Synthesis and molecular structures of S-2-FcNHCOC6H4SH and [MIII(OEP)(S-2-FcNHCOC6H4)] (Fc = ferrocenyl, M = Fe, Ga): Electrochemical contributions of intramolecular SH?O{double bond, long}C and NH?S hydrogen bonds

Article abstract of DOI:10.1016/j.jorganchem.2006.08.067

A novel redox-active thiolate ligand having a ferrocene moiety, S-2-FcNHCOC₆H₄SH (1a), and its porphyrin-thiolate compounds, [M^III(OEP)(S-2-FcNHCOC₆H₄)] (M = Fe (2a), Ga (3a)) were synthesized and characterized by X-ray analysis, spectroscopic and electrochemical measurements. The corresponding 4-substituted derivatives (1b-3b) were also synthesized to estimate the contribution of substituent effects. The formation of intramolecular SH?O{double bond, long}C or NH?S hydrogen bonds in solution was established by ¹H NMR and IR spectra. The cooperative effects of the hydrogen bonds and π-conjugation were found on redox potentials of Fc and iron-porphyrin moieties.

Full text of DOI:10.1016/j.jorganchem.2006.08.067

Journal of Organometallic Chemistry 692 (2007) 248–256
www.elsevier.com/locate/jorganchem
Synthesis and molecular structures of S-2-FcNHCOC6H4SH
and [MIII(OEP)(S-2-FcNHCOC6H4)] (Fc = ferrocenyl,
M = Fe, Ga): Electrochemical contributions of intramolecular
SHꢀ ꢀ ꢀO@C and NHꢀ ꢀ ꢀS hydrogen bonds
*
*
Taka-aki Okamura , Taku Iwamura, Hitoshi Yamamoto, Norikazu Ueyama
Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
Received 28 February 2006; accepted 26 May 2006
Available online 30 August 2006
Abstract
A novel redox-active thiolate ligand having a ferrocene moiety, S-2-FcNHCOC6H4SH (1a), and its porphyrin-thiolate compounds,
[MIII(OEP)(S-2-FcNHCOC6H4)] (M = Fe (2a), Ga (3a)) were synthesized and characterized by X-ray analysis, spectroscopic and elec-
trochemical measurements. The corresponding 4-substituted derivatives (1b–3b) were also synthesized to estimate the contribution of
1
substituent effects. The formation of intramolecular SHꢀ ꢀ ꢀO@C or NHꢀ ꢀ ꢀS hydrogen bonds in solution was established by H NMR
and IR spectra. The cooperative effects of the hydrogen bonds and p-conjugation were found on redox potentials of Fc and iron-por-
phyrin moieties.
Ó 2006 Elsevier B.V. All rights reserved.
Keywords: Ferrocene; Porphyrin; Hydrogen bond; Thiolate; Redox potential
1. Introduction
pling between ferrocene and (porphinato)iron(III) moieties
through the hydrogen bonds.
Ferrocene is the one of the most stable redox-active mol-
ecules and has been used for various applications including
receptors or electrochemical sensing of small molecules [1–
6]. In the recognition, intermolecular hydrogen bonds are
formed resulting negative shift of the redox potential of
metal center [2–6].
On the other hand, intramolecular NHꢀ ꢀ ꢀS hydrogen
bond positively shifts the redox potential of various metal
thiolates [7–13]. Especially, electron-withdrawing group,
that is CF3, strengthens the hydrogen bond which results
in a large positive shift [3,7].
2. Results
2.1. Molecular design and synthesis
Incorporation of N-alkylcarbamoyl group to benze-
nethiol presents us two types of hydrogen bonds,
SHꢀ ꢀ ꢀO@C and NHꢀ ꢀ ꢀS. In thiol (1a), the carbonyl
group forms SHꢀ ꢀ ꢀO@C hydrogen bond as shown in
Scheme 1. When SH group of 1a is deprotonated, the
amide plane is flipped around the phenyl–carbonyl bond
and NHꢀ ꢀ ꢀS hydrogen bond can form as shown for 2a
and 3a in Scheme 1. To estimate induction effects, 4-
substituted derivatives 1b–3b were synthesized. Obvi-
ously, these compounds cannot form any intramolecular
hydrogen bond.
In this paper, we design a redox-active thiolate ligand
and detect directly the electron flow or electrochemical cou-
*
Corresponding authors. Tel.: +81 6 6850 5451; fax: +81 6 6850 5474.
E-mail addresses: tokamura@chem.sci.osaka-u.ac.jp (T. Okamura),
ueyama@chem.sci.osaka-u.ac.jp (N. Ueyama).
0022-328X/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.08.067

T. Okamura et al. / Journal of Organometallic Chemistry 692 (2007) 248–256
249
Fig. 1. (a) Molecular structure of 2-FcNHCOC6H4SH (1a) and (b)
intermolecular NH ÆÆ O@C hydrogen bond chain of 1a in the crystal.
Scheme 1.
