Synthetic and structural studies on new diiron azadithiolate (ADT)-type model compounds for active site of [FeFe]hydrogenases

Article abstract of DOI:10.1039/c0dt00909a

A series of new diiron azadithiolate (ADT) complexes (1-8), which could be regarded as the active site models of [FeFe]hydrogenases, have been synthesized starting from parent complex [(μ-SCH₂)₂NCH ₂CH₂OH]Fe₂(CO)₆ (A). Treatment of A with ethyl malonyl chloride or malonyl dichloride in the presence of pyridine afforded the malonyl-containing complexes [(μ-SCH₂) ₂NCH₂CH₂O₂CCH₂CO ₂Et]Fe₂(CO)₆ (1) and [Fe₂(CO) ₆(μ-SCH₂)₂NCH₂CH ₂O₂C]₂CH₂ (2). Further treatment of 1 and 2 with PPh₃ under different conditions produced the PPh ₃-substituted complexes [(μ-SCH₂)₂NCH ₂CH₂O₂CCH₂CO₂Et]Fe ₂(CO)₅(PPh₃) (3), [(μ-SCH₂) ₂NCH₂CH₂O₂CCH₂CO ₂Et]Fe₂(CO)₄(PPh₃)₂ (4), and [Fe₂(CO)₅(PPh₃)(μ-SCH₂) ₂NCH₂CH₂O₂C]₂CH ₂ (5). More interestingly, complexes 1-3 could react with C ₆₀ in the presence of CBr₄ and 1,8-diazabicyclo[5.4.0] undec-7-ene (DBU) via Bingel-Hirsch reaction to give the C₆₀- containing complexes [(μ-SCH₂)₂NCH₂CH ₂O₂CC(C₆₀)CO₂Et]Fe ₂(CO)₆ (6), [Fe₂(CO)₆(μ-SCH ₂)₂NCH₂CH₂O₂C] ₂C(C₆₀) (7), and [(μ-SCH₂) ₂NCH₂CH₂O₂CC(C₆₀)CO ₂Et]Fe₂(CO)₅(PPh₃) (8). The new ADT-type models 1-8 were characterized by elemental analysis and spectroscopy, whereas 2-4 were further studied by X-ray crystallography and 6-8 investigated in detail by DFT methods.

Full text of DOI:10.1039/c0dt00909a

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PAPER
Synthetic and structural studies on new diiron azadithiolate (ADT)-type
model compounds for active site of [FeFe]hydrogenases†
Li-Cheng Song,* Zhao-Jun Xie, Xu-Feng Liu, Jiang-Bo Ming, Jian-Hua Ge, Xiao-Guang Zhang,
Tian-Ying Yan* and Peng Gao
Received 25th July 2010, Accepted 25th October 2010
DOI: 10.1039/c0dt00909a
A series of new diiron azadithiolate (ADT) complexes (1–8), which could be regarded as the active site
models of [FeFe]hydrogenases, have been synthesized starting from parent complex
[(m-SCH2)2NCH2CH2OH]Fe2(CO)6 (A). Treatment of A with ethyl malonyl chloride or malonyl
dichloride in the presence of pyridine afforded the malonyl-containing complexes
[(m-SCH2)2NCH2CH2O2CCH2CO2Et]Fe2(CO)6 (1) and [Fe2(CO)6(m-SCH2)2NCH2CH2O2C]2CH2 (2).
Further treatment of 1 and 2 with PPh3 under different conditions produced the PPh3-substituted
complexes [(m-SCH2)2NCH2CH2O2CCH2CO2Et]Fe2(CO)5(PPh3) (3), [(m-SCH2)2NCH2CH2O2-
CCH2CO2Et]Fe2(CO)4(PPh3)2 (4), and [Fe2(CO)5(PPh3)(m-SCH2)2NCH2CH2O2C]2CH2 (5). More
interestingly, complexes 1–3 could react with C60 in the presence of CBr4 and 1,8-diazabicyclo[5.4.0]-
undec-7-ene (DBU) via Bingel–Hirsch reaction to give the C60-containing complexes
[(m-SCH2)2NCH2CH2O2CC(C60)CO2Et]Fe2(CO)6 (6), [Fe2(CO)6(m-SCH2)2NCH2CH2O2C]2C(C60) (7),
and [(m-SCH2)2NCH2CH2O2CC(C60)CO2Et]Fe2(CO)5(PPh3) (8). The new ADT-type models 1–8 were
characterized by elemental analysis and spectroscopy, whereas 2–4 were further studied by X-ray
crystallography and 6–8 investigated in detail by DFT methods.
Introduction
Hydrogenases are natural enzymes that can catalyze H2
metabolism found in a variety of microorganisms.1,2 According
to the metal content in their active sites, hydrogenases are usually
classified as [FeFe]hydrogenases (FeFeHases), [NiFe]hydrogenases
(NiFeHases), and [Fe]hydrogenases (Hmd).3–13 FeFeHases are
mainly used for proton reduction to hydrogen and NiFeHases
used for hydrogen oxidation to protons,14–17 whereas Hmd is
utilized to activate hydrogen for use in catabolic processes of
microorganisms.12,13 Currently, FeFeHases have drawn much more
attention than NiFeHases and Hmd, largely because of their novel
structures and particularly their very fast rates for production of
“clean” and highly efficient H2 fuel.15–20 X-Ray crystallographic21–23
and FTIR spectroscopic24–26 studies revealed that FeFeHases
contain a unique active site, which consists of a diiron subsite
that carries four types of ligands: CO, CN-, [Fe4S4]-S-Cys, and a
less defined dithiolate (SCH2)2X (X = CH2, NH, or O) (Scheme 1).
