Ironcarbonyl complexes from N-(2-thienylmethylidene),benzylamines: Endo as well as exo cyclometalation and alkyl exchange

Article abstract of DOI:10.1016/S0277-5387(00)00616-1

The reaction of methyl substituted N.-(2-thienylmethylede)benzylamine (1) with Fe₂(CO)₉ in benzene gives endo cyclometalated (μ-η¹:η²-thienyl; η¹:η¹(N))hexacarbonyldiiron complexes (2 and 5), exo cyclometalated (μ-η¹:η²-phenyl; η¹:η¹(N))hexacarbonyldiiron complexes (3 and 6) and/or imidoyl triironnonacarbonyl cluster (4), in accordance with the position of methyl substituent(s). In complex 3, the thienyl unit of the original Schiff base has been replaced by a phenyl group, which comes from the same Schiff base. The X-ray structure analyses were carried out on complexes 2a, 2b, 2c and 3a.

Full text of DOI:10.1016/S0277-5387(00)00616-1

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Polyhedron 20 (2001) 353–362
Ironcarbonyl complexes from
N-(2-thienylmethylidene)benzylamines: endo as well as exo
cyclometalation and alkyl exchange
Wen-Shu Hwang a,*, Tzu-Shiuan Tzeng a, Dong-Liang Wang b, Michael Y. Chiang c
a Department of Chemistry, National Dong Hwa Uni6ersity, Hualien, Taiwan, ROC
b Department of Cosmetic Science, Chia Nan College of Pharmacy and Science, Tainan, Taiwan, ROC
c Department of Chemistry, National Sun Yat-Sen Uni6ersity, Kaohsiung, Taiwan, ROC
Received 8 September 2000; accepted 13 November 2000
Abstract
The reaction of methyl substituted N-(2-thienylmethylidene)benzylamine (1) with Fe2(CO)9 in benzene gives endo cyclometa-
lated (m-h1:h2-thienyl; h1:h1(N))hexacarbonyldiiron complexes (2 and 5), exo cyclometalated (m-h1:h2-phenyl;
h1:h1(N))hexacarbonyldiiron complexes (3 and 6) and/or imidoyl triironnonacarbonyl cluster (4), in accordance with the position
of methyl substituent(s). In complex 3, the thienyl unit of the original Schiff base has been replaced by a phenyl group, which
comes from the same Schiff base. The X-ray structure analyses were carried out on complexes 2a, 2b, 2c and 3a. © 2001 Elsevier
Science B.V. All rights reserved.
Keywords: N-(2-Thienylmethylidene)benzylamine; Diironhexacarbonyl complexes; endo Cyclometalation; exo Cyclometalation; 1,3-Hydrogen shift;
1,5-Hydrogen shift
[1f,i,j,4b]. Usually, the tendency to proceed endo cy-
clometalation is so strong that, in the presence of
1. Introduction
Pd(AcO)2, an aliphatic CꢀH bond of N-(2,4,6-
In the past decades, transition metal mediate activa-
tion of CꢀH bond remains one of the most prominent
challenges in organometallic chemistry. Cyclometala-
tion is one of the classical ways used to activate CꢀH
bond in hetero-substituted organic molecules [1].
It is well-known that N-donor ligands have a strong
tendency to give five-membered metallacycle [2]. In
trimethylbenzylidene)benzylamine is activated in prefer-
ence to the activation of an aromatic CꢀH bond and
results with the formation of a six-membered endo
metallacycle as the sole product rather than a five-mem-
bered exo metallacycle [5]. Evidence for a regiospecific
endo cyclometalation was therefore observed.
We report here the interesting results from the action
of diiron nonacarbonyl on N-(5-methyl-2-thienyl-
methylidene)benzylamines (1a–c) and N-(3-methyl-2-
systems where there is a possibility of choice between
several modes of metalation, five-membered metallacy-
cle complexes are always the major compounds ob-
tained [3]. It is also known that Schiff bases have a
strong tendency to give endo cyclometalated derivatives
[4]. Only a few exo metallcycles of Schiff bases were
obtained by CꢀH activation. They are derivatives of
2,6-disubstituted N-benzylideneamines, which contain
substituents on the ortho positions of the benzal ring
thienylmethylidene)benzylamines (1d–f). Schiff bases
1d–f have a methyl substituent block at the b-position
of the thienyl ring, which would otherwise be a site
where an endo cyclometalation might occur. During the
course of reactions, we observe products resulting from
endo cyclometalation followed by 1,3-hydrogen shift,
exo cyclometalation followed by 1,5-hydrogen shift,
endo cyclometalation induced methyl migration and
hydrogen shift, and substitution of the thienylmethyl
group of exo cyclometalated intermediate by a benzyl
group.
* Corresponding author. Tel.: +886-3-866-2769; fax: +886-3-866-
770.
E-mail address: hws@mail.ndhu.edu.tw (W.-S. Hwang).
0277-5387/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0277-5387(00)00616-1

354
W.-S. Hwang et al. / Polyhedron 20 (2001) 353–362
,
bond distances of 2.304(7) and 2.167(6) A, respectively,
and the bond distance between C(2) and C(3) is length-
ened to 1.395(8). The thienyl ring serves as a three-elec-
tron donor and bridges the two irons centers. The bond
2. Results and discussion
The thienyl Schiff bases 1a–f are prepared by normal
procedure of condensation of thienyl-2-carboxaldehyde
with the corresponding amines.
,
distance from N(1) to C(1), 1.495(7) A, is in the single
bond range and is comparable to that of N(1)ꢀC(12)
distance, 1.503(8) A. The nitrogen atom acts as another
three-electron donor bridge and the bond distances to
Fe(1) and Fe(2) are 1.992(5) and 1.968(5) A, respec-
tively. An ironꢀiron distance of 2.440(1) A is shorter
than usual for diiron complexes [6] but is in accordance
with other nitrogen-bridged diiron complexes [7]. The
Fe(1)ꢀNꢀFe(2) angle is 76.1(2)° and Fe(1)ꢀC(3)ꢀFe(2)
angle is 72.1(2)°. The compression of these two angles
from the tetrahedral value is a result of the ligand
constrains of double bridging, which also brings about
the shorter ironꢀiron distance.
The thienyl Schiff base N-(5-methyl-2-thienylmethyli-
dene)benzylamine (1a) reacts with diiron nonacarbonyl
in anhydrous benzene for 5 h at 45°C to give endo and
exo cyclometalated diironhexacarbonyl complexes,
which we formulate as 2a and 3a, respectively (Scheme
1).
