Synthesis, characterization, and electrochemical properties of benzyloxy-functionalized diiron 1,3-propanedithiolate complexes relevant to the active site of [FeFe]-hydrogenases

Article abstract of DOI:10.1021/om300136b

A series of new benzyloxy-functionalized 1,3-propanedithiolate (PDT)-type model complexes (A and 1-7) have been synthesized and structurally characterized. The benzyloxy-functionalized all-carbonyl complex [(ν-SCH ₂)₂CH(OCH₂Ph)]Fe₂(CO)₆ (A) can be prepared by condensation reaction of 2-benzyloxy-1,3-dibromopropane with the in situ generated (ν-LiS)₂Fe₂(CO)₆, whereas it reacts with the in situ formed N-heterocyclic carbene 1-mesityl-3-methylimidazol-2-ylidene (I_Mes/Me) to give the corresponding carbene monosubstituted complex [(ν-SCH₂) ₂CH(OCH₂Ph)]Fe₂(CO)₅(I _Mes/Me) (1). The PMe₃-monosubstituted complex [(ν-SCH₂)₂CH(OCH₂Ph)]Fe₂(CO) ₅(PMe₃) (2) can be prepared by substitution of the CO ligand in parent complex A with 1 equiv of PMe₃ in the presence of Me₃NO·2H₂O, whereas PPh₃-monosubstituted and PPh₃-disubstituted complexes [(ν-SCH₂) ₂CH(OCH₂Ph)]Fe₂(CO)₅(PPh ₃) (3) and [(ν-SCH₂)₂CH(OCH ₂Ph)]Fe₂(CO)₄(PPh₃)₂ (4) are prepared by reaction of A with 2 equiv of PPh₃ under similar conditions. While the PPh₃-disubstituted complex 4 can also be prepared by treatment of 3 in MeCN with 2 equiv of PPh₃ in the presence of Me₃NO·2H₂O, treatment 4 with 2 equiv of PMe₃ in refluxing toluene afforded unexpected PPh ₃/PMe₃-disubstituted complex [(ν-SCH₂) ₂CH(OCH₂Ph)]Fe₂(CO)₄(PPh ₃)(PMe₃) (5). Particularly interesting is that although the reaction of A with 1 equiv of diphosphine dppe in refluxing toluene affords the dppe-chelated single-butterfly complex [(ν-SCH₂) ₂CH(OCH₂Ph)]Fe₂(CO)₄(dppe) (6), treatment of A in MeCN with 1 equiv of dppe in the presence of Me ₃NO·2H₂O results in formation of the dppe-bridged double-butterfly complex {[(ν-SCH₂)₂CH(OCH ₂Ph)]Fe₂(CO)₅}₂(dppe) (7). All new model complexes have been chatacterized by elemental analysis, spectroscopy, and particularly for 1 and 4-7 X-ray crystallography. Furthermore, complexes A, 3, and 4 have been found to be catalysts for HOAc proton reduction to H₂ under electrochemical conditions.

Full text of DOI:10.1021/om300136b

Article
pubs.acs.org/Organometallics
Synthesis, Characterization, and Electrochemical Properties of
Benzyloxy-Functionalized Diiron 1,3-Propanedithiolate Complexes
Relevant to the Active Site of [FeFe]-Hydrogenases
Li-Cheng Song,* Wei Gao, Xiang Luo, Zhi-Xuan Wang, Xiao-Jing Sun, and Hai-Bin Song
State Key Laboratory of Elemento-Organic Chemistry, Department of Chemistry, Nankai University, Tianjin 300071, China
S
* Supporting Information
ABSTRACT: A series of new benzyloxy-functionalized 1,3-propanedithiolate
(PDT)-type model complexes (A and 1−7) have been synthesized and structurally
characterized. The benzyloxy-functionalized all-carbonyl complex [(μ-SCH2)2CH-
(OCH2Ph)]Fe2(CO)6 (A) can be prepared by condensation reaction of 2-
benzyloxy-1,3-dibromopropane with the in situ generated (μ-LiS)2Fe2(CO)6,
whereas it reacts with the in situ formed N-heterocyclic carbene 1-mesityl-3-
methylimidazol-2-ylidene (IMes/Me) to give the corresponding carbene mono-
substituted complex [(μ-SCH2)2CH(OCH2Ph)]Fe2(CO)5(IMes/Me) (1). The
PMe3-monosubstituted complex [(μ-SCH2)2CH(OCH2Ph)]Fe2(CO)5(PMe3)
(2) can be prepared by substitution of the CO ligand in parent complex A with
1 equiv of PMe3 in the presence of Me3NO·2H2O, whereas PPh3-monosubstituted
and PPh3-disubstituted complexes [(μ-SCH2)2CH(OCH2Ph)]Fe2(CO)5(PPh3)
(3) and [(μ-SCH2)2CH(OCH2Ph)]Fe2(CO)4(PPh3)2 (4) are prepared by
reaction of A with 2 equiv of PPh3 under similar conditions. While the PPh3-disubstituted complex 4 can also be prepared
by treatment of 3 in MeCN with 2 equiv of PPh3 in the presence of Me3NO·2H2O, treatment 4 with 2 equiv of PMe3 in refluxing
toluene afforded unexpected PPh3/PMe3-disubstituted complex [(μ-SCH2)2CH(OCH2Ph)]Fe2(CO)4(PPh3)(PMe3) (5).
Particularly interesting is that although the reaction of A with 1 equiv of diphosphine dppe in refluxing toluene affords the
dppe-chelated single-butterfly complex [(μ-SCH2)2CH(OCH2Ph)]Fe2(CO)4(dppe) (6), treatment of A in MeCN with 1 equiv
of dppe in the presence of Me3NO·2H2O results in formation of the dppe-bridged double-butterfly complex {[(μ-
SCH2)2CH(OCH2Ph)]Fe2(CO)5}2(dppe) (7). All new model complexes have been chatacterized by elemental analysis,
spectroscopy, and particularly for 1 and 4−7 X-ray crystallography. Furthermore, complexes A, 3, and 4 have been found to be
catalysts for HOAc proton reduction to H2 under electrochemical conditions.
