Synthesis, structural characterization, and properties of some functionalized phosphine-containing diiron complexes as models for the active site of [FeFe]-hydrogenases

Article abstract of DOI:10.1021/om300418z

The first phosphinobenzaldehyde- and phosphinoporphyrin-functionalized model complexes (1-4) have been synthesized and structurally characterized. Thus, reaction of diiron complex [(μ-SCH₂)₂CH ₂]Fe₂(CO)₆

Full text of DOI:10.1021/om300418z

Article
pubs.acs.org/Organometallics
Synthesis, Structural Characterization, and Properties of Some
Functionalized Phosphine-Containing Diiron Complexes As Models
for the Active Site of [FeFe]-Hydrogenases
Li-Cheng Song,* Liang-Xing Wang, Guo-Jun Jia, Qian-Li Li, and Jiang-Bo Ming
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China
S
* Supporting Information
ABSTRACT: The first phosphinobenzaldehyde- and phosphinoporphyrin-function-
alized model complexes (1−4) have been synthesized and structurally characterized.
Thus, reaction of diiron complex [(μ-SCH2)2CH2]Fe2(CO)6 or [(μ-
SCH2)2NC6H4CO2Me-p]Fe2(CO)6 with p-Ph2PC6H4CHO in the presence of
Me3NO gave the phosphinobenzaldehyde-functionalized model complexes [(μ-
SCH2)2CH2]Fe2(CO)5(p-Ph2PC6H4CHO) (1) and [(μ-SCH2)2NC6H4CO2Me-p]-
Fe2(CO)5(p-Ph2PC6H4CHO) (2) in 61% and 71% yields, respectively. Further
reaction of 1 or 2 with PhCHO, pyrrole, and BF3·OEt2 followed by treatment with p-
chloranil resulted in formation of the phosphinoporphyrin-functionalized model
complexes 5-{[(μ-SCH2)2CH2]Fe2(CO)5(p-Ph2PC6H4)}-10,15,20-triphenylporphyrin
(3) and 5-{[(μ-SCH2)2NC6H4CO2Me-p]Fe2(CO)5(p-Ph2PC6H4)}-10,15,20-triphenyl-
porphyrin (4) in 19% and 18% yields, respectively. While the new complexes 1−4 were
characterized by elemental analysis and spectroscopy, the structures of 1, 3, and 4 were
confirmed by X-ray crystallography. Particularly interesting is that complex 4 was found to be a catalyst for the photoinduced H2
production in the presence of the electron donor EtSH and the proton source HOAc.
Scheme 1. Basic Structure of the H-Cluster Determined by
Protein X-ray Crystallography
INTRODUCTION
■
[FeFe]-hydrogenases ([FeFe]Hases) are natural metalloen-
zymes that can catalyze the proton reduction to hydrogen at
surprising rapidity in a variety of microbes.1 In recent years,
[FeFe]Hases have received considerable attention, largely
because of their unique structure and particularly their special
function for production of hydrogen, an alternative “clean”
energy source.2,3 The X-ray crystallographic4 and IR spectro-
scopic5 studies have revealed that the active site of [FeFe]-
Hases, the so-called H-cluster,6 mainly consists of a butterfly
Fe2S2 cluster and a cubane-like Fe4S4 cluster, which are linked
together through a cysteine S atom. In addition, the two iron
atoms in the Fe2S2 cluster are coordinated by CO and CN−
diatomic ligands and are bridged by a less defined dithiolate
ligand. This dithiolate was recently suggested as an azadithiolate
(ADT, SCH2NHCH2S) in which the bridgehead N atom plays
an important role in the heterolytic cleavage or formation of
hydrogen catalyzed by the natural enzymes7,8 (Scheme 1). To
date, numerous H-cluster models have been prepared from the
simple diiron all-carbonyl complexes such as (μ-PDT)-
Fe2(CO)6 (PDT = propanedithiolate), (μ-ADT)Fe2(CO)6,
(μ-ODT)Fe2(CO)6 (ODT = oxadithiolate), (μ-TDT)-
Fe2(CO)6 (TDT = thiodithiolate), and (μ-PDS)Fe2(CO)6
(PDS = propanediselenolate) by CO substitution reactions
with various electron donors such as CN−, R3P, RNC, and
NHC ligands.9−21 This is because such simple dinuclear
complexes are known to bear striking structural similarities to
the H-cluster and the electron donors can make their iron
atoms more electron-rich and thus more easily accepting of a
proton for catalytic H2 production.
In this article, we will describe the synthesis, structural
characterization, and some properties of the novel function-
alized phosphine-containing model complexes in which two of
them contain a benzaldehyde-functionalized phosphine and
another two have a porphyrin-functionalized phosphine. It
should be pointed out that the former two were mainly used in
this article as precursors to prepare the latter two, and the latter
two actually belong to light-driven-type models since they
contain a photosensitizer porphyrin macrocycle.22−26
Received: May 15, 2012
Published: July 5, 2012
© 2012 American Chemical Society
5081
dx.doi.org/10.1021/om300418z | Organometallics 2012, 31, 5081−5088

Organometallics
Article
RESULTS AND DISCUSSION
■
Synthesis and Characterization of Model Complexes
1 and 2 with a Benzaldehyde-Functionalized Phosphine
Ligand. We found that treatment of the PDT- and ADT-type
model complexes [(μ-SCH2)2CH2]Fe2(CO)6 and [(μ-
SCH2)2NC6H4CO2Me-p]Fe2(CO)6 with 1 equiv of
Me3NO·2H2O in CH2Cl2/MeCN at room temperature,
followed by treatment with 1 equiv of p-Ph2PC6H4CHO,
gave rise to the corresponding benzaldehyde-functionalized
phosphine-substituted model complexes [(μ-SCH2)2CH2]-
F e 2 ( C O ) 5 ( p - P h 2 P C 6 H 4 C H O ) ( 1 ) a n d [ ( μ -
SCH2)2NC6H4CO2Me-p]Fe2(CO)5(p-Ph2PC6H4CHO) (2) in
61% and 71% yields, respectively (Scheme 2).