,
,
,
1
The H NMR spectrum of 2a shows the absence of a
methine proton (resonance at l 8.48 ppm in 1a) and the
addition of a pair of methylene resonances at l 3.97
and 3.83 ppm. In the aromatic region, the integrated
intensities clearly shows only six protons left, of which
one is a thienyl proton that appears at l 7.04 ppm. In
the corresponding IR spectrum, while a CꢁN stretching
mode is absent, there are three sharp and intense CꢁO
stretches appearing at 2068, 2024, and 1984 cm−1. This
result was interpreted as coordination of the imine
nitrogen of the thienyl Schiff base on one of the iron
centers, a CꢀH activation occurs at the b-carbon of the
thienyl ring to form a five-membered endo metallacycle,
and the methine group becomes a methylene by accept-
ing the hydrogen originated from the b-carbon. This
transformation follows the sequential route, coordina-
tion, endo cyclometalation, and 1,3-hydrogen shift. The
mass spectrum of the product contains a signal for the
molecular ion and six peaks corresponding to sequen-
tial CO loss products.
Competitive with the formation of 2a, 3a is observed.
The 1H NMR spectrum of 3a also shows the absence of
a methine proton and the addition of a pair of methyl-
ene resonances at l 4.09 and 3.98 ppm. There are nine
protons in the aromatic region, of which four benzene
protons down field shift to l 8.07 and 7.65 ppm with a
coupling constant JHꢀH=8.7 Hz, and no thienyl proton
is observed. In the corresponding IR spectrum, there
are three sharp and intense CꢁO stretching absorption
at 2068, 2028, and 1982 cm−1 instead of the original
CꢁN stretching mode. The mass spectrum of the
product contains a signal for the molecular ion at m/z
465 and six peaks corresponding to sequential CO loss
products, in accordance with the formulated structure.
The molecular structure of complex 3a, determined
by a single-crystal X-ray diffraction analysis, is shown
in Fig. 2. Crystal and data collection parameters are
listed in Table 1. The molecular structure clearly shows
that C(3) of the phenyl ring is s bonded to Fe(2) with
A red prism crystal of 2a was subjected to a single-
crystal X-ray analysis. Crystal and data collection
parameters are shown in Table 1. An ORTEP diagram of
2a is shown in Fig. 1. It is readily seen that C(3) of the
thienyl ring is s bonded to Fe(1) with a bond distance
,
,
a bond distance of 1.992(7) A. C(3) and C(2) are p
of 1.971(6) A. C(2) and C(3) are p bonded to Fe(2) with
Scheme 1.

W.-S. Hwang et al. / Polyhedron 20 (2001) 353–362
355
Table 1
Crystal and data collection parameters for compounds 2a, 2b, 2c and 3a
2a
2b
2c
3a
Formula
fw
C19H13Fe2NO6S
495.07
C
509.10
20H15Fe2NO6S
C20H15Fe2NO6S
509.10
C20H13Fe2NO6
475.02
Crystal system
Space group
monoclinic
P21/n (no. 14)
10.556(2)
14.184(2)
14.528(2)
triclinic
monoclinic
P21 (no. 4)
8.544(2)
9.011(3)
14.172(4)
monoclinic
P21/c (no. 14)
13.138(3)
7.258(3)
21.290(2)
(
P1 (no. 2)
,
a (A)
8.054(9)
11.459(2)
13.029(2)
64.08(1)
89.97(1)
80.43(1)
1066.3(3)
2
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
111.36(1)
100.75(3)
94.64(1)
3
,
V (A )
2025.8(6)
4
1.623
1071.9(4)
2
1.677
2023.6(6)
4
1.559
Z
Dcalc (g cm−3
)
1.586
Crystal size (mm)
T (K)
0.22×0.35×0.40
296
0.28×0.40×0.48
296
0.38×0.40×0.60
293
0.33×0.41×0.44
296
2qmax (°)
50.2
50.0
55.0
50.1
Scan type
Reflections measured: total, unique
Observed reflections [I\3|(I)]
ꢀ−2q
3978, 3762
2004
ꢀ−2q
3989, 3770
2673
ꢀ−2q
2789, 2620
2407
ꢀ−2q
4081, 3902
2130
Variables
262
271
269
262
F000
1000.00
15.69
0.039
516.00
14.93
0.036
516.00
14.85
0.024
960.00
14.68
0.058
v (Mo Ka) (cm−1
)
R
Rw
0.038
0.023
0.018
0.046
bonded to Fe(1) with bond distances of 2.186(8) and
Similar result was found from the reaction of 1b with
diiron nonacarbonyl. Two cyclometalated complexes 2b
and 3b were isolated as shown in Scheme 1. Complexes
2b and 3b were characterized spectrally and identified
to be structurally similar to that of complexes 2a and
3a, respectively. The crystal structure of complex 2b is
shown in Fig. 3. For complex 3b, it shows that the
,
2.359(8) A, respectively, and the bond distance between
,
C(3) and C(2) is lengthened to 1.392(10) A. The phenyl
ring acts as a three-electron donor and bridges the two
iron centers. The bond distances from N(1) to C(1) and
,
from N(1) to C(14) are 1.476(9) and 1.498(9) A, respec-
tively, are in the single bond range. The nitrogen atom
serves as another bridge and the bond distances to
,
Fe(1) and Fe(2) are 1.949(6) and 1.990(6) A, respec-
,
tively.
Fe(1)ꢀNꢀFe(2)
The
ironꢀiron
distance,
angle,
2.454(2)
77.0(2)°,
A,
and
bond
Fe(1)ꢀC(3)ꢀF(2) angle, 71.8(3)°, are very closely resem-
ble that of complex 2a described above. Fig. 2 also
shows that the 5-methylthienyl group of the original
Schiff base has been substituted with a phenyl ring.
Complex 3a is an unexpected product. Although the
original Schiff base contained a thienyl unit, it is miss-
ing in 3a. The Schiff base has therefore undergone a
chemical transformation. It seems that, after the coordi-
nation of the imine nitrogen to one of the iron centers,
a CꢀH activation occurs at one of the b-carbon of the
phenyl ring to form a five-membered metallacycle and
then the methine carbon adopts the hydrogen origi-
nated from the b-carbon of the phenyl ring to form an
intermediate that is similar to the complex 6 in Scheme
2 (vide infra). This is a consecutive process of coordina-
tion, exo cyclometalation, and 1,5-hydrogen shift.
