Iron carbonyl complexes from 2-[2,3-diaza-4-(2-thienyl)buta-1,3-dienyl]thiophene: N-N bond cleavage and cyclometalation

Article abstract of DOI:10.1016/S0022-328X(01)01188-3

When thienyl Schiff base 1, derived from 2-formylthiophene and hydrazine, reacted with Fe₂(CO)₉ in n-hexane, three major complexes were obtained: (1) a diironhexacarbonyl complex with two 2-thienylmethylideneamido bridging ligands 2, which resulted from the =N-N= bond cleavage of ligand 1; (2) a doubly cyclometalated di-μ-di-(η¹:η²-thienyl; η¹:η¹(N))bis(hexacarbonyldiiron) complex (3); and (3) a cyclometalated (μ-η¹:η²-thienyl; η¹:η¹(N))hexacarbonyldiiron complex (4). Molecular structures of compounds 1a, 1c, and 2a have been determined by single-crystal X-ray diffraction.

Full text of DOI:10.1016/S0022-328X(01)01188-3

Journal of Organometallic Chemistry 640 (2001) 85–92
www.elsevier.com/locate/jorganchem
Iron carbonyl complexes from
2
-[2,3-diaza-4-(2-thienyl)buta-1,3-dienyl]thiophene: NꢀN bond
cleavage and cyclometalation
a
a,
b
Chi-Jeh Lin , Wen-Shu Hwang *, Michael Y. Chiang
a
Department of Chemistry, National Dong Hwa Uni6ersity, Hualien, Taiwan, ROC
b
Department of Chemistry, National Sun Yet-Sen Uni6ersity, Kaohsiung, Taiwan, ROC
Received 25 May 2001; received in revised form 2 August 2001; accepted 4 August 2001
Abstract
When thienyl Schiff base 1, derived from 2-formylthiophene and hydrazine, reacted with Fe (CO) in n-hexane, three major
2
9
complexes were obtained: (1) a diironhexacarbonyl complex with two 2-thienylmethylideneamido bridging ligands 2, which
1
2
resulted from the ꢁNꢀNꢁ bond cleavage of ligand 1; (2)
a
doubly cyclometalated di-m-di-(h :h -thienyl;
1 2 1 1
1
1
h :h (N))bis(hexacarbonyldiiron) complex (3); and (3) a cyclometalated (m-h :h -thienyl; h :h (N))hexacarbonyldiiron complex
4). Molecular structures of compounds 1a, 1c, and 2a have been determined by single-crystal X-ray diffraction. © 2001 Elsevier
(
Science B.V. All rights reserved.
Keywords: Iron carbonyl complexes; Conjugated diimine; Cyclometalation; NꢀN Bond activation
We report here the preparation and characterization
of hexacarbonyldiiron complexes to which the ligand
bridges the diiron (FeꢀFe) unit(s) through thienyl imine
group(s) or imine nitrogen groups. The original ligand
is a Schiff base derived from 2-formylthiophene and
hydrazine, which undergoes nitrogenꢀnitrogen bond
cleavage, cyclometalation, and double cyclometalation
during the course of reaction with Fe (CO) . The choice
1
. Introduction
In the past decades, transition-metal mediated 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 ten-
dency to give five-membered metallacycle [2] and Schiff
base ligands are the compound of choice to study
cyclometalation reactions due to their strong tendency
to give endo cyclometalated derivatives [3].
The study of reactivity of organic molecules linked to
binuclear transition-metal (e.g. diiron) complexes has
received a great deal of attention during past years.
With the possibility of donating from two to eight
electrons, via the N lone-pairs, the CꢁN y-electrons,
conjugated diimine ligands are known to behave a very
versatile coordination property to the bonded metal
center [4].
2
9
of heterocyclic Schiff base stems from our interest in
the synthesis and finding the reactivity of newly synthe-
sized diiron complexes as well as their biological aspects
1
2
1
1
[
5]. The (m-h :h -thienyl; h :h (N))hexacarbonyldiiron
1 2 1 1
complexes and di-m-di-(h :h -thienyl; h :h (N))bis-
hexacarbonyldiiron) complexes show a unique binding
(
mode to which the b-carbon and a CꢁC y bond of the
bridging thiophene(s) and the imine nitrogen atom(s)
all are coordinated to the diiron (FeꢀFe) unit(s).
Furthermore, the NꢀN bond activation in various
types of organic ligands is important for its relevance
especially to catalysis and organic synthesis in general.
However, the metal-mediated NꢀN bond cleavage reac-
tions are not so many [6]. Products resulting from the
metal-mediated CꢀH activation and NꢀN activation in
the reactions were observed and reported herein.
*
Corresponding author. Fax: +886-3-8662770.
