Pyridyl- and pyrimidyl-phosphine-substituted [FeFe]-hydrogenase mimics: Synthesis, charaterization and properties

Article abstract of DOI:10.1016/j.jorganchem.2014.04.026

Two tetranuclear iron-sulphur complexes {[(μ-pdt)Fe₂(CO) ₅]₂(PNP) (2) and [(μ-pdt)Fe₂(CO) ₅]₂(PNNP) (3)} and three dinuclear ones {[(μ-pdt)Fe₂(CO)₅](PNP) (4), [(μ-pdt)

Full text of DOI:10.1016/j.jorganchem.2014.04.026

Accepted Manuscript
Pyridyl- and Pyrimidyl-Phosphine-Substituted [FeFe]-Hydrogenase Mimics: Synthesis,
Charaterization and Properties
Hong-Hua Cui, Nan-Nan Wu, Jin-Yun Wang, Ming-Qiang Hu, Hui-Min Wen, Chang-
Neng Chen
PII:
S0022-328X(14)00208-3
10.1016/j.jorganchem.2014.04.026
JOM 18561
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 5 March 2014
Revised Date: 22 April 2014
Accepted Date: 27 April 2014
Please cite this article as: H.-H. Cui, N.-N. Wu, J.-Y. Wang, M.-Q. Hu, H.-M. Wen, C.-N. Chen, Pyridyl-
and Pyrimidyl-Phosphine-Substituted [FeFe]-Hydrogenase Mimics: Synthesis, Charaterization and
Properties, Journal of Organometallic Chemistry (2014), doi: 10.1016/j.jorganchem.2014.04.026.
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ACCEPTED MANUSCRIPT
Pyridyl- and Pyrimidyl-Phosphine-Substituted [FeFe]-
Hydrogenase Mimics: Synthesis, Charaterization and
Properties
‡
a,b
‡a,b
a
a
a
Hong-Hua Cui, Nan-Nan Wu, Jin-Yun Wang, Ming-Qiang Hu, Hui-Min Wen, and
a
Chang-Neng Chen*
a
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of
b
Matter, Chinese Academy of Sciences, Fuzhou 350002, P. R. China. University of Chinese
Academy of Sciences, Beijing, 100039, P. R. China
Highlight: 1) Pyrimidyl-diphosphine substituted [Fe S ] mimics have been firstly
2
2
synthesized. 2) The pyrimidyl-diphosphine ligand PNNP can affect the features of LUMOs
when both of the P atoms are coordinated to [Fe ] units.
2 2
S
Abstract: Two tetranuclear iron-sulfur complexes {[(ꢀ-pdt)Fe (CO) ] (PNP) (2) and [(ꢀ-
2
5 2
pdt)Fe (CO) ] (PNNP) (3)} and three dinuclear ones {[(ꢀ-pdt)Fe (CO) ](PNP) (4), [(ꢀ-
2
5 2
2
5
pdt)Fe (CO) ](PNNP) (5) and [(ꢀ-pdt)Fe (CO) ](PNN) (6)} were synthesized, using two new
2
5
2
5
pyrimidyl-phosphine ligands PNNP [4,6-bis(diphenylphosphino) pyrimidine] and PNN (4-
_________________
*Corresponding author. Tel: +86 591 83792395; fax: +86 591 83792395
E-mail address: ccn@fjirsm.ac.cn
‡
H.-H. Cui and N.-N. Wu contributed equally.
1

ACCEPTED MANUSCRIPT
tertiary butyl-6-diphenylphosphino pyrimidine) together with the reported pyridyl-phosphine
PNP [bis(diphenylphosphino)pyridine] as substituents to react with Fe (ꢀ-pdt)(CO) . The
2
6
molecular structures of 2, 3 and 6 were confirmed by single-crystal X-ray analyses, which show
that all phospine ligands occupy the apical positions, while the space group of 3 (P21/n) is
different from that of 2 (P-1). Cyclic voltammograms reveal that pyrimidyl-phosphine
substituted complexes 3, 5 and 6 present two reduction waves in CH Cl solutions, while
2
2
pyridyl-phosphine substituted 2 and 4 show only one. The DFT computational studies
demonstrate that the contributions to the LUMO of 3 are comparable from the two Fe centers
] mimics in this work.
2 2
S
2 2
and ligated PNNP ligand, which is different from those of other [Fe S
Graphical abstract
The contributions to the LUMO of 3 are comparable from the two [Fe S ] centers and the ligated
2
2
PNNP, which is different from other [Fe S ] mimics, such as complex 2.
2
2
Keywords: Pyrimidyl-diphosphine ligand; [FeFe] hydrogenase; Tetranuclear iron-sulfur
complexes.
1
. Introduction
Over the past decade, intense work has been done aiming at developing effective bioinspired
complexes of the active site of [FeFe]-hydrogenase for H
2
generation.[1-2] In the known
2

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synthetic models, electron-donating phosphine ligands have been widely used by the replacement
of carbonyl ligands to mimic the CN- ligation on the Fe sites in order to prepare more stable
diiron models and avoid polymerization of the diiron units.[3-7] Among the phosphine ligands,
bisphosphine are capable of giving several coordination modes of substituted diiorn complexes,
such as bridging-form symmetric and chelating-form asymmetric isomers as well as pendant-
form and bridging-form intermolecular modes, which depend on the nature of the bidentate
phosphines and reaction conditions.[8-9] Many studies have been carried out on the asymmetry
of the diiron centre, or mixed valence Fe(I)-Fe(II) assemblies about the bisphosphine-substituted
2 2
Fe S derivatives.[10-11] The bisphosphine used in these studies are mainly the flexible ones,
such as dppm (bis(diphenylphosphino)methane) and dppe (1,2-bis(diphenylphosphino)ethane).
By comparison, rigid bidentate phosphine ligands are less employed.[12-13] In addition, the
introduction of a rigid and conjugate disulfide brigde to the diiron complexes makes the
electrochemical properties different from that with flexible bridges.[14-17] Keeping these in
mind, we aim to explore [Fe S ] complexes using rigid bisphospine ligands as bridges.
2
2
Bis(diphenylphosphino)pyridine (PNP) is widely used in preparing homonuclear or
heteronuclear metal complexes due to the presence of two different coordination sites, N and P
atoms.[18-19] It is appealing to us that the basic nitrogen atom may act as a proton relay and the
diphosphine-pyridine may result in different properties from other pyridy-phophine ligands,
which contain only one P atom.[20-21] Here we select PNP as a bridge to link Fe S centers to
2
2
study the influence of aromatic ring on the multinuclear iron-sulfur complexes. Moreover,
complexes containing pyrimidyl-phosphine are rare compared with pyridyl-phosphine ligands.
For the stronger electron-withdrawing inductive and conjugative effects of the N atoms in
pyrimidine than that in pyridine,[22] pyrimidyl-phosphine may exhibit different properties in
3