Scheme 2
Figure 1. ORTEP plot of 1 with 30% probability level ellipsoids.
bond lengths in the other phosphine-substituted derivatives of
diiron all-carbonyl model complexes.29−32
Synthesis and Characterization of Model Complexes
3 and 4 with a Porphyrin-Functionalized Phosphine
Ligand. Interestingly, complexes 3 and 4 could be prepared by
the improved Lindsey method.33 Thus, treatment of the
benzaldehyde-functionalized phosphine-containing model com-
plexes 1 and 2 with benzaldehyde and pyrrole in a 1:3:4 molar
ratio in the presence of catalyst BF3·OEt2, followed by
treatment with the oxidant p-chloranil, afforded the corre-
sponding porphyrin-functionalized phosphine-substituted
model complexes 5-{[(μ-SCH2)2CH2]Fe2(CO)5(p-
Ph2PC6H4)}-10,15,20-triphenylporphyrin (3) and 5-{[(μ-
SCH2)2NC6H4CO2Me-p]Fe2(CO)5(p-Ph2PC6H4)}-10,15,20-
triphenylporphyrin (4) in 19% and 18% yields along with a
given amount of tetraphenylporphyrin (H2TPP), respectively
(Scheme 3).
Complexes 3 and 4 are also air-stable solids, which were fully
characterized by elemental analysis, spectroscopy, and X-ray
crystal diffraction analysis. For instance, the IR spectra of 3 and
4 showed three absorption bands in the range 2044−1933 cm−1
for their terminal carbonyls and three absorption bands in the
range 1660−1350 cm−1 for the skeletal vibrations of the pyrrole
rings in their porphyrin macrocycle.34 In addition, the 1H NMR
spectra of 3 and 4 exhibited one singlet at −2.93 and −2.80
ppm for their pyrrole NH groups, and the 31P{1H} NMR
spectra of 3 and 4 showed a singlet at 66.04 and 65.60 ppm for
their P atoms, respectively.
The UV−vis absorption spectra and fluorescence emission
spectra of 3 and 4, along with those of H2TPP (for
comparison), were also dertermined. As shown in Figures 2
and 3, the UV−vis spectra of 3 and 4 display one Soret band at
418 nm in the near-UV region and four Q bands at 515−645
nm in the visible range.35 These Soret and Q bands are almost
the same as those of H2TPP determined under the same
conditions. In addition, as can be seen in Figures 4 and 5,
complexes 3 and 4 exhibit two fluorescence emission bands at
650 and 716 nm. The two emission bands are also nearly the
same as the corresponding bands of H2TPP under the same
determined conditions, although their intensities are strongly
quenched relative to those of the H2TPP bands, with a
quenching efficiency, Q, of 70% and 61%, respectively.
According to the previously reported similar cases,22,23 the
remarkably decreased intensities of the two fluorescence
Complexes 1 and 2 are air-stable red solids, which were
characterized by elemental analysis and IR, H NMR, and
1
31P{1H} NMR spectroscopy. The IR spectra of 1 and 2
displayed one strong absorption band at ca. 1704 cm−1 for their
formyl groups and three absorption bands in the range 2047−
1929 cm−1 for their terminal carbonyls. The three νCO
absorption bands of 1 and 2 are much lower than those
corresponding to their parent complexes,27,28 which is
obviously due to the increased strength of the back-bonding
between their iron atoms and the attached carbonyls caused by
CO substitution with the stronger electron-donating phosphine
ligand p-Ph2PC6H4CHO. In addition, the 1H NMR spectra of 1
and 2 exhibited a singlet at 10.06 and 10.07 ppm for their
formyl groups, whereas the 31P{1H} NMR spectra of 1 and 2
showed a singlet at 67.09 and 66.63 ppm for their P atoms,
respectively.
The molecular structure of 1 was unambiguously confirmed
by X-ray crystal diffraction analysis. While the ORTEP plot of 1
is presented in Figure 1, selected bond lengths and angles are
listed in Table 1.
Figure 1 shows that complex 1 contains a propanedithiolate
ligand, which is bridged between the Fe(1) and Fe(2) atoms of
the diiron subsite to form two fused six-membered rings of the
chair-shaped Fe(1)S(1)C(8)C(7)C(6)S(2) and boat-shaped
Fe(2)S(1)C(8)C(7)C(6)S(2). In addition, the benzaldehyde-
functionalized phosphine ligand is shown to occupy the apical
position of the square-pyramidal geometry of the Fe(2) atom
and is cis to its bridgehead C(7) atom. While the C(27)−O(6)
double-bond length is 1.209 Å, the Fe(2)−P(1) and Fe(1)−
Fe(2) single-bond lengths are equal to 2.2538 and 2.5329 Å,
which are very close to the corresponding Fe−P and Fe−Fe
5082
dx.doi.org/10.1021/om300418z | Organometallics 2012, 31, 5081−5088

Organometallics
Article
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 1
Fe(1)−S(1)
Fe(1)−S(2)
S(1)−C(8)
S(2)−C(6)
S(2)−Fe(1)−S(1)
S(2)−Fe(1)−Fe(2)
Fe(1)−S(2)−Fe(2)
C(8)−S(1)−Fe(2)
2.2734(13)
2.2590(15)
1.833(4)
Fe(1)−Fe(2)
Fe(2)−S(1)
Fe(2)−S(2)
Fe(2)−P(1)
C(8)−S(1)−Fe(1)
C(15)−P(1)−Fe(2)
C(9)−P(1)−Fe(2)
C(21)−P(1)−Fe(2)
2.5329(11)
2.2731(16)
2.2747(15)
2.2538(13)
110.46(15)
119.74(13)
111.45(11)
116.93(12)
1.824(4)
84.45(5)
56.33(4)
67.93(3)
114.12(14)
Scheme 3
Figure 3. UV−vis spectra of 4 and H2TPP in CH2Cl2 (5 × 10−6 M).
