chart 4).
Chart 4.
The CoꢀS bond of the cobaltadithiolene rings in the
alkylidene-bridged cobaltadithiolenes is also easily
cleaved by hydrogen halides to give the corresponding
three-component-adducts among cobaltadithiolene,
alkylidene, and hydrogen halide. But the three-compo-
nent-adducts are stable in the presence of an excess
amount of hydrogen halides at room temperature.
These facts suggest that the ring-opened three-compo-
nent-adducts from the imido-bridged adducts are less
stable than those from the alkylidene-bridged adducts
[3d].
Chart 5.
The most remarkable reaction of 5a and 5b is the
reformation of 2a and 2b, respectively on the treatment
with water. When we shake a dichloromethane solution
of 5 with a small amount of water, we obtain the
imido-bridged complex 2. When we use a small amount
of pyridine, the reformation of the imido-bridged ad-
duct also occurs. These facts indicate that the highly
acidic proton at the nitrogen atom is abstracted by
bases and the negatively charged nitrogen attacks the
cobalt atom to kick off the chloride anion. The facile
Chart 6.
2.3.4. Insertion of p-toluenesulfonylamino group into a
CꢀH bond in the Cp ring in the reaction of the
imido-bridged complex with PPh3
In the reaction with phosphorus compounds at ca.
80°C (under reflux) in benzene or toluene, the sul-
fonylimido-bridged complex shows an interesting reac-
tion which is not observed for the alkylidene-bridged
complexes.

380
M. Nomura et al. / Journal of Organometallic Chemistry 611 (2000) 376–385
,
Fig. 3. ORTEP drawing of [(CpꢀNHꢀSO2ꢀC6H4ꢀCH3)Co(S2C2(COOMe)2)] (7). Selected bond lengths (A): CoꢀS1 2.112(3), CoꢀS2 2.102(3), S1ꢀC1
1.697(10), S2ꢀC2 1.726(9), C1ꢀC2 1.35(1), N1ꢀC7 1.38(1). Selected bond angles (°): S1ꢀCoꢀS2 91.8(1), CoꢀS1ꢀC1 105.1(3), CoꢀS2ꢀC2 104.7(3),
S1ꢀC1ꢀC2 119.6(7), S2ꢀC2ꢀC1 118.9(7), S3ꢀN1ꢀC7 126.5(7), C7ꢀN1ꢀH11 116.8(8), S3ꢀN1ꢀH11 116.6(6). Plane angles (°): Cp ring/dithiolene ring
88.84, Cp ring/phenyl ring 89.4, dithiolene ring/phenyl ring 12.35.
The heating of 6a in a benzene solution at ca. 80°C
(under reflux) in the presence of triphenylphosphine
gives another product, [(p-toluenesulfonylimino)cyclo-
pentadienyl - (1,2 - ethylenedithiolato)cobalt(III)]. The
structure of the isolated product was determined by
X-ray diffraction analysis. The ORTEP drawing is shown
in Fig. 3, together with selected bond lengths and
angles. The structure of the cobaltadithiolene ring is
analogous to that of the original complex 1. Interest-
ingly, as shown in Fig. 3, the cobaltadithiolene ring and
the phenyl ring in the Ts group are situated face-to-face
The p-toluenesulfonylimido-bridged complex 2a
shows a reversible one-electron reduction wave at
−0.79 V (reference, FcꢀFc+) and an irreversible two-
electron reduction wave at −1.80 V and an irreversible
oxidation wave around 0.5 V. The reduction halfwave
potential of −0.79 V is more positive than the original
cobaltadithiolene 1 (E1/2(red)= −0.94 V). This shows
that the coordinated imido group lowers the electron
density at the cobalt atom.
In the first reduction process, an in-situ measurement
of the electronic absorption spectra during the elec-
trolytic reduction using an optically transparent thin-
layer electrode (OTTLE) showed the reversibility of the
reduction and re-oxidation at −0.79 V.