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iron-sulfur complexes. Thus, we designed and synthesized two new pyrimidyl-phosphine ligands,
PNNP (4, 6-bis(diphenylphosphino) pyrimidine) and PNN (4-tertiary butyl -6-
diphenylphosphino pyrimidine). Using the three above ligands as substituents, two tetranuclear
iron-sulfur complexes [(ꢀ-pdt)Fe (CO) ] (PNP) (2) and [(ꢀ-pdt)Fe (CO) ] (PNNP) (3) and three
2
5 2
2
5 2
dinuclear ones [(ꢀ-pdt)Fe (CO) ](PNP) (4), [(ꢀ-pdt)Fe (CO) ](PNNP) (5) and [(ꢀ-
2
5
2
5
pdt)Fe (CO) ](PNN) (6) were obtained. The preparations and characterizations of complexes 2-6,
2
5
and the molecular structures of 2, 3 and 6 are presented. We mainly focus on the discussion of
the properties of 2, 3 and 6 in this work. Importantly, the DFT computational studies of 2-6 show
the differences between complex 3 and other four complexes on the components of molecular
orbitals (MOs).
2
Experimental
2.1 Materials
All reactions and operations were performed under dry oxygen-free nitrogen atmosphere with
standard Schlenk techniques. Solvents used were dried and distilled according to the standard
methods. Fe (ꢀ-pdt)(CO) ,[23] and 2,6-bis(diphenylphosphino)pyridine (PNP) [19] were
2
6
prepared according to literature procedures and other materials were obtained commercially and
used without further purification. Infrared spectra were obtained on a Perkin–Elmer Spectrum
One FTIR spectrometer with KBr pellets. NMR spectra were carried out on a Bruker Avance III
(400 MHz) spectrometer. Elemental analyses were recorded on a Perkin–Elmer model 240 C
elemental analyzer. Electrospray ionization mass spectrometry was performed on a Finnigan
LCQ mass spectrometer.
2.2 Electrochemistry
4

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The cyclic voltammograms (CV) were carried out using a CH instruments Model 630A
Electrochemical Workstation in CH Cl or CH Cl /DMF mixed solutions containing 0.1 M
2
2
2
2
(
Bu N)PF as the supporting electrolyte. All electrochemical measurements were performed at a
4 6
-1
scan rate of 100 mV·s in the cathodic direction in a three-electrode cell under Ar atmosphere.
The potential was measured against a reference electrode Ag/AgCl, a 3 mm diameter glassy
carbon working electrode and a platinum counter electrode with the ferrocenium/ferrocene
+
+
(
Fc /Fc) as an internal reference and all potentials in the present work are referred to the Fc /Fc
potential.
2.3. X-ray crystallography
Single-crystal X-ray diffraction data of complexes 2 and 6 were measured on a Saturn70
diffractometer equipped with a graphite-monochromated Mo K radiation (λ= 0.71073 Å) at the
α
temperature of 293 K and the data of 3 was collected on a SuperNova, Dual, Mo K radiation,
α
Atlas diffractiometer at 293 K. Data collection, refinement and reduction were performed by
CRYSTALCLEAR program.[24] The structures were solved by direct methods with SHELXS-
9
7[25] and refined by full-matrix least-squares methods using the SHELXTL–97 program
2
package on F . Detailed crystallographic data and structural refinements information are
summarized in Table 1.
Table 1 Crystal data and structure refinement details for complexes 2, 3 and 6.
Complexes
2
3·2H O
6·H O
2
2
Molecule formula
Formula weight
T (K)
Fe S C H NO P
Fe S C H N O P
Fe S C H N O P
4
4
45 35
10
2
4
4
44 38
2
12
2
2
2
28 29
2
6
1163.32
293(2)
1200.35
293(2)
696.32
293(2)
Crystal system
Triclinic
monoclinic
Triclinic
5

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Space group
a (Å)
P-1
P21/n
P-1
9.141(2)
11.3590(5)
25.8540(12)
18.9642(8)
90
9.210(10)
10.936(12)
18.68(2)
74.39(5)
77.10(5)
73.15(5)
1713(3)
2
b (Å)
10.283(2)
27.772(7)
95.684(9)
92.450(7)
108.656(7)
2439.6(9)
2
c (Å)
α (°)
β (°)
92.046(4)
90
γ (°)
3
V (Å )
5565.8(4)
4
Z
-3
Dcalc (g·cm )
1.584
1.428
1.340
a
b
R1 / wR2 (I > 2σ(I))
0.0531/0.1423
0.0850/0.1780
0.0441/0.1387
0.0529/0.1484
0.0719/0.2121
0.1027/0.2400
0.942
a
b
R1 / wR2 (all data)
2
GOF on F
1.063
1.092
a
b
2
2
o
2 2
2 2 1/2
R1= ∑||F
o
| – |F
c
||/∑|F
o
|. wR2(F
o
) = [∑w(F
– F
c
o
) /∑w(F ) ] .
2.4. Theoretical calculations
In order to get an insight into the electronic properties of the investigated complexes 2-6, the
calculations were implemented by using Gaussian 03 program package.[26] The density
functional theory (DFT) with the hybrid Becke three-parameter Lee-Yang-Parr (B3LYP)
functional[27-28] was firstly employed for the optimization of the geometrical structures in
vacuum. The initial structures of 2, 3 and 6 were extracted from the crystallographically
determined geometries, and 4, and 5 were cut out from 2 and 3, respectively. The optimized
structures of complexes 2-6 and the protonated [2-H ], [3-2H ] and [6-2H ] are shown in
N
N
N
Figure S1 in the Supporting Information. During the optimization processes, the convergent
values of maximum force, root-mean-square (RMS) force, maximum displacement, and RMS
displacement were set by default. To precisely describe the electronic properties, the single-point
6