Scheme 1. Basic Structure of H-Cluster Obtained from
Protein Crystallography
INTRODUCTION
■
a
Hydrogenases are natural enzymes that can catalyze both
reduction of proton to dihydrogen and the oxidation of
dihydrogen to protons.1 These enzymes can be classified as two
main groups on the basis of the metal contents in their active
sites: [FeFe]-hydrogenases ([FeFe]Hases)2 and [NiFe]-hydro-
genases ([NiFe]Hases).3 In recent years, [FeFe]Hases have
drawn considerably more attention than [NiFe]Hases, largely
owing to their unusual structures and particularly their catalytic
function in the production of the “clean” and highly efficient
fuel: dihydrogen.4−7 The X-ray crystallographic,8−11 FTIR
spectroscopic,12−14 and theoretical15 studies indicated that the
active site of [FeFe]Hases (so-called H-cluster) consists of a
butterfly [Fe2S2] cluster core with one of its iron atoms linked
to a cubic [Fe4S4] cluster through the sulfur atom of a L-
cysteinyl ligand. There are also three other ligands, namely,
CO, CN−, and dithiolate, coordinated to the two Fe atoms of
the butterfly [Fe2S2] cluster core (Scheme 1). Encouraged by
the structural studies on the H-cluster, synthetic chemists have
prepared a variety of active site models for [FeFe]Hases,16,17
and some of them have been found to be catalysts for proton
reduction to dihydrogen under electrochemical conditions.18−20
a
X = CH2, NH, or O.
In order to further develop the biomimetic chemistry of the
natural enzyme [FeFe]Hases, we recently initiated a study on a
new series of diiron PDT-type model complexes, in which a
benzyloxy functionality is attached to the central bridgehead C
atom of their PDT moiety and some electron-donating ligands
Received: February 17, 2012
Published: March 27, 2012
© 2012 American Chemical Society
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Scheme 2
such as phosphine and N-heterocyclic carbene (NHC) are
bound to the iron atoms in their diiron subsite (vide infra). It
should be noted that the introduction of a benzyloxy functional
group and some stronger donor ligands in such model
complexes is to make their bridgehead C atom-attached oxygen
atom and the iron atoms in their diiron subsite more electron-
rich and thus easily accepting of protons for the catalytic H2
production. Herein we report the synthesis, structural
characterization, and some electrochemical properties of these
new diiron PDT-type model complexes.
solid. The IR spectrum of 1 showed three absorption bands in
the range 2033−1955 cm−1 for its terminal carbonyls. The
highest νCO value among the three bands is shifted by 47
cm−1 toward lower energy relative to that of parent complex A.
This is because an N-heterocyclic carbene is a stronger σ-donor
than CO with negligible π-accepting ability.25 The H NMR
1
spectrum of 1 displayed two singlets at 6.84 and 6.96 ppm for
hydrogen atoms in the CHCH unit of the imidazole ring,
two singlets at 2.00 and 2.36 ppm for hydrogen atoms of CH3
groups in its mesityl group, and a singlet at 3.86 ppm for
hydrogen atoms of the CH3 group connected to the N atom. It
also exhibited two multiplets at ca. 1.4 and 2.7 ppm for the axial
and equatorial hydrogen atoms in its two SCH2 groups,
respectively.22,23
RESULTS AND DISCUSSION
■
Synthesis and Spectroscopic Characterization of
Benzyloxy-Functionalized Complex A and Its NHC-
Substituted Complex 1. We found that complex A could
be prepared by in situ treatment of (μ-LiS)2Fe2(CO)6
generated from (μ-S2)Fe2(CO)6 and Et3BHLi21 with 2-
benzyloxy-1,3-dibromopropane in THF from −78 °C to
room temperature in 35% yield (Scheme 2). Complex A is
an air-stable red solid, which was characterized by elemental
analysis and spectroscopy. The C/H analytical data are in good
agreement with its composition, whereas its IR spectrum
showed six absorption bands in the range 2080−1928 cm−1 for
its terminal carbonyls. In addition, the 1H NMR spectrum of A
displayed a triplet at 1.54 ppm and a doublet at 2.79 ppm for
the axial and equatorial hydrogen atoms, respectively, in its two
SCH2 groups, and it displayed a multiplet at about 2.85 ppm for
the hydrogen atom attached to its bridgehead C atom.22,23
Interestingly, parent complex A could react with N-
heterocyclic carbene IMes/Me (generated in situ by reaction of
its precursor 1-mesityl-3-methylimidazolium salt IMes/Me·HI
with n-BuLi)24 in THF at room temperature to afford the
corresponding NHC-monosubstituted complex [(μ-
SCH2)2CH(OCH2Ph)]Fe2(CO)5(IMes/Me) (1), albeit in low
yield (9%) (Scheme 3). Complex 1 is also an air-stable red
Synthesis and Spectroscopic Characterization of
Monophosphine-Substituted Complexes 2−5. It was
further found that (i) treatment of A in MeCN with 1 equiv
of PMe3 in the presence of decarbonylating agent
Me3NO·2H2O26 resulted in formation of the PMe3-mono-
substituted complex [(μ-SCH2 )2 CH(OCH2 Ph)]-
Fe2(CO)5(PMe3) (2) in 47% yield; (ii) treatment of A with
2 equiv of PPh3 under similar conditions gave PPh3-
monosubstituted complex [(μ-SCH2)2CH(OCH2Ph)]-
Fe2(CO)5(PPh3) (3) and PPh3-disubstituted complex [(μ-
SCH2)2CH(OCH2Ph)]Fe2(CO)4(PPh3)2 (4) in 63% and 12%
yields, respectively; (iii) disubstituted complex 4 could also be
obtained by treatment of 3 with 2 equiv of PPh3 in the presence
of Me3NO·2H2O in MeCN at room temperature in a much
higher (80%) yield; and (iv) treatment of disubstituted
complex 4 with 2 equiv of PMe3 in refluxing toluene did not
produce the corresponding trisubstituted complex [(μ-
SCH2)2CH(OCH2Ph)]Fe2(CO)3(PPh3)2(PMe3), but instead
afforded the unexpected disubstituted complex [(μ-SCH2)2CH-
(OCH2Ph)]Fe2(CO)4(PPh3)(PMe3) (5) in 75% yield (Scheme
4). It is apparent that the easy formation of the disubstituted
ligand-exchange product 5 might be attributed to ligand PMe3
having less steric hindrance and stronger electron-donating
ability than PPh3.
Scheme 3
While 2 is an air-stable red oil and 3 is an air-stable red solid,
complexes 4 and 5 are slightly air-sensitive red solids. All these
new complexes have been characterized by elemental analysis
and IR, 1H NMR, and 31P NMR spectroscopy. For example, the
IR spectra of monosubstituted complexes 2 and 3 showed three
to four absorption bands in the range 2043−1910 cm−1 for
their terminal carbonyls, whereas disubstituted complexes 4 and
5 displayed three to four bands in the lower region 1998−1915
cm−1 for their terminal carbonyls. The highest νCO values of
2−5 are shifted by 37−82 cm−1 toward lower energy relative to
that of parent complex A. All these observations are consistent
with phosphine ligands being stronger σ-donors than CO.27
While the 1H NMR spectra of 2−5 exhibited their
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Scheme 4
corresponding organic groups, their 31P NMR spectra showed
one singlet at 26.50 ppm for the P atom in the PMe3 ligand of 2
and one singlet at 65.04 ppm for the P atom in the PPh3 ligand
of 3, two singlets at 61.60 and 62.35 ppm for the P atoms in
two PPh3 ligands of 4, and two singlets at 27.31 and 62.08 ppm
for the P atoms in the PMe3 and PPh3 ligands of 5, respectively.