Under the guidance of such structural information, many synthetic
chemists have designed and successfully synthesized a variety of
Scheme 1
model compounds for the active site of [FeFe]Hases.27–31 Now,
as a continuation of our study in this area, we wish to report
the synthesis and structural characterization of the first three
C60-containing diiron azadithiolate (ADT)-type model complexes
along with five new simple ADT-type model complexes (some
were used as starting materials for the former three complicated
models). It is worth pointing out that these diiron ADT-type
models are of particular interest. This is because recent X-ray
crystallographic and theoretical studies32 indicated that the actual
dithiolate cofactor in [FeFe]Hases is most likely an ADT ligand
in which the N atom plays a key role in the heterolytic cleavage
or formation of H2. In addition, the complicated C60-containing
ADT-type models might be potentially a new type of light-driven
models that could be able to catalyze proton reduction to hydrogen
under the irradiation of light.31d,33–38
State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry,
Nankai University, Tianjin, 30007, China. E-mail: lcsong@nankai.edu.cn
† Electronic supplementary information (ESI) available: Fig. S1a: 13C
NMR spectrum of 7; Fig. S1b: the frontier orbitals of 7; Table S1:
experimental and computational IR frequencies and intensities of 6–8.
CCDC reference numbers 783283–783285. For ESI and crystallographic
data in CIF or other electronic format see DOI: 10.1039/c0dt00909a
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Scheme 2
malonate groups, whereas the 13C NMR spectra of 1–5 showed a
singlet in the region 41.14–41.64 ppm for methylene carbon atoms
in their malonate groups. In addition, the 31P NMR spectra of 3–5
showed a singlet at ca. 65 ppm for P atoms in their PPh3 ligands.
The molecular structures of 2–4 were unequivocally confirmed
by X-ray crystallography (Fig. 1–3 and Table 1). As can be
seen intuitively in Fig. 1–3, complex 2 contains two diiron ADT
moieties bridged by a malonate group via an axial bond C15–N1
and an equatorial bond C21–N2, whereas complexes 3 and 4 each
consist of one diiron ADT moiety that is attached to an ethyl
malonate group via the equatorial C8–N1 and C43–N1 bonds,39
respectively. Similar to those previously reported PPh3-substituted
diiron dithiolate complexes,40 all the PPh3 ligands in 3 and 4 lie
in an apical position of the square-pyramidal geometry of the
corresponding iron atoms. In addition, the Fe–Fe bond lengths of
Results and discussion
Synthesis and characterization of malonyl and PPh3-containing
ADT-type models 1–5
We found that the N-hydroxyethyl functionality of parent complex
[(m-SCH2)2NCH2CH2OH]Fe2(CO)6 (A) could be easily acylated
with ethyl malonyl chloride and malonyl dichloride in CH2Cl2
in the presence of pyridine to give the malonyl-containing
model complexes [(m-SCH2)2NCH2CH2O2CCH2CO2Et]Fe2(CO)6
(1) and [Fe2(CO)6(m-SCH2)2NCH2CH2O2C]2CH2 (2) in 78%
and 61% yields, respectively. Further treatment of
1
with PPh3 in the presence of decarbonylating agent
Me3NO in MeCN or without Me3NO in xylene at re-
flux gave the PPh3-monosubstituted and disubstituted com-
plexes [(m-SCH2)2NCH2CH2O2CCH2CO2Et]Fe2(CO)5(PPh3) (3)
and [(m-SCH2)2NCH2CH2O2CCH2CO2Et]Fe2(CO)4(PPh3)2 (4) in
73% and 56% yields, respectively. In addition, the PPh3-
disubstituted double Fe/S cluster complex [Fe2(CO)5(PPh3)(m-
SCH2)2NCH2CH2O2C]2CH2 (5) could be prepared similarly by
reaction of 2 with PPh3 in MeCN in the presence of Me3NO
in 64% yield. All the aforementioned preparations are shown in
Scheme 2.
˚
2–4 lie in the range 2.5013–2.5188 A, which are very close to those
of other diiron ADT-type model complexes.41
While complex 1 is a slightly air-sensitive oil, complexes
2–5 are air-stable, red solids. All the complexes are new and
have been characterized by elemental analysis and spectroscopy.
The IR spectra of 1–5 displayed several absorption bands in the
range 2072–1925 cm-1 for their terminal carbonyls and one or two
absorption bands in the range 1751–1726 cm-1 for their malonate
1
carbonyls. The H NMR spectra of 1–5 exhibited a singlet in
the region 3.08–3.27 ppm for methylene hydrogen atoms in their
Fig. 1 Molecular structure of 2 with 30% probability level ellipsoids.