E-mail address: hws@mail.ndhu.edu.tw (W.-S. Hwang).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)01188-3

86
C.-J. Lin et al. / Journal of Organometallic Chemistry 640 (2001) 85–92
Table 1
Crystal and data collection parameters for compounds 1a, 1c, and 2a
Compound
1a
1c
2a
Empirical formula
Formula weight
Temperature (K)
Crystal system
C10H N S
220.31
296
monoclinic
C12H12N2S2
248.36
298
C16H Fe N O S (C H O)
523.29
298
monoclinic
8
2
2
8
2
2
6
2
3
6
0.4
monoclinic
Space group
P2 /n (no. 14)
P2 /n (no. 14)
C2/c (no. 15)
1
1
Unit cell dimensions
a (A
,
)
)
)
9.762(2)
11.376(1)
9.830(1)
100.82(1)
1072.2(3)
4
7.7009(9)
7.5963(6)
11.0835(6)
93.909(6)
646.86(9)
2
20.380(4)
8.070(1)
26.771(4)
95.73(1)
4381(1)
8
1.587
2102.40
0.40×0.70×0.80
55.1
b (A
,
c (A
i (°)
,
V (A )
,
3
Z
Dcalc (g cm−3)
F000
Crystal size (mm)
1.365
1.275
456.00
0.28×0.36×0.72
50.5
260.00
0.60×0.80×0.90
50.0
2
qmax (°)
Scan type
ꢀ–2q
ꢀ–2q
ꢀ–2q
No. of refins meads: total, unique
No. of obsd refins (I\3.00|(I))
No. of variables
2113, 1992
1057
127
1327, 1233
968
73
5578, 5420
3782
261
v (Mo–K ) (cm−1)
4.65
3.70
15.50
a
R
0.080
0.035
0.034
Rw
0.060
0.026
0.029
2. Results and discussion
the corresponding bond lengths and angles between two
1
a molecules in the pair are different.
The thienyl Schiff bases 1a, 1b, and 1c were prepared
The thienyl Schiff base 2-[2,3-diaza-4-(2-thienyl)buta-
by condensation of 2-formylthiophene derivatives with
hydrazine in anhydrous methanol. These compounds
were fully characterized as described in the Section 2.
The structures of compounds 1a and 1c were further
confirmed by single-crystal X-ray analysis. Crystal and
data collection parameters are shown in Table 1. Their
crystal structures are shown in Figs. 1 and 2, respec-
tively. Selected bond distances and angles are tabulated
in Table 2. The geometries of both 1a and 1c are well
planar and packed in pair in their unit cells. However,
1,3-dienyl]thiophene (1a), reacts with diiron nonacar-
bonyl in n-hexane to give three iron carbonyl
complexes, which we formulated as 2a, 3a, and 4a,
respectively, as the major products (Scheme 1).
1
The product 2a is a reddish orange solid. Its H-
NMR spectrum shows four sets of signal with the same
pattern as that of ligand 1a, indicating that two thienyl
rings as well as two imines in the complex are in the
Fig. 1. ORTEP diagram of compound 1a at the 30% probability level.
Fig. 2. ORTEP diagram of compound 1c at the 30% probability level.

C.-J. Lin et al. / Journal of Organometallic Chemistry 640 (2001) 85–92
,
) and angles (°) for compounds 1a, 1c, and 2a
87
Table 2
Selected bond lengths (A
Compound
1a
1c
2a
Bond lengths
N(1)ꢀN(1*)–N(2)ꢀN(2*)
N(1)ꢀC(1)–N(2)ꢀC(6)
C(1)ꢀC(2)–C(6)ꢀC(7)
Fe(1)ꢀFe(2)
Fe(1)ꢀN(1)–Fe(2)ꢀN(1)
Fe(1)ꢀN(2)–Fe(2)ꢀN(2)
Fe(1)ꢀC(11)–Fe(2)ꢀC(14)
Fe(1)ꢀC(12)–Fe(2)ꢀC(15)
Fe(1)ꢀC(13)–Fe(2)ꢀC(16)
1.44(1)–1.40(1)
1.286(10)–1.27(1)
1.44(1)–1.44(1)
1.412(3)
1.277(2)
1.430(2)
N(1)···N(2) 2.395
1.262(4)–1.267(4)
1.456(4)–1.450(4)
2.4349(6)
1.925(2)–1.922(2)
1.915(3)–1.917(2)
1.792(4)–1.804(4)
1.801(4)–1.803(4)
1.807(4)–1.794(4)
Bond angles
N(1*)ꢀN(1)ꢀC(1)–N(2*)ꢀN(2)ꢀC(6)
N(1)ꢀC(1)ꢀC(2)–N(2)ꢀC(6)ꢀC(7)
Fe(1)ꢀN(1)ꢀFe(2)–Fe(1)ꢀN(2)ꢀFe(2)
Fe(2)ꢀFe(1)ꢀN(1)–Fe(2)ꢀFe(1)ꢀN(2)
Fe(1)ꢀFe(2)ꢀN(1)–Fe(1)ꢀFe(2)ꢀN(2)
N(1)ꢀFe(1)ꢀN(2)–N(1)ꢀFe(1)ꢀN(2)
Fe(1)ꢀN(1)ꢀC(1)–Fe(2)ꢀN(2)ꢀC(6)
Fe(2)ꢀN(1)ꢀC(1)–Fe(1)ꢀN(2)ꢀC(6)
110.5(9)–110.8(9)
121.9(8)–122.8(8)
112.1(2)
121.7(2)
128.1(3)–128.1(3)
78.55(9)–78.9(1)
50.67(7)–50.59(7)
50.79(7)–50.52(8)
77.2(1)–77.2(1)
136.4(2)–135.3(2)
145.0(2)–145.8(2)
same chemical environment. Although three sets of
thienyl protons show a little shift, the signal corre-
sponding to the imine proton down field shifts from l
The structure of 2a was further confirmed by the
single crystal X-ray analysis. Its crystal and data collec-
tion parameters are shown in Table 1. The structure of
2a, in two stereo views, is shown in Fig. 3 [7]. Selected
bond distances and angles are tabulated in Table 2. The
structure, as shown in the figure, contains two 2-
thienylmethylideneamido groups which bridge two
8
.80 to 9.26 ppm (ligand 1a). In its IR spectrum, while
−
1
the CꢁN stretching shifted from 1608 to 1614 cm
1
appearing at 2067, 2029, and 1984 cm . The fragmen-
tation pattern of its mass spectrum shows no evidence
of peak with m/e value of 220, corresponding to ligand
in
a, there are three sharp and intense CꢁO stretches
−1
Fe(CO) units through nitrogen atoms. From this it is
3
clear that the NꢀN bond in ligand 1a had been cleaved
during the coordination reaction and the nonbonded
1a. However, peaks at m/e 110 and 111 were observed
accompany with the presence of a molecular ion peak
at m/e 500 and six peaks corresponding to sequential
CO loss products, in accordance with the formulated
structure.