However, the complex thus formed might undergo a
chemical transformation, the substitution of the thienyl
unit with a phenyl group, to form product 3a.
Fig. 1. ORTEP diagram of complex 2a at the 50% probability level.
,
Selected bond lengths (A): Fe(1)ꢀFe(2) 2.440(1), Fe(1)ꢀN 1.992(5),
Fe(2)ꢀN 1.968(5), Fe(1)ꢀC(3) 1.971(6), Fe(2)ꢀC(2), 2.304(7),
Fe(2)ꢀC(3) 2.167(6), C(2)ꢀC(3) 1.359(8), NꢀC(1) 1.495(7), NꢀC(12)
1.503(8). Bond angles (°): Fe(1)ꢀNꢀFe(2) 76.1(2), Fe(1)ꢀC(3)ꢀFe(2)
72.1(2), Fe(2)ꢀNꢀC(1) 99.5(4), Fe(2)ꢀNꢀC(12) 125.5(4), Fe(1)ꢀNꢀC(1)
113.2(4),
Fe(1)ꢀNꢀC(12)
125.3(4),
C(1)ꢀNꢀC(12)
111.1(5),
NꢀC(12)ꢀC(13) 114.0(5).

356
W.-S. Hwang et al. / Polyhedron 20 (2001) 353–362
Fig. 2. ORTEP diagram of complex 3a at the 50% probability level.
,
Selected bond lengths (A): Fe(1)ꢀFe(2) 2.454(2), Fe(1)ꢀN 1.949(6),
Fe(2)ꢀN 1.990(6), Fe(2)ꢀC(3) 1.992(7), Fe(1)ꢀC(2), 2.359(8),
Fe(1)ꢀC(3) 2.186(8), C(2)ꢀC(3) 1.392(10), NꢀC(1) 1.476(9), NꢀC(114)
1.498(9). Bond angles (°): Fe(1)ꢀNꢀFe(2) 77.0(2), Fe(1)ꢀC(3)ꢀFe(2)
Fig. 3. ORTEP diagram of complex 2b at the 50% probability level.
71.8(3),
Fe(2)ꢀNꢀC(1)
111.5(5),
Fe(2)ꢀNꢀC(14)
120.3(5),
,
Selected bond lengths (A): Fe(1)ꢀFe(2) 2.4569(8), Fe(1)ꢀN 1.989(3),
Fe(1)ꢀNꢀC(1) 99.7(4), Fe(1)ꢀNꢀC(14) 129.4(5), C(1)ꢀNꢀC(14)
111.5(5), NꢀC(14)ꢀC(15) 115.1(6).
Fe(2)ꢀN 1.967(3), Fe(1)ꢀC(3) 1.965(4), Fe(1)ꢀC(4), 2.299(4),
Fe(1)ꢀC(3) 2.173(4), C(3)ꢀC(4) 1.393(5), NꢀC(6) 1.477(4), NꢀC(7)
1.480(4). Bond angles (°): Fe(1)ꢀNꢀFe(2) 76.8(1), Fe(1)ꢀC(3)ꢀFe(2)
72.6(1), Fe(1)ꢀNꢀC(6) 98.4(2), Fe(1)ꢀNꢀC(7) 130.2(2), Fe(2)ꢀNꢀC(6)
112.3(2), Fe(2)ꢀNꢀC(7) 120.8(2), C(6)ꢀNꢀC(7) 112.8(3), NꢀC(7)ꢀC(8)
116.5(3).
5-methyl-2-thienyl group disappeared from its original
Schiff base 1b and a tolyl group took its place to
finalize the product. Obviously, a CꢀN bond cleavage
or a CꢀC bond cleavage must be involved in the course
of complex formation. In terms of bond energies of
CꢁN, CꢀN, and CꢀC bonds, it is most likely that a
CꢀN bond cleavage occurred on 1a–1b or 2a–2b. The
5-methyl-2-thienylmethyl group of the exo-cyclometa-
lated product might be substituted by a benzyl–xylyl
Scheme 2.

W.-S. Hwang et al. / Polyhedron 20 (2001) 353–362
357
m/z 649 consists with the formulated structure. The
structure of 4b is analogous to that of literature re-
ported trimetalnonacarbonyl complexes with a triply
bridging imidoyl ligand and an h2-hydride [8].
Reactions of N-(3-methyl-2-thienylmethylidene)-
benzylamine derivatives, 1d, 1e and 1f, in which the
b-position of the thienyl ring is blocked with a methyl
substituent in order to favor the exo cyclometalation to
occur, with diiron nonacarbonyl were conducted under
the same reaction condition and all complexes thus
formed were outlined in Scheme 2.
group that was cleaved from 1a–1b or 2a–2b to form
complex 3a–3b.
In order to have a better understanding of the forma-
tion of complex 3, the Schiff base 1c was prepared and
reacted with diiron nonacarbonyl under exactly the
same reaction condition. Two complexes, 2c and 4c,
were isolated after the reaction. Unfortunately, there
was no complex in the form similar to complex 3
found. The structure feature of complex 2c, as shown in
Fig. 4, closely resembles that of complexes 2a and 2b,
as explicated above. While no direct structure evidence
is available for complex 4c, we are able to deduce its
structure by its NMR, IR, and mass spectra as well as
elemental analyses. It is an imidoyl triironnonacarbonyl
cluster with the imidoyl group (ꢀCꢁNꢀ) atop on the
three-iron plane and triply bridging to the iron triangle
via two s and one p bonding, and a hydrogen atom
bridging on two irons. The fact that the disappearance
of the methine proton resonance and the appearance of
The reaction of Schiff base 1d–1e leads to the forma-
tion of three isomeric complexes, 2a–2b, 5d–5e and
6d–6e, and complex 3a–3b. Isomeric complexes 2 and 5
are different only in the location of the methyl substitu-
tent on the thienyl ring. The methyl group had been
migrated from its original b-position to the a%- and
b%-position of the thienyl ring during the course of endo
cyclometalation to form complexes 2 and 5, respec-
tively. On the other hand, complex 6 is formed as the
result of the consecutive process of imine coordination,
exo cyclometalation, and 1,5-hydrogen shift. Another
exo cyclometalated product, complex 3, which is also
found from the reaction of 1a–1b (Scheme 1) is similar
to complex 6 but with a phenyl–p-xylyl group substi-
tutes the 3-methyl-2-thienyl group. However, the reac-
tion of Schiff base 1f leads to the formation of an
imidoyl triironnonacarbonyl cluster 4f and an exo cy-
clometalated complex 6f only.