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◦
˚
Table 1 Selected bond lengths (A) and angles ( ) for 2–4
2
3
4
Fe(1)–S(1)
Fe(1)–S(2)
Fe(1)–Fe(2)
Fe(2)–S(1)
Fe(2)–S(2)
Fe(3)–Fe(4)
N(1)–C(15)
N(2)–C(21)
S(2)–Fe(1)–S(1)
S(1)–Fe(1)–Fe(2)
S(2)–Fe(1)–Fe(2)
S(1)–Fe(2)–S(2)
S(1)–Fe(2)–Fe(1)
S(2)–Fe(2)–Fe(1)
C(13)–N(1)–C(14)
C(23)–N(2)–C(22)
2.262(1)
2.271(1)
2.5043(9)
2.264(1)
2.264(1)
2.501(1)
1.463(4)
1.459(4)
84.38(4)
56.46(3)
56.34(3)
84.49(4)
56.35(3)
56.62(3)
114.3(3)
116.5(2)
Fe(1)–S(1)
Fe(1)–S(2)
Fe(1)–Fe(2)
Fe(2)–S(1)
Fe(2)–S(2)
Fe(2)–P(1)
N(1)–C(6)
N(1)–C(7)
S(2)–Fe(1)–S(1)
S(1)–Fe(2)–Fe(1)
S(2)–Fe(2)–Fe(1)
Fe(2)–S(1)–Fe(1)
Fe(2)–S(2)–Fe(1)
S(2)–Fe(1)–Fe(2)
S(1)–Fe(1)–Fe(2)
S(1)–Fe(2)–S(2)
P(1)–Fe(2)–Fe(1)
C(6)–N(1)–C(7)
2.271(1)
2.255(1)
2.519(1)
2.272(1)
2.263(1)
2.230(1)
1.444(5)
1.450(5)
84.00(5)
56.31(4)
55.98(4)
67.33(4)
67.76(4)
56.26(4)
56.36(4)
83.80(5)
153.68(4)
113.4(4)
Fe(1)–S(1)
Fe(1)–S(2)
Fe(1)–Fe(2)
Fe(2)–S(1)
Fe(2)–S(2)
Fe(1)–P(1)
Fe(2)–P(2)
N(1)–C(43)
S(2)–Fe(1)–S(1)
S(1)–Fe(2)–Fe(1)
S(2)–Fe(2)–Fe(1)
Fe(2)–S(1)–Fe(1)
Fe(2)–S(2)–Fe(1)
S(2)–Fe(1)–Fe(2)
S(1)–Fe(1)–Fe(2)
S(2)–Fe(2)–S(1)
P(1)–Fe(1)–Fe(2)
P(2)–Fe(2)–S(1)
2.259(1)
2.272(1)
2.5162(8)
2.275(1)
2.268(1)
2.2416(9)
2.242(1)
1.472(4)
83.37(4)
55.98(3)
56.43(3)
67.41(3)
67.32(3)
56.26(3)
56.61(3)
83.09(4)
155.57(3)
110.73(4)
(6), [Fe2(CO)6(m-SCH2)2NCH2CH2O2C]2C(C60) (7), and [(m-
SCH2)2NCH2CH2O2CC(C60)CO2Et]Fe2(CO)5(PPh3) (8) could be
prepared by treatment of simple models 1–3 with C60 in the
presence of CBr4 and DBU (1,8-diazabicyclo[5,4,0]undec-7-ene)
in toluene at room temperature in 26–37% yields (Scheme 3). It
is apparent that complexes 6–8 were produced through Bingel–
Hirsch reaction, which involves cyclopropanation of C60 with the
intermediate a-bromomalonate derivatives of 1–3 (formed in situ
by bromination of 1–3 with CBr4 under the action of organic base
DBU).42
Complexes 6–8 are air-stable, brown solids, which were charac-
terized by combustion analysis and various spectroscopic meth-
ods. The IR spectra of 6–8 displayed three absorption bands in
the range 2072–1932 cm-1 for their terminal carbonyls, one band
in the range 1748–1746 cm-1 for their malonate carbonyls, and
four bands in the region 1433–525 cm-1 attributed to the C–C
stretching frequencies for their C60 spheres.43 The UV/vis spectra
of 6–8 exhibited three absorption bands in the range 283–428 nm.
These UV/vis bands could be ascribed to the C60 moieties of
6–8 since they are very close to those of free C60 determined
under the identical conditions (UV/vis data for C60: lmax (loge)
Fig. 2 Molecular structure of 3 with 30% probability level ellipsoids.
1
283 (4.55), 336 (4.62), 407 (3.34) nm). The H NMR spectra of
6–8 are similar to those displayed by their precursors 1–3, except
that the singlets in the region 3.08–3.27 ppm for methylene groups
in their precursors disappeared. Obviously, this is completely in
accordance with the formation of a three-membered ring from
one of the [6,6] bonds of C60 and the malonate methylene group in
each precursor through Bingel–Hirsch reaction.42 The 13C NMR
spectra of 6–8 further proved their structures. For example, the
single-butterfly [2Fe2S] cluster complex 6, as shown in Fig. 4,
displays 18 resonance signals in the region 138–146 ppm, one
signal at 71.44 ppm, and one signal at 51.99 ppm. The former
18 signals can be assigned to 58 sp2-C atoms in its C60 sphere,
whereas the latter two signals represent two sp3-C atoms in its
C60 sphere and the methano bridge C atom in its three-membered
ring, respectively.42 Theoretically, complex 6 with Cs symmetry
should have 32 13C NMR signals for its C60 sphere.44 However, we
observed only 19 signals for its C60 sphere, due to the overlap of
some signals in very close proximity.45 In addition, the 13C NMR
Fig. 3 Molecular structure of 4 with 30% probability level ellipsoids.
Synthesis and characterization of C60-containing ADT-type models
6–8
It was further found that the C60-containing compli-
cated models [(m-SCH2)2NCH2CH2O2CC(C60)CO2Et]Fe2(CO)6
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Scheme 3
sp3-C atoms in its C60 sphere, and the signal at 51.89 ppm can
be assigned to the methano bridge C atom in its three-membered
ring.42 Therefore, the 13C NMR spectrum of complex 7 (showing 16
signals for its C60 sphere) is in good agreement with C2v symmetry
(theoretically showing 17 signals), because two theoretical signals
are overlapped at 144.97 ppm.44,45
Structural study on C60-containing models 6–8 by DFT calculations
The DFT calculations were carried out on optimizing the struc-
tures of complexes 6–8. Fig. 5 shows the DFT optimized molecular
structures of 6–8, whereas their calculated bond lengths and angles
˚
are listed in Table 2. The calculated Fe–Fe bond lengths of 2.509 A
˚
˚
for 6, 2.511 A for 7 and 2.512 A for 8 are very close to the
corresponding bond lengths of 2–4 and other similar complexes
determined by X-ray crystallography.41 In addition, the calculated
bond angles of Fe–C–O in 6–8 are in the range 177.28–179.99◦,
which are very close to those of 2–4 and their similar carbonyl
complexes.41 The PPh3 ligand in 8 occupies the apical position of
the square-pyramidal geometry of Fe atom and its three benzene
rings attached to P atom are planar and twisted in order to reduce
Fig. 4 (a) Original 13C NMR spectrum of 6. (b) Expanded 13C NMR
spectrum of 6.