N···N distance is 2.395 A. The configuration of the
,
individual molecule has idealized two-fold symmetry.
The tricarbonyl groups are eclipsed. The nitrogen and
iron atoms form a tetrahedron. The central position of
Scheme 1.

88
C.-J. Lin et al. / Journal of Organometallic Chemistry 640 (2001) 85–92
Fig. 3. ORTEP diagrams of compound 2a in two stereo-views at the 30% probability level.
2
the molecule is thus similar in shape to that of
Co (CO) . Plane calculations show that all pairs of
with the short FeꢀFe bond length and the sp hy-
bridization of nitrogen atoms.
2
8
atoms are equidistant from opposite side to the C axis,
The cleavage of the NꢀN bond during the course of
ligand coordination to form bridges through three-elec-
tron-donor nitrogen atoms might decrease the electron
density on the methine group that explains why there is
a 0.46 ppm down field chemical shift of the imine
2
which perpendicular to the mid-point of the FeꢀFe
bond. Each iron center is coordinated by two nitrogen
atoms and three carbonyls located at the corner of a
distorted octahedron. The FeꢀFe distance is only
1
protons in its H-NMR spectrum. On the other hand,
2
.4349(6) A
,
which is shorter than usual for diiron
) [8], but can be compared with
relative to the highly conjugated ligand, the bond order
of the imine group in the complex might increase due to
the rupture of the NꢀN bond and the formation of the
iminato-bridged complex that decreases the degree of
conjugation on the iminato ligand. The IR stretching
complexes (2.5–2.7 A
,
the value found in some nitrogen-bridged diiron com-
plexes [6e,9], and can be attributed to a distinct ‘bent’
ironꢀiron bond [10]. The bond distances between iron
and bridging nitrogen are Fe(1)ꢀN(1) 1.925(2) A
Fe(1)ꢀN(2) 1.915(3) A, Fe(2)ꢀN(1) 1.922(2) A, and
Fe(2)ꢀN(2) 1.917(2) A, respectively, which are shorter
than those reported nitrogen bridged diiron complexes
6e, 8e–g, 9]. The significantly shorter averaged FeꢀN
bond distance of 1.92 A in this complex can be ascribed
,
,
−
1
absorption of the CꢁN group is 1608 cm in ligand 1a
,
,
−
1
which is higher energy shifted to 1614 cm in iminato-
bridged complex and is confirmed by the shortening of
the CꢁN bond length.
,
[
The orange product 3a is a novel doubly cyclometa-
,
1
lated tetrairon complex. The H-NMR spectrum of 3a
to the structure possessing two three-coordinated trigo-
nal-like, instead of four-coordinated tetrahedral-like,
bridging nitrogen atoms, and the nitrogen atoms of the
shows the absence of the methine proton (resonance at
l 8.80 ppm in 1a) and has three sets of signal with a
ratio of 1:1:2. In the aromatic region, two doublet
signals appear at l 7.67 and 7.42 ppm with a coupling
constant JHꢀH=5.1 Hz, indicating only the protons on
the a%- and b%-carbon of the thienyl ring are left. The
most significant feature for this complex is the reso-
nance representing the methylene group that is formed
during the reaction and is observed at l 4.21 ppm in its
2
complex can be considered as sp hybridized [11]. The
bond distances between C(1) and N(1) as well as C(2)
and N(2) are 1.262(4) and 1.267(4) A
which are shorter than the CꢁN bond distance in 1a
1.27(1)–1.286(10) A), and yet are still in the range of
usual bond length of imine double bond. In the central
Fe N system, the averaged FeꢀNꢀFe bond angle is
,
, respectively,
(
,
1
13
2
2
H-NMR and at l 64.9 ppm in its C-NMR spectrum.
