Investigations on the active site models of [FeFe]-hydrogenases: synthesis, structure, and properties of N-functionalized azadithiolatodiiron complexes containing mono- And diphosphine ligands

Article abstract of DOI:10.1021/om700956e

As the new H-cluster models, a series of N-functionalized azadithiolatodiiron complexes containing mono- and diphosphine ligands 1-7 have been prepared by various methods from complexes [μ-SCH₂N(FUn)] Fe₂(CO)₆ (A, Fun=C₆H₄CHO-p; B, Fun=C₆H₄CO₂Me-p; C, Fun=CH₂CH ₂O₂CCH₂C₁₀H₇-1; D, Fun = CH₂CH₂OH) and [(μ-SCH₂)₂N(FUn)] Fe₂(CO)₅(Ph₂PH) (E, Fun = C₆H ₄OMe-p). Treatment of A and B with 1 equiv of Me₃NO · 2H₂O followed by 1 equiv of Ph₃P or Ph ₂PH affords the corresponding monophosphine-substituted complexes [(μ-SCH₂)₂N(C₆H₄CHO-p)]Fe ₂(CO)₅(Ph₃P) (1) and [(μ-SCH ₂)₂N(C₆H₄CO₂Me-P)]Fe2(CO) ₅L (2, L = Ph₃P; 3, Ph₂PH). Further treatment of B with ca. 1 equiv of Ph₂PC₂H₄PPh ₂ (dppe) produced the diphosphine dppe-bridged single model [(μ-SCH₂)₂N(C₆H₄CO ₂caret;Me-p)]Fe₂(CO)₄(dppe) (4), whereas C reacts with 1 equiv of Me₃NO · 2H₂O followed by 0.5 equiv of (η⁵-Ph₂PC₅H₄) ₂Fe (dppf) to give the diphosphine dppf-bridged double model [(μ-SCH₂)₂N(CH₂CH₂O ₂CCH₂C₁₀H₇-1)Fe₂(CO) ₅]₂(dppf) (5). While D reacts with 1 equiv of w-BuLi followed by 1 equiv of Ph₂PCl or directly reacts with 1 equiv of Ph₂PCl in the presence of Et₃N to generate N-alkoxyphosphine-substituted complex [CM-SCH₂)₂N(CH ₂CH₂OPPh_2-η¹)]Fe ₂(CO)₅ (6), treatment of E with 1 equiv of n-BuLi followed by 1 equiv of CpFe(CO)₂I yields organometallic phosphine-substituted complex [μ-SCH₂)₂N(C₆H₄OMe-P)] Fe₂(CO)₅[Ph₂PFe(CO)₂Cp] (7). AU the new model complexes 1-7 are fully characterized by elemental analysis, spectroscopy, and particularly for 1, 3, 4, 6, and 7 X-ray crystallography. More interestingly, 2 is found to be a catalyst for HOAc proton reduction to hydrogen under CV conditions. In addition, according to electrochemical and spectroelectrochemical studies, an ECEC mechanism is proposed for this electrocatalytic reaction.

Full text of DOI:10.1021/om700956e

Organometallics 2008, 27, 1409–1416
1409
Investigations on the Active Site Models of [FeFe]-Hydrogenases:
Synthesis, Structure, and Properties of N-Functionalized
Azadithiolatodiiron Complexes Containing Mono- and Diphosphine
Ligands
Li-Cheng Song,* Hu-Ting Wang, Jian-Hua Ge, Shu-Zhen Mei, Jie Gao, Liang-Xing Wang,
Bin Gai, Li-Qun Zhao, Jing Yan, and Yong-Zhen Wang
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai UniVersity,
Tianjin 300071, People’s Republic of China
ReceiVed September 26, 2007
As the new H-cluster models, a series of N-functionalized azadithiolatodiiron complexes containing
mono- and diphosphine ligands 1–7 have been prepared by various methods from complexes
[(µ-SCH2N(Fun)]Fe2(CO)6 (A,Fun)C6H4CHO-p;B,Fun)C6H4CO2Me-p;C,Fun)CH2CH2O2CCH2C10H7-
1; D, Fun ) CH2CH2OH) and [(µ-SCH2)2N(Fun)]Fe2(CO)5(Ph2PH) (E, Fun ) C6H4OMe-p). Treatment
of A and B with 1 equiv of Me3NO · 2H2O followed by 1 equiv of Ph3P or Ph2PH affords the corresponding
monophosphine-substituted complexes [(µ-SCH2)2N(C6H4CHO-p)]Fe2(CO)5(Ph3P) (1) and [(µ-
SCH2)2N(C6H4CO2Me-p)]Fe2(CO)5L (2, L ) Ph3P; 3, Ph2PH). Further treatment of B with ca. 1 equiv