spectrum of the double-butterfly [2Fe2S] cluster complex 7 (see
Fig. S1a, ESI†) exhibits 15 resonance signals in the range 138–
146 ppm, which can be attributed to 58 sp2-C atoms in its C60
sphere. The signal which appeared at 71.35 ppm represents two
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◦
˚
Table 2 Calculated bond lengths (A) and angles ( ) for 6–8
6
7
8
Fe(1)–Fe(2)
Fe(1)–S(1)
Fe(1)–S(2)
Fe(2)–S(1)
Fe(2)–S(2)
Fe(1)–C(1)
Fe(1)–C(2)
2.509
2.321
2.335
2.320
2.320
1.802
1.804
Fe(1)–Fe(2)
Fe(1)–S(1)
Fe(1)–S(2)
Fe(2)–S(1)
Fe(2)–S(2)
Fe(1)–C(1)
Fe(1)–C(2)
2.511
2.320
2.320
2.333
2.320
1.797
1.807
Fe(1)–Fe(2)
Fe(1)–S(1)
Fe(1)–S(2)
Fe(2)–S(1)
Fe(2)–S(2)
Fe(1)–C(1)
Fe(1)–C(2)
Fe(1)–P(1)
2.512
2.345
2.369
2.328
2.326
1.783
1.782
2.313
2.649
2.923
83.16
56.87
57.86
57.10
58.48
84.50
65.06
64.65
178.20
178.34
163.04
H(1)–S(1)
H(2)–S(2)
S(1)–Fe(1)–S(2)
S(1)–Fe(1)–Fe(2)
S(2)–Fe(2)–Fe(1)
S(2)–Fe(1)–Fe(2)
S(1)–Fe(2)–Fe(1)
S(2)–Fe(2)–S(1)
Fe(2)–S(2)–Fe(1)
Fe(2)–S(1)–Fe(1)
Fe(1)–C(1)–O(1)
Fe(1)–C(2)–O(2)
84.58
57.11
57.31
57.25
57.68
84.95
65.45
65.21
179.96
179.80
S(1)–Fe(1)–S(2)
S(1)–Fe(1)–Fe(2)
S(2)–Fe(2)–Fe(1)
S(2)–Fe(1)–Fe(2)
S(1)–Fe(2)–Fe(1)
S(2)–Fe(2)–S(1)
Fe(2)–S(2)–Fe(1)
Fe(2)–S(1)–Fe(1)
Fe(1)–C(1)–O(1)
Fe(1)–C(2)–O(2)
85.06
57.59
57.23
57.24
57.09
84.76
65.52
65.32
179.26
179.80
S(1)–Fe(1)–S(2)
S(1)–Fe(1)–Fe(2)
S(2)–Fe(2)–Fe(1)
S(2)–Fe(1)–Fe(2)
S(1)–Fe(2)–Fe(1)
S(2)–Fe(2)–S(1)
Fe(2)–S(2)–Fe(1)
Fe(2)–S(1)–Fe(1)
Fe(1)–C(1)–O(1)
Fe(1)–C(2)–O(2)
P(1)–Fe(1)–Fe(2)
Fig. 5 DFT optimized structures of 6–8.
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the steric hindrance. Such structural features of 8 are in good
agreement with those of PPh3-containing 3/4 and other similar
complexes.40,41 Particularly noteworthy is that complex 8 has two
intramolecular hydrogen bonds between the H atom of benzene
ring and S atom of ADT moiety in which the calculated two S–H
The electron-donating PPh3 ligand not only increases the basicity
of the Fe2S2 butterfly cluster, but also raises its orbital energy.
Thus, the HOMO orbital is switched from the C60 moiety in 6 or
7 to the Fe2S2 moiety in 8. Such a finding is in good agreement
with that reported by De Gioia on the role of the ligands on the
electronic features.46
˚
bond lengths are 2.649 and 2.923 A, respectively. For complexes
6–8, the calculated HOMO/LUMO gaps are 2.585 eV (480 nm)
for 6, 2.456 eV (505 nm) for 7, and 2.251 eV (551 nm) for 8, whereas
the calculated frequencies and intensities associated with nC O and
nC O are in accordance with the experimental values (see Table S1,
ESI†).
Conclusion
We have found that the new simple ADT-type models 1 and 2 can
be easily synthesized by acylation of parent complex A with ethyl
malonyl chloride or malonyl dichloride in the presence of pyridine,
whereas those simple models 3–5 can be readily prepared by CO
substitutions of 1 and 2 with PPh3 in the presence or absence
of decarbonylating agent Me3NO. Particularly interesting is that
the first C60-containing ADT-type models 6–8 are successfully
synthesized through Bingel–Hirsch reaction of simple models
1–3 with C60 in the presence of CBr4 and DBU. All the new
model complexes 1–8 are structurally characterized by varous
spectroscopic methods and some of them by X-ray crystallography.
While the optimized structures and frontier orbitals of 6–8 are
obtained by DFT calculations, a possible intramolecular electron
transfer for 8 could be expected from C60 moiety to the butterfly
Fe2S2 cluster.
The frontier orbitals of complex 8 are depicted in Fig. 6. As can
be seen in Fig. 6, the highest occupied molecular orbital (HOMO)
(which is suitable for proton binding and thus can influence its
protonation chemistry) is located on the Fe2S2 butterfly cluster.
This HOMO orbital is mainly characterized by a large Fe–Fe
bond density and is also contributed from 3p orbital of S atoms.
In addition, it can be seen that the lowest unoccupied molecular
orbital (LUMO) is localized on C60 consisting of a p-antibonding
orbital involving sp2-C atoms. Such an arrangement of the frontier
orbitals is analogous to that in QM/MM study of the natural
enzyme, in which HOMO is localized on Fed of the Fe2S2 butterfly
cluster with LUMO on the Fe4S4 cubane cluster.46 Therefore, the
electron transfer might be possible from C60 to the Fe2S2 butterfly
cluster during the light irradiation, as suggested by computational
studies.47 The photosensitizer C60 can accept an electron in LUMO
from an external electron donor. However, in contrast to 8, both
HOMO and LUMO of 6 (Fig. 7) and those of 7 (see Fig. S1b
for the frontier orbitals of 7, ESI†) are all located on the C60
moiety. Thus, the CO substitution by a PPh3 ligand can change the
electronic structure of the corresponding compound significantly.