The Soret band absorptions were normalized and the spectra were
amplified 10-fold in the Q-band region.
Figure 2. UV−vis spectra of 3 and H2TPP in CH2Cl2 (5 × 10−6 M).
The Soret band absorptions were normalized and the spectra were
amplified 10-fold in the Q-band region.
To further confirm the molecular structures of 3 and 4, as
well as to further understand the relationship between their
structures and properties, the X-ray crystallographic studies of 3
and 4 were undertaken. While ORTEP plots of 3 and 4 are
depicted in Figures 6 and 7, Table 2 lists their selected bond
lengths and angles.
emission bands of 3 and 4 relative to those of H2TPP could be
attributed to the strong intramolecular electron transfer (ET)
from the photoexcited state of the porphyrin macrocycle to the
diiron subsite via the coordinatively bonded phosphine moiety.
It should be noted that such an intramolecular ET is one of the
important steps required for the proton reduction to hydrogen
catalyzed by the natural enzymes.
The X-ray diffraction analysis of complex 3 revealed that (i)
it contains a diiron-PDT moiety in which the six-membered
5083
dx.doi.org/10.1021/om300418z | Organometallics 2012, 31, 5081−5088

Organometallics
Article
Figure 4. Fluorescence emission spectra (λex = 412 nm) of 3 and
H2TPP in CH2Cl2 (5 × 10−6 M).
Figure 6. ORTEP plot of 3 with 30% probability level ellipsoids.
Figure 5. Fluorescence emission spectra (λex = 410 nm) of 4 and
H2TPP in CH2Cl2 (5 × 10−6 M).
rings Fe(2)S(1)C(6)C(7)C(8)S(2) and Fe(1)S(1)C(6)C(7)-
C(8)S(2) adopt a chair conformation and a boat conformation,
respectively; (ii) the porphyrin-functionalized phosphine ligand
is connected to the Fe(1) atom of the diiron subsite and
located in an apical position of the square-pyramidal geometry
of the Fe(1) atom; (iii) the four benzene rings are twisted
relative to the planar porphyrin macrocycle with a dihedral
angle from 68.5° to 85.9° in order to minimize the steric
repulsions between the two ortho-hydrogen atoms in each of
the four phenyl groups with the two proximal pyrrole rings; and
(iv) the Fe(1)−P(1) (2.2376 Å) and Fe(1)−Fe(2) (2.5074 Å)
bond lengths are slightly shorter than the Fe(2)−P(1) and
Fe(1)−Fe(2) bond lengths in its parent complex 1, whereas the
C−N bond lengths in its pyrrole rings are almost the same
(1.366−1.378 Å) and lie between those of normal single and
double C−N bonds.36 Interestingly, in contrast to 3, the X-ray
diffraction analysis of complex 4 indicated that (i) it contains a
diiron-ADT moiety in which the boat-shaped ring Fe(1)S(1)-
C(10)N(1)C(9)S(2) is fused to a chair-shaped ring Fe(2)-
S(1)C(10)N(1)C(9)S(2) and the substituent p-MeO2C6H4 is
attached to the N(1) atom via the common axial bond N(1)−
C(6) of the aforementioned two six-membered rings; (ii)
although complex 4 includes the same porphyrin-functionalized
phosphine ligand as that of 3, it is coordinated to Fe(2) of the
Figure 7. ORTEP plot of 4 with 30% probability level ellipsoids.
diiron subsite and located in a basal position of the square-
pyramidal Fe(2); and (iii) the four benzene rings around the
porphyrin macrocycle of 4 are twisted with a smaller dihedral
5084
dx.doi.org/10.1021/om300418z | Organometallics 2012, 31, 5081−5088

Organometallics
Article
Table 2. Selected Bond Lengths (Å) and Angles (deg) for 3 and 4
Complex 3
Fe(1)−S(1)
Fe(1)−S(2)
S(1)−C(6)
S(2)−C(8)
S(1)−Fe(1)−S(2)
S(1)−Fe(1)−Fe(2)
Fe(1)−S(1)−Fe(2)
C(8)−S(2)−Fe(1)
2.2605(10)
2.2659(10)
1.822(4)
Fe(1)−Fe(2)
Fe(2)−S(1)
Fe(2)−S(2)
Fe(1)−P(1)
C(8)−S(2)−Fe(2)
C(21)−P(1)−Fe(1)
C(9)−P(1)−Fe(1)
C(15)−P(1)−Fe(1)
2.5074(7)
2.2708(10)
2.2555(11)
2.2376(10)
109.35(15)
114.10(11)
112.31(12)
120.27(12)
1.840(4)
84.43(4)
56.60(3)
67.19(3)
114.61(13)
Complex 4
Fe(1)−S(1)
Fe(1)−S(2)
S(2)−C(9)
S(1)−C(10)
2.2716(17)
2.2542(17)
1.861(5)
Fe(2)−S(1)
Fe(2)−S(2)
Fe(2)−P(1)
N(1)−C(6)
2.2538(16)
2.2728(16)
2.2397(16)
1.401(7)
1.848(5)
Fe(1)−Fe(2)
2.5434(12)
83.88(6)
O(2)−C(2)
1.185(7)
S(2)−Fe(1)−S(1)
S(2)−Fe(1)−Fe(2)
S(1)−Fe(1)−Fe(2)
Fe(2)−S(1)−Fe(1)
C(9)−S(2)−Fe(1)
C(9)−S(2)−Fe(2)
C(16)−P(1)−Fe(2)
C(28)−P(1)−Fe(2)
C(22)−P(1)−Fe(2)
C(6)−N(1)−C(10)
C(6)−N(1)−C(9)
C(10)−N(1)−C(9)
113.25(17)
118.68(18)
116.51(18)
121.0(5)
56.16(4)
55.47(5)
68.39(5)
110.45(18)
113.54(19)
123.3(5)
113.8(5)
angle, from 63.0° to 64.8°. However, the C−N bond lengths
(1.361−1.378 Å) in the pyrrole rings of 4 are also nearly the
same as those of 3 and lie between those of normal single and
double C−N bonds.36 Finally, it should be noted that although
some porphyrin-containing light-driven-type model complexes
are known,22,24,25 complexes 3 and 4 are the first prepared and
crystallographically characterized light-driven-type models
containing a porphyrin-functionalized phosphine coordinated
to an Fe atom of the diiron subsite.