of Ph2PC2H4PPh2 (dppe) produced the diphosphine dppe-bridged single model [(µ-SCH2)2N(C6H4CO2Me-
p)]Fe2(CO)4(dppe) (4), whereas C reacts with 1 equiv of Me3NO · 2H2O followed by 0.5 equiv of (η5-
Ph2PC5H4)2Fe (dppf) to give the diphosphine dppf-bridged double model [(µ-SCH2)2N(CH2CH2O2CCH2C10H7-
1)Fe2(CO)5]2(dppf) (5). While D reacts with 1 equiv of n-BuLi followed by 1 equiv of Ph2PCl or directly
reacts with 1 equiv of Ph2PCl in the presence of Et3N to generate N-alkoxyphosphine-substituted complex
[(µ-SCH2)2N(CH2CH2OPPh2-η1)]Fe2(CO)5 (6), treatment of E with 1 equiv of n-BuLi followed by 1
equiv of CpFe(CO)2I yields organometallic phosphine-substituted complex [(µ-SCH2)2N(C6H4OMe-
p)]Fe2(CO)5[Ph2PFe(CO)2Cp] (7). All the new model complexes 1–7 are fully characterized by elemental
analysis, spectroscopy, and particularly for 1, 3, 4, 6, and 7 X-ray crystallography. More interestingly, 2
is found to be a catalyst for HOAc proton reduction to hydrogen under CV conditions. In addition,
according to electrochemical and spectroelectrochemical studies, an ECEC mechanism is proposed for
this electrocatalytic reaction.
in this type of complexes is probably the actual dithiolate
cofactor of [FeFe]-hydrogenases;8 (ii) the bridgehead N atom
of this ligand could play a key role in the heterolytic cleavage
Introduction
Since the high-quality crystal structures of [FeFe]-hydroge-
nases were elucidated,1 a large number of structural and
functional model complexes for the active site of [FeFe]-
hydrogenases, the so-called H-cluster, have appeared in the
literature.2–5 Among the reported models, N-functiona-
lized azadithiolatodiiron complexes of the type [(µ-
SCH2)2N(Fun)]Fe2(CO)6-nLn (Fun ) functionality)4a,b,6,7 are of
particular interest. This is because (i) the azadithiolate ligand
9
or formation of H2; and (iii) the bridgehead N-functionality
may allow attachment of various substituents easily by func-
tional transformation reactions.10,11 Although numerous N-
functionalized azadithiolatodiiron complexes have been so far
described in the literature,4a,b,6,7 very few studies have been
carried out regarding their CO substitution and functional
transformation reactions. As a continuation of our project
* To whom correspondence should be addressed. Fax: 0086-22-
23504853. E-mail: lcsong@nankai.edu.cn.
(5) (a) Song, L.-C.; Yang, Z.-Y.; Bian, H.-Z.; Hu, Q.-M. Organometallics
2004, 23, 3082. (b) Li, H; Rauchfuss, T. B J. Am. Chem. Soc. 2002, 124,
726. (c) Song, L.-C.; Yang, Z.-Y.; Hua, Y.-J.; Wang, H.-T.; Liu, Y.; Hu,
Q.-M. Organometallics 2007, 26, 2106.
(1) (a) Peters, J. W.; Lanzilotta, W. N.; Lemon, B. J.; Seefeldt, L. C
Science 1998, 282, 1853. (b) Nicolet, Y.; Piras, C.; Legrand, P.; Hatchikian,
E. C.; Fontecilla-Camps, J. C. Structure 1999, 7, 13.
(2) (a) Darensbourg, M. Y.; Lyon, E. J.; Smee, J. J. Coord. Chem. ReV.
2000, 206–207, 533. (b) Evans, D. J.; Pickett, C. J. Chem. Soc. ReV. 2003,
32, 268. (c) Song, L.-C. Acc. Chem. Res. 2005, 38, 21.
(6) Song, L.-C.; Ge, J.-H.; Liu, X.-F.; Zhao, L.-Q.; Hu, Q.-M. J.
Organomet. Chem. 2006, 691, 5701.
(7) Stanley, J. L.; Rauchfuss, T. B.; Wilson, S. R. Organometallics 2007,
26, 1907.