78.7° and the averaged NꢀFeꢀFe bond angle is 50.64°.
The singlet signal of the methylene protons indicates
that two protons are equivalent [8f, 8g, 8i, 9f, 9h–k,
12]. In its IR spectrum, while the CꢁN stretching is
absent, there are three sharp and intense CꢁO stretches
The dihedral angle between the two planes each formed
by the two iron atoms and one bridging nitrogen atom
is 107.58°. The bond angles of Fe(1)ꢀN(1)ꢀC(1),
−
1
Fe(2)ꢀN(1)ꢀC(1),
N(2)ꢀC(6) are 136.4(2), 145.0(2), 145.8(2), and
35.3(2)°, respectively. These large angles are associated
Fe(1)ꢀN(2)ꢀC(6),
and
Fe(2)ꢀ
appearing at 2068, 2042, and 1972 cm . This result
presumably is due to the coordination of each imine
nitrogen of the thienyl Schiff base to one of the iron
1

C.-J. Lin et al. / Journal of Organometallic Chemistry 640 (2001) 85–92
89
centers of each of two diiron carbonyl moieties, cy-
clometalation occurs at the b-carbon site of each thienyl
ring and followed by the 1,3-hydrogen shift, and each
methine carbon becomes a methylene by accepting the
hydride that was removed from the b-carbon. The mass
spectrum of the product contains a signal for the
molecular ion at m/e=780 and 12 peaks corresponding
to the fragments with sequential loss of CO from this
molecular ion, in accordance with the formulated struc-
ture. A signal for the symmetrically NꢀN bond cleaved
ion at m/e 390 and six peaks corresponding to the
stepwise loss of six CO groups from the NꢀN bond
cleaved ion are also found in the same spectrum. In
complex 3a, each of two thienyl rings in the organic
ligand serves as a three-electron donor and bridges to
two iron centers of each diiron carbonyl moieties to
aged the rupture of the ꢁNꢀNꢁ bond during the course
of reaction. The formation of product 3b also gets
benefit from the same effect.
The reaction of 3-methyl-2-[2,3-diaza-4-(3-methyl-2-
thienyl)buta-1,3-dienyl]thiophene (1c), in which the b-
positions of thienyl rings are blocked with methyl
substituents, with diiron nonacarbonyl gives only the
NꢀN bond cleaved iron carbonyl complex 2c. The
product yield of 2c is lower than that of 2a and 2b and
might be attributed to the steric hindrance of the methyl
substituents on the b-position of the thienyl rings.
3
. Experimental
Diiron nonacarbonyl was prepared by photolysis of
iron pentacarbonyl (Aldrich) in glacial acetic acid [13].
1
2
furnish a m-h :h -thienyl mode of coordination. Each
nitrogen atom also serves as another three-electron
donor and bridges to two iron centers of each diiron
carbonyl moieties.
Solvents were dried (sodium–benzophenone, P O ) and
4
10
distilled under nitrogen prior to use. 2-Formylthiophene
Aldrich), 5-methyl-2-formylthiophene and 3-methyl-2-
(
1
formylthiophene (Acres) were distilled by a Kugelrohr
distillation apparatus under reduced pressure (0.1
mmHg) prior to use. All other chemicals were reagent
grade and without further purification. The NMR spec-
tra were recorded on a Varian VXR-300 NMR spec-
The H-NMR spectrum of the red product 4a shows
one methine proton at l 8.25 ppm and two methylene
protons at l 4.54 ppm in addition to the five sets of
thienyl protons in the range of l 7.77–7.11 ppm.
Among the five sets of thienyl protons, three are doublet
with a coupling constant JHꢀH=5.1 Hz, one is a doublet
with a coupling constant JHꢀH=3.6 Hz, and another set
1
13
trometer ( H, 299.95 MHz; C, 75.43 MHz). Chemical
shifts were referenced to TMS and deuterated acetone
(
Janssen) was used as a solvent and as a secondary
is a doublet of doublet with coupling constants JHꢀH
=
reference. Mass spectra were obtained from a VG-Bio-
tech Quattro 5022 spectrometer. IR spectra were
recorded from a Bio-Rad FTS-40 spectrometer. Elemen-
tal analyses were performed using a Heraeus CHNO
rapid analyzer. Crystals for X-ray diffraction were ob-
tained from acetonitrile (1a and 1c) or from acetone–
dichloromethane mixed solution (2a). A single crystal
was mounted on a glass fiber and the X-ray diffraction
intensity data were measured on a Rigaku AFC7S
diffractometer at room temperature.
5
.1 and 3.6 Hz, respectively. This result indicates that a
b-proton on one of the thienyl rings disappeared and an
extra proton added to one of the methine carbon to
make it become a methylene group during the course of
ligand coordination. The IR spectrum of the complex
−
1
shows a characteristic CꢁN stretching at 1597 cm and
three sharp and intense CꢁO stretches at 2067, 2028, and
−
1
1986 cm . The mass spectrum of 4a shows the molec-
ular ion peak and the complete loss of six CO ligands in
a sequential manner, in accordance with the formulated
structure. In contrast to complex 3a, complex 4a is a
diiron hexacarbonyl complex with cyclometalation oc-
curring only on one of the two thienylmethylidene
moieties.