Table 3. Photocatalytic H2 Production Experiments in
CH2Cl2 Solutions by Using EtSH as the Sacrificial Electron
a
Donor
electron
donor
proton
source
irradiation time
(min)
entry photocatalyst
TON
1
2
3
4
5
model 4
model 4
model 4
model 4
EtSH
EtSH
HOAc
20
20
20
0.50
0.03
0.09
0
HOAc
HOAc
HOAc
EtSH
EtSH
Photoinduced Hydrogen Production Catalyzed by Light-
Driven Model 4. The photoinduced catalytic systems for H2
production usually comprise four separate components: an
electron donor, a photosensitizer, a catalyst, and a proton
source.37−41 However, recently we reported a study on
photoinduced H2 production by using a three-component
system. This system consists of an electron donor, a proton
source, and a light-driven model that has a photosensitizer
tetraphenylporphyrin moiety covalently bonded to the bridge-
head N atom of a simple ADT-type model for the active site of
[FeFe]Hases.24 In order to examine if our light-driven models 3
and 4 could behave as photoactive catalysts to accomplish the
expected H2 production, we chose 4 to constitute a three-
component system with an electron donor and a proton source
to carry out the expected H2 production experiments. It was
found that H2 was indeed produced when a 500 W Hg lamp
with a UV cutoff filter (λ >400 nm) irradiated a CH2Cl2
solution consisting of model 4, electron donor EtSH, and
proton source HOAc (entry 1, Table 3). However, when the
same experiment was carried out in the absence of EtSH or
HOAc, only a trace amount of H2 was evolved (entries 2/3,
Table 3), and no H2 could be detected when the experiment
was run without light irradiation or in the absence of model 4
(entries 4/5, Table 3). It follows that the presence of electron
donor EtSH, proton source HOAc, and light-driven model 4, as
well as the light irradiation, are essential for such photoinduced
H2 production. Figure 8 shows the time dependence of
photoinduced H2 production. As can be seen in Figure 8, the
H2 evolution is linearly increased during the first 10 min of
20
0
a
TONs are calculated based on model 4.
Figure 8. Time dependence of photoinduced H2 production from
CH2Cl2 solutions (10 mL) consisting of EtSH (10 mM) and HOAc
(10 mM) catalyzed by model 4 (0.1 mM).
irradiation and then increased very slowly, and finally the total
20 min irradiation produces 0.5 × 10−3 mmol of H2.
CONCLUSIONS
■
We have prepared the first phosphinobenzaldehyde and
phosphinoporphyrin ligand-containing H-cluster models 1−4
via convenient synthetic routes, and their structures are fully
5085
dx.doi.org/10.1021/om300418z | Organometallics 2012, 31, 5081−5088

Organometallics
Article
71%), mp 170−172 °C. Anal. Calcd for C34H26Fe2NO8PS2: C, 52.13;
characterized by combustion analysis, various spectroscopies,
and X-ray crystallography. It is shown that the phosphino-
benzaldehyde-functionalized model complexes 1 and 2 can be
prepared by the Me3NO-promoted CO substitution reactions
of diiron complex [(μ-SCH2)2CH2]Fe2(CO)6 or [(μ-
SCH2)2NC6H4CO2Me-p]Fe2(CO)6 with p-Ph2PC6H4CHO,
whereas the improved Lindsey’s cyclization reaction of 1 or 2
with PhCHO, pyrrole, and BF3·OEt2 followed by treatment
with p-chloranil gives rise to the phosphinoporphyrin-function-
alized model complexes 3 and 4, respectively. It is interesting to
note that the phosphinobenzaldehyde and phosphinoporphyrin
ligands in 1 and 3 have been proved by X-ray crystallography to
coordinate to their square-pyramidal Fe atoms in an apical
position, whereas the phosphinoporphyrin ligand in 4 is
coordinated to its square-pyramidal Fe atom in a basal position
in order to minimize the strong steric repulsion between the N-
substituent p-MeO2CC6H4 and the bulky phosphinoporphyrin
ligand. In addition, light-driven model 4 is found to be a
catalyst for the photoinduced H2 production, although its
catalytic efficiency is considerably low. Further studies on
improvement of the photocatalytic activity of model 4 by
replacement of its terminal carbonyls with other ligands10,11
and/or by coordination of its porphyrin macrocycle with
various metal cations42,43 will be carried out in this laboratory.
H, 3.35; N, 1.79. Found: C, 52.11; H, 3.34; N, 1.75. IR (KBr disk):
1
νCO 2047 (vs), 1985 (vs), 1937 (s); νCO 1705 (s) cm−1. H NMR
(400 MHz, CDCl3): 3.06 (br s, 2H, 2SCHH), 3.86 (s, 3H, OCH3),
4.13, 4.16 (2s, 2H, 2SCHH), 6.57, 6.59 (2s, 2H, 2o-H of NC6H4), 7.50
(s, 6H, 2p-H of P(C6H5)2, 4m-H of P(C6H5)2), 7.73 (br s, 4H, 4o-H of
P(C6H5)2), 7.88−7.93 (m, 6H, 2m-H of NC6H4, C6H4CHO), 10.07
(s, 1H, CHO) ppm. 31P{1H} NMR (162 MHz, CDCl3, 85% H3PO4):
66.63 (s) ppm.