2.2. Molecular structures of 2-FcNHCOC6H4SH (1a) and
[GaIII(OEP)(S-2-FcNHCOC6H4)] (3a)
The molecular structure of 1a is shown in Fig. 1. The
thiol, 1a, forms infinite intermolecular NHꢀ ꢀ ꢀO@C hydro-
gen bond chains in the crystal. The SH group does not
form any significant hydrogen bond with an electronega-
tive atom, i.e., O or S. The SH group is directed to the
neighboring Cp (cyclopentadienyl) ring with a short con-
tact (H2–C31 = 3.27(4)), which suggests the presence of
an intermolecular SHꢀ ꢀ ꢀp interaction. The NHꢀ ꢀ ꢀO@C
hydrogen bond is more effective than SHꢀ ꢀ ꢀO@C hydrogen
bond to stabilize the packing energy.
For 3a, two independent molecules were found in the
unit cell. Two molecules do not show significant difference
each other. One of them is shown in Fig. 2. The amide NH
is directed to the thiolate S and forms intramolecular
NHꢀ ꢀ ꢀS hydrogen bond with short Nꢀ ꢀ ꢀS contact (ca.
˚
3 A). The selected bond lengths and angles are summarized
in Table 1 comparing with some analogous. Two structures
of (porphinato)gallium(III) thiolate complexes have been
known [14]. Previously, we reported a significant contribu-
tion of intramolecular NHꢀ ꢀ ꢀS hydrogen bond to the elon-
gation of Ga–S bond. The Ga–S bond distances of the
Fig. 2. Molecular structure of [GaIII(OEP)(S-2-FcNHCOC6H4)] (3a).
Two independent molecules are present in the unit cell. Two molecules do
not show significant difference each other and one of them is shown here.
The thermal ellipsoids are drawn at the 25% probability level.
˚
˚
molecules 3a are 2.320(12) A and 2.318(2) A which are
longer than that of [GaIII(OEP)(SPh)] (2.274 A) by
˚

250
T. Okamura et al. / Journal of Organometallic Chemistry 692 (2007) 248–256
Table 1
Table 3
Selected bond distances (A) and angles (°) of [GaIII(OEP)(S-2-RC6H4)]
IR spectral data in CH2Cl2 for various compounds
˚
R
Compounds
m(NH)/
m(CO)/
m(SH)/
cmꢁ1
cmꢁ1
cmꢁ1
FcNHCO (3a)
H
CF3CONHa
2-FcNHCOC6H4SH (1a)
4FcNHCOC6H4SH (1b)
3424
3440
3195
3441
3184
3445
3044
3450
3439
1667
1672
1651
1671
1651
1670
1623
1645
1673
2547
2583
Ga1–S1
2.320(2)
+0.046
2.318(2)
+0.044
2.049(5)
2.028(4)
2.046(5)
2.057(4)
2.045
0.418(3)
1.791(6)
103.0(2)
95.6(6)
2.274(2)
0
2.315(3)
+0.041
2.054(9)
2.022(6)
2.03(1)
2.005(7)
2.04
0.3856
1.753(9)
104.1(4)
ꢁ103.0(9)
2.92(1)
Difference
Ga1–N1p
Ga1–N2p
Ga1–N3p
Ga1–N4p
Mean
Ga1–N4
S1–C11
Ga1–S1–C11
[FeIII(OEP)(S-2-FcNHCOC6H4)] (2a)
[FeIII(OEP)(S-4-FcNHCOC6H4)] (2b)
[GaIIIOEP](S-2-FcNHCOC6H4)] (3a)
[GaIII(OEP)(S-4-FcHCOC6H4)] (3b)
(NEt4)[S-2-FcNHCOC6H4] (4a)
(NEt4)[S-4-FcNHCOC6H4] (4b)
FcNHCOC6H5
–
–
–
–
–
–
–
2.044(5)
2.055(4)
2.039(5)
2.049(3)
2.047
0.412(3)
1.779(6)
101.9(2)
2.043(6)
2.054(5)
2.038(6)
2.044(6)
2.045
0.457
1.761(9)
103.5(3)
93.1(9)
Ga1–S1–C11–C12 ꢁ102.4(6)
molecular structures of 1a and 2a illustrated in Scheme 1.
This proposal is supported by H NMR spectra discussed
N1ꢀ ꢀ ꢀS1
3.075(5)
2.318
3.078(6)
2.313
–
–
1
(N1)Hꢀ ꢀ ꢀS1
2.390
below.
a
The data have been reported [14].
1
The H NMR signals of amide NH and SH protons for
these compounds are listed in Table 2. The down-field-
shifted signals indicate the formation of intramolecular
hydrogen bonds. Especially, 4a indicates extraordinary
large value (14.21 ppm) for an amide proton. The other
NH peaks were found in usual region. The substituent
effect of thiolate anion is limited within a relatively small
shift (1.1 ppm for 4b). Acylaminoferrocenes form relatively
strong hydrogen bonds due to the acidic NH proton
induced by delocalization of electron on NH to Cp ring
as described in the previous papers [16–18].
In the porphinato compounds, [M(OEP)(S-2-FcNH-
COC6H4)] (M = FeIII(2a) and GaIII (3a)), NHꢀ ꢀ ꢀS hydro-
gen bonds were detected by IR absorption in
dichloromethane (Table 3). The NH stretching band of
3a was found at a lower wavenumber (3184 cmꢁ1) than
that of 2a (3195 cmꢁ1). Such a stronger NHꢀ ꢀ ꢀS has been
found previously, which is caused by a more ionic Ga–S
bond than Fe–S [14]. The ionic bond prevents the decrease
of electron density on S by p-donation from the thiolato
ligand to the metal ion and the electron-rich sulfur has con-
siderably strong ability of hydrogen bond formation.