On the other hand, after the irreversible second re-
duction process, the wave corresponding to the re-oxi-
dation of 1a− appeared; the reductant of the original
complex is regenerated by the second reduction and the
spectral change using OTTLE showed the regeneration
of the original complex, as shown in Fig. 5.
,
at a separation of ca. 3.5 A. The distance suggests an
intramolecular p–p interaction between the cobalta-
dithiolene ring and the phenyl ring.
In the product, p-toluenesulfonylamino group is
bonded to a carbon atom of the cyclopentadienyl ring.
Two different mechanisms are conceivable. One mecha-
nism involves the intermediary formation of nitrene
species and the other involves the intramolecular migra-
tion of the sulfonylimido group. We can not yet decide
the mechanism.
The first step to form an ylide structure is similar to
the reaction of di(methoxycarbonyl)-methylene-bridged
complex with trimethyl phosphite to give the three-
component adduct having S-ylide structure [9].
The second process of the reaction of the imido-
bridged complex with trimethylphosphine is different
from that of the di(methoxycarbonyl)methylene-
bridged complex with trimethyl phosphite. In the reac-
tion of alkylidene-bridged adducts, a similar alkylidene
transfer has never been observed.
2.3.5. Electrochemical beha6ior of the
sulfonylimido-bridged adduct by CV and OTTLE
Fig. 4. Cyclic voltammograms (6=100 mV s−1, b=1.6 mm, Pt disk)
of 1 mmol dm−3 complex in CH3CN containing 0.1 mol dm−3
TEAP: 2a (solid line) and 1(dotted line).
The cyclic voltammogram of complex 2a is shown in
Fig. 4, together with that of the original complex.

M. Nomura et al. / Journal of Organometallic Chemistry 611 (2000) 376–385
381
potential value is around −0.6 V. When the species
X+ was re-reduced, 1a was rapidly generated. The
complex X+ is relatively stable, but the neutral X is
very unstable. The structure of the complex X formed
by the oxidation has not yet been clarified, but it would
be an SꢀC bond cleaved product, because X easily
regenerates the original complex 1a. In contrast, the
coordinated methylene increases the electron density of
the cobalt atom.
In Fig. 6, the electrochemical behavior of a series of
the imido-bridged complexes 2 is compared with those
of methylene-bridged adduct, substituted Cp com-
plexes, and the original complex. The reversible reduc-
tion half-wave potentials were shifted to the positive
side as follows: [(CpꢀH)Coꢀ{S2C2(COOMe)2}(CH2)]B
[(CpꢀNHTs)Co{S2C2(COOMe)2}]B[(CpꢀH)Co{S2C2-
(COOMe)2}] B [(CpꢀH)Co{S2C2(COOMe)2}(NꢀCO-
O E t ) ] B [ ( C p ꢀ N H M s ) C o { S 2 C 2(C O O M e)2}]
B[(Cp−H)Co{S2C2(COOMe)2}(N−Ts)]B[(CpꢀH)-Co-
{S2C2(COOMe)2}(NꢀMs)]. Electrochemical behavior of
the imido-bridged complexes is now under detailed
investigation by using CV and OTTLE measurements.
Fig. 5. Electronic spectral change of 2a during reduction and re-oxi-
dation: after the reduction at −1.8 V for 30 s, the potential was
stepped from −1.8 (for 30 s) to −0.9 V (for 30 s); sampling interval,
2 s.
3. Experimental
Scheme 3.
3.1. General
Reactions were carried out under argon by means of
standard Schlenk techniques.