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DFT calculations were performed based on the optimized structures by considering the solvent
effects of dichloromethane solutions in the help of conductor-like polarizable continuum model
method (CPCM).[29-30] All of the calculations were implemented at the 6-31G* basis set level.
Visualization of the optimized structures and frontier molecular orbitals were performed by
GaussView. Ros & Schuit method (C-squared population analysis method, SCPA)[31] is
supported to partition orbital composition analysis by using Multiwfn 2.4 program.[32]
2.5 Synthesis
2.5.1. Synthesis of 4, 6-bis(diphenylphosphino)pyrimidine (PNNP)
Compound diphenyphosphine (Ph PH) (2.0mL, 11mmol) in dry tetrahydrofuran (THF) (20 mL)
2
was added to the THF solution containing excess lithium (0.152 g, 20mmol) in ice bath. Then the
mixture was warmed to the room temperature and refluxed for 2 hours. After cooling down, the
red solution was added dropwise to the solution of 4,6-dichloropyrimidine (0.9 g, 5 mmol) in
THF (10 mL) at 0 ℃. The new pale yellow mixture was then stirred at 40 ℃ until the reaction
was completely finished. Saturated NH
The aqueous phase was extracted with dichloromethane (3*50 mL) and the organic phase was
dried with anhydrous Na SO overnight. After solvent was removed, the crude product was
4
Cl solution was added after the solvent was evaporated.
2
4
purified by chromatography on silica gel (100-200) with dichloromethane/petroleum (3:1 v/v)
and dichloromethane as gradient eluent to give an off-white solid. The yield was 1.42 g (63.1%).
Anal. Calcd. for C H N P : C, 74.99%; H, 4.94%; N, 6.25%. Found: C, 75.06%; H, 4.82%; N,
28
22
2 2
+
1
6
.17%. ESI-MS calculated for C H N P , found [M+H] : 449.6. H NMR (400 MHz, DMSO):
28 22 2 2
3
1
δ 9.16 (s, 1H), 7.42 – 7.27 (m, 20H), 6.60 (s, 1H). P NMR (162MHz, DMSO): δ -4.45 (s).
2.5.2. Synthesis of 4-tertiary butyl-6-diphenylphosphino pyrimidine (PNN)
7

ACCEPTED MANUSCRIPT
A solution of tert-BuLi in hexane (2.5M, 6.0 mL) was dropwised slowly to the solution of
Ph PH (10 mmol, 1.8 mL) in tetrahydrofuran (30 mL) at -78 ℃. The resulting mixture was
2
stirred for one hour and warmed slowly to 0 ℃. Then the red solution was transferred dropwise
to the THF solution of 4,6-dichloropyrimidine (1.5 g, 10 mmol). After stirring for one hour at
this temperature, the mixture was warmed to the room temperature for another 5 hours. The
solvent was removed in vacuum and saturated NH Cl solution was added. The aqueous phase
4
was extracted with dichloromethane (3*40 mL) and the organic phase was dried with anhydrous
Na SO overnight. After solvent was removed, the crude product was purified by
2
4
chromatography on silica gel (100-200) with dichloromethane/petroleum (3:2 v/v) and
dichloromethane as gradient eluent to give off-white products PNN and PNNP. The yields of
them were 1.10 g (34.4%) and 1.17 g (52%), respectively. Anal. Calcd for C20
21 2
H N P: C,
7
4.98%; H, 6.61%; N, 8.74%. Found: C, 74.85%; H, 6.70%; N, 8.68%. ESI-MS calculated for
+
1
C H N P, found [M+H] : 321.2. H NMR (400 MHz, DMSO): δ 8.89 (s, 1H), 7.37 – 7.24 (m,
20
21
2
3
1
1
0H), 7.19 (s, 1H), 3.42 (s, 9H). P NMR (162 MHz, DMSO) δ -3.06 (s).
2
.5.3. Synthesis of [(µ-pdt)Fe (CO) ] (PNP) (2)
2 5 2
A solution of Fe
2
(ꢀ-pdt)(CO)
6
3 2
(0.780 g, 2 mmol) and Me NO·2H O (0.244 g, 2.2 mmol) in 20
ml acetonitrile was stirred for 15 min at room temperature. Then the ligand
bis(diphenylphosphino)pyridine (0.449 g, 1mmol) was added and the reaction mixture was
stirred for 12 hours at room temperature. The resulted solution was evaporated under reduced
pressure. The residue was purified by chromatography on silica gel (100-200) with
dichloromethane/petroleum (3:2 v/v) as eluent to give a red solid. The yield was 0.806 g (69.3%).
The crystals of 2 suitable for X-ray crystallography study were grown upon slow diffusion of
hexane into a dichloromethane solution containing 2 at 4 ℃ . Anal. Calcd. for
8

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Fe
4
S
4
C
45
H35NO10
2
P : C, 46.46%; H, 3.03%; N, 1.20%. Found: C, 46.53%; H, 3.27%; N, 1.14%.
–
1
ESI-MS calculated for Fe S C H NO P , found [M]: 1163.8. IR (KBr, cm ): ν(CO) 2043,
4
4
45 35
10 2
1
1
1
978, 1932. H NMR (400 MHz, DMSO): δ 8.12 (s, 1H), 7.81 (s, 2H), 7.63 – 7.29 (m, 20H),
3
1
.77 – 1.64 (m, 4H), 1.26 (s, 6H), 1.05 (s, 2H). P NMR (162MHz, DMSO): δ 66.84 (s).
2
.5.4. Synthesis of [(µ-pdt)Fe (CO) ] (PNNP) (3)
2
5 2
The product was synthesized in the similar way as 2, except that the ligand PNNP (0.449 g,
1
mmol) was added instead of PNP.The crude product was purified by column chromatography
on silica gel (100-200) with dichloromethane/petroleum (1:1 v/v) as eluent to give 3 as a red
solid. The yield was 0.838 g (72%). Diffusion of hexane into the dichloromethane solution
containing 3 at 4 ℃ gave the crystals suitable for X-ray crystallography study. Anal. Calcd. for
Fe S C H N O P : C, 45.39%; H, 2.94%; N, 2.41%. Found: C, 45.73%; H, 3.12%; N, 2.64%.
4
4
44 34
2
10 2
–
1
ESI-MS calculated for Fe S C H N O P , found [M]: 1164.2. IR (KBr, cm ): ν(CO) 2044,
4
4
44 34
2
10 2
1
1
7
983, 1937. H NMR (400 MHz, DMSO): δ 9.66 (s, 1H), 7.68 – 7.61 (m, 8H), 7.53 (dq, J = 14.2,
3
1
.1 Hz, 12H), 7.09 (s, 1H), 1.76 (d, J = 10.3 Hz, 4H), 1.46 (s, 6H), 1.25 (s, 2H). P NMR
(
162MHz, DMSO): δ 67.48 (s).
.5.5. [(µ-pdt)Fe (CO) ](PNP) (4)
The product was obtained following the same synthetic strategy as 2, except that one equivalent
Fe (ꢀ-pdt)(CO) (0.388 g, 1 mmol) was used. The crude product was purified by column
2
2
5
2
6
chromatography on silica gel (100-200) with dichloromethane/petroleum (2:1 v/v) as eluent to
give 4 as the main product. The yield was 0.475 g (59%). Anal. Calcd. for Fe S C H NO P : C,
2
2
37 29
5 2
5
5.18%; H, 3.63%; N, 1.74%. Found: C, 55.09%; H, 3.78%; N, 1.67%. ESI-MS calculated for
–
1
1
Fe
2 2 37 5 2
S C H29NO P , found [M]: 805.6. IR (KBr, cm ): ν(CO) 2042, 1979, 1956, 1930. H NMR
(400 MHz, DMSO): δ 8.12 (s, 1H), 7.82 (s, 2H), 7.59 (d, J = 8.1 Hz, 4H), 7.48 (d, J = 6.8 Hz,
9