˚
˚
0.046 A and 0.044 A, respectively. These results strongly
suggest the presence of interactions between the amide
NH and the thiolato S.
2.3. Detection of hydrogen bonds
The stretching bands of amide and thiol groups are sum-
marized in Tables 2 and 3. The formation of intra- or inter-
molecular hydrogen bonds were established by the
significant lower-wavenumber shift. In the solid state, the
thiol, 2-FcNHCOC6H4SH (1a), shows m(NH), m(C@O),
and m(SH) bands at 3301, 1637, and 2575 cmꢁ1, respec-
tively. The lower-shifted bands indicate the presence of
intermolecular NHꢀ ꢀ ꢀO@C hydrogen bonds in the compar-
ison with free m(NH) (3439 cmꢁ1) and m(C@O) (1673 cmꢁ1
)
of FcNHCOCH3. These results are consistent with the
crystal structure. On the other hand, 1a forms an intramo-
lecular SHꢀ ꢀ ꢀO@C hydrogen bond in chloroform-d1.
m(NH) (1665 cmꢁ1) and m(SH) (2564 cmꢁ1) were observed
at lower wavenumbers. Such a hydrogen-bonded SH was
also detected as a minor peak in the solid state (Table 2).
When 1a was deprotonated to (NEt4)[S-2-FcNHCOC6H4]
(4a), unusually low-wavenumber-shifted m(NH) was found
at 3044 cmꢁ1, while 4-substituted derivative (4b) shows no
significant shift [15]. These results agree with the proposed
1
2.4. H NMR of porphinato compounds
The porphinato compounds have been known for the
large dipolar shift caused by the expanded ring current.
[Ga(OEP)(S-2-FcNHCOC6H4)] (3a) exhibits proton reso-
Table 2
IR and 1H NMR spectral data of thiols and thiolates
Compounds
IR/cmꢁ1
1HNMR d/ppm
m(NH)
m(CO)
m(SH)
NH
SH
2-FcNHCOC6H4SH (1a)
4-FcNHCOC6H4SH (1b)
In CDCl3
Solid
In CDCl3
Solid
In CDCl3
In CDCl3
In CDCl3
3432
3301
3447
3309
3044
3450
3446
1665
2564
2575 (2560)
2587
2573, 2563
–
–
–
7.10
4.66
–
3.59
–
–
–
–
1637, (1627)a
1672
–
–
7.10
1633
1623
1645
1673
(NEt4)[S-2-FcNHCOC6H4] (4a)
(NEt4)[S-4-FcNHCOC6H4] (4b)
FcNHCOC6H5
14.21
8.26
7.16
a
The minor peaks (30% intensity) are shown in the parentheses.

T. Okamura et al. / Journal of Organometallic Chemistry 692 (2007) 248–256
251
nances of ethyl groups at 3.91, 4.02 (CH2), and 1.87(CH3)
ppm in benzene-d6. These values were found in a reason-
able region for 5-coordinated porphinato(thiolato)
compounds reported previously [14]. Furthermore, para-
magnetic iron(III) center effectively shifts the proton signal
by electron spin–nuclear spin interactions through bonds
and/or space. The observed chemical shifts of 2a and 2b
in benzene-d6 are shown in Table 4.
In the case of paramagnetic compounds, the signal signs
of the aromatic protons are explained by the alternative
rule of electron spins in a conjugated system [7,8]. The
N1H signal of 2a was found as a very broad peak that
2
was confirmed at ꢁ98.4 ppm by H NMR of NH-deuter-
ated 2a (Fig. 3). When an amide group was introduced to
4-position, [Fe(OEP)(S-4-FcNHCOC6H4)] (2b), the NH
peak was found at 33.7 ppm. The unusual upper-field shift
of 2a strongly suggests the presence of a direct interaction
through NHꢀ ꢀ ꢀS hydrogen bond. If the NHꢀ ꢀ ꢀS bond is not
present, the signal must be found at a lower field as found
for 2b. Moreover, the shift (ca. ꢁ100 ppm) is larger than
the reported values (ca. ꢁ50 ppm) for hydrogen-bonded
compounds, e.g., [Fe(OEP)(S-2-CF3CONHC6H4)] [7]. In
the case of 2b, FeIII-thiolate bond is broken to form FeII
and disulfide by redox equilibrium [19]. The presence
Fig. 3. (a) 2H NMR spectrum of [FeIII(OEP)(S-2-FcNDCOC6H4)] in
benzene and (b) 1H NMR spectrum of [FeIII(OEP)(S-2-FcNHCOC6H4)]
(2a) in benzene-d6 at 30 °C.
1
(20%) of [FeII(OEP)] was detected by H NMR. Such a
Table 5
Electrochemical properties of the compounds in CH2Cl2
behavior has been known for usual iron(III) (thiolato)por-
phinato complexes.
Compounds
E1/2 vs. Ag/Ag+
Fc (FeIII/FeII)a
[FeIII/II(OEP)(SR)]
2.5. Electrochemical studies
2-FcNHCOC6H4SH (1a)
4-FcNHCOC6H4SH (1b)
[FeIII(OEP)(S-2-FcNH-
COC6H4)] (2a)
98
80
72
–
–
The compounds 1a–3b show reversible FeIII/FeII redox
couple due to ferrocene moiety in dichloromethane. The
iron(III) porphinato derivatives, 2a and 2b, show addi-
tional quasi-reversible one. The E1/2 values (vs. Ag/Ag+)
are summarized in Table 5. These values were within an
error of about 2 mV for several measurements. Non-substi-
tuted ferrocene indicated the redox potential at 191 mV
under the same condition. The 2-substituted derivatives
exhibit more positive potential than the 4-substituted ones.