Experimental
Materials and instruments
All reactions were performed using standard Schlenk and
vacuum-line techniques under N2 atmosphere. Dichloromethane
and acetonitrile were distilled over CaH2 under N2. Toluene
was purified by distillation under N2 from sodium/
benzophenone ketyl. 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU),
CBr4, PPh3, Me3NO·2H2O and other materials were avail-
able commercially and used as received. Complex [(m-
SCH2)2NCH2CH2OH]Fe2(CO)6,48 ethyl malonyl chloride49 and
malonyl dichloride50 were prepared according to literature pro-
cedure. Preparative TLC was carried out on glass plates (26 ¥
20 ¥ 0.25 cm) coated with silica gel H (10–40 mm). IR spectra
1
were recorded on a Bio-Rad FTS 6000 spectrophotometer. H
NMR, 31P NMR and 13C NMR spectra were obtained on a Bruker
Avance 300 or 400 NMR, or a Varian Mercury Plus 400 NMR
spectrometer. UV-vis spectra were taken on a Hitachi U-3900
spectrometer. Elemental analyses were performed on an Elementar
Vario EL analyzer. Melting points were determined on a Yanaco
MP-500 apparatus and were uncorrected.
Fig. 6 Frontier orbitals of 8: HOMO (left) and LUMO (right).
Preparation of [(l-SCH2)2NCH2CH2O2CCH2CO2Et]Fe2(CO)6 (1)
To a solution of [(m-SCH2)2NCH2CH2OH]Fe2(CO)6 (A) (0.108 g,
◦
0.25 mmol) in CH2Cl2 (15 mL) at 0 C was added ethyl malonyl
chloride (0.06 mL, 0.5 mmol) and pyridine (0.04 mL, 0.5 mmol).
The reaction mixture was stirred at 0 ◦C for 15 min, and then
at room temperature for 3 h. Volatiles were removed under
vacuum and the residue was subjected to TLC separation using
CH2Cl2/petroleum ether (v/v = 2 : 1) as eluent. From the main
red band, 1 (0.106 g, 78%) was obtained as a red oil. Calc. for
C15H15Fe2NO10S2: C, 33.05; H, 2.77; N, 2.57. Found: C, 33.02;
H, 2.60; N, 2.68. IR (KBr disk): nmax/cm-1 2071 (s), 2026 (vs),
Fig. 7 Frontier orbitals of 6: HOMO (left) and LUMO (right).
842 | Dalton Trans., 2011, 40, 837–846
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1
1964 (vs) (C O); nmax/cm-1 1726 (vs) (C O) cm-1. H NMR
disk): nmax/cm-1 1995 (vs), 1951 (vs), 1932 (vs) (C O); nmax/cm-1
1
(300 MHz, CDCl3, d): 1.22 (t, 3H, J = 7.2 Hz, CH3), 2.92 (t, 2H,
J = 5.4 Hz, NCH2CH2O), 3.27 (s, 2H, O2CCH2CO2), 3.53 (s, 4H,
2NCH2S), 3.95 (t, 2H, J = 5.4 Hz, NCH2CH2O), 4.13 (q, 2H, J =
7.2 Hz, CH2CH3). 13C NMR (100.6 MHz, CDCl3, d): 14.26 (CH3),
41.59 (O2CCH2CO2), 53.34 (NCH2S), 55.56 (NCH2CH2O), 61.84
(OCH2CH3), 63.22 (OCH2CH2N), 166.41 (C O), 207.86 (C O).
1751 (s) (C O) cm-1. H NMR (300 MHz, CDCl3, d): 1.25 (t,
3H, J = 7.2 Hz, CH3), 1.42 (t, 2H, J = 6.0 Hz, NCH2CH2O),
1.80 (s, 4H, 2NCH2S), 3.08 (s, 2H, O2CCH2CO2), 3.18 (t, 2H,
J = 5.7 Hz, NCH2CH2O), 4.14 (q, 2H, J = 7.2 Hz, CH2CH3),
7.38, 7.68 (2 s, 30H, 6C6H5). 31P NMR (162 MHz, CDCl3, 85%
H3PO4, d): 61.74 (s). 13C NMR (75.4 Hz, CDCl3, d): 14.13 (CH3),
41.27 (O2CCH2CO2), 47.47, 50.78 (NCH2S), 56.51 (NCH2CH2O),
61.26, 61.57 (2OCH2), 128.28, 128.42, 129.60, 133.45, 133.52,
136.73, 137.23 (C6H5), 165.87, 166.09 (C O), 209.74, 215.34
(C O).
Preparation of [Fe2(CO)6(l-SCH2)2NCH2CH2O2C]2CH2 (2)
To a solution of A (0.200 g, 0.46 mmol) in CH2Cl2 (15 mL) at 0 ◦C
was added pyridine (0.04 mL, 0.50 mmol) and malonyl dichloride
(0.023 mL, 0.22 mmol). The reaction mixture was stirred at 0 ◦C
for 15 min, and then at room temperature for 4 h. Volatiles were
removed under vacuum and the residue was subjected to TLC
separation using CH2Cl2/petroleum ether (v/v = 2 : 1) as eluent.