Synthesis and Spectroscopic Characterization of
Diphosphine-Substituted Complexes 6 and 7. More
interestingly, parent complex A could react with 1 equiv of
diphosphine dppe in refluxing toluene to afford the dppe-
chelated single-butterfly complex [(μ-SCH2)2CH(OCH2Ph)]-
Fe2(CO)4(Ph2PCH2CH2PPh2) (6) in 18% yield, whereas A
reacted with 1 equiv of dppe in the presence of Me3NO·2H2O
in MeCN at room temperature to give the dppe-bridged
double-butterfly complex {[(μ-SCH2)2CH(OCH2Ph)]-
Fe2(CO)5}2(Ph2PCH2CH2PPh2) (7) in 16% yield (Scheme 5).
Complexes 6 and 7 are air-stable solids, which were also
Scheme 5
1
characterized by elemental analysis and IR, H NMR, and 31P
NMR spectroscopy. For instance, their IR spectra showed three
to four absorption bands in the range 2046−1891 cm−1 for
their terminal carbonyls. Similar to monophosphine-substituted
complexes 2−5, the highest νCO values of diphosphine-
substituted 6 and 7 are shifted respectively by 64 and 34 cm−1
toward lower energy relative to that of parent complex A due to
the same reason indicated above.27 The 1H NMR spectrum of 6
exhibited two multiplets at ca. 1.4 and 2.5 ppm for the axial and
equatorial hydrogen atoms in its two SCH2 groups, whereas 7
displayed one triplet and one doublet at 1.31 and 2.29 ppm for
the axial and equatorial hydrogen atoms in its four SCH2
groups, respectively.22,23 The 31P NMR spectra of 6 and 7
showed a singlet at 91.02 and 59.32 ppm for the P atoms in the
chelated and bridged dppe ligands of 6 and 7, respectively.
Crystal Structures of 1 and 4−7. The molecular
structures of 1 and 4−7 were investigated by X-ray
crystallography. While their ORTEP drawings are depicted in
Figures 1−5, Table 1 lists their selected bond lengths and
angles. As can be seen intuitively from Figures 1−5, all these
complexes contain a benzyloxy group-substituted propane-
dithiolate ligand bridged between two iron atoms to form two
fused six-membered rings with a chair and a boat conformation.
In addition, the benzyloxy group and one hydrogen atom are
attached to the bridgehead C atom (namely, C7 for 1, C22 for
4, C9 for 5, C6 for 6, and C7/C7A for 7) via the common
equatorial and axial bonds of the two fused six-membered rings,
respectively. Apparently, this is in order to avoid the strong
steric repulsions of the bulky benzyloxy group with the apical
CO and the substituted ligands in these complexes. Similar
cases were also observed in other bridgehead C atom-
substituted PDT-type model complexes.22,23 Also, as can be
seen intuitively from Figures 1−3, the substituted ligand IMes/Me
in 1 and the two PPh3 in 4 are all located in apical positions of
the square-pyramidal geometries of the corresponding iron
atoms, whereas the PPh3 and PMe3 ligands in 5 lie in an apical
and a basal positions of its two iron atoms, respectively. In
addition, as shown in Figures 4 and 5, the two Ph2P moieties of
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pounds.19,20,29 In addition, in contrast to A and 3, Figure 8
shows that when the first 2 mM HOAc was added, both peaks
of the first and second reductions of 4 increased remarkably
and continuously increased linearly with increments of the acid
concentration. Such double electrocatalytic processes for
proton reduction to H2 catalyzed by similar [FeFe]-hydro-
genase model complexes were also previously observed.30
Particularly noteworthy is that the first electrocatalytic process
catalyzed by 4 is most likely to have an ECCE electrochemical
mechanism,31 whereas its second electrocatalytic process
probably has an EECC electrochemical mechanism caused by
an electrocatalytic reaction involving a species derived from 4.30
Finally, it is worth pointing out that the two catalytic potentials
of 4 are all less negative than the two corresponding potentials
of A and 3 as a result of the existence of two stronger electron-
donating PPh3 ligands.
Figure 1. Molecular structure of 1 with 30% probability level
ellipsoids. Hydrogen atoms are omitted for clarity.
CONCLUSIONS
■
We have prepared a series of new benzyloxy-functionalized
butterfly Fe/S cluster complexes (A and 1−7) as the active site
models of [FeFe]Hases. While A is prepared by ring-closure
reaction of PhCH2OCH(CH2Br)2 with (μ-LiS)2Fe2(CO)6, its
CO substitution derivatives 1−7 are prepared by reactions of A
with PMe3, PPh3, and dppe under the corresponding
conditions. From a synthetic view, the ring-closure method to
give parent complex A, the ligand exchange method between 4
and PMe3 to afford 5, and the formation of two types of dppe-
substituted derivatives 6 and 7 are of particular interest. The
molecular structures of complexes 1 and 4−7 have been
confirmed by X-ray crystal diffraction analysis. Particularly
noteworthy is that the two monophosphine ligands PPh3 in 4
are coordinated to its two Fe atoms with a symmetrically
substituted apical/apical coordination mode, whereas the
monophosphine ligands PPh3 and PMe3 in 5 are coordinated
to its two Fe atoms with an apical/basal coordination mode. In
addition, the diphosphine ligand dppe in 6 is chelated to one of
its two Fe atoms in its single-butterfly cluster core with an
apical/basal coordination mode, whereas the dppe ligand in 7 is
bridged respectively to two Fe atoms in its two butterfly cluster
cores with an apical/apical coordination mode. It is worth
pointing out that complexes A, 3, and 4 have been proved to be
catalysts for proton reduction to hydrogen under electro-
chemical conditions. Further studies on electrocatalytic
mechanisms for such H2 production processes will be carried
out in the near future in our laboratory.
dppe in 6 are indeed chelated to one iron atom (Fe2) in its
single-butterfly cluster core, and those two PPh2 moieties in 7
are bridged to two iron atoms (Fe2/Fe2A) in its two butterfly
subcluster cores, respectively. Although the Fe−Fe bond
lengths of 1 (2.5223 Å), 4 (2.5319 Å), 5 (2.5534 Å), 6
(2.545 Å), and 7 (2.5167 Å) are very close to the
corresponding bond length of the reduced form of [FeFe]-
Hases (2.55 Å),11 they are obviously shorter than that of the
oxidized form (2.62 and 2.60 Å)8,9 of [FeFe]Hases.