From these results, we propose the redox mechanism
shown in Scheme 3: the sulfonyl-imido-bridged complex
2a showed reversible redox behavior on these CV time
scales at −0.79 V. Reversibility in cyclic voltam-
mogram shows that one-electron reduction does not
cause any bond cleavage. Two-electron reduction of 2a
affords an anion radical having a lifetime of a few
seconds and then it eliminates the imido moiety to give
more stable 1a−. Then, we could see the regeneration
of the original complex by an OTTLE measurement. In
the irreversible oxidation process, the cation radical
2a+ has a lifetime of a few seconds, and then it is
converted to a species X+, of which the re-reduction
NMR spectra were measured with a JEOL JNM-
GX270, LA300, or LA500 spectrometer. Mass and FT
IR spectra were recorded on a JEOL JMS-SX102A and
Shimadzu model FTIR 8600PC, respectively. UV–vis
spectra were recorded on Hitachi model U-3210 or
Shimadzu model UV-2500PC. Cyclic voltammograms
were measured with model CV-50W of BAS Co. Ele-
mental analyses were determined by using a Shimadzu
PE2400-II instrument. Products were purified by
preparative HPLC, model LC-908 or model LC-08,
produced by Japan Analytical Industry Co.
Fig. 6. Effects of the structure of the complexes on E1/2(red).

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M. Nomura et al. / Journal of Organometallic Chemistry 611 (2000) 376–385
3.2. Materials
124 (29, [CpCo+]). Anal. Found: C, 33.99; H, 3.21; N,
3.50: S, 22.72. Calc. for C12H14NO6S3Co: C, 34.04; H,
3.33; N, 3.31: S, 22.81%.
The starting cobaltadithiolene complex [CpCo(S2C2-
(COOMe)2)] (1) was synthesized in a one-pot reaction
of [CpCo(CO)2], DMAD, and elemental sulfur [14].
p-Toluenesulfonyl azide (N3Ts), methanesulfonyl
azide (N3Ms), and ethyl azidoformate (N3COOEt) were
synthesized in the reaction of p-toluenesulfonyl chlo-
ride, methanesulfonyl chloride, and ethyl chloroacetate
with sodium azide, respectively, [15]. N-(Phenyliodo-
nio)-p-toluenesulfonamidate (4a) was prepared accord-
ing to the report by Okawara et al. [12b].
3.3.3. Reaction with ethyl azidoformate azide
The cobaltadithiolene complex 1 (0.17 mmmol) was
treated with ethyl azidoformate (0.97 mmol) under
reflux in benzene (30 cm3) under a stream of Ar for 24
h. After the solvent was removed under reduced pres-
sure, the residue was chromatographed by flush column
chromatography using silica gel (Wako-gel C-300; elu-
ent, mixed solvent of CH2Cl2–Et2O (1:3 v/v). An
ethoxycarbonylimido-bridged complex 2c was obtained
1
3.3. Formation of imido-bridged complexes
([CpCo(S2C2(COOMe)2)(NR)] 2)
as crystalline solid in 64% yield. m.p. 160–162°C. H-
NMR (CDCl3): l=2.39 (t, J=6.71 Hz, 3H, CH3), 3.82
(s, 3H, OCH3), 3.88 (s, 3H, OCH3), 4.06 (q, J=6.71
Hz, CH2), 5.53 (s, 5H, Cp). 13C-NMR (CDCl3): l=
14.7 (CH3), 52.7 (OCH3), 53.3 (OCH3), 67.4 (CH2), 86.2
(Cp), 128.1 (dithiolene ring carbon), 161.7 (CO), 166.2
(CO), 176.4 (CO), and 179.3 (dithiolene ring carbon).
MS (EI, 70 eV) m/z (rel. intensity) 417 (4.3, [M+]), 330
(87, [M+−NCOOEt]), 188 (100, [CpCoS+2 ]), 124 (32,
[CpCo+]). Anal. Found: C, 40.34; H, 3.89; N, 3.25.
Calc. for C14H16NO6S2Co: C, 40.29; H, 3.89; N, 3.36%.
3.3.1. Reaction with p-toluenesulfonyl azide
The cobaltadithiolene complex 1 (1.0 mmol) was
treated with p-toluenesulfonyl azide (1.0 mmol) under
reflux in benzene (10 cm3) under a stream of Ar for 2 h.