(3) (a) Gloaguen, F.; Lawrence, J. D.; Schmidt, M.; Wilson, S. R.;
Rauchfuss, T. B. J. Am. Chem. Soc. 2001, 123, 12518. (b) Lyon, E. J.;
Georgakaki, I. P.; Reibenspies, J. H.; Darensbourg, M. Y. J. Am. Chem.
Soc. 2001, 123, 3268. (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) Nehring, J. L.; Heinekey,
D. M. Inorg. Chem. 2003, 42, 4288.
(8) (a) Nicolet, Y.; Lemon, B. J.; Fontecilla-Camps, J. C.; Peters, J. W.
Trends Biochem. Sci. 2000, 25, 138. (b) Nicolet, Y.; De Lacey, A. L.;
Vernède, X.; Fernandez, V. M.; Hatchikian, E. C.; Fontecilla-Camps, J. C.
J. Am. Chem. Soc. 2001, 123, 1596.
(9) Fan, H.; Hall, M. B. J. Am. Chem. Soc. 2001, 123, 3828.
(10) (a) Song, L.-C.; Tang, M.-Y.; Su, F.-H.; Hu, Q.-M. Angew. Chem.,
Int. Ed. 2006, 45, 1130. (b) Song, L.-C.; Tang, M.-Y.; Mei, S.-Z.; Huang,
J.-H.; Hu, Q.-M. Organometallics 2007, 26, 1575.
(4) (a) Lawrence, J. D.; Li, H.; Rauchfuss, T. B. Chem. Commun. 2001,
1482. (b) Song, L.-C.; Ge, J.-H.; Zhang, X.-G.; Liu, Y.; Hu, Q.-M. Eur.
J. Inorg. Chem. 2006, 3204. (c) Schwartz, L.; Eilers, G.; Eriksson, L.;
Gogoll, A.; Lomoth, R.; Ott, S. Chem. Comm. 2006, 520.
(11) Tard, C.; Liu, X.; Ibrahim, S. K.; Bruschi, M.; De Gioia, L.; Davies,
S. C.; Yang, X.; Wang, L.-S.; Sawers, G.; Pickett, C. J. Nature 2005, 433,
610.
10.1021/om700956e CCC: $40.75
2008 American Chemical Society
Publication on Web 03/14/2008

1410 Organometallics, Vol. 27, No. 7, 2008
Song et al.
Scheme 1
Scheme 4
Scheme 2
Scheme 5
Scheme 3
associated with N-functionalized azadithiolate (ADT) model
complexes, we recently began to study their CO substitution
and functional transformations aimed at obtaining N-function-
alized ADT models with phosphine ligands. This is because
phosphines are known to be good surrogates for cyanide ligand
found in the natural enzymes.12 In this paper, we report the
synthesis, structural characterization, and electrochemical prop-
erties regarding such new complexes. Furthermore, the elec-
trocatalytic H2 production catalyzed by one of the synthesized
new models is also described.
CH2O2CCH2C10H7-1)]Fe2(CO)6 (C)13 reacted with 1 equiv of
Me3NO · 2H2O followed by 0.5 equiv of organometallic diphos-
phine (η5-Ph2PC5H4)2Fe (dppf) at room temperature to give the
dppf-bridged double model 5 in 30% yield (Scheme 4).
More interestingly, when N-hydroxyethyl complex [(µ-
SCH2)2NCH2CH2OH]Fe2(CO)6 (D)13 reacted with 1 equiv of
n-BuLi at –40 °C followed by treatment of the corresponding
O-Li intermediate M1 with ca. 1 equiv of Ph2PCl from –40
°C to room temperature, N-alkoxyphosphine-substituted complex
6 was produced in 10% yield via CO substitution of the
intermediate M2 by its pendent alkoxyphosphine moiety (Scheme
5). Model 6 could also be prepared by a simple and convenient
method with a much higher yield (53%), which involves reaction
of D with ca. 1 equiv of Ph2PCl in the presence of excess Et3N
from 0 °C to room temperature (Scheme 5).
In principle, the organic phosphine Ph2PH-containing com-
plexes such as 3 and [(µ-SCH2)2N(C6H4OMe-p)]Fe2(CO)5-
(Ph2PH) (E)4b could be converted to organometallic phosphine-
containing complexes by functionalization of their P-H bonds.
For example, model 7, which contains an extremely unstable
organometallic phosphine ligand Ph2PFe(CO)2Cp,14 might be
obtained in 60% yield by reaction of E with 1 equiv of n-BuLi
at –40 °C and subsequent treatment of the corresponding P-Li
intermediate M3 with 1 equiv of CpFe(CO)2I from –40 °C to
room temperature (Scheme 6).