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3
1
6
H), 7.39 (s, 4H), 7.35 – 7.30 (m, 8H), 1.70 (s, 3H), 1.43 (d, J = 13.6 Hz, 2H), 1.24 (s, 1H). P
NMR (162 MHz, DMSO): δ 65.72 (s), -4.14 (s).
.5.6. Synthesis of [(µ-pdt)Fe (CO) ](PNNP) (5)
2
2
5
The product was obtained following the same synthetic strategy as 3, except that one equivalent
Fe (ꢀ-pdt)(CO) (0.388 g, 1 mmol) was used. Red solid was obtained and the yield was 0.492 g
2
6
(
61%). Anal. Calcd for Fe
2
S
2
C
36
H
28
N
2
O
5
P
2
: C, 53.62%; H, 3.59%; N, 3.47%. Found: C, 53.51%;
, found [M]: 806.4. IR (KBr,
cm ): ν(CO) 2044, 1982, 1955, 1931. H NMR (400 MHz, DMSO); δ 9.40 (s, 1H), 7.67 – 7.26
H, 3.74%; N, 3.38%. ESI-MS calculated for Fe
2 2 37 28 2 5 2
S C H N O P
–
1
1
3
1
(
m, 20H), 6.88 (s, 1H), 1.75 (d, J = 10.6 Hz, 3H), 1.46 (s, 2H), 1.24 (s, 1H). P NMR (162 MHz,
DMSO): δ 66.51 (s), -3.76 (s).
2
.5.7. [(µ-pdt)Fe (CO) ](PNN) (6)
2 5
2 6 3 2
A solution of Fe (ꢀ-pdt)(CO) (0.339 g, 1 mmol) and Me NO·2H O (0.122 g, 1.1 mmol) in 15
ml acetonitrile was stirred for 10 minutes at room temperature. Then the ligand PNN (0.321 g,
mmol) was added and the reaction mixture was stirred for 12 hours at room temperature. The
1
resulted solution was evaporated under reduced pressure. The resulted residue was purified by
chromatography on silica gel (100-200) with dichloromethane/petroleum (1:3 v/v) and
dichloromethane gradient eluent to give 6 as a red solid. The yield was 0.471 g (69.3%). The
crystals of 6 suitable for X-ray crystallography study were grown upon diffusion of diethyl ether
into a dichloromethane-methanol mixed solution containing 6 at 4
℃
. Anal. Calcd for
Fe P: C, 49.58%; H, 4.01%; N, 4.13%. Found: C, 49.52%; H, 4.10%; N, 4.17%.
2 2 28 27 2 5
S C H N O
+
–1
2 2 28 27 2 5
ESI-MS calculated for Fe S C H N O P, found [M+H] : 679.7. IR (KBr, cm ): ν(CO) 2049,
1
1
980, 1954, 1932. H NMR (400 MHz, DMSO): δ 9.65 (s, 1H), 8.05 (d, J = 2.6 Hz, 1H), 7.85 –
10

ACCEPTED MANUSCRIPT
7
1
.78 (m, 4H), 7.63 (d, J = 5.7 Hz, 6H), 3.59 (s, 9H), 1.86 – 1.77 (m, 2H), 1.48 – 1.35 (m, 3H),
3
1
.17 (s, 1H). P NMR (162MHz, DMSO): δ 73.01 (s).
3
Results and discussions
3.1. Preparation and spectroscopic characterization of complexes
The new ligand 4,6-bis(diphenylphosphino)pyrimidine (PNNP) was obtained by the reaction of
,6-dichloropyrimidine with two equivalent lithium diphenylphosphide (Ph PLi), which was
4
2
prepared by diphenylphosphine (Ph PH) and lithium in dry, oxygen-free tetrahydrofuran as
2
shown in Scheme 1. If one equivalent Ph PH was added using Li as base, the resulting product
2
Scheme 1 Synthetic routes for ligands PNNP and PNN. Reagents and conditions: 1) THF, Li, 0
℃; 2) THF, tert-BuLi, -78 ℃.
was also the diphosphine ligand, PNNP, with unreacted 4,6-dichloropyrimidine. Changing the
dropping order of the reactants or further lowering the ratio of Ph PH to 4,6-dichloropyrimidine
2
did not change the final product and only PNNP was obtained rather than the wanted complex, of
which only one chlorine was substituted. However, if 1.5 equivalent tert-butyllithium based on
Ph PH was used as base with the equivalent starting reactants, there were two products,
2
disubstituted phosphine compound (PNNP) and asymmetrically substituted 4-tertiary butyl-6-
diphenylphosphino pyrimidine (PNN). The final products of the above reactions indicate that
complex 4,6-dichloropyrimidine has high reactivity and low selectivity of the two chlorine
11

ACCEPTED MANUSCRIPT
atoms. Ligand 2,6-bis(diphenylphosphino)pyridine (PNP) was prepared on the improved
procedures according to the literature through the reaction of 2,6-dichloropyridine and lithium
diphenylphosphide, which was produced by chlorodiphenyl phosphine and lithium in dry THF
solution.[19] Besides, ligands PNNP and PNN are less stable than PNP, which brown slowly if
they are exposed to the air.
Scheme 2 Synthetic routes for complexes 2-6.
As shown in Scheme 2, the mono-substituted tetranuclear derivates 2 and 3, were prepared via
the reaction of Fe (ꢀ-pdt)(CO) (1) with decarbonylation agent Me NO·2H O followed by
2
6
3
2
addition of 1/2 equivalent PNP and PNNP in MeCN solution, respectively. In order to make a
comparison, the corresponding mono-substituted dinuclear complexes 4 and 5 were synthesized,
when one equivalent PNP and PNNP were used, respectively. Complex 6 was prepared in the
12