From the main red band, 2 (0.130 g, 61%) was obtained as a red
solid, mp 98–100 ◦C. Calc. for C23H18Fe4N2O16S4: C, 29.70; H,
1.95; N, 3.01. Found: C, 30.04; H, 1.99; N, 2.90. IR (KBr disk):
Preparation of [Fe2(CO)6(PPh3)(l-SCH2)2NCH2CH2O2C]2CH2
(5)
To a solution of 2 (0.108 g, 0.12 mmol) and PPh3 (0.061 g,
0.23 mmol) in CH3CN (10 mL) was added a solution of
Me3NO·2H2O (0.026 mg, 0.23 mmol) in CH3CN (5 mL). After
the mixture was stirred at room temperature for 2 h, volatiles were
removed under vacuum, and then the residue was subjected to
TLC separation using acetone/petroleum ether (v/v = 3 : 5) as
eluent. From the main red band, 5 (0.104 g, 64%) was obtained
as a red solid, mp 62–63 ◦C. Calc. for C57H48Fe4N2O14P2S4: C,
48.95; H, 3.46; N, 2.00. Found: C, 49.12; H, 3.40; N, 2.04. IR
(KBr disk): nmax/cm-1 2043 (vs), 1982 (vs), 1931 (s) (C O);
n
max/cm-1 2072 (s), 2025 (vs), 1956 (vs) (C O); nmax/cm-1 1729
(s) (C O) cm-1. H NMR (400 MHz, CDCl3, d): 2.92 (t, 4H,
J = 6.8 Hz, 2NCH2CH2O), 3.25 (s, 2H, O2CCH2CO2), 3.52 (s,
8H, 4NCH2S), 3.95 (t, 4H, J = 6.8 Hz, 2NCH2CH2O). 13C NMR
(75.4 Hz, CDCl3, d): 41.14 (O2CCH2CO2), 53.12 (NCH2S), 55.36
(NCH2CH2O), 63.10 (2OCH2), 165.88 (C O), 207.62 (C O).
1
n
max/cm-1 1744 (s) (C O) cm-1. 1H NMR (300 MHz, CDCl3, d):
Preparation of [(l-SCH2)2NCH2CH2O2CCH2CO2Et]Fe2(CO)5-
2.39 (br.s, 4H, 2NCH2CH2O), 2.44, 2.98 (2d, 8H, J = 12.0 Hz,
11.4 Hz, 4 NCH2S), 3.17 (s, 2H, O2CCH2CO2), 3.76 (t, 4H,
J = 5.7 Hz, 2NCH2CH2O), 7.26–7.69 (m, 30H, 6C6H5) ppm. 31P
NMR (162 MHz, CDCl3, 85% H3PO4, d): 65.89 (s). 13C NMR
(75.4 Hz, CDCl3, d): 41.15 (O2CCH2CO2), 50.79 (NCH2S), 56.35
(NCH2CH2O), 62.41 (OCH2), 128.42, 128.55, 130.17, 133.44,
133.59, 135.42, 135.95 (C6H5), 165.81 (C O), 209.71, 213.35,
213.49 (C O).
(PPh3) (3)
To a solution of 1 (0.168 g, 0.31 mmol) and PPh3 (0.081 g,
0.31 mmol) in CH3CN (20 mL) was added Me3NO·2H2O
(0.034 mg, 0.31 mmol), and then the mixture was stirred at room
temperature for 4 h. Volatiles were removed under vacuum and the
residue was subjected to TLC separation using CH2Cl2/petroleum
ether (v/v = 5 : 2) as eluent. From the main red band, 3 (0.176 g,
73%) was obtained as a red solid, mp 112–114 ◦C. Calc. for
C32H30Fe2NO9PS2: C, 49.32; H, 3.88; N, 1.80. Found: C, 49.51;
H, 3.90; N, 1.84. IR (KBr disk): nmax/cm-1 2044 (vs), 1993 (vs),
1956 (vs), 1925 (vs) (C O); nmax/cm-1 1734 (vs) (C O) cm-1.
1H NMR (400 MHz, CDCl3, d): 1.27 (t, 3H, J = 7.2 Hz, CH3),
2.39 (br.s, 2H, NCH2CH2O), 2.45, 2.97 (2d, 4H, J = 10.4 Hz,
11.6 Hz, 2NCH2S), 3.26 (s, 2H, O2CCH2CO2), 3.76 (br.s, 2H,
NCH2CH2O), 4.17 (q, 2H, J = 7.2 Hz, CH2CH3), 7.42, 7.66
(2 s, 15H, 3C6H5). 31P NMR (162 MHz, CDCl3, 85% H3PO4,
d): 64.79 (s). 13C NMR (100.6 MHz, CDCl3, d): 14.32 (CH3),
41.64 (O2CCH2CO2), 50.97 (NCH2S), 56.63 (NCH2CH2O), 61.86
(OCH2CH3), 62.59 (OCH2CH2N), 128.63, 128.73, 130.35, 133.64,
133.75, 135.73, 136.13 (C6H5), 166.36, 166.41 (C O), 209.92,
213.56, 213.66 (C O).
Preparation of [(l-SCH2)2NCH2CH2O2CC(C60)CO2Et]Fe2(CO)6
(6)
To a solution of 1 (0.043 g, 0.078 mmol), CBr4 (0.026 g,
0.078 mmol) and C60 (0.040 g, 0.055 mmol) in toluene (30 mL)
was added DBU (23.8 mL, 0.158 mmol), and then the mixture
was stirred at room temperature overnight. After volatiles were
removed under vacuum, the residue was subjected to TLC
separation using CH2Cl2/petroleum ether (v/v = 2 : 1) as eluent.
From the purple band, unreacted C60 was recovered (0.014 g,
35%). From the main brown band, 6 (0.016 g, 35% yield based on
consumed C60) was obtained as a brown solid, mp > 300 ◦C. Calc.
for C75H13Fe2NO10S2: C, 71.28; H, 1.04; N, 1.11. Found: C, 71.09;
H, 1.14; N, 0.99. IR (KBr disk): nmax/cm-1 2071 (s), 2031 (vs),
1993 (vs) (C O); nmax/cm-1 1746 (s) (C O) cm-1. 1H NMR
(300 MHz, CDCl3, d): 1.47 (t, 3H, J = 7.2 Hz, CH3), 3.20 (t,
2H, J = 5.4 Hz, NCH2CH2O), 3.69 (s, 4H, 2NCH2S), 4.36 (t, 2H,
J = 5.4 Hz, NCH2CH2O), 4.56 (q, 2H, J = 7.2 Hz, CH2CH3).