Preparation of 5-{[(μ-SCH2)2CH2]Fe2(CO)5(p-Ph2P C6H4)}-
10,15,20-Triphenylporphyrin (3). The mixture of 1 (547 mg,
0.84 mmol), PhCHO (0.25 mL, 2.52 mmol), pyrrole (0.23 mL, 3.36
mmol), and BF3·OEt2 (0.043 mL, 0.34 mmol) in CH2Cl2 (340 mL)
was stirred in the dark at room temperature for 16 h to give a brown-
red solution. After p-chloranil (826 mg, 3.36 mmol) was added and the
new mixture was refluxed for 2 h, solvents were removed under
reduced pressure and the residue was subjected to flash column
chromatography (Al2O3, CH2Cl2). The eluate was reduced to a
suitable volume for TLC separation (CH2Cl2/petroleum ether, 1:1).
From the first purple band, H2TPP (90 mg, 17%) was obtained as a
1
purple solid, which was identified by comparison of its IR and H
NMR spectra with those of the authentic sample.34,47 From the second
purple-red band, complex 3 was obtained as a purple-red solid (180
mg, 19%), mp 184 °C (dec). Anal. Calcd for C64H45Fe2N4O5PS2: C,
66.45; H, 3.92, N, 4.84. Found: C, 66.42; H, 3.98; N, 4.81. IR (KBr
disk): νNH 3316 (m); νCO 2043 (vs), 1981 (vs), 1933 (s); νpyrrole ring
1
1558 (m), 1473 (m), 1350 (m) cm−1. H NMR (400 MHz, DMSO-
d6): −2.93 (s, 2H, 2NH), 1.32−1.71 (m, 4H, CHHCH2CHH), 1.96−
2.01 (m, 2H, CHHCH2CHH), 7.63−7.66 (m, 2H, 2p-H of P(C6H5)2),
7.70−7.73 (m, 4H, 4m-H of P(C6H5)2), 7.82, 7.84 (2s, 9H, 6m-H of
3C6H5, 3p-H of 3C6H5 in porphyrin) 7.92−7.98 (m, 6H, 2o-H of
PC6H4, 4o-H of P(C6H5)2), 8.21, 8.22 (2s, 6H, 6o-H of 3C6H5 in
porphyrin), 8.40, 8.42 (2s, 2H, 2m-H of PC6H4), 8.83, 8.86 (2s, 8H,
8CH of pyrrole rings) ppm. 31P{1H} NMR (162 MHz, CDCl3, 85%
H3PO4): 66.04 (s) ppm. UV−vis (CH2Cl2): λmax (log ε) 418 (4.69),
515 (3.36), 550 (3.01), 589 (2.80), 645 (2.67) nm.
EXPERIMENTAL SECTION
■
General Comments. All reactions were performed using standard
Schlenk and vacuum-line techniques under an atmosphere of highly
purified N2. Dichloromethane was distilled over CaH2 under N2.
Acetonitrile was distilled once from P2O5 and then from CaH2 under
N2. Me3NO·2H2O, EtSH, HOAc, BF3·OEt2, benzaldehyde, and
2,3,5,6-tetrachlorobenzoquinone (p-chloranil) were availably commer-
cially and used as received. Pyrrole was freshly distilled before use.
H2TPP,44 [(μ-SCH2)2CH2]Fe2(CO)6,45 p-Ph2PC6H4CHO,46 and [(μ-
Preparation of 5-{[(μ-SCH2)2NC6H4CO2Me-p]Fe2(CO)5(p-
Ph2PC6H4)}-10,15,20-Triphenylporphyrin (4). A solution of 2
(525 mg, 0.67 mmol), PhCHO (0.20 mL, 2.01 mmol), pyrrole (0.19
mL, 2.68 mmol), and BF3·OEt2 (0.034 mL, 0.27 mmol) in CH2Cl2
(268 mL) was stirred in the dark at room temperature for 16 h to give
a brown-red solution. To this solution was added p-chloranil (659 mg,
2.68 mmol), and the new mixture was heated at reflux for 2 h to give a
brown-black solution. Then, the same workup as for 3 afforded H2TPP
(74 mg, 18%) and complex 4 as a purple-red solid (145 mg, 17%), mp
172 °C (dec). Anal. Calced for C71H50Fe2N5O7PS2: C, 66.00; H, 3.90;
N, 5.42. Found: C, 66.13; H, 3.64; N, 5.47. IR (KBr disk): νNH 3316
(m); νCO 2044 (vs), 1984 (vs), 1938 (s); νCO 1714 (s); νpyrrole ring
28
SCH2)2NC6H4CO2Me-p]Fe2(CO)6 were prepared according to the
published procedures. Preparative TLC was carried out on glass plates
(26 × 20 × 0.25 cm) coated with silica gel H (10−40 μm). IR spectra
1
were recorded on a Bruker Vector 22 infrared spectrophotometer. H
and 31P{1H} NMR spectra were recorded on a Varian Mercury Plus
400 NMR spectrometer or a Bruker Avance 300 NMR spectometer.
Elemental analyses were performed on an Elementar Vario EL
analyzer. Melting points were determined on a Yanaco MP-500
apparatus and were uncorrected.
Preparation of [(μ-SCH2)2CH2]Fe2(CO)5(p-Ph2PC6H4CHO) (1).
To the red solution of [(μ-SCH2)2CH2]Fe2(CO)6 (405 mg, 1.05
mmol) in CH2Cl2 (10 mL) was added a solution of Me3NO·2H2O
(116 mg, 1.05 mmol) in MeCN (10 mL), and then the mixture was
stirred at room temperature for about 20 min until its color turned
dark brown. After a CH2Cl2 (10 mL) solution of p-Ph2PC6H4CHO
(305 mg, 1.05 mmol) was added and the new mixture was stirred for
an additional 1 h, solvents were removed at reduced pressure and the
residue was subjected to TLC separation by using acetone/petroleum
ether (1:3 v/v) as eluent to give 1 as a red solid (412 mg, 61%), mp
158−160 °C. Anal. Calcd for C27H21Fe2O6PS2: C, 50.03; H, 3.27.
