Synthesis, characterization and crystal structures of carboxy- functionalized diiron propanedithiolate complexes

Article abstract of DOI:10.1016/j.poly.2013.01.048

Four new carboxy-functionalized diiron propanedithiolate complexes 1-4 have been successfully synthesized and fully characterized. The all-carboxyl complexes [(μ-SCH₂)₂CHCO₂CH ₂CH₂Cl][Fe₂(CO)₆] (1) and [(μ-SCH₂)₂CHCO₂C₆H ₄I-p][Fe₂(CO)₆] (2) were prepared by the condensation reaction of the known complex [(μ-SCH₂) ₂CHCO₂H][Fe₂(CO)₆] (A) with ClCH₂CH₂OH and p-IC₆H₄OH in the presence of 4-dimethylaminopyridine (DMAP) and dicyclohexylcarbodiimide (DCC) in yields of 46% and 66%, whereas the phosphine-substituted complexes [(μ-SCH₂)₂CHCO₂CH₂CH ₂Cl][Fe₂(CO)₅PPh₃] (3) and [(μ-SCH₂)₂CHCO₂CH₂CH ₂Cl][Fe₂(CO)₄(PPh₃)₂] (4) were further synthesized through the carbonyl substitution reaction of 1 with PPh₃ using the decarbonylating agent Me₃NO·2H ₂O in yields of 44% and 41%. The new complexes 1-4 were characterized by combustion analysis, IR and ¹H, ¹³C and ³¹P NMR spectroscopic techniques. The molecular structures of 1-4 were unequivocally determined by single crystal X-ray diffraction analysis, in which the carboxy-functionalized substituent attached to the bridgehead-C atom resides in an equatorial position of the six-membered rings in the solid state.

Full text of DOI:10.1016/j.poly.2013.01.048

Polyhedron 53 (2013) 144–149
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, characterization and crystal structures of carboxy-functionalized
diiron propanedithiolate complexes
⇑
Pei-Hua Zhao , Ya-Qing Liu, Gui-Zhe Zhao
Research Center for Engineering Technology of Polymeric Composites of Shanxi Province, College of Materials Science and Engineering, North University of China, Taiyuan 030051,
PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Four new carboxy-functionalized diiron propanedithiolate complexes 1–4 have been successfully synthe-
Received 12 September 2012
Accepted 11 January 2013
Available online 9 February 2013
sized and fully characterized. The all-carboxyl complexes [(
[( -SCH2)2CHCO2C6H4I-p][Fe2(CO)6] (2) were prepared by the condensation reaction of the known com-
plex [( -SCH2)2CHCO2H][Fe2(CO)6] (A) with ClCH2CH2OH and p-IC6H4OH in the presence of 4-dimethyl-
aminopyridine (DMAP) and dicyclohexylcarbodiimide (DCC) in yields of 46% and 66%, whereas the
phosphine-substituted complexes [( -SCH2)2CHCO2CH2CH2Cl][Fe2(CO)5PPh3] (3) and [( -SCH2)2CHCO2-
CH2CH2Cl][Fe2(CO)4(PPh3)2] (4) were further synthesized through the carbonyl substitution reaction of
1 with PPh3 using the decarbonylating agent Me3NOꢀ2H2O in yields of 44% and 41%. The new complexes
1–4 were characterized by combustion analysis, IR and 1H, 13C and 31P NMR spectroscopic techniques.
The molecular structures of 1–4 were unequivocally determined by single crystal X-ray diffraction anal-
ysis, in which the carboxy-functionalized substituent attached to the bridgehead-C atom resides in an
equatorial position of the six-membered rings in the solid state.
l-SCH2)2CHCO2CH2CH2Cl][Fe2(CO)6] (1) and
l
l
Keywords:
l
l
Diiron propanedithiolate
Carboxy-functionalized
Synthesis
Crystal structure
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
[(l-SCH2)2CHCO2C6H4I-p][Fe2(CO)6] (2) [(
l-SCH2)2CHCO2CH2-
CH2Cl][Fe2(CO)5PPh3]
(3)
and
[(l-SCH2)2CHCO2CH2CH2Cl]-
In the 1980s, Seyferth et al. reported that the diiron propanedi-
[Fe2(CO)4(PPh3)2] (4).
thiolate complex [(
prepared via two methods: by the reaction of (
(generated in situ from ( -S2)Fe2(CO)6 and LiBEt3H in THF at
l
-SCH2)2CH2][Fe2(CO)6] could be commonly
l
-LiS)2Fe2(CO)6
2. Experimental
l
ꢁ78 °C) with BrCH2CH2CH2Br [1], or by the reaction of Fe3(CO)12
with HSCH2CH2CH2SH at reflux in toluene or THF [2,3]. More
recently, Darensbourg and co-workers covered that the carboxy-
2.1. Materials and methods
All reactions and operations were carried out under a dry, oxy-
gen-free nitrogen atmosphere with standard Schlenk and vacuum-
line techniques. CH2Cl2 and MeCN were distilled with CaH2 under
N2. Dicyclohexylcarbodiimide (DCC), N,N-dimethylaminopyridine
(DMAP), ClCH2CH2OH, p-IC6H4OH, Me3NOꢀ2H2O, PPh3, and other
materials were commercially available and used as received.