3.1. Synthesis of thienyl Schiff bases 2-[2,3-diaza-4-
(
2-thienyl)buta-1,3-dienyl]-thiophene (1a),
2
5
2
-[2,3-diaza-4-(5-methyl-2-thienyl)buta-1,3-dienyl]-
-methylthiophene (1b), and 2-[2,3-diaza-4-(3-methyl-
-thienyl)buta-1,3-dienyl]-3-methylthiophene (1c)
A similar result was found from the reaction of
-methyl-2-[2,3-diaza-4-(5-methyl-2-thienyl)buta-1,3-
5
dienyl]thiophene (1b), with diiron nonacarbonyl under
exactly the same reaction condition as that of 1a. An
iron carbonyl complex with NꢀN bond cleaved ligand
The synthesis of Schiff base employed the usual
approach of condensation in alcohol solution [14]. 2-
Formylthiophene, 5-methyl-2-formylthiophene, or 3-
methyl-2-formylthiophene (40 mmol) and N H ·H O
2
b, and two cyclometalated complexes 3b and 4b, were
isolated as shown in Scheme 1. Complexes 2b, 3b, and
b were characterized to be spectrally and structurally
2
4
2
(
(
Acros, 20 mmol) were heated at reflux in 95% ethanol
E. Merck, 100 ml) for 24 h. The solvent was removed
4
similar to that of complexes 2a, 3a, and 4a, respectively.
While the yield of 4b is much lower than that of 4a, the
yields of 2b and 3b are higher than that of 2a and 3a.
The product yield of 2b is twice as much as that of 2a.
Obviously, the inductive effect of the methyl sub-
stituents on the a%-carbon of the thienyl rings encour-
by filtration. The precipitate was washed with several
portions of ether to give pure yellow product.
3.1.1. Compound 1a
96% yield. m.p. 148–149 °C. H-NMR: l 8.80 (s,
1
2H), 7.69 (d, JHꢀH=5.1 Hz, 2H), 7.60 (d, JHꢀH=3.6

90
C.-J. Lin et al. / Journal of Organometallic Chemistry 640 (2001) 85–92
1
3
1
Hz, 2H), 7.20 (dd, JHꢀH=3.6, 5.1 Hz, 2H). C-NMR:
l 156.6, 140.1, 134.0, 131.2, 128.9. IR (KBr film) wCꢁN:
1
62 °C. H-NMR: l 7.69 (d, J
=5.1 Hz, 2H), 7.42
HꢀH
13
(d, JHꢀH=5.1 Hz, 2H), 4.21 (s, 4H). C-NMR: l
211.8, 154.8, 140.5, 132.2, 115.6, 64.9. IR (CHCl ) wCꢁO:
2068, 2024, 1972 cm . MS (FAB): m/e 780 (M ), 752
(M −CO), 724 (M −2CO), 696 (M −3CO), 668
M −4CO), 640 (M −5CO), 612 (M −6CO), 584
(M −7CO), 556 (M −8CO), 528 (M −9CO), 500
−
1
+
608 cm . MS (FAB): m/e 220 (M ). Anal. Calc. for
C H N S : C, 54.55; H, 3.64; N, 12.73; S, 29.10.
Found: C, 54.54; H, 3.70; N, 12.72; S, 29.12%.
3
+
−
1
1
0
8
2 2
+
+
+
+
+
+
(
+
+
+
3
.1.2. Compound 1b
7% yield. m.p. 138–139 °C. H-NMR: l 8.60 (s,
H), 7.30 (d, JHꢀH=3.6 Hz, 2H), 6.84 (d, JHꢀH=3.6
Hz, 2H), 2.51 (s, 6H). C-NMR: l 155.0, 145.3,
36.5, 133.2, 126.3, 14.5. IR (KBr film) wCꢁN: 1606
1
+
+
+
9
(M −10CO), 472 (M −11CO), 444 (M −12CO),
+
+
2
388 (M −12CO−Fe), 332 (M −12CO−2Fe), 276
13
+
+
+
+
(M −12CO−3Fe), 220 (L ), 390 (M /2), 362 (M /
2−CO), 334 (M /2−2CO), 306 (M /2−3CO), 278
(M /2−4CO), 250 (M /2−5CO), 222 (M /2−
6CO), 166 (M /2−6CO−Fe), 110 (L /2). Anal. Calc.
+
+
1
−
1
+
+
+
+
cm . MS (FAB): m/e 248 (M ). Anal. Calc. for
C H N S : C, 58.06; H, 4.84; N, 11.29; S, 25.81.
+
+
1
2
12
2 2
Found: C, 58.02; H, 4.88; N, 11.22; S, 25.78%.
for Fe C H N O S : C, 33.85; H, 1.03; N, 3.59; S,
4
22
8
2
12 2
8
.21. Found: C, 33.82; H, 1.06; N, 3.61; S, 8.26%.