The trend, thiol > Fe-porphyrin > Ga-porphyrin, was
found for these derivatives, which is consistent with the
covalency of S–X where X is proton or metal ion, suggest-
ing that it reflects the electronic negativity on the sulfur
atom.
ꢁ770
[FeIII(OEP)(S-4-FcNH-
COC6H4)] (2b)
57
65
43
ꢁ890
[GaIII(OEP)(S-2-FcNH-
COC6H4)] (3a)
[GaIII(OEP)(S-4-FcNH-
COC6H4)] (3b)
–
–
a
Non-substituted ferrocene shows E1/2 = 191 mV under the same
conditions.
significantly positive-shifted than the reported value
(ꢁ0.52 V) for singly hydrogen-bonded complex,
[FeIII(OEP)(S-2-CF3CONHC6H4)]. The less reversibility
(Ipa/Ipc = 0.33 for 2a 0.49 for 2b) in the comparison with
reported compounds [7] is caused by unstable FeII–S bond.
When the iron(III) is reduced to iron(II), the electron den-
sity on the iron center increases, which results in the
decrease of electron donation from S to Fe.
At the metalloporphyrin site, 2a shows a remarkable
positive shift (by 120 mV) than 2b. According to the
reported conditions, the redox potentials were observed
at ꢁ0.48 V (vs. SCE) for 2a, ꢁ0.60 for 2b, and ꢁ0.68 V
for [Fe(OEP)(SPh)], respectively. The redox potential is
Table 4
1H NMR chemical shifts (ppm) for [FeIII(OEP)(SAr)] (SAr = S-2-FcNHCOC6H4 (2a), S-4-FcNHCOC6H4 (2b)) in benzene-d6
Complexes
meso-H
a-CH2
b-CH3
2,6-H
3,5-H
4-H
NHa
2a
2b
a
ꢁ46.7
ꢁ47.6
42.9, 39.9
39.2, 38.0
6.6
6.2
ꢁ87.0
ꢁ94.4
58.9, 51.6
58.9
ꢁ78.0
ꢁ98.4
–
33.7
2H NMR in benzene.

252
T. Okamura et al. / Journal of Organometallic Chemistry 692 (2007) 248–256
3. Discussion
geometrical differences from [GaIII(OEP)(SPh)] are listed
in Table 1. The significant elongation of Ga–S bond reflects
the effectively strong NHꢀ ꢀ ꢀS hydrogen bond of 3a. The
reported structural similarity between GaIII and FeIII por-
phyrin complexes [14] and spectral data ensure the validity
of the analogy despite the structure of 3b has not been
determined.
3.1. Hydrogen bonds in solution and in the solid state
The thiol, 1a, is intermolecularly NHꢀ ꢀ ꢀO@C hydrogen
bonded in the crystal, which is established by X-ray analy-
sis and IR spectra. When it is dissolved in a less polar
solvent such as dichloromethane or chloroform, intramo-
lecular SHꢀ ꢀ ꢀO@C hydrogen bond is formed instead of
the cleavage of intermolecular hydrogen bonds, which
should be preferable in a dilute solution. Such a behavior
has been found generally in many compounds with hydro-
gen bonding ability. In this case, the formation of
SHꢀ ꢀ ꢀO@C bond minimizes the total energy in solution.
IR and 1H NMR spectra support the presence of this com-
petitive formation of hydrogen bond.
3.3. Electrochemical contribution of the hydrogen bonds and
p-conjugation to the redox potential
The electrochemical interactions through SHꢀ ꢀ ꢀO@C
and NHꢀ ꢀ ꢀS hydrogen bonds are illustrated in Fig. 4 with
each redox potential vs. Ag/Ag+ in acetonitrile. Inductive
effects are evaluated by non-hydrogen-bonded 1b. When
SHꢀ ꢀ ꢀO@C hydrogen bond is formed, the electron on car-
bonyl oxygen is used to form Hꢀ ꢀ ꢀO bond and the defi-
ciency of electron on O is supplied from ferrocene moiety
through p-conjugation of amide group. The observed more
positive redox potential of 1a than 1b is explained reason-
ably. In contrast to this, the formation of NHꢀ ꢀ ꢀS hydro-
gen bond results the opposite flow of electrons. When the
electron on sulfur is used to form Hꢀ ꢀ ꢀS bond, the electron
density of sulfur should decrease and the N-Fc moiety
becomes electron-rich. The metalloporphyrin supplies elec-
tron to the electron-deficient sulfur or the donation from
sulfur to metal ion decreases. Consequently, the redox
potential of ferrocene should shift negatively. In more ionic
Ga–S bond, negative charge on the sulfur atom remains,
which results more negative redox potential of ferrocenyl
group. The unexpected small values for the 4-substituted
derivatives (2b and 3b) are probably caused by efficient
substituent effect, that is the p-substituent of benzene ring
permits electron flow from thiolate anion to the ferrocenyl
In the thiolate compounds, remarkably strong hydrogen
bonds were found in both solution and the solid state. The
strongest hydrogen bond was detected in thiolate anion, 4a,
1
by IR and H NMR spectra. The strength of hydrogen
1
bond is estimated by IR and H NMR spectra using char-
acteristic NH stretching band and the chemical shift of
amide proton. Extraordinary values, 14.21 ppm (chemical
shift of NH) and 3044 cmꢁ1 (m(NH)), strongly suggest the
presence of exceedingly strong hydrogen bonds. Strong
interaction through NHꢀ ꢀ ꢀS hydrogen bond was also found
in paramagnetic shift of NH (ca. ꢁ100 ppm) for 2a.