containing diiron propanedithiolate complex [(l-SCH2)2CHCO2-
H][Fe2(CO)6] was synthesized using the same method as Seyferth’s
group [4], which was regarded as the active site model of [FeFe]-
hydrogenase that catalyzed the production/uptake of dihydrogen
and featured a butterfly 2Fe2S subunit, having CO/CN ligands, a
bridging dithiolate ligand as well as a cysteinyl-S-linked cubic
4Fe4S cluster [5–10]. Notably, the design of models for [FeFe]-
hydrogenase was of great interest in the field of bioorganometallic
chemistry. This interest was attributed to the need to develop an
efficient and inexpensive catalyst for the generation of hydrogen,
a clean and ideal alternative to fossil fuels [11–13].
[(l-SCH2)2CHCO2H][Fe2(CO)6] was prepared according to the liter-
ature [4]. Preparative TLC was carried out on glass plates
(25 cm ꢂ 20 cm ꢂ 0.25 cm) coated with silica gel H (10–40 mm).
IR spectra were recorded on a Nicolet 670 FTIR spectrometer. 1H,
13C and 31P NMR spectra were obtained on a Bruker Avance
400 MHz spectrometer. Elemental analyses were performed on a
Perkin–Elmer 240C analyzer. Melting points were determined on
a YRT-3 apparatus and are uncorrected.
In order to extend this kind of [FeFe]-hydrogenase model, we
herein report the synthesis, characterization and crystal structures
of four new carboxy-functionalized diiron propanedithiolate
complexes, namely [(l-SCH2)2CHCO2CH2CH2Cl][Fe2(CO)6] (1),
2.2. Synthesis of [(l-SCH2)2CHCO2CH2CH2Cl][Fe2(CO)6] (1)
⇑
A CH2Cl2 (20 mL) solution of [(
(0.430 g, 1.0 mmol), DCC (0.206 g, 1.0 mmol) and DMAP (0.013 g,
l-SCH2)2CHCO2H][Fe2(CO)6]
Corresponding author. Tel./fax: +86 351 3559669.
E-mail address: zph2004@yahoo.com.cn (P.-H. Zhao).
0277-5387/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2013.01.048

P.-H. Zhao et al. / Polyhedron 53 (2013) 144–149
145
Table 1
Crystal data and structural refinements details for complexes 1–4.
Complex
1
2
3
4
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C
12H9ClFe2O8S2
C16H9Fe2IO8S2
631.95
113(2)
0.71073
triclinic
C29H24ClFe2O7PS2
726.72
113(2)
0.71073
monoclinic
P2(1)/c
11.366(5)
16.097(8)
16.849(8)
90
96.729(7)
90
C46H39ClFe2O6P2S2
960.98
113(2)
0.71073
triclinic
492.46
113(2)
0.71073
monoclinic
P2(1)/c
10.399(3)
8.829(2)
19.620(5)
90
92.026(5)
90
1800.1(8)
4
1.810
ꢀ
ꢀ
P1
P1
7.600(5)
10.929(6)
14.691(7)
15.099(7)
65.017(16)
81.94(3)
87.78(3)
2175.2(19)
2
b (Å)
c (Å)
11.525(7)
12.378(8)
102.320(5)
96.523(16)
105.282(13)
1005.0(11)
2
a
(°)
b (°)
c
(°)
V (Å3)
3061(3)
4
1.577
1.268
Z
Dcalc (g cmꢁ3
)
2.088
3.228
1.467
0.946
l
(mmꢁ1
)
2.027
F(000)
976
612
1480
988
Crystal size (mm)
hmin, hmax (°)
Reflections collected/unique
Rint
0.20 ꢂ 0.18 ꢂ 0.08
1.96, 27.83
18181/4272
0.0416
0.20 ꢂ 0.18 ꢂ 0.10
1.71, 27.85
10560/4700
0.0311
0.24 ꢂ 0.20 ꢂ 0.16
1.76, 27.91
30899/7224
0.0419
0.30 ꢂ 0.24 ꢂ 0.20
1.50, 25.02
17337/7455
0.1075
hkl Range
ꢁ13 6 h 6 13
ꢁ11 6 k 6 11
ꢁ24 6 l 6 25
100.0
4272/20/236
0.996
ꢁ9 6 h 6 9
ꢁ15 6 k 6 15
ꢁ16 6 l 6 16
98.7
4700/0/262
1.011
ꢁ14 6 h 6 14
ꢁ21 6 k 6 21
ꢁ19 6 l 6 22
98.9
7224/0/379
1.044
ꢁ12 6 h 6 13
ꢁ17 6 k 6 17
ꢁ17 6 l 6 17
97.1
7455/86/586
1.059
Completeness to hmax (%)
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
R1/wR2 [I > 2
r
(I)]
0.0273/0.0568
0.0362/0.0591
0.804/ꢁ0.474
0.0227/0.0438
0.0296/0.0445
0.626/ꢁ0.701
0.0231/0.0552
0.0277/0.0564
0.319/ꢁ0.417
0.0749/0.1983
0.0831/0.2072
0.753/ꢁ0.775
R1/wR2 (all data)
Largest difference peak/hole (e Aꢁ3
)
Scheme 1. Preparation of the all-carbonyl complexes 1 and 2.