After the solvent was removed under reduced pressure,
the residue was chromatographed by flush column
chromatography using silica gel (Wako-gel C-300; elu-
ent, mixed solvent of CH2Cl2–Et2O (5:1 v/v). An p-
toluenesulfonylimido-bridged complex 2a was obtained
as crystalline solid in 76% yield. Green crystals; m.p.
3.3.4. Reaction of 1 with N-(phenyliodonio)-p-
toluenesulfonamidate (4a) in the absence of catalyst or
in the presence of catalysts
177–178°C (dec.). IR (KBr disk) 1736 and 1703 cm−1
.
1H-NMR (CDCl3): l=2.39 (s, 3H, CH3), 3.57 (s, 3H,
OCH3), 3.79 (s, 3H, CH3), 5.77 (s, 5H, Cp), 7.23 (d,
J=7.94 Hz, 2H, Ar), 7.73 (d, J=7.94 Hz, 2H, Ar).
13C-NMR (CDCl3): l=21.6 (CH3), 52.1 (OCH3), 53.4
(OCH3), 84.4 (Cp), 127.2 (CH), 128.4 (dithiolene ring
carbon), 129.4 (CH), 137.5, 143.4, 161.3 (CO), 165.8
(CO), and 185.3 (dithiolene ring carbon). MS (EI, 70
eV) m/z (rel. intensity) 499 (3.7, [M+]), 330 (94, [M+−
NTs]), 188 (100, [CpCoS+2 ]), 124 (34, [CpCo+]). Anal.
Found: C, 43.11; H, 3.58; N, 2.74. Calc. for
C18H18NO6S3Co: C, 43.29; H, 3.63; N, 2.80%.
A dichloromethane solution (20 cm3) of 1 (0.34
mmol) and 4a (0.34 mmol) was stirred in benzene (10
cm3) at room temperature. Reaction time of five min-
utes was enough for the formation of the imido-bridged
complex. The reaction mixture was submitted to flush
column chromatography using silica gel column
(Wako-gel C-300) and dichloromethane–hexane (5:1
v/v) as an eluent. A p-toluenesulfonylimido-bridged
complex 2a was obtained in 27% yield.
Similar reactions were carried out in the presence of
catalysts (0.03 mmol). The results are shown in the text.
3.3.2. Reaction with methanesulfonyl azide
The cobaltadithiolene complex 1 (0.3 mmmol) was
treated with methanesulfonyl azide (1.0 mmol) under
reflux in benzene (10 cm3) under a stream of Ar for 5 h.
After the solvent was removed under reduced pressure,
the residue was chromatographed by flush column
chromatography using silica gel (Wako-gel C-300; elu-
ent, mixed solvent of CH2Cl2–hexane (10:1 v/v). A
methanesulfonylimido-bridged complex 2b was ob-
tained as crystalline solid in 75% yield. Green crystals;
3.4. Reaction of imido-bridged adducts with hydrogen
chloride
3.4.1. Ring opening reaction of imido-bridged complex
with hydrogen chloride
To a dichloromethane solution (20 cm3) of imido-
bridged complex (2) (0.10 mmol) was added 20 ml of