Since the free Schiff base itself was stable to the
reaction condition, the iron center must be responsible
for the methyl migration and the formation of products
2 and 5. A plausible explanation can be suggested as
the following. Upon coordination of the methine nitro-
gen of the 3-methylthienyl Schiff base to one of the iron
centers, an endo cyclometalation induced car-
bonꢀcarbon bond cleavage occurs between the methyl
group and the b-carbon of the thienyl ring to form a
stable five-membered metalacycle. The cleaved methyl
group attacks the b%- or a%-carbon of the thienyl ring
and leads to the activation of the b%- or a%-hydrogen.
Finally, the methine carbon becomes a methylene group
by adopting the hydrogen originated from the b%- or
a%-carbon and the nitrogen coordinates to another iron
center concomitantly to give the product 2 or 5. The
methyl migration process might be similar to the irid-
ium catalyzed ethyl migration reaction of 1,1-diethylcy-
clopentadiene reported by Crabtree et al. [9]. In their
case, the driving force is the formation of an ethylcy-
clopentadienylꢀiridiumꢀethyl intermediate. Further in-
vestigation of the mechanism concerning the methyl
migration is in progress.
1
a singlet resonance at l −26.2 ppm in the H NMR
spectrum of complex 4c indicates that the hydrogen is
removed from the methine group and a bridging metal
hydride is formed. In its IR spectrum, the CꢀN stretch-
ing frequency of 1348 cm−1 (relative to the correspond-
ing band at 1632 cm−1 in the free Schiff base 1c)
indicating a partial double bond feature of a coordi-
nated imidoyl group [8d,e]. The significant shift to the
lower frequency is attributed to the two s and one p
donation and back p accepting of the highly conjugated
imidoyl ligand. There are also four sharp and intense
CꢀO stretches appearing at 2088, 2052, 2016, and 1972
cm−1. The mass spectrum shows the entirely loss of
nine COs successively, and the molecular ion peak at
Fig. 4. ORTEP diagram of complex 2c at the 50% probability level.
,
Selected bond lengths (A): Fe(1)ꢀFe(2) 2.4454(5), Fe(1)ꢀN 1.977(3),
Fe(2)ꢀN 1.998(3), Fe(2)ꢀC(3) 1.956(4), Fe(1)ꢀC(4), 2.246(4),
Fe(1)ꢀC(3) 2.188(4), C(3)ꢀC(4) 1.404(4), NꢀC(6) 1.498(4), NꢀC(7)
1.492(4). Bond angles (°): Fe(1)ꢀNꢀFe(2) 75.94(10), Fe(1)ꢀC(3)ꢀFe(2)
72.1(1), Fe(1)ꢀNꢀC(6) 97.8(2), Fe(1)ꢀNꢀC(7) 128.4(2), Fe(2)ꢀNꢀC(6)
111.9(2), Fe(2)ꢀNꢀC(7) 122.8(2), C(6)ꢀNꢀC(7) 113.4(5), NꢀC(7)ꢀC(8)
110.6(3).
It is interesting to find that if the reaction time of
ligand 1d–1e was prolonged from 5 to 8 h at 45°C in
benzene, only 3a–3b and 6d–6e two complex products
were isolated. The yield of product 3a–3b increases

358
W.-S. Hwang et al. / Polyhedron 20 (2001) 353–362
about 4% and the yield of 6a–6e decreases about 4%.
This amount is about the sum of products 2a–2b and
5d–5e that disappeared during the prolonged reaction.
On the other hand, if the reaction was stopped after 3
h of reaction under the same reaction condition, ca. 8%
of complex 2a–2b and ca. 9% of complex 5d–5e were
obtained accompanying with ca. 5% of complex 3a–3b
and ca. 20% of complex 5d–6e. Therefore, the forma-
tion of benzyl–p-xylyl substituted product 3 might be
suggested to follow the underlying process:
activation of an aromatic CꢀH bond to form a five-
membered exo metallacycle. In our case, although the
activation of the thienyl-methyl bond with the forma-
tion of a five-membered endo metallacycle is observed
due to the endo effect, an activation of a phenyl CꢀH
bond with the formation of a five-membered exo metal-
lacycle is found to be more favorable.
It is noteworthy that with a methyl substituent added
on the benzylic carbon of the ligand, the reaction of
1c–1f gives no product in the form similar to complex
3. Instead, an imidoyl triiron cluster is formed due to
the electronic effect in both 1c and 1f cases with about
the equal amount. The activation of CꢀH bond takes
place only at the b-carbon of the thienyl ring (endo
cyclometalation) in the case of 1c. However, if a methyl
group blocked the b-carbon of the thienyl ring, it takes
place only at the b-carbon of the phenyl ring (exo
cyclometalation). The behavior of these two ligands
toward the regioselective cyclometalation is not clear at
this stage. The impact of the various substituents on the
benzylic carbon of the ligand will be further
investigated.
A reaction of equimolar quantities of complex 2a–2b
and complex 6d–6e was conducted under exactly the
same reaction condition. More than 90% of complex
3a–3b, 82% of 2,3-dimethylthiophene, and 70% of 5-
methyl-2-(aminomethyl)thiophene were obtained and
no any thienyl-contained complex was found, confirm-
ing the substitution process suggested.
There are two potential sites, the b-position of
thienyl ring and the b-position of phenyl ring, in the
Schiff base 1 that might involve in the cyclometalation
and leads to the formation of endo and/or exo five-
membered metalacycle. In the case of 1a–1b, The prod-
ucts and yields distribution, as shown in Scheme 1,
clearly shows that the CꢀH activation that occurs at the
b-position of thienyl ring is relatively more favorable
than that of phenyl ring (with ca. 44–17% ratio). The
minor exo cyclometalated intermediate 6 thus formed
might react with excess amount of endo cyclometalated
product 2 and leads to the formation of net products 2
and 3. In the case of 1d–1e, because a methyl group has
blocked the b-position of thienyl ring, the CꢀH activa-
tion that occurs at the b-position of the phenyl ring
becomes the favorite one (31% for 1d and 37% for 1e).
Although certain amount of endo cyclometalated com-
plexes 2 and 5 could be formed via an endo cyclometa-
lation induced methyl migration process (ca. 26%), they
were eventually converted to the final complex 3 in the
presence of complex 6. The result is completely differ-
ent from that of the action of Pd(II) on N-(2,4,6-
trimethylbenzylidene)benzylamines reported by Albert
et al. [5]. In their case, activation of a CꢀH bond of
ortho-methyl group with the formation of a six-mem-
bered endo metallcycle takes place in preference to the
3. Experimental
Diiron nonacarbonyl was prepared by photolysis of
iron pentacarbonyl (Aldrich) in glacial acetic acid [10].