Scheme 2. Preparation of the phosphine-substituted complexes 3 and 4.

146
P.-H. Zhao et al. / Polyhedron 53 (2013) 144–149
Fig. 3. Molecular structure of 3 with thermal ellipsoids at 50% probability.
Fig. 1. Molecular structure of 1 with thermal ellipsoids at 50% probability.
for C12H9ClFe2O8S2: C, 29.27; H, 1.84. Found: C, 29.48; H, 2.10%. IR
(KBr disk, cmꢁ1):
mC„O 2076 (vs), 2033 (vs), 1993 (vs); mC(O)O 1738
(s). 1H NMR (400 MHz, CDCl3, TMS, ppm): 4.31 (s, 2H, OCH2), 3.65
(s, 2H, CH2Cl), 2.90 (s, 2H, 2SCHaHe), 2.17 (s, 1H, CH), 1.75 (s, 2H,
2SCHaHe). 13C NMR (100.6 MHz, CDCl3, TMS, ppm): 207.39 (s,
FeCO), 170.61 (s, C(O)O), 64.69 (s, OCH2), 48.00 (s, CH), 41.27 (s,
CH2Cl), 24.68 (s, SCH2).
2.3. Synthesis of [(l-SCH2)2CHCO2C6H4I-p][Fe2(CO)6] (2)
The procedure was similar to that of 1 except p-IC6H4OH
(0.264 g, 1.2 mmol) was used instead of ClCH2CH2OH (0.1 mL,
1.5 mmol). Complex 2 (0.419 g, 66%) was obtained as a red solid.
Mp: 140–141 °C. Anal. Calc. for C16H9Fe2IO8S2: C, 30.41; H, 1.44.
Found: C, 30.55; H, 1.70%. IR (KBr disk, cmꢁ1): mC„O 2084 (s),
2068 (s), 2042 (vs), 2006 (vs); mC(O)O 1743 (s). 1H NMR (400 MHz,
CD3COCD3, TMS, ppm): 7.76, 6.96 (d, d, J = 8.8, 8.8 Hz, 2H, 2H,
PhH), 3.19 (dd, J = 13.6, 3.6 Hz, 2H, 2SCHaHe), 2.54 (m, 1H, CH),
2.01 (d, J = 13.6 Hz, 2H, 2SCHaHe). 13C NMR (100.6 MHz, CD3COCD3,
TMS, ppm): 208.76 (s, FeCO), 169.99 (s, C(O)O), 151.56 (s, PhC),
139.37 (s, PhCH), 124.91 (s, PhCH), 90.47 (s, PhC), 49.06 (s, CH),
25.06 (s, SCH2).
2.4. Synthesis of [(
l-SCH2)2CHCO2CH2CH2Cl][Fe2(CO)5PPh3] (3) and
[(l-SCH2)2CHCO2CH2CH2Cl][Fe2(CO)4(PPh3)2] (4)
A mixture of 2 (0.221 g, 0.45 mmol), PPh3 (0.131 g, 0.50 mmol),
and Me3NOꢀ2H2O (0.056 g, 0.50 mmol) were dissolved in MeCN
(15 mL). The mixture was stirred at room temperature for 2 h to
give a black-red solution. The solvent was removed on a rotary
evaporator and the residue was subjected to preparative TLC sepa-
ration using CH2Cl2/petroleum ether (v/v = 2:3) as the eluent. Two
main red bands were collected. From the first brown-red band,
complex 3 (0.144 g, 44%) was obtained as a brown-red solid. Mp:
133–134 °C. Anal. Calc. for C29H24ClFe2O7PS2: C, 47.93; H, 3.33.
Found: C, 48.17; H, 3.19%. IR (KBr disk, cmꢁ1): mC„O 2045 (vs),
1983 (vs), 1936 (vs); mC(O)O 1736 (m). 1H NMR (400 MHz, CDCl3,
TMS, ppm): 7.67 (s, 6H, 3m-PhH), 7.45 (s, 9H, 3o, p-PhH), 4.05 (s,
Fig. 2. Molecular structure of 2 with thermal ellipsoids at 50% probability.