13C NMR (75.4 MHz, CDCl3, d): 14.36 (CH3), 51.99 (O2CCCO2),
53.21 (NCH2S), 55.15 (NCH2CH2O), 63.61 (OCH2CH3), 64.56
(OCH2CH2N), 163.33 (C O), 207.58 (C O), C60: 71.44 (2sp3-
C), 138.74 (2C), 139.18 (2C), 141.05 (2C), 141.87 (2C), 142.23
(4C), 142.99 (2C), 143.07 (8C), 143.15 (1C), 143.91 (4C), 144.56
(1C), 144.72 (8C), 144.83 (1C), 144.94 (2C), 145.04 (8C), 145.13
Preparation of [(l-SCH2)2NCH2CH2O2CCH2CO2Et]-
Fe2(CO)4(PPh3)2 (4)
A solution of 1 (0.166 g, 0.30 mmol) and PPh3 (0.183 g, 0.70 mmol)
in xylene (20 mL) was stirred and heated to reflux for 1 h. Volatiles
were removed under vacuum and the residue was subjected to
TLC separation using CH2Cl2/petroleum ether (v/v = 3 : 1) as
eluent. From the main red band, 4 (0.170 g, 56%) was obtained as
a red solid, mp 78–80 ◦C. Calc. for C49H45Fe2NO8P2S2: C, 58.06;
H, 4.47; N, 1.38. Found: C, 57.92; H, 4.50; N, 1.30. IR (KBr
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(2C), 145.24 (4C), 145.33 (4C), 145.42 (1C). UV/vis (toluene): lmax
(loge) 283 (4.72), 329 (4.65), 422 (3.84) nm.
25%). From the main brown band, 8 (0.014 g, 37% yield based
on consumed C60) was obtained as a brown solid, mp 116–
118 ◦C. Calc. for C92H28Fe2NO9PS2: C, 73.76; H, 1.88; N, 0.94.
Found: C, 73.62; H, 1.90; N, 0.91. IR (KBr disk): nmax/cm-1 2042
(vs), 1981 (vs), 1932 (s) (C O); nmax/cm-1 1746 (s) (C O) cm-1.
1H NMR (400 MHz, CDCl3, d): 1.44 (br.s, 3H, CH3), 2.56 (br.s,
2H, NCH2CH2O), 2.64, 3.08 (2br.s, 4H, 2NCH2S), 4.11 (br.s, 2H,
2NCH2CH2O), 4.52 (br.s, 2H, CH2CH3), 7.41, 7.66 (2 s, 15H,
3C6H5). 31P NMR (121 MHz, CDCl3, 85% H3PO4, d): 65.05 (s).
13C NMR (75.4 MHz, CDCl3, d): 14.37 (CH3), 50.99 (NCH2S),
52.00 (O2CCCO2), 56.14 (NCH2CH2O), 63.59 (OCH2CH3), 64.36
(OCH2CH2N), 128.45, 128.57, 130.24, 133.45, 133.60, 135.35,
135.87 (C6H5), 163.25 (C O), 207.60, 209.68, 213.30, 213.45
(C O), C60: 71.46 (2sp3-C), 138.80 (2C), 139.13 (2C), 141.02
(4C), 141.83 (2C), 141.90 (2C), 142.22 (4C), 143.05 (8C), 143.13
(2C), 143.91 (4C), 144.57 (1C), 144.68 (8C), 144.83 (1C), 144.93
(2C), 145.06 (4C), 145.12 (4C), 145.23 (4C), 145.31 (4C). UV/vis
(toluene): lmax(loge) 283 (4.84), 329 (4.69), 428 (3.74) nm.
Preparation of [Fe2(CO)6(l-SCH2)2NCH2CH2O2C]2C(C60) (7)
A solution of 2 (0.102 g, 0.11 mmol), CBr4 (0.037 g, 0.11 mmol),
C60 (0.060 g, 0.083 mmol) and DBU (33 mL, 0.22 mmol) in toluene
(45 mL) was stirred at room temperature overnight. Volatiles were
removed under vacuum to leave a residue, which was subjected
to TLC separation using CH2Cl2/petroleum ether (v/v = 2 : 1)
as eluent. From the purple band, unreacted C60 was recovered
(0.022 g, 37%). From the main brown band, 7 (0.023 g, 26% yield
based on consumed C60) was obtained as a brown solid, mp >
300 ◦C. Calc. for C83H16Fe4N2O16S4: C, 60.47; H, 0.98; N, 1.70.
Found: C, 60.22; H, 1.08; N, 1.66. IR (KBr disk): nmax/cm-1 2072
(s), 2031 (vs), 1993 (vs) (C O); nmax/cm-1 1748 (s) (C O) cm-1.
1H NMR (300 MHz, CDCl3, d): 3.12 (br.s, 4H, 2NCH2CH2O),
3.61 (s, 8H, 4NCH2S), 4.29 (br.s, 4H, 2NCH2CH2O). 13C NMR
(100.6 MHz, CDCl3, d): 51.89 (O2CCCO2), 53.36 (NCH2S),
55.22 (NCH2CH2O), 64.94 (NCH2CH2O), 163.43 (C O), 207.79
(C O), C60: 71.35 (2sp3-C), 139.06 (4C), 141.37 (4C), 142.01 (4C),
142.43 (4C), 143.27 (4C), 143.33 (4C), 143.41 (2C), 144.13 (4C),
144.71 (2C), 144.97 (8C), 145.01 (4C), 145.08 (4C), 145.21 (2C),
145.50 (4C), 145.58 (4C). UV/vis (toluene): lmax (log e) 283 (4.76),
329 (4.69), 418 (3.79) nm.