Solvents were dried (sodium–benzophenone, P4O10)
and distilled under nitrogen prior to use. All other
chemicals were reagent grade and without further
purification. The NMR spectra were recorded on a
Varian VXR-300 NMR spectrometer (1H, 299.95 MHz;
13C, 75.43 MHz). Chemical shifts were referenced to
TMS and deuterated acetone (Janssen) was used as a
solvent and as a secondary reference. Mass spectra were
obtained from a VG-Biotech Quattro 5022 spectrome-
ter. IR spectra were recorded from a Bio-Rad FTS-40
spectrometer. Elemental analyses were performed using
a Heraeus CHNO rapid analyzer. Crystals for X-ray
diffraction were obtained by sublimation (2a) or from
n-hexane solution (3a, 2b and 2c). A single crystal was
mounted on a glass fiber and the X-ray diffraction

W.-S. Hwang et al. / Polyhedron 20 (2001) 353–362
359
intensity data were measured on a Rigaku AFC7S
diffractometer at room temperature.
J=5.1 Hz, 1H), 4.76 (s, 2H), 2.41 (s, 3H). 13C NMR: l
154.8, 141.3, 141.1, 137.0, 131.7, 129.2, 129.0, 128.8,
121.6, 65.2, 13.9. IR (CHCl3) wCꢁN: 1632 cm−1. MS
(EI): m/z 215(M+). Anal. Calc. for C13H13NS: C, 72.56;
H, 6.05; N, 6.51. Found: C, 72.56; H, 6.08; N, 6.55%.
3.1. Synthesis of N-(5-methyl-2-thienylmethylidene)-
benzylamine (1a), N-(5-methyl-2-thienylmethylidene)-
p-xylylamine (1b), N-(5-methyl-2-thienylmethylidene)-
1-phenylethylamine (1c), N-(3-methyl-2-thienyl-
methylidene)benzylamine (1d), N-(3-methyl-2-thienyl-
methylidene)-p-xylylamine (1e) and N-(3-methyl-2-
thienylmethylidene)-1-phenylethylamine (1f)
3.1.5. Compound 1e
Yield 95%, 9.07 g. H NMR: l 8.63 (s, 1H), 7.39(d,
1
J=5.1 Hz, 1H), 7.26 (d, J=7.8 Hz, 2H), 7.15 (d,
J=7.8 Hz, 2H), 6.90 ( d, J=5.1 Hz, 1H), 4.73 (s, 2H),
2.39 (s, 3H), 2.32 (s, 3H). 13C NMR: l 154.0, 140.6,
137.5, 136.7, 136.5, 131.2, 129.4, 128.5, 128.4, 64.7,
21.0, 13.7. IR (CHCl3) wCꢁN: 1626 cm−1. MS (FAB):
m/z 229 (M+). Anal. Calc. for C14H15NS: C, 73.36; H,
6.55; N, 6.11. Found: C, 73.26; H, 6.62; N, 6.09%.
The synthesis of Schiff base employed the usual
approach of condensation in alcohol solution [11].
Equimolar quantities of 5-methyl-2-thiophenecarbox-
aldehyde
or
3-methyl-2-thiophenecarboxaldehyde
(Aldrich, 4.3 ml, 40 mmol) and amine (E. Merck,
benzylamine 4.25 g, p-methylbenzylamine 4.81 g, or
1-phenylethylamine 4.81 g, 40 mmol) were heated at
reflux in 95% ethanol (E. Merck, 100 ml) for 24 h. The
solvent was removed in vacuo. The residue was distilled
with a Kugelrohr distillation apparatus under reduced
pressure (0.1 mmHg). A pale yellow Schiff base was
obtained.
3.1.6. Compound 1f
Yield 94%, 8.98 g. H NMR: l 8.65 (s, 1H), 7.47 (d,
1
J=7.5 Hz, 2H), 7.40 (d, J=5.1 Hz, 1H), 7.34 (t,
J=7.5 Hz, 2H), 7.23 (t, J=7.2 Hz, 1H), 6.90 (d,
J=5.1 Hz, 1H), 4.56 (q, J=6.6 Hz, 1H), 2.38 (s, 3H),
1.54 (d, J=6.6 Hz, 3H). 13C NMR: l 152.0, 146.2,
140.7, 136.6, 131.2, 128.7, 128.5, 127.1, 127.0, 69.8,
25.4, 13.6. IR (CHCl3) wCꢁN: 1617 cm−1. MS (FAB):
m/z 229 (M+). Anal. Calc. for C14H15NS: C, 73.36; H,
6.55; N, 6.11. Found: C, 73.38; H, 6.67; N, 6.11%.
3.1.1. Compound 1a
1
Yield 95%, 8.07 g. H NMR: l 8.48 (s, 1H), 7.32 (m,
4H), 7.23 (m, 2H), 6.80 (d, J=3.3 Hz, 1H), 4.71 (s,
2H), 2.48 (s, 3H). 13C NMR: l 155.5, 144.3, 141.3,
140.5, 131.8, 128.8, 128.4, 127.2, 126.4, 64.5, 15.5. IR
(CHCl3) wCꢁN: 1630 cm−1. MS (EI): m/z 215 (M+).
Anal. Calc. for C13H13NS: C, 72.56; H, 6.05; N, 6.51.
Found: C, 72.66; H, 6.01; N, 6.52%.
3.2. Reaction of Schiff base 1 with Fe2(CO)9 in benzene
In a typical reaction, 8.0 mmol of compound 1 in 30
ml of anhydrous benzene was added dropwise to a 70
ml of anhydrous benzene solution containing 16.0
mmol of Fe2(CO)9 in the dark under nitrogen and the
reaction mixture was heated at 45°C for 5 h. The
reaction mixture was filtered through Celite 545 and the
solvent was removed under reduced pressure. The
residue was chromatographed on a silica gel column
with ethyl acetate–chloroform–n-hexane (1:5:20) as
eluent. Substantial amount of Fe3(CO)9, dimethylthio-
phene, and methyl-2-(aminomethyl)thiophene were also
collected accompany with the complex products.