0.1 mmol) was stirred at room temperature for 5 min. To this
mixture ClCH2CH2OH (0.08 mL, 1.2 mmol) was added, and the
new mixture was stirred at room temperature for 12 h. The solvent
was removed on a rotary evaporator and the residue was subjected
to preparative TLC separation using CH2Cl2/petroleum ether
(v/v = 1:2) as the eluent. From the main red band, complex 1
(0.226 g, 46%) was obtained as a red solid. Mp: 70–71 °C. Anal. Calc.

P.-H. Zhao et al. / Polyhedron 53 (2013) 144–149
147
Fig. 4. Molecular structure of 4 with thermal ellipsoids at 50% probability.
2H, OCH2), 3.46 (s, 2H, CH2Cl), 2.27 (d, J = 11.2 Hz, 2H, 2SCHaHe),
1.69 (br s, 3H, 2SCHaHe, CH). 13C NMR (100.6 MHz, CDCl3, TMS,
presence of DCC as a dehydrating agent in CH2Cl2 followed by
the addition of 1.2 equiv. of ClCH2CH2OH or p-IC6H4OH afforded
2
ppm): 213.50 (d, JPC = 9.9 Hz, PFeCO), 208.85 (s, FeCO), 170.96 (s,
the carboxy-functionalized all-carboxyl complex [(
l-SCH2)2-
C(O)O), 135.82 (d, 1JPC = 40.2 Hz, ipso-PhC), 133.32 (d, 2JPC = 10.9 Hz,
CHCO2CH2CH2Cl][Fe2(CO)6] (1) or [( -SCH2)2CHCO2C6H4I-p][Fe2(-
l
3
o-PhCH), 130.40 (s, p-PhCH), 128.68 (d, JPC = 9.5 Hz, m-PhCH),
CO)6] (2) in 46% or 66% yield, respectively.
64.11 (s, OCH2), 47.43 (s, CH), 41.27 (s, CH2Cl), 24.92 (s, SCH2).
31P NMR (161.9 MHz, CDCl3, 85% H3PO4, ppm): 63.47 (s). From
the second dark-red band, complex 4 (0.189 g, 41%) was obtained
as a dark-red solid. Mp: 173–174 °C. Anal. Calc. for C46H39ClFe2O6-
PS2: C, 57.49; H, 4.09. Found: C, 57.23; H, 4.38%. IR (KBr disk,
cmꢁ1): mC„O 1997 (vs), 1954 (vs), 1935 (vs); mC(O)O 1734 (m). 1H
NMR (400 MHz, CDCl3, TMS, ppm): 7.72 (s, 12H, 6m-PhH), 7.39
(s, 18H, 6o, p-PhH), 3.81 (s, 2H, OCH2), 3.28 (s, 2H, CH2Cl), 1.76
(br s, 5H, 2SCH2, CH). 13C NMR (100.6 MHz, CDCl3, TMS, ppm):
Complexes 1 and 2 are stable in air and are soluble in most or-
ganic solvents, such as dichloromethane, acetone and ethyl acetate
etc., and they have been fully characterized by elemental analysis,
IR, 1H NMR and 13C NMR spectroscopy. The IR spectra of 1 and 2
display three or four strong absorption bands in the range 2084–
1993 cmꢁ1 for their terminal carbonyls and one absorption band
at 1738 or 1743 cmꢁ1 for their ester carbonyl.
The 1H NMR spectra display a singlet at 2.17 ppm for 1 and
2.54 ppm for 2, ascribed to the methine proton attached to the
bridgehead-C atom of their propanedithiolate moieties. The 1H
NMR spectra show two singlets at 2.90 and 1.75 ppm for 1 and a
double-doublet as well as a doublet at 3.19 and 2.01 ppm for 2,
which are assigned to the equatorial and axial protons for their
SCH2 groups. Meanwhile, the 1H NMR spectrum of 1 exhibits two
singlets at 4.31 and 3.65 ppm for the methylene protons in its
ClCH2CH2O group, whereas that of 2 displays two doublets at
7.76 and 6.96 ppm for the aryl protons in its p-IC6H4O group. Addi-
tionally, the 13C NMR spectra of 1 and 2 demonstrate a singlet at
about 208 ppm for their terminal coordinated carbonyls and a sin-
glet at approximately 170 ppm for their ester carbonyls.
2
215.62, 214.66 (2d, JPC = 10.9, 9.7 Hz, PFeCO), 171.31 (s, C(O)O),
1
136.79, 136.23 (2d, JPC = 36.3, 35.9 Hz, ipso-PhC), 133.48 (d,
2
3JPC = 9.3 Hz, m-PhCH), 129.87 (s, p-PhCH), 128.57 (d, JPC = 9.5 Hz,
o-PhCH), 63.56 (s, OCH2), 47.47 (s, CH), 41.21 (s, CH2Cl), 22.75 (s,
SCH2). 31P NMR (161.9 MHz, CDCl3, 85% H3PO4, ppm): 61.68 (s),
60.49 (s).