Previously, we reported a strong intramolecular NHꢀ ꢀ ꢀS
hydrogen bond in five-membered ring of 2-acylaminoben-
1
zenethiolate; however the IR and H NMR data did not
show such a large shift [12]. In six-membered ring described
in this paper, the location and direction of amide NH
toward the neighboring thiolate are the most appropriate
to the formation of hydrogen bonds. Furthermore, the
electron-deficient ferrocenyl group efficiently decreases
the electron density on NH, which results in the increase
of hydrogen bonding ability [16,18]. Replacement of ferr-
ocenyl group by alkyl group, that is (NEt4)[S-2-t-BuNH-
COC6H4], increases m(NH) to 3153 cmꢁ1 in chloroform
[15]. When a metal ion coordinates to the thiolate, the elec-
tron density on S decreases by electron donation from sul-
fur atom to the electron-deficient metal ion. The degree of
electron donation depends on the M–S bond character.
Ionic Ga–S bond tends to remain the electron on sulfur
but the relatively covalent Fe–S bond uses the electrons
for the linkage [14]. The found tendency of hydrogen bond
strength, 4a > 2a > 3a, is a reasonable result.
3.2. Significant contribution of the hydrogen bonds to M–S
bond length
We have systematically demonstrated the contribution
of NHꢀ ꢀ ꢀS hydrogen bonds to the M–S bond lengths. In
the case of porphyrins, it has been found that the hydrogen
bond elongates the M–S bond at the axial position [8,14].
This fact is explained by the decrease of p-donation capa-
bility of thiolato ligand by the adjacent amide NH. The
Fig. 4. Electronic interaction through intermolecular NHꢀ ꢀ ꢀS and
SHꢀ ꢀ ꢀO@C hydrogen bonds in 1a, 2a, and 3a. The arrows indicate
schematically the electron flow. The redox potentials (E1/2) are shown vs.
Ag/Ag+ in acetonitrile.

T. Okamura et al. / Journal of Organometallic Chemistry 692 (2007) 248–256
253
group through p-conjugation system in quionid form. In
the case of 2a and 3a, part of the electrons is used for the
hydrogen bond and the localization of electron there pre-
sumably restricts the effective flow of electron to the ferro-
cene moiety, which results a small positive shift.
NaBH4 (90 mg, 2.3 mmol) and stirred overnight. The
resulting clear solution was concentrated under reduced
pressure, and then 2 M HCl aq was added. The product
was extracted with ethyl acetate and the organic layer
was washed with saturated NaCl aqueous solution and
dried over anhydrous sodium sulfate. Removal of solvents
1
4. Conclusions
gave the product. Yield: 36 mg (73%). H NMR (303 K,
chloroform-d1): d 4.06 (s, 2H, Cp), 4.22 (s, 5H, Cp), 4.66
(s, 1H, SH), 4.71 (s, 2H, Cp), 7.10 (br, 1H, NH), 7.20 (t,
1H, J = 6.0 Hz, Ph), 7.30 (t, 1H, J = 6.0 Hz, Ph), 7.37 (d,
1H, J = 7.6 Hz, Ph), 7.48 (d, 1H, J = 7.6 Hz, Ph). Anal.
Calc. for C17H15Fe1N1O1S1 Æ (H2O)0.8: C, 59.91; H, 4.55;
N, 4.11. Found: C, 59.73; H, 4.45; N, 4.18. MS (ESI): Calc.
m/z = 338.0 (M+H+); Found 338.0.
The redox-active thiolate ligand having ferrocene moiety
provided a delicate detection of the electron flow through
SHꢀ ꢀ ꢀO@C and NHꢀ ꢀ ꢀO@C hydrogen bonds. In the por-
phyrin-thiolate compounds, the electron flows from por-
phyrin to ferrocene through NHꢀ ꢀ ꢀS hydrogen bond and
p-conjugation system were detected. The electron-deficient
ferrocene moiety strengthens NHꢀ ꢀ ꢀS hydrogen bond
resulting a significantly long M–S bond and a remarkably
positive redox potential of metalloporphyrin.
5.3. Tetramethylammonium 2-(ferronyl
carbamoyl)benzenethiolate, (NEt4)[S-2-FcNHCOC6H4]
(4a)
5. Experimental
Tetramethylammonium thiophenolate (181 mg, 0.46
mmol) and 2,20-dithio bis(N-ferrocenyl benzamide)
(200 mg, 0.30 mmol) were dissolved in EtOH (8 mL). After
stirred for 1 h, the precipitate was removed by filtration.