concentrated hydrochloric acid. The suspension was
stirred under Ar for 5 min. The water was removed
with anhydrous MgSO4 and the solvent was distilled
under reduced pressure and the HCl adduct was ob-
tained as brown crystals. The three-component adduct
[CpCo(S2C2(COOMe)2)(NTs)(HCl)] (5a) of 2a and HCl
was obtained in 81% yield: Brown crystals, m.p. 88–90
°C (dec.). 1H-NMR (CDCl3): l=2.50 (s, 3H, CH3),
1
m.p. 165–167°C (dec.). H-NMR (CDCl3): l=3.07 (s,
3H, CH3), 3.77 (s, 3H, OCH3), 3.85 (s, 3H, CH3), 5.73
(s, 5H, Cp). 13C-NMR (CDCl3): l=41.9 (CH3), 52.6
(OCH3), 53.4 (OCH3), 84.3 (Cp), 115.0 (dithiolene ring
carbon), 161.4 (CO), 165.7 (CO), and 185.2 (dithiolene
ring carbon). MS (EI, 70 eV) m/z (rel. intensity) 423
(2.9, [M+]), 330 (87, [M+−NMs]), 188 (100, [CpCoS+2 ]),

M. Nomura et al. / Journal of Organometallic Chemistry 611 (2000) 376–385
383
3.53 (s, 3H, OCH3), 3.86 (s, 3H, OCH3), 5.39 (s, 5H,
Cp), 7.45 (d, J=7.93 Hz, 2H, Ar), 7.86 (s, 1H, NH),
and 7.97 (d, J=7.93 Hz, 2H, Ar). MS (FAB, 70 eV)
m/z 536 ([M++1]). Anal. Found: C, 40.11; H, 3.81; N,
2.60. Calc. for C18H19ClCoNO6S3: C, 40.34; H, 3.57; N,
2.61%. The three-component adduct [CpCo(S2C2-
(COOMe)2)(NMs)(HCl)] (5b) of 2a and HCl was ob-
tained in 80% yield: Brown crystals. H-NMR (CDCl3):
l=3.33 (s, 3H, CH3), 3.77 (s, 3H, OCH3), 3.86 (s, 3H,
OCH3), 5.70 (s, 5H, Cp), and 7.87 (s, 1H, NH). The
products were separated by flush column chromatogra-
phy using silica gel (C-300) (eluent, acetone-diethyl
ether (1:1 v/v)). The dark-brown solid was obtained in
94% yield as a three-component adduct [CpCo(S2C2-
(COOMe)2)(NMs)(PPh3)] (6b). Brown crystals: 1H-
NMR (CDCl3): l=2.93 (s, 3H, CH3), 3.51 (s, 3H,
OCH3), 3.70 (s, 3H, CH3), 5.34 (s, 5H, Cp), 7.43–7.71
(m, 15H, Ph), MS (FAB, 70 eV), m/z 686 ([M++1]).
For the reaction at elevated temperature, a benzene
solution of complex 2a (0.1 mmol) and triphenylphos-
phine (0.2 mmol) was refluxed for 5 h. The products
were separated by flush column chromatography using
silica gel (C-300) (eluent, CH2Cl2–diethyl ether 2:1
v/v)). The blue–violet solid was obtained in 44% yield
1
three-component
adduct
[CpCo(S2C2(COOMe)2)-
(NCOOEt)ꢀ(HCl)] (5c) of 2a and HCl was obtained in
80% yield: MS (FAB, 70 eV) m/z 454 ([M++1]).
1H-NMR (CDCl3): l=1.30 (t, J=6.71 Hz, 3H, CH3),
3.76 (s, 3H, OCH3), 3.87 (s, 3H, OCH3), 4.26 (q,
J=6.71 Hz, 3H, CH3), 5.63 (s, 5H, Cp), and 6.94 (s,
1H, NH).