2.5. X-ray structure determination
Single crystals of 1–4 suitable for X-ray diffraction analysis
were grown by slow evaporation of a CH2Cl2/hexane solution at
5 °C. Single crystals of 1–4 were mounted on a Rigaku MM-007
CCD diffractometer. Data were collected at 113 (2) K by using a
3.2. Synthesis and spectroscopic characterization of the phosphine-
substituted complexes 3 and 4
graphite monochromator with Mo Ka radiation (k = 0.71073 Å) in
the scanning mode. Data collection, reduction and absorption
x–u
corrections were performed by the CRYSTALCLEAR program [14]. The
structures were solved by direct methods using the SHELXS-97
program [15] and refined by full-matrix least-squares techniques
As shown in Scheme 2, reaction of the parent complex [(l-
SCH2)2CHCO2CH2CH2Cl][Fe2(CO)6] (1) with 1.0 equiv. of Me3-
NOꢀ2H2O in MeCN followed by addition of 1.1 equiv. of PPh3 at
(
SHELXL-97) [16] on F2. Hydrogen atoms were located using the
room temperature gave the PPh3-monosubstituted complex [(l-
geometric method. A summary of the cell parameters, data
collection and structure refinement is list in Table 1.
SCH2)2CHCO2CH2CH2Cl][Fe2(CO)5PPh3] (3) and the PPh3-disubsti-
tuted complex [( -SCH2)2CHCO2CH2CH2Cl][Fe2(CO)4(PPh3)2] (4)
l
in 44% and 41% yields, respectively.
3. Results and discussion
Complex 3 is an air-stable brown-red solid, whereas complex 4
is a slightly air-sensitive dark-red solid. Their molecular structures
were fully characterized by elemental analysis, IR, 1H NMR, 13C
NMR and 31P NMR spectroscopy. While the IR spectrum of 3 dis-
plays three strong absorption bands in the range 2045–
1936 cmꢁ1 for its terminal carbonyls, that of 4 exhibits three strong
absorption bands in the lower range of 1997–1935 cmꢁ1 for its
3.1. Synthesis and spectroscopic characterization of the all-carbonyl
complexes 1 and 2
As shown in Scheme 1, treatment of the starting material
[(l-SCH2)2CHCO2H][Fe2(CO)6] (A) with 0.1 equiv. of DMAP in the

148
P.-H. Zhao et al. / Polyhedron 53 (2013) 144–149
Table 2
7.70 and 7.40 ppm are attributed to the phenyl protons of the
PPh3 ligand. Furthermore, the 31P NMR spectra demonstrate one
singlet at 64.37 ppm for the phosphorus atom of the PPh3 ligand
in 3 and two singlets at 61.68 and 60.49 ppm for the two phospho-
rus atoms of the two PPh3 ligands in 4 [18]. In addition, the 13C
NMR spectrum of 3 exhibits a doublet at 213.50 ppm with a cou-
pling constant 2JP–C = 9.9 Hz for the PFe(CO)2 coordinated carbonyls
and a singlet at 208.85 ppm for the terminal carbonyls of Fe(CO)3
[19], whereas that of 4 displays two doublets at 215.62 and
Selected bond lengths (Å) and angles (°) for 1–4.
Complex 1
Fe(1)–Fe(2)
Fe(1)–S(1)
Fe(1)–S(2)
Fe(2)–S(2)
Fe(2)–S(1)
O(1)–C(1)
O(2)–C(2)
O(3)–C(3)
O(4)–C(4)
O(5)–C(5)
S(1)–Fe(1)–S(2)
S(1)–Fe(1)–Fe(2)
S(2)–Fe(1)–Fe(2)
S(2)–Fe(2)–S(1)
2.498(7)
2.260(7)
2.262 (7)
2.253(8)
2.259 (7)
1.136(2)
1.139(2)
1.142(2)
1.144(2)
1.141(2)
84.85(3)
56.43(2)
56.24(2)
85.09(2)
Fe(1)–C(2)
Fe(1)–C(3)
Fe(1)–C(1)
Fe(2)–C(6)
Fe(2)–C(4)
Fe(2)–C(5)
O(6)–C(6)
O(7)–C(10)
O(8)–C(10)
O(8)–C(11)
S(2)–Fe(2)–Fe(1)
S(1)–Fe(2)–Fe(1)
Fe(2)–S(1)–Fe(1)
Fe(2)–S(2)–Fe(1)
1.796(2)
1.798(2)
1.820(2)
1.796(2)
1.798(2)
1.807(2)
1.143(3)
1.212(3)
1.327(3)
1.444(2)
56.60(2)
56.47(2)
67.11(2)
67.16(2)
2
214.66 ppm with the corresponding coupling constant JP–C = 10.9
and 9.7 Hz for the PFe(CO)2 coordinated carbonyls, indicating that
the two PPh3 ligands of 4 are coordinated to the two iron atoms of
the diiron subsite [20].