ACCEPTED MANUSCRIPT
similar way as that for 4 or 5 but using one equivalent PNN as ligand. The crude products of 2-6
were all purified by chromatography on silica gel (100-200) in good to moderate yields.
1
31
Complexes synthesized were all characterized by H NMR, P NMR, infrared spectroscopy
(
IR), elemental analyses, ESI-MS spectrometry, and singlecrystal X-ray crystallography for 2, 3
and 6. Positive ion ESI-MS of the complexes showed the corresponding molecular ion peaks as
the principal peaks.
3
1
The P NMR spectra of 2, 3 and 6 show one singlet at δ = 66.84, 67.48 and 73.01 ppm,
respectively. The value of 3 shifts to lower magnetic field by 0.64 ppm compared with that of 2.
This indicates that ligand PNNP is a slightly weaker electron donor than PNP. For the poorer
electron-donating ability of PNN in 6 than that of PNNP in 3, there is also a 5.53 ppm shift of 6
3
1
to lower magnetic field than that of 3. In addition, the only one P NMR signal observed in the
spectrum of 2 or 3 suggests that the two P atoms in PNNP or PNP have the same chemical
3
1
environment. There are two P NMR peaks, 65.72 and -4.14 ppm for 4 and 66.51 and -3.76 ppm
for 5, respectively, corresponding to the ligated P atom and uncoordinated one in them.
−
1
The IR spectra of 2-6 each displays four characteristic peaks in the region of 1930–2049 cm ,
corresponding to the carbonyl stretching pattern for terminally bonded CO groups. The IR data
of ν(CO) of them, together with that of compound 1, are listed in Table 2 for a clear comparison.
Table 2 Comparison of ν(CO) bands in 2-6 with 1.
-1
a
−1
Complexes
ν(CO) KBr/cm
ν (CO) KBr/cm
1st
1
2
3
4
2074, 2036, 1995
0
2041, 1977, 1985, 1933
2044, 1983, 1957, 1935
2042, 1979, 1956, 1930
33
30
32
13

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5
2044, 1982, 1955, 1931
2049, 1980, 1954, 1932
30
25
6
a
ν (CO) = ν (CO) -ν (CO)
mono-substituted
1st
1st
1
1st
For the electron-donating effects of phosphine ligands PNP, PNNP and PNN on the [FeFe]
centers, CO bands in the IR spectra of 2-6 shift to lower energy compared to those of 1. The
-1
addition of one N atom in ligand PNNP results in a 3 cm blue-shift of the first (CO) band of 3
compared with that of 2. The same trend can be observed for the dinuclear complex 5 compared
with 4. However, the comparable values of the first (CO) bands of PNP-substituted 2 and 4 (or
2 2
PNNP-substituted 3 and 5) indicate that the addition of another Fe S unit to the ligand PNNP or
PNP has little effect on the IR spectra.
3.2. Molecular Structures of 2, 3 and 6
The red crystals of 2, and 3 suitable for X-ray diffraction were grown upon slow diffusion of
hexane into dichloromethane solution at 4℃, and the one of 6 were grown upon diffusion of
diethyl ether into a dichloromethane-methanol mixed solution containing 6 at 4
℃
. The
crystallographic structures of 2, 3 and 6 are displayed in Figure 1 and the selected bond lengths
and angles are listed in Table S1 (Supporting Information). For the tetranuclear complexes 2
14

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Figure 1 ORTEP views of complexes 2, 3 and 6 with 30% probability level ellipsoids (the
hydrogen atoms are omitted for clarity.).
and 3, each Fe S butterfly unit has a square pyramidal structure and is attached to one P atom
2
2
of the diphosphine bridge. As the usual behaviour of the reported mono- or di-phosphine
ligands,[33-36] each P atom of the diphospine in 2 and 3 selected the apical position. However,
the space group of 2 is P-1,which is different from P21/n of 3. Besides, both the tilts of the
propanedithiolate rings in 2 are away from the ligand PNP, while the two six-membered rings of
the propanedithiolate in 3 are towards PNNP moiety.
The Fe-Fe distances of 3 [2.5109(6) and 2.5188(6) Å] are comparable to that of [(ꢀ-
pdt)Fe (CO) ] [2.5103(11) Å][37] and slightly shorter than those of 2 [2.5232(9) and 2.5209(10)
2
6
2 2
Å]. But the Fe-Fe distance of each Fe S unit in 2 is comparable, which suggests that the ligand
15

ACCEPTED MANUSCRIPT
2 2
PNP has the same effect on the two linked Fe S centers. The same trend can be concluded for
PNNP in the complex 3. For the dinuclear complex 6, the structure is also the expected square-
based-pyramidal coordination geometry and the P atom occupies an apical position as those in 2
and 3. The middle C atom in –SCH CH CH S- is disordered in two positions.
2
2
2
The crystal structures and metric data of Fe···N distances of 2, 3 and 6 (Table S1) suggest that
the N atoms in 2 and 3 are fixed and hardly swinged due to the steric hindrance of two
coordinated Fe
different positions compared to those in 3. As shown in Table S1, the shortest Fe···N distance
3.585 Å) in the solid state is the one in complex 6, which is also shorter than those using
Ph PCH Py and Ph PPy as mono-substituted ligands (3.919 and 3.653 Å, respectively).[38]
2 2
S units. But the orientations of the pyrimidyl-nitrogen atoms in 6 change to
(
2
2
2
Moreover, both of the distances of N atoms in pyrimidine ring to the nearest Fe atom in complex
(3.635, 3.859 Å) are apparently closer than those (4.492, 4.713 Å) in pyridine in 2.
3
3.3. Electrochemical properties
3.3.1. Cyclic voltammograms of 2-6
Table 3 Reduction potentials of complexes 2-6 in CH Cl or CH Cl /DMF solutions.
2
2
2
2
red1
+
red2
1/2
+
Complexes
E
1/2
(V) vs. Fc /Fc
E
(V) vs. Fc /Fc
2
3
4
5
-2.06
-2.04
-2.05
-2.02
-1.83
---
-2.25
---
-2.17
-2.07
a
6
a
Mixed solution of CH
2
Cl
2
/DMF (4:1) was used.
16

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2 2
Cyclic voltammogram (CV) measurements were carried out on complexes 2-6 in dry CH Cl or
CH Cl /DMF solutions for the poor solubility of 2, 3 and 6 in Me CN. The reduction potentials
2
2
3
+
of them are listed in Table 3 and all vs. Fc /Fc, unless otherwise noted.
PNP-substituted complexes 2 and 4 display irreversible reduction peaks at -2.06 and -2.05 V,
respectively, in CH Cl solutions. The comparable values suggest that the addition of another
2
2
2 2
Fe S unit to the ligand PNP has little effect on the reduction potential. Detailed experiments
were carried out to study the reduction processes of them in THF solutions using 1mm diameter
glassy carbon working electrode. The reduction wave of 2 splits into three peaks in THF
solution(Figure S2a, Supporting Information).[16, 17] The first one is ascribed to the reduction
of ligand PNP and the other couple of peaks are obviously the one-electron reduction processes
of the two Fe S centers as other PR -monosubstituted diiron derivatives.[21, 39-42] This is
2
2
3
somewhat different from the results of dppe-substituted tetranuclear complexes [{ꢀ-
SCH ) CH }Fe (CO) (Ph -PCH )] and [{ꢀ-(SCH ) N(CH CH CH )}Fe (CO) (Ph -PCH )] , in
(
2
2
2
2
5
2
2
2
2 2
2
2
3
2
5
2
2
2
2 2
which only the Fe S centers are reduced by one step at ca. -2.0 V with consumptions of 2
electrons, respectively.
For the PNNP and PNN substituted complexes 3, 5 and 6, there are two reduction events for
each one. The first reduction potentials of 3 and 5 are -2.04 V and -2.02 V, respectively, in
CH Cl solutions. The one of 6 in CH Cl /DMF solution shifts positively to -1.83 V in
2
2
2
2
CH Cl /DMF solution. The second reduction potentials of 3, 5 and 6 (-2.25, -2.17 and -2.07 V)
2
2
are comparable to those of tetranuclear dppe-substituted complexes, which are ascribed to the
Ⅰ
Ⅰ
Ⅰ
0
reduction processes of [Fe Fe ] to [Fe Fe ]. Further CV experiments in THF show that the
reduction waves of 3 splits to two couple of peaks, while there are only three ones of 5 for the
absence of one [Fe S ] unit (Figure S2b, 2c, Supporting Information). Bulk electrolysis in
2
2
17