as
a
substituted Cp complex [(CpꢀNHTs)Co-
(S2C2(COOMe)2)]. Blue crystals; m.p. 209–211°C
(dec.). UV–vis (CH2Cl2) u(m) 717 (557), 572 (5350), 362
1
(3110), 294 (16700). H-NMR (CDCl3): l=2.25 (s, 3H,
3.4.2. Regeneration of the imido-bridged adduct due to
CH3), 3.89 (s, 6H, OCH3), 5.07 (t, J=2.44 Hz, 2H,
Cp), 5.66 (t, J=2.44 Hz, 2H, Cp), 6.98 (d, J=7.94 Hz,
2H, Ar), 7.21 (s, 1H, NH), 7.37 (d, J=7.94 Hz, 2H,
Ar). 13C-NMR (CDCl3): l=21.2 (CH3), 52.7 (OCH3),
69.5 (Ar), 74.6 (Ar), 112.0 (Ar), 127.1 (Ar), 129.1 (Cp),
131.0 (CꢀSO2), 144.1 (CpꢀN), 158.1 (dithiolene C), and
165.4 (CꢁO). MS (EI, 70 eV) m/z (rel. intensity) 499
([M+], 94), 356 ([CpNHTsS2+−1], 24), 91 ([C6H4CH+3 ],
100). Anal. Found: C, 41.36; H, 3.37; N, 2.83. Calc. for
C18H20NO7S3Co: C, 41.78; H, 3.90; N, 2.71%.
The reaction of methanesulfonylimido-bridged com-
plex (0.1 mmol) with triphenylphosphine (0.3 mmol)
was refluxed in benzene (10 cm3) for 5 h to give 32% of
a blue crystalline product which is a methanesulfonyl
substituted Cp complex. M.p.: 181–183°C. 1H-NMR
(CDCl3) 5.85 (t, J=2.0 Hz, 2H, Cp), 5.16 (t, J=2.0
Hz, 2H, Cp), 3.89 (s, 6H, OCH3), 2.72 (s, 3H, CH3).
13C-NMR (CDCl3) 165.9 (CꢁO), 158.4 (dithiolene C),
132.2 (Cp(CꢀN), 75.2 (Cp(CꢀH)), 69.7 (Cp(CꢀH)) 53.2
(OCH3), 37.7 (CH3). UV–vis (CH2Cl2) umax (m) 712
(687), 571 (6150), 361 (3670), 291 (17300). MS (EI, 70
eV) m/z (rel. intensity) 423 ([M+], 100), 280
([(CpNHMs)CoS+2 −1], 34). Anal. Found: C, 34.05; H,
3.15; N, 3.17, Calc. for C12H14O6NS3Co: C, 34.00; H,
3.33; N, 3.33%.
ring reformation t with bases
A
dichloromethane solution of [CpCo(S2C2-
(COOMe)2)(NTs)(HCl)] (5a) was shaken with water in
a separatory funnel. The organic layer was dried over
MgSO4 and the solvent was removed under reduced
pressure. The formation of the imido-bridged com-
plexes 2a was confirmed by H-NMR. The reaction of
5a with pyridine was also performed in
dichloromethane solution by adding a small amount of
pyridine. After evaporation of solvent, the imido-
bridged complex 2a was identified by H-NMR.
1
a
1
3.5. Reaction of imido-bridged adducts with
triphenylphosphine
The p-toluenesulfonylimido-bridged complex 2a (0.1
mmol) was treated with triphenylphosphine (0.11
mmol) in dichloromethane at room temperature. The
reaction occurs at once and the color changed from
green to brown. The products were separated by flush
column chromatography using silica gel (C-300) (elu-
ent, acetone-diethyl ether (1:1 v/v)). The dark-brown
solid was obtained in 95% yield as a three-component
adduct [CpCo(S2C2(COOMe)2)(NTs)(PPh3)]. Brown
crystals: m.p. 127–129°C (dec.). IR (KBr disk) 1736
and 1703 cm−1 1H-NMR (CDCl3): l=2.37 (s, 3H,
.
CH3), 2.72 (s, 3H, OCH3), 3.67 (s, 3H, CH3), 5.40 (s,
5H, Cp), 7.18 (d, J=7.93 Hz, 2H, Ph), 7.31–7.34 (m,
Ph), 7.46–7.52 (m, Ph), 7.76 (m, Ph), and 7.78 (d,
J=7.93 Hz, 2H, Ph). MS (FAB, 70 eV) m/z 762
([M++1]), 500 ([M+−PPh3+1]), and 262 ([PPh+3 ]).