3.3. Crystal structures of complexes 1–4
Complex 2
Fe(1)–Fe(2)
Fe(1)–S(1)
Fe(1)–S(2)
Fe(2)–S(1)
Fe(2)–S(2)
O(1)–C(1)
O(2)–C(2)
O(3)–C(3)
O(4)–C(4)
2.518(2)
2.234(2)
2.243(2)
2.238(2)
2.247(2)
1.142(3)
1.137(3)
1.144(3)
1.141(3)
1.142(3)
85.08(4)
55.81(3)
84.90(4)
55.64(5)
Fe(1)–C(1)
Fe(1)–C(3)
Fe(1)–C(2)
Fe(2)–C(4)
Fe(2)–C(5)
Fe(2)–C(6)
O(6)–C(6)
O(7)–C(10)
O(8)–C(10)
O(8)–C(11)
S(2)–Fe(1)–Fe(2)
S(2)–Fe(2)–Fe(1)
Fe(1)–S(1)–Fe(2)
Fe(1)–S(2)–Fe(2)
1.796(3)
1.798(3)
1.805(3)
1.792(3)
1.803(3)
1.809(3)
1.137(3)
1.188(3)
1.344(3)
1.411(3)
55.95(4)
55.82(2)
68.55(4)
68.23(5)
The molecular structures of 1–4 have been further confirmed by
single crystal X-ray diffraction analysis. ORTEP views of 1–4 are
illustrated in Figs. 1–4 and selected bond lengths as well as angles
are given in Table 2.
As shown in Figs. 1 and 2, complexes 1 and 2 contain a butterfly
[Fe2S2] cluster with six carbonyl ligands and one propanedithiolate
unit that is linked to the ester moiety via the bridgehead C8 atom.
The ester substituent in 1 and 2 resides in the sterically-favored
equatorial position of two fused six-membered Fe2S2C3 rings, in
which one ring (C8C9S2Fe2S1C7 for 1 or C8C9S2Fe1S1C7 for 2)
has a chair conformation and the other ring (C8C9S2Fe1S1C7 for
1 or C8C9S2Fe2S1C7 for 2) adopts a boat conformation. This is
O(5)–C(5)
S(1)–Fe(1)–S(2)
S(1)–Fe(1)–Fe(2)
S(1)–Fe(2)–S(2)
S(1)–Fe(2)–Fe(1)
good agreement with the parent complex [(
H][Fe2(CO)6] [21] and other carboxy-functionalized all-carbonyl
diiron propanedithiolate complexes, such as [( -SCH2)2-
l-SCH2)2CHCO2-
Complex 3
Fe(1)–Fe(2)
Fe(1)–S(1)
Fe(1)–S(2)
Fe(2)–C(1)
Fe(2)–C(3)
Fe(2)–C(2)
O(1)–C(1)
O(2)–C(2)
O(3)–C(3)
O(4)–C(4)
2.518(9)
2.270(9)
2.276(1)
1.793(2)
1.795(2)
1.806(2)
1.144(2)
1.145(2)
1.140(2)
1.155(2)
Fe(1)–P(1)
Fe(1)–C(4)
Fe(1)–C(5)
Fe(2)–S(2)
Fe(2)–S(1)
Cl(1)–C(11)
O(5)–C(5)
O(6)–C(9)
O(7)–C(9)
O(7)–C(10)
2.253(9)
1.769(2)
1.778(2)
2.249(1)
2.266(9)
1.787(2)
1.151(2)
1.205(2)
1.344(2)
1.453(2)
l
CHCONHR][Fe2(CO)6] (R = Ph, Et, CH2CO2But) [4,21], which indi-
cates that the carboxylic functionality does not affect the overall
geometry of the diiron propanedithiolate complex. It was worth
finding out that the dihedral angle between the ester group
(O7C10O8) and the phenyl group (C11–C16) in 2 is 6.7°, demon-
strating that the carboxy-functionalized substituent (p-IC6H4-
C(O)O–) of 2 is almost planar. The Fe–Fe bond length of 1
(2.498(7) Å) is shorter than that of 2 (2.518(2) Å) and analogous
S(1)–Fe(1)–S(2)
S(1)–Fe(1)–Fe(2)
S(2)–Fe(1)–Fe(2)
S(2)–Fe(2)–S(1)
S(2)–Fe(2)–Fe(1)
S(1)–Fe(2)–Fe(1)
84.18(2)
56.21(2)
55.68(2)
84.89(2)
56.69(3)
56.35(2)
Fe(2)–S(1)–Fe(1)
Fe(2)–S(2)–Fe(1)
P(1)–Fe(1)–S(1)
P(1)–Fe(1)–S(2)
P(1)–Fe(1)–Fe(2)
C(9)–O(7)–C(10)
67.44(3)
67.63(2)
111.27(3)
108.04(2)
157.82(2)
115.48(1)
complexes such as [(l-SCH2)2CHCOR][Fe2(CO)6] (R = NHPh
(2.514 Å), NHEt (2.517 Å), NHCH2CO2But (2.514 Å), and OH
(2.513 Å)) [4,21], and significantly shorter than those found in
the crystal structures of the natural enzymes Clostridium pasteuri-
anum and Desulfovibrio desulfuricans (2.55–2.62 Å) [22,23].