Electrochemistry of A, 3, and 4. The electrochemical
properties of parent complex A and its phosphine-substituted
complexes 3 and 4 were investigated by using cyclic
voltammetry. It is shown that parent complex A exhibits one
quasi-reversible reduction at −1.61 V, one irreversible
reduction at −2.12 V, and one irreversible oxidation at +0.70
V (see Table 2). All three redox events could be assigned to the
one-electron processes from FeIFeI to FeIFe0, FeIFe0 to Fe0Fe0,
and FeIFeI to FeIFeII couples, respectively (supported by the
calculated value of 1.10 Farady/equiv obtained by study of the
bulk electrolysis of a MeCN solution of A at −1.80 V).28
Similarly, complex 3 displays one quasi-reversible reduction
at −1.63 V, one irreversible reduction at −2.41 V, and one
irreversible oxidation at +0.40 V, whereas 4 shows two
irreversible reductions at −1.96/−2.26 V and one irreversible
oxidation at +0.07 V (see Table 2). The first and second
reduction peaks of 3 and 4 could also be assigned to the one-
electron reduction processes from FeIFeI to FeIFe0 and FeIFe0
to Fe0Fe0 couples, whereas the oxidation peaks of 3 and 4 could
be attributed to their one-electron oxidation processes from the
FeIFeI to FeIFeII couple, respectively (supported by the
calculated values of 1.11 and 1.05 Farady/equiv obtained by
study of the bulk electrolysis of a MeCN solution of 3 at −1.85
V and 4 at −2.20 V, respectively).
The cyclic voltammograms of A, 3, and 4 in the presence of
HOAc and without HOAc (for comparison) are presented in
Figures 6−8. As shown in Figures 6 and 7, when the first 2 mM
HOAc was added, the first reduction peaks of A and 3
increased slightly, but they did not continuously increase with
subsequent addition of the acid. However, in contrast to this,
their second reduction peaks grew up remarkably with
continuous addition of the acid. Such observations are
consistent with those previously reported for proton reduction
catalyzed by similar [FeFe]-hydrogenase model com-
EXPERIMENTAL SECTION
■
General Comments. All reactions were performed using standard
Schlenk and vacuum-line techniques under highly prepurified N2.
Toluene and THF were distilled under N2 from sodium/
benzophenone ketyl, whereas MeCN was distilled under N2 from
CaH2. (μ-S2)Fe2(CO)6,32 2-benzyloxy-1,3-dibromopropane,33 1-mesi-
tyl-3-methylimidazolium salt,24 and 1,2-bis(diphenylphosphino)ethane
(dppe)34 were prepared according to the published methods. Et3BHLi
(1 M in THF), n-BuLi (2.5 M in hexane), PMe3 (1 M in toluene),
PPh3, and other chemicals were purchased from commercial suppliers
and used as received. Preparative TLC was carried out on glass plates
(25 × 15 × 0.25 cm) coated with silica gel G (10−40 μm). IR spectra
1
were recorded on a Bio-Rad FTS 135 infrared spectrophotometer. H
and 31P NMR spectra were taken on a Bruker Avance 300 NMR or a
Varian Mercury Plus 400 NMR spectrometer. Elemental analyses were
performed with an Elementar Vario EL analyzer. Melting points were
determined on a Yanaco MP-500 apparatus and were uncorrected.
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Table 1. Selected Bond Lengths (Å) and Angles (deg) for 1, 4, 5, 6, and 7
1
Fe(1)−S(2)
Fe(1)−C(16)
Fe(2)−S(2)
S(1)−C(6)
2.2605(11)
1.974(4)
2.2536(11)
1.821(3)
1.448(4)
105.14(10)
84.39(4)
55.97(3)
67.58(3)
113.1(2)
Fe(1)−S(1)
Fe(1)−Fe(2)
Fe(2)−S(1)
O(6)−C(9)
2.2740(11)
2.5223(8)
2.2613(12)
1.418(4)
1.512(5)
108.05(11)
55.90(3)
84.84(4)
67.94(3)
112.7(3)
O(6)−C(7)
C(6)−C(7)
C(16)−Fe(1)−S(2)
S(2)−Fe(1)−S(1)
S(1)−Fe(1)−Fe(2)
Fe(2)−S(1)−Fe(1)
C(9)−O(6)−C(7)
C(16)−Fe(1)−S(1)
S(2)−Fe(1)−Fe(2)
S(2)−Fe(2)−S(1)
Fe(2)−S(2)−Fe(1)
C(8)−C(7)−C(6)
4
5
6
7
Fe(1)−C(1)
Fe(1)−P(1)
Fe(1)−S(1A)
S(1)−C(21)
1.764(2)
2.2503(7)
2.2764(7)
1.823(3)
1.279(6)
94.38(8)
109.81(3)
83.22(4)
56.26(2)
67.65(3)
Fe(1)−C(2)
Fe(1)−S(1)
Fe(1)−Fe(1A)
S(1)−Fe(1A)
1.785(2)
2.2721(9)
2.5319(8)
2.2764(7)
1.390(4)
97.51(8)
106.85(3)
156.667(18)
56.09(3)
130.8(3)
O(3)−C(23)
O(3)−C(22)
C(1)−Fe(1)−P(1)
P(1)−Fe(1)−S(1)
S(1)−Fe(1)−S(1A)
S(1)−Fe(1)−Fe(1A)
Fe(1)−S(1)−Fe(1A)
C(2)−Fe(1)−P(1)
P(1)−Fe(1)−S(1A)
P(1)−Fe(1)−Fe(1A)
S(1A)−Fe(1)−Fe(1A)
C(23)−O(3)−C(22)
Fe(1)−P(1)
Fe(1)−S(1)
Fe(2)−P(2)
Fe(2)−S(1)
2.2287(14)
2.2621(14)
2.2430(12)
2.2717(12)
1.428(5)
Fe(1)−S(2)
Fe(1)−Fe(2)
Fe(2)−S(2)
S(1)−C(8)
2.2555(11)
2.5534(9)
2.2549(11)
1.824(4)
1.441(5)
166.71(5)
55.51(3)
108.25(4)
68.55(4)
113.9(3)
O(5)−C(11)
O(5)−C(9)
P(1)−Fe(1)−S(2)
S(2)−Fe(1)−S(1)
S(1)−Fe(1)−Fe(2)
P(2)−Fe(2)−S(1)
Fe(2)−S(2)−Fe(1)
90.69(4)
P(1)−Fe(1)−S(1)
S(2)−Fe(1)−Fe(2)
P(2)−Fe(2)−S(2)
Fe(1)−S(1)−Fe(2)
C(11)−O(5)−C(9)
84.23(4)
55.90(3)
103.98(5)
68.96(4)
Fe(1)−S(2)
Fe(1)−Fe(2)
Fe(2)−P(2)
Fe(2)−S(2)
2.261(2)
2.545(2)
2.200(2)
2.265(2)
1.432(7)
84.40(9)
55.64(6)