X-Ray structure determinations of 2–4†
Single crystals of 2, 3 and 4 suitable for X-ray diffraction analyses
were grown by slow evaporation of the diethyl ether–hexane
solutions at 4 ◦C. A single crystal of 2, 3 or 4 was mounted on a
Rigaku MM-007 (rotating anode) diffractometer equipped with
Saturn 70CCD. Data were collected at 113(2) K, using a confocal
Preparation of [(l-SCH2)2NCH2CH2O2CC(C60)CO2Et]Fe2(CO)5-
(PPh3) (8)
˚
monochromator with Mo-Ka radiation (l = 0.71070 A) in the
w-f scanning mode. Data collection, reduction and absorption
correction were performed by CRYSTALCLEAR program.51 All
the structures were solved by direct methods using the SHELXS-
97 program52 and refined by full-matrix least-squares techniques
(SHELXL-97)53 on F2. Hydrogen atoms were located using the
geometric method. Details of crystal data, data collections, and
structure refinements are summarized in Table 3.
A solution of 3 (0.036 g, 0.046 mmol), CBr4 (0.015 g, 0.046 mmol),
C60 (0.024 g, 0.033 mmol) and DBU (14 mL, 0.092 mmol) in toluene
(30 mL) was stirred at room temperature overnight. Volatiles were
removed under vacuum and the residue was subjected to TLC
separation using CH2Cl2/petroleum ether (v/v = 2 : 1) as eluent.
From the purple band, unreacted C60 was recovered (0.006 g,
Table 3 Crystal data and structure refinements details for 2–4
Compound
2
3
4
Formula
Mw
C46H36Fe8N4O32S8
1860.07
113(2)
C32H30Fe2NO9PS2
779.36
113(2)
Monoclinic
P21/n
9.602(2)
13.745(3)
26.295(5)
90
99.03(3)
90
3428(1)
4
0.18 ¥ 0.14 ¥ 0.10
1.510
1.068
1600
24 433
6044
C49H45Fe2NO8P2S2
1013.62
113(2)
T/K
Crystal system
Triclinic
Triclinic
¯
¯
Space group
P1
P1
˚
a/A
11.678(2)
13.501(3)
22.620(5)
76.07(3)
81.03(3)
86.86(3)
3419(1)
2
11.763(2)
12.631(3)
15.726(3)
83.04(3)
88.31(3)
86.74(3)
2315.1(8)
2
˚
b/A
˚
c/A
a/◦
b/◦
g /◦
3
˚
V/A
Z
Crystal size/mm
0.20 ¥ 0.16 ¥ 0.12
1.807
1.980
1864
23 566
12 008
1.55/25.02
0.0377
0.0741
0.16 ¥ 0.14 ¥ 0.10
1.454
0.841
1048
15 730
8091
1.63/25.02
0.0404
0.1044
Dc/g cm-3
m/mm-1
F(000)
Reflns collected
Reflns u◦nique
qmin/max
/
3.07/25.02
0.0541
0.0878
1.006
0.429/-0.397
Final R
Final Rw
GOF on F2
1.023
0.477/-0.570
1.043
1.206/-1.063
-3
˚
Drmax/min/e A
844 | Dalton Trans., 2011, 40, 837–846
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©

View Article Online
DFT computational details
29 B. E. Barton and T. B. Rauchfuss, Inorg. Chem., 2008, 47, 2261–2263.
30 M. H. Cheah, C. Tard, S. J. Borg, X.-M. Liu, S. K. Ibrahim, C. J. Pickett
and S. P. Best, J. Am. Chem. Soc., 2007, 129, 11085–11092.
31 (a) G. Eilers, L. Schwartz, M. Stein, G. Zampella, L. De Gioia, S. Ott
and R. Lomoth, Chem.–Eur. J., 2007, 13, 7075–7084; (b) S. Ezzaher, J.-
F. Capon, F. Gloaguen, F. Y. Pe´tillon, P. Schollhammer and J. Talarmin,
Inorg. Chem., 2009, 48, 2–4; (c) L.-C. Song, C.-G. Li, J. Gao, B.-S. Yin,
X. Luo, X.-G. Zhang, H.-L. Bao and Q.-M. Hu, Inorg. Chem., 2008,
47, 4545–4553; (d) L.-C. Song, X.-F Liu, J.-B Ming, J.-H Ge, Z.-J Xie
and Q.-M. Hu, Organometallics, 2010, 29, 610–617; (e) W.-G. Wang,
H.-Y. Wang, G. Si, C.-H. Tung and L.-Z. Wu, Dalton Trans., 2009,
2712–2720; (f) J. Windhager, M. Rudolph, S. Bra¨utigam, H. Go¨rls and
W. Weigand, Eur. J. Inorg. Chem., 2007, 2748–2760; (g) M. K. Harb,
J. Windhager, A. Daraosheh, H. Go¨rls, L. T. Lockett, N. Okumura,
D. H. Evans, R. S. Glass, D. L. Lichtenberger, M. El-khateeb and W.
Weigand, Eur. J. Inorg. Chem., 2009, 3414–3420; (h) R. J. Wright, C.
Lim and T. D. Tilley, Chem.–Eur. J., 2009, 15, 8518–8525.
32 (a) Y. Nicolet, A. L. De Lacey, X. Verne`de, V. M. Fernandez, E. C.
Hatchikian and J. C. Fontecilla-Camps, J. Am. Chem. Soc., 2001, 123,
1596–1601; (b) H.-J. Fan and M. B. Hall, J. Am. Chem. Soc., 2001, 123,
3828–3829.
Geometry optimization has been carried out with Gaussian03.54
The electronic wave function was determined with the hybrid
B3LYP55 level of theory. The 6-31G(d) basis set is applied on C, H,
O, and N atoms, and an all-electron valence triple-z basis set with
polarization functions (TZVP)56 on Fe, S, and P atoms. Normal
mode frequencies were calculated on the optimized structure to
confirm that the minimum is located.
Acknowledgements
We are grateful to the National Natural Science Foundation of
China (20772059, 20972073) and the Tianjin Natural Science
Foundation (09JCZDJC27900) for financial support.
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