Complex 4
Fe(1)–Fe(2)
Fe(2)–C(3)
Fe(2)–C(4)
Fe(2)–P(2)
Fe(2)–S(2)
Fe(2)–S(1)
O(1)–C(1)
O(2)–C(2)
O(3)–C(3)
O(4)–C(4)
As shown in Figs. 3 and 4, complexes 3 and 4 are composed of
their precursor 1 and one or two PPh3 ligands. The ester substitu-
ent and one hydrogen atom attached to the bridgehead-C atom in 3
and 4 occupy the equatorial and axial position of two fused six-
membered rings, respectively, which is in good agreement with
the parent complex 1. The one or two PPh3 ligands are all located
in apical positions of the square–pyramidal geometries of the Fe1
atom in 3 or Fe1 and Fe2 in 4, which is in accordance with previous
similar diiron propanedithiolate complexes with monophosphine-
2.534(2)
1.766(5)
1.775(6)
2.256(2)
2.265(2)
2.292(2)
1.150(6)
1.156(6)
1.165(6)
1.151(6)
Fe(1)–C(2)
Fe(1)–C(1)
Fe(1)–P(1)
Fe(1)–S(2)
Fe(1)–S(1)
C(10)–Cl(1)
O(5)–C(8)
O(6)–C(8)
O(6)–C(9)
O(6)–C(90)
1.764(5)
1.779(5)
2.244(2)
2.257(2)
2.279(2)
1.782(8)
1.198(7)
1.301(7)
1.444(8)
1.467(9)
S(2)–Fe(1)–S(1)
S(2)–Fe(1)–Fe(2)
S(1)––Fe(1)–Fe(2)
S(2)–Fe(2)–Fe(1)
S(1)–Fe(2)––Fe(1)
S(2)–Fe(2)–S(1)
84.14(5)
56.06(4)
56.56(5)
55.77(5)
56.09(4)
83.68(5)
P(1)–Fe(1)–S(2)
P(1)–Fe(1)–S(1)
P(1)–Fe(1)–Fe(2)
P(2)–Fe(2)–S(2)
P(2)–Fe(2)–S(1)
P(2)–Fe(2)–Fe(1)
107.39(5)
106.41(6)
154.71(4)
101.64(6)
114.07(6)
154.15(5)
monosubtituted ligands such as [(l-SCH2)2CH2][Fe2(CO)5L]
(L = PPh3 [17], P(OEt)3 [17], PhPMe2 [17], Ph2PNH(2-NH2Ph) [24],
Ph2PNH(CH2)2NMe2 [24], Ph2P(2-Me2NCH2Ph) [24], Ph2P(CH2CO2-
H) [25] and Ph2P(2-NHPy) [26]), and [(
PPh3] [18] or those with monophosphine-disubtituted ligands
such as [( -SCH2)2CH2][Fe2(CO)4(PPh3)2] [17] and [( -SCH2)2-
l-SCH2)2CHOH][Fe2(CO)5-
l
l
CHOH][Fe2(CO)4(PPh3)2] [18]. It should be noted that the two
PPh3 ligands in 4 are coordinated to two Fe atoms with a symmet-
rically substituted apical/apical coordination configuration, which
is well consistent with two doublets at 215.62 and 214.66 ppm
for two kinds of terminal carbonyls in its 13C NMR spectrum and
two singlets at 61.68 and 60.49 ppm for two phosphorus atoms
coordinated to two iron atoms in its 31P NMR spectrum. In
terminal carbonyls. Obviously, the highest mC„O values of 3 and 4
are shifted by 31 and 99 cmꢁ1 toward lower frequencies relative
to that of their precursor 1, respectively. This is because PPh3 is a
stronger electron-donating ligand than CO [17]. The 1H NMR spec-
tra of 3 and 4 show that in addition to the corresponding organic
groups of their precursor 1, the surplus two singlets at about

P.-H. Zhao et al. / Polyhedron 53 (2013) 144–149
149
addition, the Fe1–Fe2 bond lengths of 3 (2.518(9) Å) and 4
References
(2.534(2) Å) are obviously longer than that of the precursor 1
(2.498(7) Å), demonstrating that the monophosphine-substituted
ligand PPh3 has a certain effect on the Fe–Fe bond length of the car-
boxy-functionalized diiron propanedithiolate complex.