ACCEPTED MANUSCRIPT
CH
2
Cl
2
solutions indicates that complex 3 obtains 4.13 electrons, two for the reduction of ligand
Ⅰ
Ⅰ
Ⅰ
0
PNNP and the other two for the two [Fe S ] cores from [Fe Fe ] to [Fe Fe ].[43]
2
2
3
.3.2. Electrocatalytic reduction of protons from acetic acid and trifluoroacetic acid with 2, 3
and 6 as catalysts.
Firstly, the protonation process of 3 was studied by P NMR spectroscopy in CD Cl at room
3
1
3
3
1
temperature. Figure 2 shows the variation of the P resonances with the addition of 0-3 equiv.
trifluoroacetic acid (TFA) to the solution of 3.
3
1
Figure 2 P NMR spectra for the protonation of 3 in CD Cl at room
3
temperature.
3
1
There is only one P resonance at 67.53 ppm for PNNP in the complex 3 (Figure 2a). When 1
equiv. TFA is added, one additional sharp signal appears at 67.87 ppm (Figure 2b), which shifts
only about 0.3 ppm to the low field compared with that of unprotonated PNNP in 3. The only
one additional signal suggests that both of the N atoms in PNNP are protonated and a new
18

ACCEPTED MANUSCRIPT
3
1
N
species [3-2H ] is generated. Upon addition of 3 equiv. TFA, the P signal of 3 completely
3
1
disappears and only one P signal can be observed (Figure 2c). This implicates that complex 3
has been quantitatively transformed to the doubly protonated species [3-2HN].
The cyclic voltammograms, mainly on complexes 2, 3 and 6 in the presence of acetic acid
(HOAc) and TFA, were carried out to investigate the electrocatalytic proton reduction processes.
The current height of the reduction peak of 2 is slightly enhanced with an increase in the
concentration of HOAc (Figure S3a, Supporting Information). The same trend can be observed
for the first reduction event of 3, whereas the second one remains almost unchanged (Figure S3b,
Supporting Information). After HOAc is added to the solution of 6, a new reduction peak is
generated at about -1.71 V and the original two waves shift negatively to -1.96 and -2.12 V,
respectively (Figure S3c). According to the reported pyridyl-phosphine monosubstituted
derivatives,[38] the peak at -1.71 V can be ascribed to the reduction of the protonation of the
pyrimidyl-nitrogen atom. The new wave keeps unchanged with the concentration of HOAc
increasing, and the changes of the other two reduction processes are the same as those of
complex 3. It is worth noticing that there is no new reductive event for the tetranuclear complex
3
, which also contains pyrimidyl ligand.
19

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3
Figure 3 Cyclic voltammograms of 2 (a), 3 (b) and 6 (c) (1.0 mM) in the presence of CF COOH
-1
4 6 2 2
at scan rate of 100 mV s in 0.1M n-Bu NPF CH Cl solutions.
When TFA is used, the current heights of the reduction events of 2, 3 and 6 are enhanced
greatly (Figure 3). Moreover, new reductive waves are observed at -1.72 V for 2, -1.52 V for 3
and -1.72 V for 6, respectively, which result from the protonation of the pyridyl-nitrogen atom
and pyrimidyl-nitrogen atoms. Complexes 2 and 3 display similar CV features upon the addition
of TFA in the range of 0-7 mM. The current heights increase with the addition of TFA with
potentials negatively shifting. As shown in Figure 3, there are 200 mV positive shifts for the first
reduction process of [3-2H ] compared with those of [2-H ] and [6-2H ], which indicates that
N
N
N
[
3-2H ] is much easier to be reduced. We consider the ligand PNNP in complex 3 as a special
N
20

ACCEPTED MANUSCRIPT
“bridge”, which can influence the electron character of the whole complex, when the two P
atoms are both coordinated to metal centers.
.4. DFT computational studies
3
The density functional theory (DFT) method was employed in the Gaussian 03 program to get
an in-depth understanding of the electron characters of complexes 2-6. The energies of the
selected molecular orbitals (MOs) and the component (%) to the MO in terms of the composing
units are listed in Table S2. The plots of the highest occupied molecular orbitals (HOMOs) and
lowest unoccupied molecular orbitals (LUMOs) of 2, 3 and 6 are displayed in Figure 5 and those
of 4, 5 and the protonated species [2-H ], [3-2H ] and [6-2H ] are shown in Figure S4 for a
N
N
N
comparison. As shown in Table S2, the LUMO orbital energy of 3 is -0.20 eV lower than that of
2
, suggesting that it is easier for 3 to accept an electron than 2.
The major contributions to the HOMOs of 2-6 are all from one diiorn unit together with the
surrounding P atoms (Table S2). The LUMO of 2 is mainly resident on one Fe
2 2
S center (78.1%)
along with the ligated PPh unit (9.57%), while the other Fe and the pyridyl contribute only a
2
2 2
S
little. Similar results of the PNP-substituted dinuclear complex 4 can be obtained. However, the
contributions
21

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Figure 5 Plots of the HOMO and LUMO orbitals of complexes 2, 3 and 6 in the ground state by
DFT method at the B3LYP level (isovalue = 0.03) (the hydrogen atoms are omitted for clarity.).
to the LUMO of 3 are comparable from the two Fe S centers (30.75% and 31.43%) and ligated
2
2
PNNP (37.82%), which also can be seen from the plot shown in Figure 5. This suggests that
electron injected may delocalize in the whole complex of 3. Moreover, when only one P atom in
PNNP is coordinated (5), the primary contribution to LUMO is from the diiorn core (77.49%),
while the contribution from ligand PNNP lowers down to 22.51%. Complex 6 has similar result,
and the contributions from Fe S core and ligand PNN are 77.34% and 22.66%, respectively. The
2
2
differences between the contributions to LUMOs of PNNP-substituted tetranuclear 3 and
dinuclear 5 indicate that the model of metal-PNNP-metal (M-PNNP-M) can make the
contribution to LUMO come from the whole molecular 3. The differences between the LUMOs
of pyrimidyl and pyridyl phosphine-substituted complexes may explain why two reduction
processes were observed in 3, 5 and 6 and only one for 2 and 4.
N N N
The LUMO orbital energies of protonated [2-H ], [3-2H ] and [6-2H ] are -3.45, -5.08 and -
4
.59 eV, respectively, as shown in Table S2. The lower LUMO orbital energy of [3-2HN]
suggests an easier acceptance of electrons for it. Figure S4 shows the contributions to LUMOs of
them are all mainly from the protonated pyrimidyl or pyridyl groups. Those results further
evidence the adscription of the first reduction events of complexes 2, 3 and 6 in Figure 3.
4
Conclusions
In this work, a pyrimidyl group is firstly introduced to the phosphine ligand and two new
ligands, PNNP and PNN, have been designed and synthesized depending on the reaction
conditions. These two ligands together with the pyridyl ligand PNP were reacted with Fe (ꢀ-
2
22