3.1.2. Compound 1b
Yield 91%, 8.27 g. H NMR: l 8.39 (s, 1H), 7.26 (m,
1
2H), 7.18 (m, 3H), 6.78 (d, J=3.3 Hz, 1H), 4.70 (s,
2H), 2.45 (s, 3H), 2.33 (s, 3H). 13C NMR: l 155.2,
144.2, 141.4, 137.4, 136.5, 131.7, 129.5, 128.4, 126.4,
64.4, 21.0, 15.5. IR (CHCl3) wCꢁN: 1630 cm−1. MS (EI):
m/z 229 (M+). Anal. Calc. for C14H15NS: C, 73.36; H,
6.55; N, 6.11. Found: C, 73.46; H, 6.58; N, 6.09%.
3.1.3. Compound 1c
Yield 93%, 8.45 g. H NMR: l 8.42 (s, 1H), 7.43 (d,
3.2.1. Reaction of 1a with Fe2(CO)9 to gi6e
[v-N-(((2,3-p1:p2)-5-methyl-2-thienyl)methyl)-
p1:p1-(N)-benzylamino]hexacarbonyldiiron (2a) and
[v-N-(((1,2-p1:p2)-phenyl)methyl)-p1:p1-(N)-
benzylamino]hexacarbonyldiiron (3a)
1
J=7.5 Hz, 2H), 7.33 (t, J=7.5 Hz, 2H), 7.25 (d,
J=7.5 Hz, 1H), 7.19 (d, J=3.3 Hz, 1H), 6.77 (d,
J=3.3 Hz, 1H), 4.50 (q, J=6.6 Hz, 1H), 2.46 (s, 3H),
1.50 (d, J=6.6 Hz, 3H). 13C NMR: l 153.2, 146.1,
144.1, 141.4, 131.6, 128.7, 127.0, 126.9, 126.3, 69.4,
25.2, 15.4. IR (CHCl3) wCꢁN: 1624 cm−1. MS (FAB):
m/z 229 (M+). Anal. Calc. for C14H15NS: C, 73.36; H,
6.55; N, 6.11. Found: C, 73.46; H, 6.58; N, 6.08%.
1
Complex 2a (28.8% yield): H NMR: l 7.43 (m, 5H),
7.04 (s, 1H), 3.97 (s, 2H), 3.83 (s, 2H), 2.43 (s, 3H). 13C
NMR: l 211.6, 160.4, 147.9, 138.4, 137.4, 130.9, 129.4,
129.3, 114.9, 72.2, 68.8, 15.8. IR (CHCl3) wCO: 2068,
2024, 1984 cm−1. MS (EI): m/z 495 (M+), 467 (M+−
CO), 439 (M+−2CO), 411 (M+−3CO), 383 (M+−
4CO), 355 (M+−5CO), 327 (M+−6CO), 215 (L+).
Anal. Calc. For Fe2C19H13NSO6: C, 46.06; H, 2.63; N,
2.83. Found: C, 46.05; H, 2.73; N, 2.86%. Complex 3a
3.1.4. Compound 1d
Yield 93%, 7.92 g. H NMR: l 8.69 (s, 1H), 7.44 (d,
J=5.1 Hz, 1H), 7.32 (m, 4H), 7.23 (m, 1H), 6.92 (d,
1

360
W.-S. Hwang et al. / Polyhedron 20 (2001) 353–362
1
(15.6% yield): H NMR: l 8.07 (d, J=8.7 Hz, 1H),
7.65 (d, J=8.7 Hz, 1H), 7.42 (m, 6H), 7.14 (t, J=7.8
Hz, 1H), 4.09 (s, 2H), 3.98 (s, 2H). 13C NMR: l 211.4,
151.4, 146.9, 138.5, 131.7, 131.0, 129.8, 129.5, 129.3,
126.9, 126.6, 72.6, 71.6. IR (CHCl3) wCO: 2068, 2028,
1982 cm−1. MS (EI): m/z 475 (M+), 447 (M+−CO),
419 (M+−2CO), 391 (M+−3CO), 363 (M+−4CO),
335 (M+−5CO), 307 (M+−6CO), 195 (L+). Anal.
Calc. For Fe2C20H13NO6: C, 50.50; H, 2.74; N, 2.95.
Found: C, 50.38; H, 2.83; N, 2.95%.
Fe2C20H15NO6S: C, 47.15; H, 2.95; N, 2.75. Found: C,
47.21; H, 2.92; N, 2.79%. Complex 4c (16.6% yield):
1H NMR: l 7.40 (m, 5H), 7.12 (d, J=3.6 Hz, 1 H),
6.86 (d, J=3.6 Hz, 1 H), 5.60 (q, J=6.6 Hz, 1H),
2.52 (s, 3H), 1.59 (d, J=6.6 Hz, 3H), −26.2 (s, 1H).
13C NMR: l 211.1, 162.2, 155.6, 137.8, 134.6, 128.2,
126.6, 126.5, 125.0, 123.4, 64.4, 19.5, 11.8. IR (CHCl3)
wCO: 2081, 2047, 2012 cm−1, wCN: 1343 cm−1. MS
(FAB): m/z 649 (M+), 565 (M+−3CO), 509 (M+−
3COꢀFe), 453 (M+−5COꢀFe), 425 (M+−6COꢀFe),
397 (M+−7COꢀFe), 369 (M+−8COꢀFe), 341 (M+
−9COꢀFe), 228 (L+−1). Anal. Calc. For
Fe3C23H15NO9S: C, 42.53; H, 2.31; N, 2.16. Found: C,
42.38; H, 2.28; N, 2.19%.
3.2.2. Reaction of 1b with Fe2(CO)9 to gi6e
[v-N-(((2,3-p1:p2)-5-methyl-2-thienyl)methyl)-
p1:p1-(N)-p-xylylamino]hexacarbonyldiiron (2b) and
[v-N-(((1,2-p1:p2)-p-tolyl)methyl)-p1:p1-(N)-p-
xylylamino]hexacarbonyldiiron (3b)
Complex 2b (25.2% yield): 1H NMR: l 7.28 (d,
J=8.1 Hz, 2H), 7.22 (d, J=8.1 Hz, 2H), 7.04 (s, 1H),
3.92 (s, 2H), 3.82 (s, 2H), 2.43 (s, 3H), 2.33 (s, 3H).