The solvent was removed under reduced pressure. The
crude product was recrystallized from CH3CN/diethyl
ether. 1H NMR (CDCl3): d 1.12 (12H, t, J = 6.8 Hz,
CH3), 3.04 (8H, q, J = 7.2 Hz, CH2), 3.98 (2H, s, Cp),
4.19 (5H, s, Cp), 4.79 (2H, s, Cp), 6.77 (1H, t, J = 7.6 Hz,
Ph), 6.90 (1H, t, J = 7.6 Hz, Ph), 7.64 (1H, d, J = 8.0 Hz,
Ph), 8.16 (1H, d, J = 8.0 Hz, Ph), 14.23 (1H, br, NH).
All procedures were performed in argon atmosphere by
Schlenk technique. All solvents except for water were dried
over calcium hydride and distilled under argon before use.
The synthetic procedures of acetylaminoferrocene [17],
aminoferrocene [16], and [GaIII(OEP)(OMe)] (OEP = octa-
ethylporphinato) [14] were described in the previous paper.
[FeIII(OEP)(OMe)] was synthesized by the literature
method [20].
5.1. 2,20-Dithiobis(N-ferrocenylbenzamide)
A
mixture of 2,20-dithiodibenzoic acid (2.97 g,
5.4. 4,40-Dithiodibenzoic acid
9.71 mmol), thionyl chloride (20 mL) and a catalytic
amount of DMF (two drops) was refluxed for 3 h. And
then excess thionyl chloride was removed in vacuo, and
the residue was dissolved in THF (50 mL). The solution
was added slowly to a solution of aminoferrocene (3.90 g,
19.4 mmol) and triethylamine (2.69 mL, 19.4 mmol) in
THF (10 mL) at 0 °C. After stirring overnight at room tem-
perature, the solution was concentrated to dryness under
reduced pressure. The residue was suspended in ethyl ace-
tate (300 mL) and insoluble product was collected with fil-
tration. The product was washed with NaHCO3 aq and
Crystallized sodium sulfide (Na2S Æ 9H2O, 19.0 g,
79.2 mmol) and powdered sulfur (2.54 g, 79.4 mmol) were
dissolved in water (20 mL) by heating and stirring. An
aqueous solution (8 mL) of NaOH (3.0 g, 75 mmol) was
added to the solution, and cooled to 0 °C. para-Aminoben-
zoic acid (10.0 g, 72.9 mmol) was dissolved in a mixture of
water (80 mL) and concentrated hydrochloric acid
(15 mL), and cooled to 0 °C. An aqueous solution of
NaNO2 (5.02 g, 72.8 mmol) was added to the solution of
Na2S and sulfur below 5 °C. And this solution was added
to the solution of p-aminobenzoic acid below 5 °C. The
mixture was stirred for 1 h at 0 °C, and continued stirring
for 2 h at room temperature. Addition of 6 M HCl aq
(20 mL) gave precipitate, which was collected with filtra-
tion, and washed with water, n-hexane and diethyl ether.
The precipitate was dissolved in 1MNaOH aq (30 mL),
and removed the precipitate with filtration. Addition of
concentrated hydrochloric acid (25 mL) to the filtrate gave
precipitate, which was collected with filtration, and washed
with water and diethyl ether. The residue was recrystallized
from THF/diethyl ether. Yield: 1.67 g (15%) 1H NMR
(dimethyl sulfoxide-d6): d 7.64 (4H, d, J = 8.4 Hz, Ph),
7.93 (4H, d, J = 8.4 Hz, Ph), 9.99 (2H, br, COOH). MS
(ESI): Calc. m/z = 305.0 (MꢁH+); Found 305.0.
1
water, and then dried in vacuo. Yield: 4.20 g (47%). H
NMR (303 K, dimethyl sulfoxide-d6): d 4.02 (s, 4H, Cp),
4.17 (s, 10H, Cp), 4.76 (s, 4H, Cp), 7.34 (t, 2H,
J = 8.0 Hz, Ph), 7.48 (t, 2H, J = 8.0 Hz, Ph), 7.63 (d, 2H,
J = 8.0 Hz, Ph), 7.72 (d, 2H, J = 8.0 Hz, Ph), 9.99 (s, 2H,
NH). Anal. Calc. for C34H28Fe2N2O2S2 Æ (H2O)0.8: C,
59.46; H, 4.34; N, 4.08. Found: C, 59.47; H, 4.10; N,
4.09. MS (ESI): Calc. m/z = 672.0 (M+); Found 672.0.
5.2. 2-Mercapto-N-ferrocenylbenzamide, 2-
FcNHCOC6H4SH (1a)
To the suspension of 2,20-dithiobis(N-ferrocenylbenza-
mide) (50 mg, 0.074 mmol) in ethanol (3 mL) was added

254
T. Okamura et al. / Journal of Organometallic Chemistry 692 (2007) 248–256
5.5. 4,40-Dithiobis(N-ferrocenylbenzamide)
J = 8.0 Hz, Ph), 7.50 (2H, d, J = 8.4 Hz, Ph), 8.26 (1H,
s, NH).