1
3
.1.3. Compound 1c
5% yield. m.p. 148–150 °C. H-NMR: l 8.80 (s,
H), 7.56 (d, JHꢀH=5.1 Hz, 2H), 7.00 (d, JHꢀH=5.1
Complex 4a: 18.5% yield; m.p. 89−90 °C. H-NMR: l
8.25 (s, 1H), 7.77 (d, JHꢀH=5.1 Hz, 1H), 7.58 (d,
JHꢀH=5.1 Hz, 1H), 7.45 (d, JHꢀH=5.1 Hz, 1H), 7.42
(d, JHꢀH=3.6 Hz, 1H), 7.11 (d, JHꢀH=3.6, 5.1 Hz, 1H),
1
9
2
13
Hz, 2H), 2.45 (s, 6H). C-NMR: l 154.9, 143.7,
33.7, 132.0, 130.2, 14.1. IR (KBr film) wCꢁN: 1600
13
1
4.54 (s, 2H).
C-NMR:
l
211.2, 154.3, 145.3,
−
1
+
cm . MS (FAB): m/e 248 (M ). Anal. Calc. for
140.6, 139.7, 132.8, 131.9, 130.2, 128.7, 117.0, 68.7. IR
−
1
−1
C H N S : C, 58.06; H, 3.84; N, 11.29; S, 25.81.
Found: C, 58.07; H, 4.85; N, 11.26; S, 25.80%.
(CHCl ) wCꢁN: 1597 cm , wCꢁO: 2066, 2026, 1981 cm
.
1
2
12
2
2
3
+
+
+
+
MS (FAB): m/e 500 (M ), 472 (M −CO), 444 (M
2CO), 416 (M −3CO), 388 (M −4CO), 360 (M
−5CO), 332 (M −6CO), 276 (M −6CO−Fe), 220
+
+
−
+
+
3
.2. Reaction of Schiff base 1 with Fe (CO) in
2
9
+
n-hexane
(L ). Anal. Calc. for Fe C H N O S : C, 38.40; H,
2
16
8
2
6 2
1
.60; N, 5.60; S, 12.80. Found: C, 38.41; H, 1.62; N,
In a typical reaction, 8.0 mmol of compound 1 in 30
ml of anhydrous n-hexane was added gradually to a 70
ml of anhydrous n-hexane solution containing 30.0
mmol of Fe (CO) in the dark under nitrogen and the
5.63; S, 12.76%.
3.2.2. Reaction of 1b with Fe (CO) to gi6e di-v-
(5-methyl-2-thienylmethylideneamido)bis(tricarbonyl-
iron) (2b), [di-v-N,N%-1,2-bis((((2,3-p :p )-5-methyl-
2-thienyl)methyl)-p :p (N))-diaza]bis(hexacarbonyl-
diiron) (3b), and [v-N-(((2,3-p :p )-5-methyl-2-
thienyl)methyl)-p :p (N)-5-methyl-2-thienyl-
methylidenehydrazonato]hexacarbonyldiiron (4b)
Complex 2b: 44.7% yield; m.p. 140 °C (dec.). H-
NMR: l 9.10 (s, 2H), 7.22 (d, JHꢀH=3.6 Hz, 2H), 6.90
2
9
2
9
1
2
reaction mixture was refluxed for 6 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 n-hexane
as eluent to separate the reddish orange product 2,
orange product 3, and red product 4. Substantial
amount of Fe (CO) was also collected.
1
1
1
2
1
1
1
3
12
13
(
d, JHꢀH=3.6 HZ, 2H), 2.57 (s, 6H). C-NMR:
3
.2.1. Reaction of 1a with Fe (CO) to gi6e di-v-
l
211.7, 166.5, 145.0, 139.2, 132.0, 126.5, 15.2.
IR
2
9
−
1
−1
(
2-thienylmethylideneamido)bis(tricarbonyliron) (2a),
(CHCl ) wCꢁN: 1614 cm , wCꢁO: 2065, 2027, 1982 cm
MS (FAB): m/e 528 (M ), 500 (M −CO), 472 (M
−2CO), 444 (M −3CO), 316 (M −4CO), 388 (M
−5CO), 360 (M −6CO), 304 (M −6CO−Fe), 124
(L /2). Anal. Calc. for Fe C H N O S : C, 40.91; H,
2.27; N, 5.30; S, 12.12. Found: C, 40.89; H, 2.30; N,
5.31; S, 12.16%. Complex 3b: 14.6% yield. H-NMR: l
7.07 (s, 2H), 4.11 (s, 4H), 2.45 (s, 6H). C-NMR: l
.
3
1
2
+
+
+
[di-v-N,N%-1,2-bis((((2,3-p :p )-2-thienyl)methyl)-
1
1
+
+
+
p :p (N))-diaza]bis(hexacarbonyldiiron) (3a), and
1
2
1
1
+
+
(v-N-(((2,3-p :p )-2-thienyl)methyl)-p :p (N)-2-
+
thienylmethylidenehydrazonato]hexacarbonyldiiron (4a)
2
18 12
2
6 2
1
Complex 2a: 21.5% yield; m.p. 124–125 °C. H-
1
NMR: l 9.26 (s, 2H), 7.79 (d, JHꢀH=4.8 Hz, 2H), 7.45
13
(
d, JHꢀH=3.6 Hz, 2H), 7.23 (d, JHꢀH=3.6, 4.8 Hz, 2H).