13C NMR: l 211.1, 159.8, 147.3, 138.4, 136.9, 135.0,
130.2, 129.4, 114.4, 71.4, 68.2, 20.7, 15.2. IR (CHCl3)
wCO: 2061, 2021, 1976 cm−1. MS (FAB): m/z 509
(M+), 481 (M+−CO), 453 (M+−2CO), 425 (M+−
3CO), 397 (M+−4CO), 369 (M+−5CO), 341 (M+
−6CO), 229 (L+). Anal. Calc. For Fe2C20H15NO6S:
C, 47.15; H, 2.95; N, 2.75. Found: C, 47.28; H, 2.91;
3.2.4. Reaction of 1d with Fe2(CO)9 to gi6e
[v-N-(((2,3-p1:p2)-5-methyl-2-thienyl)methyl)-
p1:p1-(N)-benzylamino]hexacarbonyldiiron (2a),
[v-N-(((1,2-p1:p2)-phenyl)methyl)-p1:p1-(N)-
benzylamino]hexacarbonyldiiron (3a),
[v-N-(((2,3-p1:p2)-4-methyl-2-thienyl)methyl)-
p1:p1-(N)-benzylamino]hexacarbonyldiiron (5d) and
[v-N-(((1,2-p1:p2)-phenyl)methyl)-p1:p1-(N)-3-
methyl-2-thienylmethylamino]hexacarbonyldiiron (6d)
Complex 2a, 3.2% yield. Complex 3a, 18.0% yield.
1
1
N, 2.78%. Complex 3b (18.5% yield): H NMR: l 7.84
Complex 5d (3.4% yield): H NMR: l 7.43. (m, 5H),
(s, 1H), 7.57 (d, J=8.1 Hz, 1H), 7.32 (d, J=8.1 Hz,
2H), 7.22 (m, 3H), 4.02 (s, 2H), 3.90 (s, 2H), 2.33 (s,
3H), 2.29 (s, 3H). 13C NMR: l 211.4, 149.3, 148.0,
138.4, 136.0, 135.1, 133.0, 130.3, 129.4, 129.3, 121.4,
71.7, 70.7, 20.7, 20.6. IR (CHCl3) wCO: 2047, 2018,
1992 cm−1. MS (FAB): m/z 503 (M+), 475 (M+−
CO), 447 (M+−2CO), 419 (M+−3CO), 391 (M+−
4CO), 363 (M+−5CO), 335 (M+−6CO), 223 (L+).
Anal. Calc. For Fe2C22H17NO6: C, 52.49; H, 3.38; N,
2.78. Found: C, 52.60; H, 3.41; N, 2.72%.
7.25 (s, 1H), 4.05 (s, 2H), 3.88 (s, 2H), 2.40 (s, 3H).
13C NMR: l 211.4, 152.0, 146.2, 140.6, 136.6, 131.1,
128.7, 128.4, 127.1, 126.9, 72.1, 68.7, 13.4. IR (CHCl3)
wCO: 2067, 2022, 1982 cm−1. MS (EI): m/z 495 (M+),
467 (M+−CO), 439 (M+−2CO), 411 (M+−3CO),
383 (M+−4CO), 355 (M+−5CO), 327 (M+−6CO),
215 (L+). Anal. Calc. For C19H13Fe2NO6S: C, 46.06;
H, 2.63; N, 2.83. Found: C, 46.07; H, 2.71; N, 2.81%.
1
Complex 6d (12.8% yield): H NMR: l 8.06 (d, J=8.1
Hz, 1H), 7.68 (d, J=8.1 Hz, 1H), 7.42 (d, J=5.1 Hz,
1H), 7.37 (m, 1H), 7.15 (m, 1H), 6.87 (d, J=5.1 Hz,
1H), 4.22 (s, 2H), 3.93 (s, 2H), 2.37 (s, 3H). 13C
NMR: l 211.4, 149.5, 147.7, 136.8, 136.0, 131.0, 129.8,
129.6, 128.8, 126.4, 125.2, 71.2, 64.3, 20.6, 14.0. IR
(CHCl3) wCO: 2068, 2026, 1984 cm−1. MS (EI): m/z
495 (M+), 467 (M+−CO), 439 (M+−2CO), 411
(M+−3CO), 383 (M+−4CO), 355 (M+−5CO), 327
3.2.3. Reaction of 1c with Fe2(CO)9 to gi6e
[v-N-(((2,3-p1:p2)-5-methyl-2-thienyl)methyl)-
p1:p1-(N)-1-phenylethylamino]hexacarbonyldiiron (2c)
and [v3-((N-1-p)-1-phenylethyl-(5-methyl-2-thienyl)-
formidoyl-N,C)]nonacarbonyl-v-hydrido-triangulo-
triiron (4c)
(M+−6CO),
215
(L+).
Anal.
Calc.
For
Complex 2c (26.8% yield): 1H NMR: l 7.44 (m,
5H), 7.04 (s, 1H), 3.92 (d, J=15 Hz, 1H), 3.87 (d,
J=15 Hz, 1H), 3.70 (q, J=6.9 Hz, 1H), 2.42 (s, 3H),
1.57 (s, 3H). 13C NMR: l 160.1, 147.4, 142.4, 136.7,
129.1, 128.8, 128.7, 113.5, 73.4, 61.4, 20.7, 15.3. IR
(CHCl3) wCO: 2070, 2030, 1991 cm-1. MS (FAB): m/z
509 (M+), 481 (M+−CO), 453 (M+−2CO), 425
(M+−3CO), 397 (M+−4CO), 369 (M+−5CO), 341
C19H13Fe2NO6S: C, 46.06; H, 2.63; N, 2.83. Found: C,
46.18; H, 2.67; N, 2.81%.
If the reaction was proceeded for 8 h under the
same condition, only two complexes, 3a (22.8% yield)
and 6d (8.9% yield), were obtained.
If the reaction was stopped after 3 h of reaction,
8.0% of 2a, 5.2% of 3a, 9.2% of 5d, and 19.8% of 6d
were isolated.
(M+−6CO),
229
(L+).
Anal.
Calc.