Results and Discussion
Synthesis and Spectroscopic Characterization of Phos-
phine-Containing N-Functionalized Models 1–7. Treatment
of N-benzaldehyde complex [(µ-SCH2)2NC6H4CHO-p)]Fe2-
(CO)6 (A)10a with
1 equiv of decarbonylating agent
Me3NO · 2H2O3a in MeCN at room temperature, followed by 1
equiv of Ph3P, gave the corresponding Ph3P-monosubstituted
complex 1 in 52% yield (Scheme 1). Similarly, when N-benzoic
ester complex [(µ -SCH2)2N(C6H4CO2Me-p)]Fe2(CO)6 (B)6
reacted with 1 equiv of Me3NO · 2H2O followed by 1 equiv of
Ph3P or Ph2PH, the corresponding Ph3P- and Ph2PH-monosub-
stituted complexes 2 and 3 were produced in 76% and 94%
yields, respectively (Scheme 2).
Interestingly, further treatment of complex B with ca. 1 equiv
of organic diphosphine Ph2PC2H4PPh2 (dppe) in refluxing xylene
afforded the dppe-bridged single model 4 in 67% yield (Scheme
3), whereas naphthylacetic ester complex [(µ-SCH2)2N(CH2-
All the new complexes 1–7 have been fully characterized by
1
elemental analysis and IR, H NMR, and 31P NMR spectros-
(12) (a) Zhao, X.; Chiang, C.-Y.; Miller, M. L.; Rampersad, M. V.;
Darensbourg, M. Y. J. Am. Chem. Soc. 2003, 125, 518. (b) Song, L.-C.;
Yang, Z.-Y.; Bian, H.-Z.; Liu, Y.; Wang, H.-T.; Liu, X.-F.; Hu, Q.-M.
Organometallics 2005, 24, 6126. (c) van der Vlugt, J. I.; Rauchfuss, T. B.;
Wilson, S. R. Chem.-Eur. J. 2006, 12, 90. (d) Ezzaher, S.; Capon, J.-F.;
Gloaguen, F.; Pétillon, F. Y.; Schollhammer, P.; Talarmin, J. Inorg. Chem.
2007, 46, 9863.
(13) Song, L.-C.; Yin, B.-S.; Li, Y.-L.; Zhao, L.-Q.; Ge, J.-H.; Yang,
Z.-Y.; Hu, Q.-M. Organometallics 2007, 26, 4921.
(14) (a) Weers, J. J.; Eyman, D. P. J. Organomet. Chem. 1985, 286,
47. (b) Buckett-StLaurent, J. C. T. R.; Haines, R. J.; Nolte, C. R.; Steen,
N. D. C. T. Inorg. Chem. 1980, 19, 577.

ActiVe Site Models of [FeFe]-Hydrogenases
Organometallics, Vol. 27, No. 7, 2008 1411
Scheme 6
Figure 1. Molecular structure of 1 with 30% probability level
ellipsoids.
copy. The elemental analysis data of 1–7 are in good agreement
with their compositions shown in Schemes 1, 2, 3, 4, 5, and 6.
The IR spectra of 1–7 showed three to four absorption bands
in the range 2047–1909 cm-1 for their terminal carbonyls, and
1–5 displayed one additional band in the region 1735–1695
cm-1 for their aldehyde and ester carbonyls. It is noteworthy
that for terminal carbonyls the three IR bands of 4 are located
at lower frequencies than those of 5, which is consistent with 4
having two P donors at its diiron unit (see its crystal structure
below) and 5 having only one P donor at each of its two diiron
units as shown in Scheme 4.15 In addition, the almost identical
νCt O IR band pattern of 5 and [(µ-ODT)Fe2(CO)5]2(dppf) [2047
(vs), 1983 (vs), 1933 (s)]12b further supports that 5 has the same
type of structure as that of the crystallographically characterized
[(µ-ODT)Fe2(CO)5]2(dppf).12b The 1H NMR spectra of 1–7
exhibited all their organic groups. For example, 1 showed a
singlet at 9.79 ppm for its CHO group, 2–4 a singlet at ca. 3.87
ppm for their CO2Me groups, 5 a singlet at 3.98 ppm for its
CH2 group attached to the naphthalene ring, 6 three triplets at
2.87, 3.86, and 3.91 ppm for its N(CH2)2O group, and 7 a singlet
at 4.77 ppm for its Cp group. In addition, 3 displayed a doublet
at 6.24 ppm for its PH group, whereas 1–7 displayed two singlets
Figure 2. Molecular structure of 3 with 30% probability level
ellipsoids.
or two doublets for their SCH2N groups, respectively. The 31
P
NMR spectrum of 3 showed a doublet at 47.20 ppm for the P
atom in its Ph2PH ligand and that of 6 a singlet at 172.47 ppm
for the P atom in its N-alkoxyphosphine ligand, whereas the
other models displayed a singlet in the range 56–65 ppm for
their P atoms in the corresponding mono- and diphosphine
ligands.