1
1660 (m), 1474 (m), 1351 (m) cm−1. H NMR (400 MHz, CDCl3):
−2.80 (s, 2H, 2NH), 3.26 (br s, 2H, 2SCHH), 3.87 (s, 3H, OCH3),
4.28, 4.31(2s, 2H, 2SCHH), 6.66, 6.68 (2s, 2H, 2o-H of NC6H4), 7.60,
7.61 (2s, 6H, 4m-H of P(C6H5)2, 2p-H of P(C6H5)2), 7.75, 7.77 (2s,
9H, 6m-H of 3C6H5, 3p-H of 3C6H5 in porphyrin), 7.92, 7.94 (2s, 2H,
2m-H of NC6H4), 7.99−8.03 (m, 4H, 4o-H of P(C6H5)2), 8.08−8.13
(m, 2H, 2o-H of PC6H4), 8.19, 8.22 (2s, 6H, 6o-H of 3C6H5 in
porphyrin), 8.30, 8.32 (2s, 2H, 2m-H of PC6H4), 8.81, 8.85 (2s, 8H,
8CH of pyrrole rings) ppm. 31P{1H} NMR (162 MHz, CDCl3, 85%
H3PO4): 65.60 (s) ppm. UV−vis (CH2Cl2): λmax (log ε) 418 (4.63),
515 (3.30), 549 (2.97), 589 (2.78), 645 (2.66) nm.
Photoinduced H2 Production Catalyzed by Light-Driven
Model 4. A 30 mL Schlenk flask fitted with a N2 inlet tube, a serum
cap, a magnetic stir-bar, and a water-cooling jacket was charged with
model 4 (1.29 mg, 0.001 mmol), EtSH (7 μL, 0.1 mmol), HOAc (6
μL, 0.1 mmol), and CH2Cl2 (10 mL). While stirring, the resulting
solution was thoroughly deoxygenated by bubbling with nitrogen and
then was irradiated through a Pyrex glass filter (λ > 400 nm) using a
500 W Hg lamp at about 25 °C (controlled by the cooling jacket). The
purpose of using such a UV cutoff filter is to obtain visible light and to
avoid decomposition of EtSH.35 During the photoinduced catalysis,
the evolved H2 was withdrawn periodically using a gastight syringe,
Found: C, 50.08; H, 3.44. IR (KBr disk): νCO 2046 (vs), 1986 (vs),
1
1929 (s); ν
1703 (s) cm−1. H NMR (300 MHz, DMSO-d6):
CO
1.05−1.47 (m, 4H, CHHCH2CHH), 1.76−1.82 (m, 2H,
CHHCH2CHH), 7.58−7.65 (m, 10H, 2C6H5), 7.74−7.80 (m, 2H, 2
m-H of C6H4CHO), 8.05, 8.07 (2s, 2H, 2 o-H of C6H4CHO), 10.06
(s, 1H, CHO) ppm. 31P{1H} NMR (121 MHz, CDCl3, 85% H3PO4):
67.09 (s) ppm.
Preparation of [(μ-SCH2)2NC6H4CO2Me-p]Fe2(CO)5(p-
Ph2PC6H4CHO) (2). The same procedure was followed as for 1,
except that [(μ-SCH2)2NC6H4CO2Me-p]Fe2(CO)6 (440 mg, 0.84
mmol), Me3NO·2H2O (93 mg, 0.84 mmol), and p-Ph2PC6H4CHO
(245 mg, 0.84 mmol) were utilized and by using acetone/petroleum
ether (1:3 v/v) as eluent. 2 was separated as a red solid (471 mg,
5086
dx.doi.org/10.1021/om300418z | Organometallics 2012, 31, 5081−5088

Organometallics
Article
Table 4. Crystal Data and Structural Refinement Details for 1, 3, and 4
1
3
4
mol formula
mol wt
C27H21Fe2O6PS2
648.23
C64H45Fe2N4O5PS2·2CH2Cl2
1326.68
C71H52Fe2N5O7PS2
1293.97
cryst syst
space group
a/Å
monoclinic
P21/c
monoclinic
P21/c
triclinic
P1
̅
8.523(5)
17.128(9)
18.972(11)
90
15.0944(6)
8.8897(3)
46.427(2)
90
12.102(2)
14.449(3)
17.298(3)
78.937(5)
85.694(6)
86.281(5)
2956.2(9)
2
b/Å
c/Å
α/deg
β/deg
95.871(5)
90
97.235(2)
90
γ/deg
V/Å3
2755(3)
4
6180.1(4)
4
Z
Dc/g·cm−3
abs coeff/mm−1
F(000)
1.563
1.426
1.454
1.303
0.789
0.651
1320
2720
1336
2θmax/deg
no. of rflns
no. of indep rflns
index ranges
55.76
55.78
54.00
25 473
48 749
30 573
6554
14 228
10 413
−10 ≤ h ≤ 11
−22 ≤ k ≤ 22
−24 ≤ l ≤ 24
0.940
−19 ≤ h ≤ 19
−11 ≤ k ≤ 11
−61 ≤ l ≤ 60
1.120
−14 ≤ h ≤ 14
−17≤ k ≤ 17
−20 ≤ l ≤ 20
1.050
goodness of fit
R
0.0539
0.0734
0.0742
Rw
0.1463
0.1683
0.1455
largest diff peak and hole/e Å−3
0.318/−0.589
0.980/−1.037
0.648/−0.524
which was analyzed by gas chromatography on a Shimadazu GC-2014
instrument with a thermal conductivity detector and a carbon
molecular sieve column (3 mm × 2.0 m) and N2 as the carrier gas.
The total amount of H2 produced during 20 min irradiation is 0.5 ×
10−3 mmol.
ACKNOWLEDGMENTS
■
We are grateful to the National Natural Science Foundation of
China (21132001, 20972073), 973 (2011CB935902), and the
Tianjin Natural Science Foundation (09JCZDJC27900) for
financial support.