ACCEPTED MANUSCRIPT
pdt)(CO)
6
to give the mono-substituted derivatives 2-6. The crystal structures of tetranuclear
iron-sulfur complexes 2 and 3 occupy different space groups (P-1 and P21/n, respectively) due
to the different bridges between the two Fe S units in them. For the stronger electron-
2
2
withdrawing inductive and conjugative effect of the two N atoms in pyrimidyl ring than that in
pyridyl, the electron characters of PNNP- or PNN-substituted derivatives are different from that
of PNP-substituted ones. Complexes 3, 5 and 6 containing pyrimidyl display two reduction
waves; one is ascribed to the reductive process of diiron center, the other is the reduction of the
pyrimidyl unit. While both of the PNP-substituted complexes 2 and 4 show only one reductive
I
0
I
I
wave of Fe Fe /Fe Fe . The theoretical studies of PNP-substituted 2 and 4, PNNP-substituted
dinuclear 5 and PNN-substituted 6 demonstrate that the contributions to LUMOs mainly come
from one Fe S unit along with the surrounded P atoms. But for the PNNP-substituted
2
2
tetranuclear complex 3, the LUMO is comparably resident on the whole molecular.
Acknowledgements
This investigation was based on work supported by the National Natural Science Foundation of
China (Nos. 21101153, 21231003, 21203195 and 21303201).
Appendix A. Supplementary data
The supplementary crystallographic data have been deposited at the Cambridge Crystallographic
Data Center as .cif files, with CCDC number 970444, 970445 and 970446. These data can be
obtained free of charge viawww.ccdc.cam.ac.uk/data_request/cif. Supporting Figures and CIF
files giving the electrochemistry, DFT computational studies can be found in the online version.
References
23

ACCEPTED MANUSCRIPT
[1] C. Tard, C.J. Pickett Chem. Rev. 109 (2009) 2245–2274.
[
2] G.A.N. Felton, C.A. Mebi, B.J. Petro, A.K. Vannucci, D.H. Evans, R.S. Glass, D.L.
Lichtenberger J. Organomet. Chem. 694 (2009) 2681–2699.
[
3] J.I. Van Der Vlugt, T.B. Rauchfuss, S.R. Wilson Chem. Eur. J. 12 (2005) 90–98.
4] D. Chong, I.P. Georgakaki, R. Mejia-Rodriguez, J. Sanabria-Chinchilla, M.P. Soriaga, M.Y.
Darensbourg Dalton Trans. 21 (2003) 4158–4163.
[
[5] L. Schwartz, G. Eilers, L. Eriksson, A. Gogoll, R. Lomoth, S. Ott Chem. Commun. 5 (2006)
520–522.
[
6] G. Si, W.G. Wang, H.Y. Wang, C.H. Tung, L.Z. Wu Inorg. Chem. 47 (2008) 8101–8111.
7] W.F. Liaw, N.H. Lee, C.H. Chen, C.M. Lee, G.H. Lee, S.M. Peng J. Am. Chem. Soc. 122
[
(2000) 488–494.
[
[
[
[
8] S. Ezzaher, J.F. Capon, F. Gloaguen, F.Y. Pétillon, P. Schollhammer, J. Talarmin, N.
Kervarec Inorg. Chem. 48 (2009) 2–4.
9] S. Ghosh, G. Hogarth, N. Hollingsworth, K.B. Holt, I. Richards, M.G. Richmond, B.E.
Sanchez, D. Unwin Dalton Trans. 42 (2013) 6775–6792.
10] W.G. Wang, M.J. Nilges, T.B. Rauchfuss, M. Stein J. Am. Chem. Soc. 135 (2013)
3633−3639.
11] D. Chouffai, G. Zampella, J.F. Capon, L. De Gioia, F. Gloaguen, F.Y. Pétillon, P.
Schollhammer, J. Talarmin Inorg Chem 50 (2011) 12575–12585.
[
12] L.C. Song, Z.Y. Yang, H.Z. Bian, Q.M. Hu, Organometallics 23 (2004) 3082–3084.
13] Y.T. Si, K. Charreteur, J.F. Capon, F. Gloaguen, F.Y. Pétillon, P. Schollhammer, J.
Talarmin J. Inorg Biochem 104 (2010) 1038–1042.
[
24

ACCEPTED MANUSCRIPT
[
[
[
[
14] J. F. Capon, F. Gloaguen, P. Schollhammer, J. Talarmin J. Electroanal.Chem. 595 (2006)
47–52.
15] G.A.N. Felton, A.K. Vannucci, J.Z. Chen, L.T. Lockett, N. Okumura, B.J. Petro, U.I. Zakai,
D.H. Evans, R.S. Glass, D.L. Lichtenberger J. Am. Chem. Soc. 129 (2007) 12521-12530.
16] L. Chen, M. Wang, F. Gloaguen, D.H. Zheng, P.L. Zhang, L.C. Sun Inorg. Chem. 52 (2013)
1
798−1806.
17] L. Chen, M. Wang, F. Gloaguen, D.H. Zheng, P.L. Zhang, L.C. Sun Chem. Eur. J. 18 (2012)
3968–13973.
1
[18] G.R. Newkome, D.W. Evans, F.R. Fronczek Inorg. Chem. 26 (1987) 3500.
[19] F.E. Wood, M.M. Olmstead, A.L. Balch J. Am. Chem. Soc 105 (1983) 6334–6335.
[20] R. Hourihane, G. Gray, T. Spalding, T. Deeney J. Organomet. Chem. 642 (2002) 40–47.
[21] P. Li, M. Wang, C.J. He, G.G. Li, X.Y. Liu, C.N. Chen, B. Åkermark, L.C. Sun Eur. J.
Inorg. Chem. 2005 2506–2513.
[22] Q.Y. Xing, W.W. Pei, R.Q. Xu, J. Pei Basic Organic Chemistry, third ed., Higher Education
Press, Beijing, 2005.
[23] A. Winter, L. Zsolnai, G.Z. Huttner, Naturforsch, 37b (1982) 1430–1436.
[24] G.M. Sheldrick SADABS, University of Gttingen: Göttingen, Germany, (1996).
[25] G.M. Sheldrick SHELXTL. Version 5.1, Siemens Analytical X-ray Instruments Inc.,
Madison, Wisconsin, USA, (1994).
[
26] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J.
A. Montgomery, T. Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J.
Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G. A. Petersson, H.
Nakatsuji, M. Hada, M. Ehara, K. Toyota, R.; Fukuda, J. Hasegawa, M. Ishida, T. Nakajima,
25