A suspension of 4,40-dithiodibenzoic acid (502 mg,
1.64 mmol), thionyl chloride (4 mL) and a catalytic
amount of DMF (two drops) was refluxed for 1 h. And
then excess thionyl chloride was removed in vacuo, and
the residue was dissolved in THF (20 mL). The solution
was added slowly to a THF solution (5 mL) of aminofer-
rocene (722 mg, 3.59 mmol) and triethylamine (0.5 mL,
3.59 mmol) at 0 °C. The solution was stirred overnight
at room temperature. Then the solution was concentrated
to dryness under reduced pressure, and the residue was
washed with ethyl acetate (300 mL) and water (200 mL)
to remove soluble materials. The insoluble product was
collected with filtration, washed with 4% NaHCO3 aq
and water, and then dried in vacuo over P2O5. Yield:
725 mg (66%). 1H NMR (303 K, dimethyl sulfoxide-d6):
d 4.03 (s, 4H, Cp), 4.11 (s, 10H, Cp), 4.77 (s, 4H, Cp),
7.67 (d, 4H, J = 8.4 Hz, Ph), 7.92 (d, 4H, J = 8.0 Hz,
Ph), 9.73 (br, 2H, NH). Anal. Calc. for C34H28Fe2N2O2-
S2 Æ (H2O)0.8: C, 59.46; H, 4.34; N, 4.08. Found: C,
59.51; H, 4.36; N, 4.15. MS (ESI): Calc. m/z = 672.0
(M+); Found 672.0.
5.8. [FeIII(OEP)(S-2-FcNHCOC6H4)] (2a)
[FeIII(OEP)(OMe)] (19.86 mg, 32.0 lmol) and 1a
(10.68 mg, 31.7 lmol) were dissolved in 30 mL of toluene.
The mixture was stirred for 1 h at room temperature.
Removal of the solvent gave purple solid in a quantitative
1
yield. H NMR (303 K, benzene-d6): d ꢁ98.4 (1H, NH),
ꢁ87.0 (1H, Ph 6-H), ꢁ78.0 (1H, Ph 4-H), ꢁ46.7 (4H,
meso-H), 1.48 (2H, Cp), 1.57 (5H, Cp), 5.40 (2H, Cp),
6.6 (24H, b-CH3), 42.9, 42.9, 39.9 (16H, a-CH2), 58.9,
51.6 (2H, Ph 3,5-H). MS (ESI): Calc. m/z = 924.3 (M+);
Found 924.3.
5.9. [FeIII(OEP)(S-4-FcNHCOC6H4)] (2b)
[FeIII(OEP)(OMe)] (20.23 mg, 32.6 lmol) and 1b
(10.94 mg, 32.4 lmol) were dissolved in 30 mL of toluene.
The mixture was stirred for 1 h at room temperature.
Removal of the solvent gave purple solid in a quantitative
1
yield. H NMR (303 K, benzene-d6): d ꢁ94.4 (1H, Ph 2,6-
H), ꢁ47.6 (4H, meso-H), 3.88 (2H, Cp), 4.02 (5H, Cp), 4.51
(2H, Cp), 6.18 (24H, b-CH3), 33.7 (1H, NH), 38.0, 39.2
(16H, a-CH2), 58.9 (2H, br, Ph 3,5-H). MS (ESI): Calc.
m/z = 924.3 (M+); Found 923.9.
5.6. 4-Mercapto-N-ferrocenylbenzamide,
4-FcNHCOC6H4SH (1b)
To the suspension of 4,40-dithiobis(N-ferrocenylbenza-
mide) (200 mg, 0.29 mmol) in a mixture of ethanol
(8 mL) and THF (18 mL) was added NaBH4 (350 mg,
9.3 mmol) and the mixture was stirred overnight. The
resulting clear solution was concentrated under reduced
pressure, and then 2 M HCl aq was added to the residue.
The precipitate was extracted with ethyl acetate. The
organic layer was washed with saturated NaCl aq and
dried over anhydrous sodium sulfate. The solution was
concentrated to dryness under reduced pressure and then
5.10. [GaIII(OEP)(S-2-FcNHCOC6H4)] (3a)
[GaIII(OEP)(OMe)] (40 mg, 63.1 lmol) and 1a (21.3 mg,
63.1 lmol) were dissolved in 8 mL of dichloromethane. The
mixture was stirred for 1 h at room temperature. The sol-
vent was removed under reduced pressure to give a crude
product, which was recrystallized from toluene/acetoni-
1
trile. Yield: 15 mg (25%). H NMR (303 K, benzene-d6):
d 1.87 (t, 24H, J = 7.6 Hz, b-CH3), 3.53 (s, 5H, Cp), 3.57
(d, 1H, J = 7.6 Hz, Ph 6-H), 4.04 (s, 2H, Cp), 3.91, 4.02
(m, 16H, a-CH2), 4.29 (s, 2H, Cp), 6.03 (t, 1H,
J = 7.6 Hz, Ph 4-H), 6.59 (t, 1H, J = 7.6 Hz, Ph 5-H),
7.75 (s, 1H, NH), 8.01 (d, 1H, J = 8.0 Hz, Ph 3-H), 10.22
(s, 4H, meso-H). MS (ESI): Calc. m/z = 938.3 (M+H+);
Found 938.1.
1
dried over P2O5. Yield: 132 mg (68%). H NMR (303 K,
chloroform-d1): d 3.59 (1H, s, SH), 4.06 (s, 2H, Cp), 4.19
(s, 5H, Cp), 4.71 (s, 2H, Cp), 7.09 (br, 1H, NH), 7.33 (d,
2H, J = 8.0 Hz, Ph), 7.67 (d, 1H, J = 8.0 Hz, Ph). Anal.