In addition, the solid-state structures of 1–4 are stabilized by
van der Waals’ interactions and intermolecular hydrogen bonds,
as observed in their crystal packing diagrams (as shown in Figs.
5–8 in the Supporting Information).
[1] D. Seyferth, R.S. Henderson, L.-C. Song, J. Organomet. Chem. 192 (1980) C1.
[2] A. Winter, L. Zsólnai, G. Huttner, Z. Naturforsch., B 37 (1982) 1430.
[3] D. Seyferth, G.B. Womack, M.K. Gallagher, M. Cowie, B.W. Hames, J.P. Fackler
Jr., A.M. Mazany, Organometallics 6 (1987) 283.
[4] C.M. Thomas, O. Rudiger, T.B. Liu, C.E. Carson, M.B. Hall, M.Y. Darensbourg,
Organometallics 26 (2007) 3976.
[5] M.Y. Darensbourg, E.J. Lyon, J.J. Smee, Coord. Chem. Rev. 206–207 (2000) 533.
[6] L.-C. Song, Acc. Chem. Res. 38 (2005) 21.
[7] J.C. Fontecilla-Camps, A. Volbeda, C. Cavazza, Y. Nicolet, Chem. Rev. 107 (2007)
4273.
[8] F. Gloaguen, T.B. Rauchfuss, Chem. Soc. Rev. 38 (2009) 100.
[9] M. Fontecave, V. Artero, C. R. Chim. 14 (2011) 362.
[10] X.-F. Liu, Z.-Q. Jiang, Z.-J. Jia, Polyhedron 33 (2012) 166.
[11] D.J. Evans, C.J. Pickett, Chem. Soc. Rev. 32 (2003) 268.
[12] J.F. Capon, F. Gloaguen, P. Schollhammer, J. Talarmin, Coord. Chem. Rev. 249
(2005) 1664.
[13] R.M. Navarro, M.C. Sánchez-Sánchez, M.C. Alvarez-Galvan, F. del Valle, J.L.G.
Fierro, Energy Environ. Sci. 2 (2009) 35.
[14] CRYSTALCLEAR 1.3.6., Rigaku and Rigaku/MSC, The Woodlands, TX, 2005.
[15] G.M. Sheldrick, SHELXS97, A Program for Crystal Structure Solution, University of
Göttingen, Germany, 1997.
4. Conclusions
In summary, we have successfully synthesized a series of new
carboxy-functionalized diiron propanedithiolate complexes, 1–4.
While the all-carboxyl complexes 1 and 2 are prepared using the
condensation reaction of A with ClCH2CH2OH and p-IC6H4OH in
high yields, respectively, the phosphine-substituted complexes 3
and 4 are further synthesized by the carbonyl displacement reac-
tions of 1 with PPh3 in moderate yields. The molecular structures
of 1–4 are characterized by elemental analysis, IR and NMR spec-
troscopies, as well as by X-ray crystallography.
[16] G.M. Sheldrick, SHELXL97,
A Program for Crystal Structure Refinement,
University of Göttingen, Germany, 1997.
[17] P. Li, M. Wang, C. He, G. Li, X. Liu, C. Chen, B. Åkermark, L. Sun, Eur. J. Inorg.
Chem. (2005) 2506.
[18] L.-C. Song, W. Gao, X. Luo, Z.-X. Wang, X.-J. Sun, H.-B. Song, Organometallics 31
(2012) 3324.
[19] X.-F. Liu, B.-S. Yin, J. Coord. Chem. 63 (2010) 4061.
[20] E.J. Lyon, I.P. Georgakaki, J.H. Reibenspies, M.Y. Darensbourg, J. Am. Chem. Soc.
123 (2001) 3268.
[21] P.I. Volkers, T.B. Rauchfuss, S.R. Wilson, Eur. J. Inorg. Chem. (2006) 4793.
[22] J.W. Peters, W.N. Lanzilotta, B.J. Lemon, L.C. Seefeldt, Science 282 (1998) 1853.
[23] Y. Nicolet, C. Piras, P. Legrand, E.C. Hatchikian, J.C. Fontecilla-Camps, Structure
7 (1999) 13.
Acknowledgements
This work is financially supported by the National Natural
Science Foundation of China (No. 51102216) and the Shanxi
Province Science Foundation for Youths (No. 2012021007-4).
[24] Z. Wang, W.-F. Jiang, J.-H. Liu, W.-N. Jiang, Y. Wang, B. Åkermark, L. Sun, J.
Organomet. Chem. 693 (2008) 2828.
Appendix A. Supplementary data
[25] Z.-B. Zhao, M. Wang, W.-B. Dong, P. Li, Z. Yua, L. Sun, J. Organomet. Chem. 694
(2009) 2309.
[26] X.-F. Liu, X.-W. Xiao, J. Organomet. Chem. 696 (2011) 2767.
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.poly.2013.01.048.