ACCEPTED MANUSCRIPT
Y. Honda, O.; Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross, C.
Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C.
Pomelli, J. W. Ochterski, K. Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg, V. G.
Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D.
Rabuck, K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J.
Cioslowski, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D.
J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, M. Challacombe, P. M. W.
Gill, B. Johnson, W.; Wong, M. W. Chen, C. Gonzalez and J. A. Pople, Gaussian 03,
revision D.02. Gaussian, Inc.: Wallingford, CT, 2004.
[
[
[
[
[
[
[
27] A.D. Becke J. Chem. Phys. 98 (1993) 5648-5652.
28] C.T. Lee, W.T. Yang, R.G. Parr Phys. Rev. B 37 (1988) 785–789.
29] V. Barone, M. Cossi J. Phys. Chem. A 102 (1998) 1995–2001.
30] M. Cossi, N. Rega, G. Scalmani, V. Barone, J. Comput. Chem. 24 (2003) 669–681.
31] P. Ros, G.C.A. Schuit Theo. Chim. Acta (Berl.) 4 (1966) 1–12.
32] T. Lu, F.W. Chen J. Comp. Chem. 33 (2012) 580–592.
33] X. Zhao, I.P. Georgakaki, M.L. Miller, R. Mejia-Rodriguez, C.Y. Chiang, M.Y.
Darensbourg Inorg. Chem. 41 (2002) 3917-3928.
[
34] W. Gao, J. Liu, B. Åkermark, L.C. Sun Inorg. Chem.45 (2006) 9169-9171.
35] F. Gloaguen, J.D. Lawrence, T.B. Rauchfuss, M. Benard, M.M. Rohmer Inorg. Chem. 41
[
(2002) 6573–6582.
[36] S. Ott, M. Borgström, M. Kritikos, R. Lomoth, J. Bergquist, B. Åkermark, L.
Hammarström, L.C. Sun Inorg. Chem. 43 (2004) 4683–4692.
26

ACCEPTED MANUSCRIPT
[
[
[
37] F. Gloaguen, J.D. Lawrence, M. Schmidt, S.R. Wilson, T.B. Rauchfuss J. Am. Chem. Soc.
1
23 (2001) 12518–12527.
38] P. Li, M. Wang, L. Chen, J.H. Liu, Z.B. Zhao, L.C. Sun Dalton Trans. 11 (2009) 1919–
926.
39] J.F. Capon, S.E. Hassnaoui, F. Gloaguen, P. Schollhammer, J. Talarmin Organometallics 24
2005) 2020–2022.
1
(
[40] T. Li, M.Y. Darensbourg J. Am. Chem. Soc. 129 (2007) 7008–7009.
[
41] D. Morvan, J.F. Capon, F. Gloaguen, A. Le Goff, M. Marchivie, F. Michaud, P.
Schollhammer, J. Talarmin, J.J. Yaouanc, R. Pichon, N. Kervarec Organometallics 26 (2007)
2042–2052.
[
42] S. Ezzaher, P.Y. Orain, J.F. Capon, F. Gloaguen, F.Y. Pétillon, T. Roisnel, P.
Schollhammer, J. Talarmin Chem. Commun. 27 (2008) 2547–2549.
[
43] W.M. Gao, J.E. Bjo1m, J.H. Liu, C.N. Chen, L. Eriksson, L.H. Weng, L. Åkermark, L.C.
Sun Inorg. Chem. 46 (2007) 1981-1991.
27

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Supporting Information
Pyridyl- and Pyrimidyl-Phosphine-Substituted
FeFe]-Hydrogenase Mimics: Synthesis, Charaterization
and Propertoties
[
a,b
a,b
a
a
a
a,b
Hong-Hua Cui, Nan-Nan Wu, Jin-Yun Wang, Ming-Qiang Hu, Hui-Min Wen, Xiao-Wei Song,
a
and Chang-Neng Chen*
a
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter,
b
Chinese Academy of Sciences, Fuzhou 350002, P. R. China. University of Chinese Academy of
Sciences, Beijing, 100039, P. R. China. E-mail: ccn@fjirsm.ac.cn.
2
[2-HN]
3
[3-2HN]
4
5

ACCEPTED MANUSCRIPT
6
[6-2HN]
Figure. S1. The optimized structures of complexes 2-6 and protonated [2-H ], [3-2H ] and [6-2H ] in the
N
N
N
ground state by DFT method at the B3LYP level. Purple, yellow, orange, red, blue, and gray spheres
represent the iron, sulfur, phosphorus, oxygen, nitrogen, and carbon atoms, respectively. For clarity, the
hydrogen atoms are omitted.
Table S1 Selected bond lengths (Å) and angles (degrees) for complexes 2, 3 and 6.
Complexes
Fe(1)–C(1)
Fe(1)–C(2)
Fe(1)–C(3)
Fe(2)–C(4)
Fe(2)–C(5)
Fe(2)–S(1)
Fe(2)–S(2)
Fe(4)–S(3)
Fe(4)–S(4)
Fe(2)–P(1)
Fe(4)–P(2)
Fe(2)–Fe(1)
Fe(4)–Fe(3)
2
3
6
1.766(6)
1.813(5)
1.802(6)
1.772(5)
1.773(4)
2.2626(14)
2.2623(12)
2.2692(14)
2.2656(14)
2.2315(11)
2.2290(12)
2.5232(9)
2.5209(10)
4.713
1.794(4)
1.789(4)
1.795(5)
1.771(3)
1.775(3)
2.2606(8)
2.2714(9)
2.2575(8)
2.2721(9)
2.2155(7)
2.2184(8)
2.5109(6)
2.5188(6)
3.635
1.78(3)
1.752(9)
1.792(7)
1.784(6)
1.780(6)
2.273(3)
2.276(2)
-----
-----
2.254(2)
-----
2.542(3)
-----
a
Fe---N
3.585
4.492
3.859
5.72
Fe(2)–S(1)–Fe(1)
67.78(4)
67.77(4)
67.51(2)
67.40(3)
67.77(8)
67.83(8)
Fe(1)–S(2)–Fe(2)
a
The Fe atoms are the ones only in one [Fe S ] unit.
2
2