84.51(10)
55.71(6)
68.38(6)
Fe(1)−S(1)
Fe(2)−P(1)
Fe(2)−S(1)
S(1)−C(5)
2.269(2)
2.195(2)
2.260(2)
1.823(5)
1.434(6)
55.86(5)
85.79(7)
55.98(6)
114.0(5)
68.43(6)
O(5)−C(8)
O(5)−C(6)
S(2)−Fe(1)−S(1)
S(1)−Fe(1)−Fe(2)
S(1)−Fe(2)−S(2)
S(2)−Fe(2)−Fe(1)
Fe(2)−S(1)−Fe(1)
S(2)−Fe(1)−Fe(2)
P(1)−Fe(2)−P(2)
S(1)−Fe(2)−Fe(1)
C(8)−O(5)−C(6)
Fe(1)−S(2)−Fe(2)
Fe(1)−S(1)
Fe(1)−Fe(2)
Fe(2)−S(1)
O(6)−C(9)
2.2503(12)
2.5167(9)
2.2574(11)
1.402(5)
1.831(4)
56.20(3)
106.58(4)
152.53(3)
55.88(3)
67.88(4)
Fe(1)−S(2)
Fe(2)−P(1)
Fe(2)−S(2)
O(6)−C(7)
2.2534(11)
2.2394(11)
2.2703(12)
1.434(4)
1.507(5)
56.52(3)
84.50(4)
55.93(3)
114.0(3)
67.60(4)
S(1)−C(6)
C(6)−C(7)
S(1)−Fe(1)−Fe(2)
P(1)−Fe(2)−S(2)
P(1)−Fe(2)−Fe(1)
S(2)−Fe(2)−Fe(1)
Fe(1)−S(1)−Fe(2)
S(2)−Fe(1)−Fe(2)
S(1)−Fe(2)−S(2)
S(1)−Fe(2)−Fe(1)
C(9)−O(6)−C(7)
Fe(1)−S(2)−Fe(2)
Preparation of [(μ-SCH2)2CH(OCH2Ph)]Fe2(CO)6 (A). A red
solution of (μ-S2)Fe2(CO)6 (0.344 g, 1.00 mmol) in THF (25 mL)
was cooled to −78 °C, and then Et3BHLi (2.0 mL, 2.00 mmol) was
added. The mixture was stirred at −78 °C for 15 min to give an
emerald green solution containing (μ-LiS)2Fe2(CO)6. After 2-
benzyloxy-1,3-dibromopropane (0.308 g, 1.00 mmol) was added, the
new mixture was warmed to room temperature and stirred at this
temperature for 12 h. Volatiles were removed in vacuo, and the residue
was subjected to TLC separation using CH2Cl2/petroleum ether (1:3
v/v) as eluent. From the main red band, A was obtained as a red solid
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Article
Figure 2. Molecular structure of 4 with 30% probability level
ellipsoids. Hydrogen atoms are omitted for clarity.
Figure 4. Molecular structure of 6 with 30% probability level
ellipsoids. Hydrogen atoms are omitted for clarity.
Figure 3. Molecular structure of 5 with 30% probability level
ellipsoids. Hydrogen atoms are omitted for clarity.
(0.174 g, 35%), mp 59−60 °C. Anal. Calcd for C16H12Fe2O7S2: C,
39.05; H, 2.46. Found: C, 38.85; H, 2.59. IR (KBr disk): νCO 2080
1
(vs), 2033 (vs), 2007 (vs), 1981 (vs), 1960 (vs), 1928 (m) cm−1. H
NMR (400 MHz, CDCl3, TMS): 1.54 (t, 2Ha, JHaHe = JHaHa′ = 11.2
Hz), 2.79 (d, 2He, JHeHa = 12.0 Hz), 2.82−2.90 (m, 1Ha′), 4.46 (s, 2H,
OCH2), 7.31−7.35 (m, 5H, C6H5) ppm (Ha and He represent the
axially and equatorially bonded H atoms in CH2S groups, whereas Ha′
and He′ represent those axially and equatorially bonded to the
bridgehead C atom).
Preparation of [(μ-SCH2)2CH(OCH2Ph)]Fe2(CO)5(IMes/Me) (1).
To a stirred suspension of 1-mesityl-3-methylimidazolium salt
IMes/Me·HI (0.818 g, 2.50 mmol) in THF (20 mL) was slowly added
a solution of n-BuLi (2.5 M in hexane) (1.10 mL, 2.75 mmol) to give a
yellowish solution. After stirring at room temperature for an additional
Figure 5. Molecular structure of 7 with 30% probability level
ellipsoids. Hydrogen atoms are omitted for clarity.
10 min, A (0.246 g, 0.50 mmol) was added and the new mixture was
stirred at room temperature for 4.5 h. The resulting deep-red solution
was evaporated to dryness under vacuum. The residue was subjected
to TLC separation using CH2Cl2/petroleum ether (1:1.5 v/v) as
eluent. From the main red band, 1 was obtained as a red solid (0.031 g,
9%), mp 180−181 °C. Anal. Calcd for C28H28Fe2N2O6S2: C, 50.62; H,
4.25; N, 4.22. Found: C, 50.41; H, 4.13; N, 4.11. IR (KBr disk): νCO
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Organometallics
Article
a
Table 2. Electrochemical Data of A, 3, and 4
complex
Epc/V
Epa/V
A
−1.61
−2.12
−1.63
−2.41
−1.96
−2.26
+0.70
3
4
+0.40
+0.07
a
All potentials versus Fc/Fc+.
Figure 8. Cyclic voltammograms of 4 (1.0 mM) with HOAc (0−10
mM) in 0.1 M n-Bu4NPF6/MeCN at a scan rate of 100 mV·s−1.
12.4 Hz, JHeHa′ = 3.6 Hz), 2.85−2.93 (m, 1Ha′), 4.46 (s, 2H, OCH2),
7.28−7.35 (m, 5H, C6H5) ppm. 31P{1H} NMR (162 MHz, CDCl3,
85% H3PO4): 26.50 (s) ppm.
Preparation of [(μ-SCH2)2CH(OCH2Ph)]Fe2(CO)5(PPh3) (3) and
[(μ-SCH2)2CH(OCH2Ph)]Fe2(CO)4(PPh3)2 (4). Method (i), Prepara-
tion of 3 and 4 from Parent Complex A: To a red solution of A (0.246
g, 0.50 mmol) in MeCN (15 mL) were added PPh3 (0.262 mL, 1.00
mmol) and Me3NO·2H2O (0.056 g, 0.50 mmol). The mixture was
stirred at room temperature for 1 h until complete consumption of A,
as indicated by TLC. The resulting deep red solution was evaporated
to dryness under vacuum. The residue was subjected to TLC
separation using CH2Cl2/petroleum ether (1:3 v/v) as eluent. From
the two major red bands, 3 (0.228 g, 63%) and 4 (0.058 g, 12%) were
obtained as a red solid, respectively. 3: mp 135−136 °C. Anal. Calcd
for C33H27Fe2O6PS2: C, 54.57; H, 3.75. Found: C, 54.69; H, 3.75. IR
Figure 6. Cyclic voltammograms of A (1.0 mM) with HOAc (0−10
mM) in 0.1 M n-Bu4NPF6/MeCN at a scan rate of 100 mV·s−1.