Calc. for C174H15FeNOS Æ (H2O)0.7: C, 58.37; H, 4.73; N,
4.00. Found: C, 58.34; H, 4.61; N, 4.06. MS (ESI): Calc.
m/z = 337.0 (M+); Found 337.0.
5.11. [GaIII(OEP)(S-4-FcNHCOC6H4)] (3b)
5.7. Tetraethylammonium 4-(N-ferronycarbamoyl)
benzenethiolate, (NEt4)[S-4-FcNHCOC6H4] (4b)
[GaIII(OEP)(OMe)] (107 mg, 169 lmol) and 1b
(57.5 mg, 170 lmol) were dissolved in 45 mL of toluene.
The mixture was stirred for 1 h at room temperature. The
solvent was removed under reduced pressure to give a
crude product, which was recrystallized from THF/tolu-
Tetraethylammonium thiophenolate (92.2 mg, 0.385
mmol) and 4-mercapto-N-ferrocenylbenzamide (125 mg,
0.372 mmol) were dissolved in EtOH (10 mL). After stir-
red for 5 h, the precipitate was removed with filtration.
The solvent was removed under reduced pressure. The
crude product was recrystallized from CH3CN and diethyl
ether. 1H NMR (CDCl3): d 1.19 (12H, t, J = 6.8 Hz,
CH3), 3.16 (8H, q, J = 7.2 Hz, CH2), 3.98 (2H, s, Cp),
4.16 (5H, s, Cp), 4.91 (2H, s, Cp), 7.45 (2H, d,
1
ene. Yield: 67 mg (42%). H NMR (303 K, chloroform-
d1): d 1.96 (t, 24H, J = 7.6 Hz, b-CH3), 3.74 (s, 5H, Cp),
3.83 (d, 2H, J = 7.6 Hz, 2, 6-H), 4.17 (m, 20H, a-CH2,
Cp), 6.52 (s, 1H, NH), 6.90 (d, 2H, J = 7.6 Hz, Ph 3,5-
H), 10.31 (s, 4H, meso-H). MS (ESI): Calc. m/z = 938.3
(M+H+); Found 938.1.

T. Okamura et al. / Journal of Organometallic Chemistry 692 (2007) 248–256
255
5.12. Physical measurements
5.13.4. Crystallographic data for 3a
ꢀ
C58.5H65ON6SGaFe, fw 1025.8, triclinic, space group P1,
1
˚
The H NMR spectra were measured on a Jeol GSX-
a = 15.02(2), b = 17.12(2), c = 21.12(2) A, a = 109.32(4)°, b
3
˚
400 spectrometer. IR spectra were recorded on a Jasco
FT/IR-8300 spectrometer. Samples were prepared as
CH2Cl2 solution or KBr pellet. Electrochemical measure-
ments were carried out on a BAS 100 B/W using three elec-
trode method. Sample was prepared as 2.5 mM CH2Cl2
solution including 0.2 M tetra-n-butylammonium perchlo-
rate as a supporting electrolyte. Scan rate was 100 mV/s.
E1/2 value was referenced to non-aqueous Ag/Ag+ elec-
trode at room temperature. ESI-MS spectra were mea-
sured on a Finnigan mat LCQ ion trap spectrometer
using methanol solution.
= 97.04(4)°, c = 91.51(5)°, V = 5075(11) A , Z = 4,
F(000) = 2156, dcalc = 1.343 g cmꢁ3
,
l = 0.905 mmꢁ1
,
17597 unique reflections, R1 = 0.0573 [I > 2.0r(I)],
wR2 = 0.0742 (all data), GOF 1.00, 1190 parameters.
Acknowledgement
This work was supported by the Grant-in-Aid from the
Ministry of Education, Culture, Sports, Science, and
Technology.
Appendix A. Supplementary material
5.13. X-ray crystallography
Crystallographic data for structural analysis have been
deposited with the Cambridge Crystallographic Data Cen-
tre, CCDC Nos. 299299 and 299300 for compounds 1a and
3a. Copies of this information may be obtained free of
charge from The Director, Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK
(fax: +44 1223 336003; e-mail: deposit@ccdc.cam.ac.uk
or www: http://www.ccdc.cam.ac.uk). Supplementary data
associated with this article can be found, in the online ver-
sion, at doi:10.1016/j.jorganchem.2006.08.067.
5.13.1. 2-FcNHCOC6H4SH (1a)
A suitable single orange crystal grown from ethyl ace-
tate was shielded in a glass capillary under argon atmo-
sphere. X-ray measurement was performed at 23 °C using
the x scan technique up to 2hmax = 55° on a Rigaku
AFC5R diffractometer with graphite monochromated
˚
MoKa radiation (0.71069 A). Unit cell dimensions were
obtained by least-square refinement with 25 reflections.
Three standard reflections were chosen and their intensities
did not change during the data collection. The structure
was solved by direct method (SIR92) [21] using teXsan crys-
tallographic software package of the Molecular Structure
Corporation. Refinements were carried out on F2. All
non-hydrogen atoms were refined anisotropically. The car-
bon-bonded hydrogen atoms were placed in the calculated
positions. The nitrogen and sulfur-bonded hydrogen atoms
were located from a difference Fourier map. The position
of the hydrogen atom of thiol group is refined using the
fixed isotropic thermal factor.
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256
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