For

W.-S. Hwang et al. / Polyhedron 20 (2001) 353–362
361
3.2.5. Reaction of 1e with Fe2(CO)9 to gi6e
[v-N-(((2,3-p1:p2)-5-methyl-2-thienyl)methyl)-
p1:p1-(N)-p-xylylamino]hexacarbonyldiiron (2b),
[v-N-(((1,2-p1:p2)-p-tolyl)methyl)-p1:p1-(N)-p-
xylylamino]hexacarbonyldiiron (3b), [v-N-(((2,3-p1:p2)-
4-methyl-2-thienyl)methyl)-p1:p1-(N)-p-xylylamino]-
hexacarbonyldiiron (5e) and [v-N-(((1,2-p1:p2)-
p-tolyl)methyl)-p1:p1-(N)-3-methyl-2-t
NMR: l 8.05 (d, J=8.1 Hz, 1H), 7.70. (d, J=8.1 Hz,
1H), 7.44 (d, J=5.1 Hz, 1H), 7.36 (m, 1H), 7.15 (m,
1H), 6.89 (d, J=5.1 Hz, 1H), 4.52 (q, J=6.0 Hz, 2H),
4.40 (d, J=15 Hz, 1H), 4.15 (d, J=15 Hz, 1H), 2.32
(s, 3H), 0.88 (d, J=6.0 Hz, 3H). 13C NMR: l 211.7,
150.1, 147.0, 136.7, 135.4, 131.0, 130.2, 130.1, 126.6,
126.5, 125.1, 74.5, 60.8, 24.3, 14.1. IR (CHCl3) wCO
:
2062, 2022, 1979 cm−1. MS (FAB): m/z 509 (M+), 481
(M+−CO), 453 (M+−2CO), 425 (M+−3CO), 397
(M+−4CO), 369 (M+−5CO), 341 (M+−6CO), 229
(L+). Anal. Calc. For C20H15Fe2NO6S: C, 47.15; H,
2.95; N, 2.75. Found: C, 47.23; H, 2.91; N, 2.79%.
hienylmethylamino]hexacarbonyldiiron (6e)
Complex 2b, 2.3% yield. Complex 3b, 22.4% yield.
1
Complex 5e (2.2% yield): H NMR: l 7.30 (d, J=8.1
Hz, 2H), 7.26 (s, 1H), 7.21 (d, J=8.1 Hz, 2H), 4.00 (s,
2H), 3.90 (s, 2H), 2.42 (s, 3H), 2.35 (s, 3H). 13C NMR:
l 211.3, 156.2, 145.8, 137.7, 136.5, 133.3, 129.7, 128.8,
127.6, 71.3, 68.0, 20.5, 13.1. IR (CHCl3) wCO: 2060,
2018, 1974 cm−1. MS (FAB): m/z 509 (M+), 481
(M+−CO), 453 (M+−2CO), 425 (M+−3CO), 397
(M+−4CO), 369 (M+−5CO), 341 (M+−6CO), 229
(L+). Anal. Calc. For C20H15Fe2NO6S: C, 47.15; H,
2.95; N, 2.75. Found: C, 47.06; H, 2.98; N, 2.74%.
3.3. Reaction of complex 2a–2b with complex 6d–6e
to gi6e complex 3a–3b
Equimolar quantities (1.0 mmol) of complexes 2a–2b
and 6d–6e in a 30 ml anhydrous benzene solution were
stirred under nitrogen at 45°C for 4 h. The reaction
mixture was filtered through Celite 545 and the solvent
was removed under reduced pressure. The residue was
chromatographed on a silica gel column with ethyl
acetate–chloroform–n-hexane (1:5:20) as eluent. The
products thus isolated were identified to be 3a (91%
yield)–3b (94% yield); 2,3-dimethylthiophene (84–81%
1
Complex 6e (14.6% yield): H NMR: l 7.84 (s, 1H),
7.61 (d, J=8.1 Hz, 1H), 7.39 (d, J=5.1 Hz, 1H), 7.25
(d, J=8.1 Hz, 1H), 6.86 (d, J=5.1 Hz, 1H), 4.20 (s,
2H), 3.92 (s, 2H), 2.39 (s, 3H), 2.30 (s, 3H). 13C NMR:
l 211.3, 149.6, 146.9, 137.1, 136.1, 133.6, 133.2, 129.9,
129.2, 124.8, 122.5, 70.9, 63.8, 20.6, 13.9. IR (CHCl3)
wCO: 2061, 2020, 1973 cm−1. MS (FAB): m/z 509 (M+),
481 (M+−CO), 453 (M+−2CO), 425 (M+−3CO),
397 (M+−4CO), 369 (M+−5CO), 341 (M+−6CO),
229 (L+). Anal. Calc. For C20H15Fe2NO6S: C, 47.15; H,
2.95; N, 2.75. Found: C, 47.18; H, 2.98; N, 2.73%.
If the reaction was proceeded for 8 h under the same
condition, only two complexes, 3b (26.6% yield) and 6e
(10.2% yield), were obtained.
1
yield): H NMR: l 7.10 (d, J=5.1 Hz, 1H), 6.55 (d,
J=5.1 Hz, 1H), 2.36 (s, 3H), 2.25 (s, 3H). MS (EI):
m/z 112 (M+); 5-methyl-2-(aminomethyl)thiophene
1
(73–70% yield) H NMR: l 6.57 (m, 2H), 3.86 (s, 2H),
2.40 (s, 3H), 1.50 (s, 2H). MS (EI): m/z 127 (M+).
4. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC no. 146435 for complex 2a, CCDC
no. 146436 for complex 3a and CCDC no. 146438 for
complex 2c. Copies of this information may be ob-
tained from The Director, CCDC, 12 Union Road,
Cambridge, CB2 1EZ, UK (fax: +44-1233-336033;
e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
If the reaction was stopped after 3 h of reaction,
8.2% of 2b, 5.6% of 3b, 8.8% of 5e, and 20.6% of 6e
were isolated.
3.2.6. Reaction of 1f with Fe2(CO)9 to gi6e
[v3-((N-1-p)-1-phenylethyl-(3-methyl-2-thienyl)-
formidoyl-N,C)]nonacarbonyl-v-hydrido-triangulo-
triiron (4f) and [v-N-(((1,2-p1:p2)-1-phenyl)ethyl)-
p1:p1-(N)-3-methyl-2-thienylmethylamino]-
hexacarbonyldiiron (6f)
Complex 4f (16.4% yield): 1H NMR: l 7.49 (d,
J=4.8 Hz, 1H), 7.35 (m, 5H), 7.02 (d, J=4.8 Hz, 1H),
5.33 (q, J=6.6 Hz, 1H), 2.48 (s, 3H), 1.83 (d, J=6.6
Hz, 3H), −25.9 (s, 1H). 13C NMR: l 210.2, 150.1,
147.1, 144.5, 143.4, 133.2, 131.8, 129.3, 128.9, 125.6,
66.0, 17.2, 11.2. IR (CHCl3) wCO: 2081, 2045, 2010
cm−1. MS (FAB): m/z 649 (M+), 621 (M+−CO), 593
(M+−2CO), 565 (M+−3CO), 537 (M+−4CO), 509
(M+−5CO), 481 (M+−6CO), 425 (M+−8CO), 397
Acknowledgements
Financial support from the National Science Council
(Taiwan, ROC) is gratefully acknowledged.
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