X-ray Structure Determinations of 1, 3, and 4. Single crystals
of 1, 3, and 4 suitable for X-ray diffraction analyses were grown by
slow evaporation of a CH2Cl2 solution of 1 and a slow diffusion of
MeOH to CH2Cl2 solution of 3 or 4 at room temperature. A single
crystal of 1, 3, or 4 was mounted on a Rigaku MM-007 (rotating
anode) diffractometer equipped with a Saturn 70CCD. Data were
collected at room temperature for 1 and 113 K for 3 and 4, using a
confocal monochromator with Mo Kα radiation (λ = 0.71070 Å) in
the ω−ϕ scanning mode. Data collection, reduction, and absorption
correction were performed with the CRYSTALCLEAR program.48
The structures were solved by direct methods using the SHELXS-97
program49 and refined by full-matrix least-squares techniques
(SHELXL-97)50 on F2. Hydrogen atoms were located by using the
geometric method. Details of crystal data, data collections, and
structure refinements are summarized in Table 4.
REFERENCES
■
(1) (a) Adams, M. W. W.; Stiefel, E. I. Science 1998, 282, 1842.
(b) Cammack, R. Nature 1999, 397, 214.
(2) (a) Evans, D. J.; Pickett, C. J. Chem. Soc. Rev. 2003, 32, 268.
(b) Song, L.-C. Acc. Chem. Res. 2005, 38, 21. (c) Lubitz, W.; Tumas,
W. Chem. Rev. 2007, 107, 3900.
(3) (a) Graetzel, M. Acc. Chem. Res. 1981, 14, 376. (b) Bard, A. J.;
Fox, M. A. Acc. Chem. Res. 1995, 28, 141. (c) Alper, J. Science 2003,
299, 1686.
(4) (a) Peters, J. W.; Lanzilotta, W. N.; Lemon, B. J.; Seefeldt, L. C.
Science 1998, 282, 1853. (b) Nicolet, Y.; Piras, C.; Legrand, P.;
Hatchikian, E. C.; Fontecilla-Camps, J. C. Structure 1999, 7, 13.
̀
(c) Nicolet, Y.; De Lacey, A. L.; Vernede, X.; Fernandez, V. M.;
Hatchikian, E. C.; Fontecilla-Camps, J. C. J. Am. Chem. Soc. 2001, 123,
1596. (d) Lemon, B. J.; Peters, J. W. Biochemistry 1999, 38, 12969.
(5) (a) Pierik, A. J.; Hulstein, M.; Hagen, W. R.; Albracht, S. P. J. Eur.
J. Biochem. 1998, 258, 572. (b) De Lacey, A. L.; Stadler, C.; Cavazza,
C.; Hatchikian, E. C.; Fernandez, V. M. J. Am. Chem. Soc. 2000, 122,
11232. (c) Chen, Z.; Lemon, B. J.; Huang, S.; Swartz, D. J.; Peters, J.
W.; Bagley, K. A. Biochemistry 2002, 41, 2036.
(6) Adams, M. W. W. Biochim. Biophys. Acta 1990, 1020, 115.
(7) Nicolet, Y.; Lemon, B. J.; Fontecilla-Camps, J. C.; Peters, J. W.
Trends Biochem. Sci. 2000, 25, 138.
(8) Fan, H.; Hail, M. B. J. Am. Chem. Soc. 2001, 123, 3828.
(9) (a) Gloaguen, F.; Lawrence, J. D.; Schmidt, M.; Wilson, S. R.;
Rauchfuss, T. B. J. Am. Chem. Soc. 2001, 123, 12518. (b) Liu, T.;
Darensbourg, M. Y. J. Am. Chem. Soc. 2007, 129, 7008. (c) Liu, Y.-C.;
Lee, C.-H.; Lee, G.-H.; Chiang, M.-H. Eur. J. Inorg. Chem. 2011, 1155.
(10) Nehring, J. L.; Heinekey, D. M. Inorg. Chem. 2003, 42, 4288.
ASSOCIATED CONTENT
■
S
* Supporting Information
Full tables of crystal data, atomic coordinates and thermal
parameters, and bond lengths and angles for 1, 3, and 4 as CIF
files. This material is available free of charge via the Internet at
http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: lcsong@nankai.edu.cn.
Notes
The authors declare no competing financial interest.
5087
dx.doi.org/10.1021/om300418z | Organometallics 2012, 31, 5081−5088

Organometallics
Article
(11) Capon, J.-F.; Hassnaoui, S. E.; Gloaguen, F.; Schollhammer, P.;
Talarmin, J. Organometallics 2005, 24, 2020.
(43) Okura, I. Coord. Chem. Rev. 1985, 68, 53.
(44) Adler, A. D.; Longo, F. R.; Finarelli, J. D.; Goldamcher, J.;
Assour, J.; Korsakoff, L. J. Org. Chem. 1967, 32, 476.
(45) Seyferth, D.; Henderson, R. S.; Song, L.-C. J. Organomet. Chem.
1980, 192, C1.
(46) Wang, Y.; Lai, C. W.; Kwong, F. Y.; Jia, W.; Chan, K. S.
Tetrahedron 2004, 60, 9433.
(12) (a) Lawrence, J. D.; Li, H.; Rauchfuss, T. B. Angew. Chem., Int.
Ed. 2001, 40, 1768. (b) Song, L.-C.; Ge, J.-H.; Zhang, X.-G.; Liu, Y.;
Hu, Q.-M. Eur. J. Inorg. Chem. 2006, 3204. (c) Schwartz, L.; Eilers, G.;
Eriksson, L.; Gogoll, A.; Lomoth, R.; Ott, S. Chem. Commun. 2006,
520.
(47) Bookser, B. C.; Bruice, T. C. J. Am. Chem. Soc. 1991, 113, 4208.
(48) CRYSTALCLEAR 1.3.6; Rigaku and Rigaku/MSC: The
Woodlands, TX, USA, 2005.
(13) Song, L.-C.; Yang, Z.-Y.; Bian, H.-Z.; Wang, H.-T.; Liu, Y.; Liu,
X.-F.; Hu, Q.-M. Organometallics 2005, 24, 6126.
(14) Jablonskyte, A.; Wright, J. A.; Pickett, C. J. Eur. J. Inorg. Chem.