1
3
C-NMR: l 212.0, 167.2, 141.8, 132.1, 130.5, 128.8. IR
211.9, 158.7, 147.3, 137.6, 119.3, 65.3, 15.9. IR (CHCl )
3
+
−
1
−1
−1
(CHCl ) wCꢁN: 1608 cm , wCꢁO: 2067, 2029, 1984 cm
.
w
CꢁO
: 2065, 2022, 1978 cm . MS (FAB): m/e 808 (M ),
3
+
+
+
+
+
+
+
MS (FAB): m/e 500 (M ), 472 (M −CO), 444 (M
−
−
780 (M −CO), 752 (M −2CO), 724 (M −3CO),
696 (M −4CO), 668 (M −5CO), 640 (M −6CO),
612 (M −7CO), 584 (M −8CO), 556 (M −9CO),
528 (M −10CO), 500 (M −11CO), 472 (M −
12CO), 416 (M −12CO−Fe), 360 (M −12CO−
2Fe), 304 (M −12CO−3Fe), 248 (L ), 404 (M /2),
+
+
+
+
+
2CO), 416 (M −3CO), 388 (M −4CO), 360 (M
+
+
+
+
+
5CO), 332 (M −6CO), 276 (M −6CO−Fe), 110
+
+
+
+
(
L /2). Anal. Calc. for Fe C H N O S : C, 38.40; H,
2
16
8
2
6 2
+
+
1
5
.60; N, 5.60; S, 12.80. Found: C, 38.36; H, 1.63; N,
.62; S, 12.83%. Complex 3a: 10.8% yield; m.p. 61−
+
+
+

C.-J. Lin et al. / Journal of Organometallic Chemistry 640 (2001) 85–92
91
+
+
+
(
c) H. Alper, W.G. Root, J. Am. Chem. Soc. 97 (1975) 4251;
(d) M.I. Bruce, Angew. Chem. Int. Ed. Engl. 16 (1977) 73;
e) G.R. Newkome, W.E. Puckett, W.K. Gupta, G.E. Kiefer,
3
3
(
66 (M /2−CO), 348 (M /2−2CO), 320 (M /2−
+
+
CO), 292 (M /2−4CO), 264 (M /2−5CO), 236
M /2−6CO), 180 (M /2−6CO−Fe), 124 (L /2).
Anal. Calc. for Fe C H N O S : C, 35.64; H, 1.49;
N, 3.47; S, 7.92. Found: C, 35.58; H, 1.52; N, 3.50; S,
.94%. Complex 4b: 6.8% yield. H-NMR: l 8.09 (s,
H), 7.20 (d, JHꢀH=3.6 Hz, 1H), 7.09 (s, 1H), 6.79 (d,
(
+
+
+
Chem. Rev. 86 (1986) 451;
(f) P.W. Clark, S.F. Dyke, G. Smit, C.H.L. Kennard, J.
Organomet. Chem. 330 (1987) 427;
(
(
(
(
(
4
24 12
2
12
2
1
g) I. Omae, Coord. Chem. Rev. 83 (1988) 137;
h) A.D. Ryabov, Chem. Rev. 90 (1990) 403;
i) J. Albert, J. Barro, J. Granell, J. Organomet. Chem. 408
1991) 115;
7
1
JHꢀH=3.6 Hz, 1H), 4.42 (s, 2H), 2.49 (s, 3H), 2.46 (s,
1
3
3H).
C-NMR:
l
211.3, 158.6, 147.9, 145.3, 137.8,
j) J. Alber, R.M. Ceder, M. G o´ mez, J. Granell, J. Sales,
1
37.4, 132.4, 127.7, 127.2, 113.5, 69.3, 15.8, 15.7.
IR
Organometallics 11 (1992) 1536;
k) J. Alber, J. Granell, R. Moragas, J. Sales, M. Font-Bard ´ı a,
X. Solans, J. Organomet. Chem. 494 (1995) 95;
l) K.A. Azam, R. Dilshad, S.E. Kabir, M.A. Mottalib, M.B.
−
1
−1
(
(CHCl ) wCꢁN: 1596 cm , wCꢁO: 2065, 2025, 1983 cm
.
3
+
+
+
MS (FAB): m/e 528 (M ), 550 (M −CO), 472 (M
−
−
(
+
+
+
2CO), 444 (M −3CO), 416 (M −4CO), 388 (M
Hursthouse, K.M.A. Malik, Polyhedron 19 (2000) 1081.
+
+
5CO), 360 (M −6CO), 304 (M −6CO−Fe), 248
[
2] A.C. Cope, E.C. Friedrich, J. Am. Chem. Soc. 90 (1968) 909.
[3] (a) J. Albert, J. Granell, J. Sales, J. Organomet. Chem. 273
(1984) 393;
+
(
L ). Anal. Calc. for Fe C H N O S : C, 40.91; H,
2
18 12
2
6 2
2
5
.27; N, 5.30; S, 12.12. Found: C, 40.95; H, 2.29; N,
.29; S, 12.10%.