1
(KBr disk): νCO 2043 (vs), 1981 (vs), 1948 (s), 1933 (s) cm−1. H
NMR (400 MHz, CDCl3, TMS): 1.36 (t, 2Ha, JHaHe = JHaHa′ = 12.0
Hz), 2.13−2.18 (m, 1Ha′), 2.39 (dd, 2He, JHeHa = 12.8 Hz, JHeHa′ = 4.0
Hz), 3.63 (s, 2H, OCH2), 6.96−7.22 (m, 5H, C6H5CH2), 7.43−7.68
(m, 15H, (C6H5)3P) ppm. 31P{1H} NMR (162 MHz, CDCl3, 85%
H3PO4): 65.04 (s) ppm. 4: mp 185−186 °C. Anal. Calcd for
C50H42Fe2O5P2S2: C, 62.51; H, 4.41. Found: C, 62.47; H, 4.56. IR
1
(KBr disk): νCO 1998 (vs), 1954 (vs), 1937 (vs) cm−1. H NMR
(300 MHz, CDCl3, TMS): 1.71−2.00 (m, 5H, OCH, 2SCH2), 3.31 (s,
2H, OCH2), 6.73−7.71 (m, 35H, 7C6H5) ppm. 31P{1H} NMR (162
MHz, CDCl3, 85% H3PO4): 61.60 (s), 62.35 (s) ppm. Method (ii),
Preparation of 4 from Monosubstituted Complex 3: To a red solution
of 3 (0.363 g, 0.50 mmol) in MeCN (15 mL) were added PPh3 (0.262
mL, 1.00 mmol) and Me3NO·2H2O (0.056 g, 0.50 mmol). After the
mixture was stirred at room temperature for 12 h and the same workup
as that described above, 4 (0.384 g, 80%) was obtained.
Figure 7. Cyclic voltammograms of 3 (1.0 mM) with HOAc (0−10
mM) in 0.1 M n-Bu4NPF6/MeCN at a scan rate of 100 mV·s−1.
Preparation of [(μ-SCH2)2CH(OCH2Ph)]Fe2(CO)4(PPh3)(PMe3)
(5). To a red solution of 4 (0.482 g, 0.50 mmol) in toluene (15 mL)
was added PMe3 (1.0 mL, 1.00 mmol), and then the mixture was
stirred at reflux for 4.5 h. After removal of solvent at reduced pressure,
the residue was subjected to TLC separation using CH2Cl2/petroleum
ether (1:3 v/v) as eluent. From the main red band, 5 was obtained as a
red solid (0.292 g, 75%), mp 89−90 °C. Anal. Calcd for
C35H36Fe2O5P2S2: C, 54.28; H, 4.69. Found: C, 54.36; H, 4.68. IR
(KBr disk): νCO 1998 (s), 1986 (vs), 1948 (vs), 1915 (vs) cm−1. 1H
NMR (300 MHz, CDCl3, TMS): 0.85 (t, 2Ha, JHaHe = JHaHa′ = 7.5 Hz),
1.40 (d, 9H, JPH = 9.0 Hz, 3CH3), 2.13 (dd, 2He, JHeHa = 12.3 Hz, JHeHa′
= 3.9 Hz), 2.72−2.81 (m, 1Ha′), 4.14 (s, 2H, OCH2), 7.02−7.19 (m,
5H, C6H5CH2), 7.34−7.68 (m, 15H, (C6H5)3P) ppm. 31P{1H} NMR
(162 MHz, CDCl3, 85% H3PO4): 27.31 (s), 62.08 (s) ppm.
1
2033 (vs), 1973 (vs), 1955 (vs) cm−1. H NMR (400 MHz, CDCl3,
TMS): 1.36−1.50 (m, 2Ha), 2.00 (s, 6H, 2o-CH3 of C6H2), 2.36 (s,
3H, p-CH3 of C6H2), 2.66−2.69 (m, 2He), 3.86 (s, 3H, NCH3), 4.18−
4.33 (m, 3H, 1Ha′, OCH2), 6.84 (s, 1H, MeNCHCH), 6.96 (s, 1H,
MesNCHCH), 7.00 (s, 2H, 2m-H of Mes), 7.12−7.30 (m, 5H,
C6H5) ppm.
Preparation of [(μ-SCH2)2CH(OCH2Ph)]Fe2(CO)5(PMe3) (2). To
a red solution of A (0.246 g, 0.50 mmol) in MeCN (15 mL) were
added PMe3 (0.50 mL, 0.50 mmol) and Me3NO·2H2O (0.056 g, 0.50
mmol). The mixture was stirred at room temperature for 2.5 h to give
a deep-red solution. Volatiles were removed in vacuo, and the residue
was subjected to TLC separation using CH2Cl2/petroleum ether (1:5
v/v) as eluent. From the main red band, 2 was obtained as a red oil
(0.128 g, 47%). Anal. Calcd for C18H21Fe2O6PS2: C, 40.02; H, 3.92.
Found: C, 40.16; H, 4.09. IR (KBr disk): νCO 2034 (vs), 1944 (vs),
1910 (vs) cm−1. 1H NMR (400 MHz, CDCl3, TMS): 1.47 (d, 9H, JPH
Preparation of [(μ-SCH2)2CH(OCH2Ph)]Fe2(CO)4(dppe) (6). To
a red solution of A (0.100 g, 0.20 mmol) in toluene (15 mL) was
added dppe (0.081 g, 0.20 mmol), and then the mixture was stirred at
reflux for 4.5 h. After solvent was removed at reduced pressure, the
residue was subjected to TLC separation using CH2Cl2/petroleum
= 9.6 Hz, 3CH3), 1.51 (d, 2Ha, JHaHe = 11.6 Hz), 2.81 (dd, 2He, JHeHa
=
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Organometallics
Article
ether (2:1 v/v) as eluent. From the main brown band, 6 was obtained
as a brown solid (0.030 g, 18%), mp 178−179 °C. Anal. Calcd for
C40H36Fe2O5P2S2: C, 57.57; H, 4.35. Found: C, 57.35; H, 4.36. IR
(KBr disk): νCO 2016 (vs), 1950 (vs), 1934 (vs), 1891 (s) cm−1. 1H
NMR (300 MHz, CDCl3, TMS): 1.36−1.45 (m, 2Ha), 2.22−2.32 (m,
1Ha′), 2.45−2.69 (m, 6H, 2He, 2PCH2), 3.54 (s, 2H, OCH2), 6.82−
7.73 (m, 25H, 5C6H5) ppm. 31P{1H} NMR (162 MHz, CDCl3, 85%
H3PO4): 91.02 (s) ppm.