Anal. Found: C, 56.47; H,4.46; N, 1.93%. Calc. for
C36H33NO6PS3Co: C, 56.76; H, 4.37; N, 1.84%.
The methanesulfonylimido-bridged complex 2b (0.1
mmol) was treated with triphenylphosphine (0.11
mmol) in dichloromethane at room temperature for 30
min. The color changed from green to brown. The
3.6. Crystal data and structure determination of
complexes 2a, 2b, and 7a
Detail are given in Table 1. Suitable crystals of
complexes 2a, 2b, and 7a were grown from CH2Cl2–
hexane solution at room temperature. All measure-
ments were made on Rigaku AFC5S four-circle
diffractometers with graphite- monochromated Mo Ka
radiation. The structures were solved by direct methods
and expanded using Fourier techniques [16]. The non-

384
M. Nomura et al. / Journal of Organometallic Chemistry 611 (2000) 376–385
Table 1
Crystal data and data collection parameters
2a
2b
7a
Formula
C18H18NO6S3Co
499.46
Monoclinic
C2/c (c15)
C
423.36
Monoclinic
P21/n (c14)
12H14NO6S3Co
C18H18NO6S3Co
499.46
Triclinic
Formula weight
Crystal system
Space group
(
P1 (c2)
Unit cell dimensions
,
a (A)
13.744(4)
19.832(4)
15.085(1)
95.6900
4091(1)
8
10.297(8)
8.68(1)
18.75(1)
93.52(6)
1672(2)
4
11.056(2)
11.775(2)
9.003(2)
106.79(1)
1119.0(4)
2
,
b (A)
,
c (A)
i (°)
V (A )
3
,
Z
2q Range (°)
Dcalc (g cm−3
F(000)
25(20.2–24.8)
1.622
2048.00
11.81
25(27.5–29.5)
1.681
864.00
14.27
296
25(28.6–29.9)
1.536
532.00
10.85
296
)
v (Mo Ka) (cm−1
T (K)
)
296
Crystal size (mm)
Scan type
0.17×0.17×0.33
ꢀ–2q
6.0
(1.05+0.30 tanq)
55.0
0.10×0.17×0.43
ꢀ–2q
6.0
(1.21+0.30 tanq)
55.0
0.07×0.13×0.43
ꢀ–2q
6.0
(1.37+0.30 tanq)
55.0
Scan speed (° min–1
Scan width (°)
2qmax (°)
)
Unique data (Rint
)
4864 (0.033)
2588
280
0.046, 0.056
1.39
0.55, −0.81
4102 (0.023)
2291
222
0.037, 0.030
1.62
0.27, −0.25
5144 (0.021)
3149
289
0.067, 0.097
4.64
Number of observations
Number of variables
R1, wR2 (all data)
Goodness-of-fit on F2
−3
,
Largest difference peak and hole (e A
)
hydrogen atoms were refined anisotropically. Idealized
positions were used for the TEXSAN crystallographic
software package of Molecular Structure Corp. [17].
e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
Acknowledgements
3.7. CV measurements
The study was supported by grants-in-aid for Scien-
tific Research Nos.09440247, 09640673, and 11640571
and grants-in-aid on Priority Area-Researches on ‘In-
terelement’ nos. 09239246 and 11120251 from the Min-
istry of Education, Science, Sports and Culture, Japan.
All the electrochemical measurements were done in 1
(CV) or 1.0 mmol dm−3 (OTTLE) acetonitrile solu-
tions containing 0.1 (CV) or 0.1 mmol dm−3 (OTTLE)
[35] tetraethyl-ammonium perchlorate (TEAP) at 25°C.
A stationary platinum disk (1.6 mm in diameter) (CV)
or platinum wire served as a working electrode. A
coiled platinum wire served as a counter electrode, with
the reference electrode as AgꢀAgNO3 corrected for junc-
tion potentials by being referenced internally to the
FcꢀFc+.
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