(
b) J. Albert, M. G o´ mez, J. Granell, J. Sales, X. Solans,
Organometallics 9 (1990) 1405.
[
4] (a) F. Mull, G. van Koten, K. Vrieze, K.A.A. Duineveld, D.
Heijdenrijk, A.N.S. Mak, C.H. Stam, Organometallics 8 (1989)
1324;
3
.2.3. Reaction of 1c with Fe (CO) to gi6e
2
9
di-v-(3-methyl-2-thienylmethylideneamido)-
bis(tricarbonyliron) (2c)
(
b) F. Mull, G. van Koten, K. Vrieze, D. Heijdenrijk,
Organometallics 8 (1989) 33;
c) F. Mull, G. van Koten, K. Vrieze, D. Heijdenrijk, B.B.
Krijnen, C.H. Stam, Organometallics 8 (1989) 41;
d) F. Mull, G. van Koten, M.J.A. Kraakman, K. Vrieze, D.
Heijdenrijk, M.C. Zoutberg, Organometallics 8 (1989) 1331;
e) F. Mull, G. van Koten, L.H. Polm, K. Vrieze, M.C. Zout-
berg, D. Heijdenrijk, E. Kragten, C.H. Stam, Organometallics 8
1989) 1340.
1
Complex 2c: 8.4% yield. H-NMR: l 9.27 (s, 2H),
(
7
2
1
.68 (d, JHꢀH=5.1 Hz, 2H), 7.03 (d, JHꢀH=5.1 Hz,
13
H), 2.37 (s, 6H).
C-NMR:
l
212.5, 165.8,
(
41.1, 135.0, 131.9, 129.5, 14.0. IR (CHCl ) wCꢁN: 1607
3
−
1
−1
(
cm , w : 2062, 2023, 1980 cm . MS (FAB): m/e
5
−
−
Calc. for Fe C H N O S : C, 40.91; H, 2.27; N, 5.30;
S, 12.12. Found: C, 40.92; H, 2.29; N, 5.32; S, 12.09%.
CꢁO
+
+
+
+
+
28 (M ), 500 (M −CO), 472 (M −2CO), 444 (M
3CO), 316 (M −4CO), 388 (M −5CO), 360 (M
6CO), 304 (M −6CO−Fe), 124 (L /2). Anal.
(
+
+
[
[
5] J. Sovill, C.F. Klayman, J. Med. Chem. 25 (1982) 126.
6] (a) L.S. Hegedus, A. Krama, Organometallics 3 (1984) 1263;
(b) F.A. Cotton, S.A. Duraj, W.J. Roth, J. Am. Chem. Soc. 106
+
+
2
18 12
2
6 2
(
(
1984) 4749;
c) K. Weiss, P. Kindl, Angew. Chem. Int. Ed. Engl. 13 (1984)
6
29;
(
d) A. Albini, H. Kisch, J. Organomet. Chem. 94 (1975) 75;
4
. Supplementary material
(e) D. Bright, O.S. Mills, Chem. Commun. (1967) 245.
7] The asymmetric unit cell contains one diiron complex and
roughly 0.4 acetone molecule. The acetone molecule sits on a
two-fold axis passing through O(7)ꢀC(17) (the carbonyl group of
acetone molecule). The H atoms on acetone molecule were not
located and hence not put in for the final cycle of calculation.
The site occupancy factor (s.o.f=0.4) of acetone molecule was
assigned to obtain reasonable temperature factors for the atoms
in acetone molecule.
[
[
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC no. 163161 for compound 1a,
163162 for compound 1c, and 163163 for complex 2a.
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (Fax: +44-1223-336033;
e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
8] (a) A.E. Ogilva, M. Draganjic, T.B. Rauchfuss, S.R. Wilson,
Organometallics 7 (1988) 1171;
(
b) J.M. Cassidy, K.H. Whitmire, G.J. Long, I. Organomet.
Chem. 427 (1992) 355;
(
(
c) W. Petz, F.Z. Weller, Kristallogr. 212 (1997) 157;
d) H.B. Chin, M.B. Smith, R.D. Wilson, R. Bau, J. Am. Chem.
Soc. 96 (1974) 5285;
e) H.-J. Kn o¨ lker, E. Baum, P. Gonser, G. Rohde, H. R o¨ ttele,
Acknowledgements
(
Organometallics 17 (1998) 3916;
Financial support from the National Science Council
Taiwan, ROC) is gratefully acknowledged.
(f) D.L. Wang, W.S. Hwang, L. Lee, M.Y. Chiang, J.
Organomet. Chem. 579 (1999) 211;
(
(
g) W.S. Hwang, D.L. Wang, M.Y. Chiang, J. Organomet.
Chem. 613 (2000) 231;
h) F. Ortega-Jim e´ nez, C. Ortega-Alfaro, J.G. L o´ pez-Cort e´ s, R.
(
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(
(
(
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(
(
(
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(
(
i) W. Imhof, J. Organomet. Chem. 533 (1997) 31;
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