ACKNOWLEDGMENTS
■
We are grateful to 973 (2011CB935902), the National Natural
Science Foundation of China (21132001, 20972073), and the
Tianjin Natural Science Foundation (09JCZDJC27900) for
financial support.
REFERENCES
■
Preparation of {[(μ-SCH2)2CH(OCH2Ph)]Fe2(CO)5}2(dppe) (7).
To a red solution of A (0.100 g, 0.20 mmol) in MeCN (10 mL) were
added dppe (0.081 g, 0.20 mmol) and Me3NO·2H2O (0.023 g, 0.20
mmol). The mixture was stirred at room temperature for 10 h to give a
red solution. Volatiles were removed in vacuo, and the residue was
subjected to TLC separation using CH2Cl2/petroleum ether (1:2 v/v)
as eluent. From the main red band, 7 was obtained as a red solid
(0.022 g, 17%), mp 180 °C (dec). Anal. Calcd for C56H48Fe4O12P2S4:
C, 50.70; H, 3.65. Found: C, 50.63; H, 3.88. IR (KBr disk): νCO 2046
(1) (a) Adams, M. W. W.; Stiefel, E. I. Science 1998, 282, 1842.
(b) Cammack, R. Nature 1999, 397, 214. (c) Nicolet, Y.; Cavazza, C.;
Fontecilla-Camps, J. C. J. Inorg. Biochem. 2002, 91, 1. (d) Tamagnini,
P.; Axelsson, R.; Lindberg, P.; Oxelfelt, F.; Wunschiers, R.; Lindblad, P.
Microbiol. Mol. Biol. Rev. 2002, 66, 1.
(2) (a) Nicolet, Y.; Lemon, B. J.; Fontecilla-Camps, J. C.; Peters, J.
W. Trends Biochem. Sci. 2000, 25, 138. (b) Peters, J. W. Curr. Opin.
Struct. Biol. 1999, 9, 670.
(3) (a) Przybyla, A. E.; Robbins, J.; Menon, N. Jr.; Peck, H. D. FEMS
Microbiol. Rev. 1992, 88, 109. (b) Garcin, E.; Vernede, X.; Hatchikian,
E. C.; Volbeda, A.; Frey, M.; Fontecilla-Camps, J. C. Structure 1999, 7,
557. (c) Volbeda, A.; Fontecilla-Camps, J. C. Dalton Trans. 2003,
4030.
̈
1
(vs), 1981 (vs), 1933 (s) cm−1. H NMR (400 MHz, CDCl3, TMS):
1.31 (t, 4Ha, JHaHe = JHaHa′ = 11.6 Hz), 2.29 (d, 4He, JHeHa = 11.6 Hz),
2.34−2.40 (m, 2Ha′), 2.65 (s, 4H, 2PCH2), 4.00 (s, 4H, OCH2), 7.09−
7.57 (m, 30H, 6C6H5) ppm. 31P{1H} NMR (162 MHz, CDCl3, 85%
H3PO4): 59.32 (s) ppm.
(4) Alper, J. Science 2003, 299, 1686.
X-ray Structure Determinations of 1 and 4−7. Single crystals
of 1 and 4−7 suitable for X-ray diffraction analysis were grown by slow
evaporation of their CH2Cl2/petroleum ether solutions at about −4
°C. Each crystal was mounted on a Rigaku MM-007 (rotating anode)
diffractometer equipped with a Saturn 70CCD. Data were collected at
room temperature, using a confocal monochromator with Mo Kα
radiation (λ = 0.71070 or 0.71073 Å) in the ω−ϕ scanning mode.
Data collection, reduction, and absorption correction were performed
with the CRYSTALCLEAR program.35 The structures were solved by
direct methods using the SHELXS-97 program36 and refined by full-
matrix least-squares techniques (SHELXL-97)37 on F2. Hydrogen
atoms were located by using the geometric method. Details of crystal
data, data collections, and structure refinements are summarized in
Tables 3 and 4, respectively, in the Supporting Information.
Electrochemistry. A solution of 0.1 M n-Bu4NPF6 in MeCN
(Fisher Chemicals, HPLC grade) was used as electrolyte in all cyclic
voltammetric experiments. The electrolyte solution was degassed by
bubbling with N2 for at least 10 min before measurement.
Electrochemical measurements were made using a BAS Epsilon
potentiostat. All voltammograms were obtained in a three-electrode
cell with a 3 mm diameter glassy carbon working electrode, platinum
counter electrode, and Ag/Ag+ (0.01 M AgNO3/0.1 M n-Bu4NPF6 in
MeCN) reference electrode under a N2 atmosphere. The working
electrode was polished with 1 μm alumina paste and sonicated in water
for about 10 min prior to use. Bulk electrolyses were carried out under
N2 on a glassy carbon rod (A = 2.9 cm2) in a two-compartment,
gastight, H-type electrolysis cell containing 25 mL of MeCN. All
potentials are quoted against the ferrocene/ferrocenium (Fc/Fc+)
potential. Gas chromatography was performed with a Shimadzu GC-
2014 gas chromatograph under isothermal conditions with nitrogen as
a carrier gas and a thermal conductivity detector.
(5) Darensbourg, M. Y.; Lyon, E. J.; Smee, J. J. Coord. Chem. Rev.
2000, 206−207, 533.
(6) Evans, D. J.; Pickett, C. J. Chem. Soc. Rev. 2003, 32, 268.
(7) Adams, M. W. W. Biochim. Biophys. Acta, Bioenerg. 1990, 1020,
115.
(8) Peters, J. W.; Lanzilotta, W. N.; Lemon, B. J.; Seefeldt, L. C.
Science 1998, 282, 1853.
(9) Nicolet, Y.; Piras, C.; Legrand, P.; Hatchikian, C. E.; Fontecilla-
Camps, J. C. Structure 1999, 7, 13.
(10) Lemon, B. J.; Peters, J. W. Biochemistry 1999, 38, 12969.
̀
(11) 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.
(12) Pierik, A. J.; Hulstein, M.; Hagen, W. R.; Albracht, S. P. J. Eur. J.
Biochem. 1998, 258, 572.
(13) De Lacey, A. L.; Stadler, C.; Cavazza, C.; Hatchikian, E. C.;
Fernandez, V. M. J. Am. Chem. Soc. 2000, 122, 11232.