̇
(49) Sheldrick, G. M. SHELXS97, A Program for Crystal Structure
2011, 1033.
Solution; University of Gottingen: Germany, 1997.
̈
(15) Song, L.-C.; Yang, Z.-Y.; Hua, Y.-J.; Wang, H.-T.; Liu, Y.; Hu,
Q.-M. Organometallics 2007, 26, 2106.
(16) Song, L.-C.; Gai, B.; Wang, H.-T.; Hu, Q.-M. J. Inorg. Biochem.
2009, 103, 805.
(50) Sheldrick, G. M. SHELXL97, A Program for Crystal Structure
Refinement; University of Gottingen: Germany, 1997.
̈
(17) Daraosheh, A. Q.; Harb, M. K.; Windhager, J.; Gorls, H.; EI-
̈
khateeb, M.; Weigand, W. Organometallics 2009, 28, 6275.
(18) Harb, M. K.; Windhager, J.; Daraosheh, A.; Gorls, H.; Lockett,
̈
L. T.; Okumura, N.; Evans, D. H.; Glass, R. S.; Lichtenberger, D. L.;
EI-khateeb, M.; Weigand, W. Eur. J. Inorg. Chem. 2009, 3414.
(19) Harb, M. K.; Apfel, U.-P.; Sakamoto, T.; EI-khateeb, M.;
Weigand, W. Eur. J. Inorg. Chem. 2011, 986.
(20) Windhager, J.; Gorls, H.; Petzold, H.; Mloston, G.; Linti, G.;
̈
Weigand, W. Eur. J. Inorg. Chem. 2007, 4462.
(21) Si, G.; Wang, W.-G.; Wang, H.-Y.; Tung, C.-H.; Wu, L.-Z. Inorg.
Chem. 2008, 47, 8101.
(22) Song, L.-C.; Tang, M.-Y.; Su, F.-H.; Hu, Q.-M. Angew. Chem.,
Int. Ed. 2006, 45, 1130.
(23) Song, L.-C.; Tang, M.-Y.; Mei, S.-Z.; Huang, J.-H.; Hu, Q.-M.
Organometallics 2007, 26, 1575.
(24) Song, L.-C.; Wang, L.-X.; Tang, M.-Y.; Li, C.-G.; Song, H.-B.;
Hu, Q.-M. Organometallics 2009, 28, 3834.
(25) Kluwer, A. M.; Kapre, R.; Hartl, F.; Lutz, M.; Spek, A. L.;
Brouwer, A. M.; van Leeuwen, P. W. N. M.; Reek, J. N. H. Proc. Natl.
Acad. Sci. U. S. A. 2009, 106, 10460.
(26) Samuel, A. P. S.; Co, D. T.; Stern, C. L.; Wasielewski, M. R. J.
Am. Chem. Soc. 2010, 132, 8813.
(27) Lyon, E. J.; Georgakaki, I. P.; Reibenspies, J. H.; Darensbourg,
M. Y. Angew. Chem., Int. Ed. 1999, 38, 3178.
(28) Song, L.-C.; Ge, J.-H.; Liu, X.-F.; Zhao, L.-Q.; Hu, Q.-M. J.
Organomet. Chem. 2006, 691, 5701.
(29) Song, L.-C.; Li, C.-G.; Gao, J.; Yin, B.-S.; Luo, X.; Zhang, X.-G.;
Bao, H.-L.; Hu, Q.-M. J. Inorg. Biochem. 2008, 102, 1973.
(30) Song, L.-C.; Ge, J.-H.; Zhang, X.-G.; Liu, Y.; Hu, Q.-M. Eur. J.
Inorg. Chem. 2006, 3204.
(31) Huo, F.; Huo, J.; Chen, G.; Guo, D.; Peng, X. Eur. J. Inorg.
Chem. 2010, 3942.
(32) Wen, N.; Xu, F.; Feng, Y.; Du, S. J. Inorg. Biochem. 2011, 105,
1123.
(33) Lindsey, J. S.; Schreiman, I. C.; Hsu, H. C.; Kearney, P. C.;
Marguerettaz, A. M. J. Org. Chem. 1987, 52, 827.
(34) Thomas, D. W.; Martell, A. E. J. Am. Chem. Soc. 1959, 81, 5111.
(35) Shaw, J. L.; Garrison, S. A.; Aleman
Modarelli, D. A. J. Org. Chem. 2004, 69, 7423.
́
, E. A.; Ziegler, C. J.;
(36) (a) Silvers, S. J.; Tulinsky, A. J. Am. Chem. Soc. 1967, 89, 3331.
(b) Sessler, J. L.; Johnson, M. R.; Creager, S. E.; Fettinger, J. C.; Ibers,
J. A. J. Am. Chem. Soc. 1990, 112, 9310.
(37) Ozawa, H; Haga, M.; Sakai, K. J. Am. Chem. Soc. 2006, 128,
4926.
(38) Rau, S.; Walther, D.; Vos, J. G. Dalton Trans. 2007, 915.
(39) Fihri, A.; Artero, V.; Razavet, M.; Baffert, C.; Leibl, W.;
Fontecave, M. Angew. Chem., Int. Ed. 2008, 47, 564.
(40) Rosenthal, J.; Bachman, J.; Dempsey, J. L.; Esswein, A. J.; Gray,
T. G.; Hodgkiss, J. M.; Manke, D. R.; Luckett, T. D.; Pistorio, B. J.;
Veige, A. S.; Nocera, D. G. Coord. Chem. Rev. 2005, 249, 1316.
(41) Amao, Y.; Tomonou, Y.; Ishikawa, Y.; Okura, I. Int. J. Hydrogen
Energy 2002, 27, 621.
(42) Darwent, J. R.; Douglas, P.; Harriman, A.; Porter, G.; Richoux,
M.-C. Coord. Chem. Rev. 1982, 44, 83.
5088
dx.doi.org/10.1021/om300418z | Organometallics 2012, 31, 5081−5088