(14) Chen, Z.; Lemon, B. J.; Huang, S.; Swartz, D. J.; Peters, J. W.;
Bagley, K. A. Biochemistry 2002, 41, 2036.
(15) Fan, H.-J.; Hall, M. B. J. Am. Chem. Soc. 2001, 123, 3828.
(16) (a) Zhao, X.; Georgakaki, I. P.; Miller, M. L.; Yarbrough, J. C.;
Darensbourg, M. Y. J. Am. Chem. Soc. 2001, 123, 9710. (b) Boyke, C.
́
A.; Rauchfuss, T. B.; Wilson, S. R.; Rohmer, M.-M.; Benard, M. J. Am.
Chem. Soc. 2004, 126, 15151. (c) Razavet, M.; Davies, S. C.; Hughes,
D. L.; Barclay, J. E.; Evans, D. J.; Fairhurst, S. A.; Liu, X.; Pickett, C. J.
Dalton Trans. 2003, 586. (d) Song, L.-C.; Cheng, J.; Yan, J.; Wang, H.-
T.; Liu, X.-F.; Hu, Q.-M. Organometallics 2006, 25, 1544. (e) Wang,
W.-G.; Wang, H.-Y.; Si, G.; Tung, C.-H.; Wu, L.-Z. Dalton Trans.
2009, 2712. (f) Zhan, C.; Wang, X.; Wei, Z.; Evans, D. J.; Ru, X.; Zeng,
X.; Liu, X. Dalton Trans. 2010, 39, 11255. (g) Xu, F.; Du, S.; Liu, Y.;
Hassan, J.; Zhang, J.; Bond, A. M. Dalton Trans. 2011, 40, 10907.
(17) (a) Li, H.; Rauchfuss, T. B. J. Am. Chem. Soc. 2002, 124, 726.
(b) Song, L.-C.; Yang, Z.-Y.; Bian, H.-Z.; Hu, Q.-M. Organometallics
2004, 23, 3082. (c) Schwartz, L.; Eilers, G.; Eriksson, L.; Gogoll, A.;
Lomoth, R.; Ott, S. Chem. Commun. 2006, 520. (d) Song, L.-C.; Tang,
M.-Y.; Su, F.-H.; Hu, Q.-M. Angew. Chem., Int. Ed. 2006, 45, 1130.
ASSOCIATED CONTENT
■
S
* Supporting Information
Full tables of crystal data, atomic coordinates, thermal
parameters, and bond lengths and angles for 1 and 4−7 as
CIF files. This material is available free of charge via the
Internet at http://pubs.acs.org.
(e) Apfel, U.-P.; Kowol, C. R.; Kloss, F.; Gorls, H.; Keppler, B. K.;
Weigand, W. J. Organomet. Chem. 2011, 696, 1084. (f) Apfel, U.-P.;
Kowol, C. R.; Halpin, Y.; Kloss, F.; Kubel, J.; Gorls, H.; Vos, J. G.;
Keppler, B. K.; Morera, E.; Lucente, G.; Weigand, W. J. Inorg. Biochem.
̈
̈
̈
2009, 103, 1236. (g) Jablonskyte, A.; Wright, J. A.; Pickett, C. J. Eur. J.
Inorg. Chem. 2011, 1033.
(18) Gloaguen, F.; Lawrence, J. D.; Rauchfuss, T. B. J. Am. Chem. Soc.
2001, 123, 9476.
(19) Chong, D.; Georgakaki, I. P.; Mejia-Rodriguez, R.; Sanabria-
Chinchilla, J.; Soriaga, M. P.; Darensbourg, M. Y. Dalton Trans. 2003,
4158.
̇
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: lcsong@nankai.edu.cn.
Notes
The authors declare no competing financial interest.
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Article
(20) Capon, J.-F.; Gloaguen, F.; Schollhammer, P.; Talarmin, J.
Coord. Chem. Rev. 2005, 249, 1664.
(21) Seyferth, D.; Henderson, R. S.; Song, L.-C. J. Organomet. Chem.
1980, 192, C1.
(22) Song, L.-C.; Li, C.-G.; Gao, J.; Yin, B.-S.; Luo, X.; Zhang, X.-G.;
Bao, H.-L.; Hu, Q.-M. Inorg. Chem. 2008, 47, 4545.
(23) Winter, A.; Zsolnai, L.; Huttner, G. Z. Naturforsch. 1982, 37b,
1430.
(24) Arduengo, A. J. III; Rasika Dias, H. V.; Harlow, R. L.; Kline, M.
J. Am. Chem. Soc. 1992, 114, 5530.
(25) Elschenbroich, C. Organometallics; Wiley-VCH: Weinheim,
Germany, 2006.
(26) (a) Albers, M. O.; Coville, N. J. Coord. Chem. Rev. 1984, 53, 227.
(b) Shen, J.-K.; Gao, Y.-C.; Shi, Q.-Z.; Basolo, F. Coord. Chem. Rev.
1993, 128, 69.
(27) Collman, J. P.; Hegedus, L. S. Principles and Applications of
Organotransition Metal Chemistry; University Science Books: Califonia,
1980.
(28) Zanello, P. Inorganic Electrochemistry Theory, Practice and
Application; Thomas Graham House: Cambridge, UK, 2003.
(29) Song, L.-C.; Yang, Z.-Y.; Bian, H.-Z.; Liu, Y.; Wang, H.-T.; Liu,
X.-F.; Hu, Q.-M. Organometallics 2005, 24, 6126.
(30) Borg, S. J.; Behrsing, T.; Best, S P.; Razavet, M.; Liu, X.; Pickett,
C. J. J. Am. Chem. Soc. 2004, 126, 16988.
(31) Mejia-Rodriguez, R.; Chong, D.; Reibenspies, J. H.; Soriaga, M.
P.; Darensbourg, M. Y. J. Am. Chem. Soc. 2004, 126, 12004.
(32) Seyferth, D.; Henderson, R. S.; Song, L.-C. Organometallics
1982, 1, 125.
(33) Kasireddy, K.; Ali, S. M.; Ahmad, M. U.; Choudhury, S.; Chien,
P.-Y.; Sheikh, S.; Ahmad, I. Bioorg. Chem. 2005, 33, 345.
(34) Bricklebank, N.; Godfrey, S. M.; McAuliffe, C. A.; Deplano, P.;
Mercuri, M. L.; Sheffield, J. M. Dalton Trans. 1998, 2379.
(35) Sheldrick, G. M. SADABS, A Program for Empirical Absorption
Correction of Area Detector Data; University of Gottingen: Germany,
̈
1996.
(36) Sheldrick, G. M. SHELXS97, A Program for Crystal Structure
Solution; University of Gottingen: Germany, 1997.
̈
(37) Sheldrick, G. M. SHELXL97, A Program for Crystal Structure
Refinement; University of Gottingen: Germany, 1997.
̈
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