Crystal Structures of 1, 3, 4, 6, and 7. The molecular
structures of 1, 3, 4, 6, and 7 were further investigated by X-ray
crystallography. Their ORTEP plots are presented in Figures
1, 2, 3, 4, and 5, Tables 1 and 2 list the selected bond lengths
and angles, respectively. As can be seen intuitively in Figures
1, 2, 3, 4, and 5, complexes 1, 3, 4, 6, and 7 all have a
functionalized azadithiolate ligand bridged between two iron
atoms to form two fused six-membered rings with a chair and
a boat conformation, respectively. While the N-functionalized
substituents of 1, 3, 4, and 6 are attached to the common N1
atom of the two six-membered rings by an axial bond N1-C26,
N1-C8, N1-C7, or N1-C8, the N-functionalized substituent
of 7 is connected to N1 by an equatorial N1-C27 bond.
Particularly noteworthy is that although the monophosphine
ligands of 1, 3, 6, and 7 are all located in the apical position of
the square-pyramidal geometry of their iron atoms, the diphos-
Figure 3. Molecular structure of 4 with 30% probability level
ellipsoids.
phine ligand of 4 is connected to its two atoms with a cisoid
basal/basal coordination mode. The Fe-Fe bond lengths of 1
(2.5066 Å), 3 (2.5003 Å), 4 (2.5511 Å), 6 (2.5127 Å), and 7
(2.5224 Å) are slightly shorter than the corresponding bond
lengths of the phosphine-substituted complexes [(µ-SCH2)2-
N(C6H4OMe-p)]Fe2(CO)5(Ph3P) (2.554 Å)4b and {[(µ
-SCH2)2O]Fe2(CO)5}2(dppf) (2.5430 Å),12b but they are very
(15) Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principles
and Applications of Organotransition Metal Chemistry, 2nd ed.; University
Science Books: Mill Valley, CA, 1987.
(16) Lyon, E. J.; Georgakaki, I. P.; Reibenspies, J. H.; Darensbourg,
M. Y. Angew. Chem., Int. Ed. 1999, 38, 3178.

1412 Organometallics, Vol. 27, No. 7, 2008
Song et al.
the electrochemical window of solvent MeCN) and two ir-
reversible oxidation events at +0.34 and +0.61 V. The three
observed redox events are all one-electron processes, which were
supported by the calculated value of 0.94 faraday/equiv
(obtained through study of bulk electrolysis of a MeCN solution
of 2 at -1.87 V) and the calculated value of (ip/ν1/2)/(it1/2) )
3.6 (obtained through study of CV and chronoamperometry
(CA) of 2).21 In addition, they could be assigned to the reduction
of FeIFeI to FeIFe0, the oxidation of FeIFeI to FeIFeII, and the
oxidation of FeIFeII to FeIIFeII, respectively. The electrochemical
behavior of 2 is very similar to that of its parent complex B,
except that the observed reduction and oxidation peaks of 2
are shifted toward the cathodic direction by an average 200 mV,
as compared to those corresponding to complex B.6 Actually,
such cathodic shifts are due to the increase of electron density
at its diiron center originated from replacement of a CO ligand
of B by the stronger electron-donating ligand Ph3P.
Figure 4. Molecular structure of 6 with 30% probability level
ellipsoids.
The cyclic voltammogram of 2 in the presence of HOAc is
shown in Figure 7. For comparison, the cyclic voltammogram
of 2 without HOAc is also included. As shown in Figure 7,
when 1–9 mM HOAc was added, the initial first reduction peak
of 2 at -1.67 V slightly increased, but it did not grow with
sequential addition of the acid. In addition, upon addition of
1–9 mM HOAc, a new reduction peak at ca. -2.13 V appeared,
which grew dramatically with increasing concentration of the
acid. These observations are typical of a catalytic proton
reduction process.6,20,22 To further confirm this, we carried out
bulk electrolysis of a MeCN solution containing HOAc (25 mM)
and 2 (0.5 mM) at -2.20 V. During 0.5 h of the bulk
electrolysis, 14.6 F per mol of 2 passed, which corresponds to
7.3 turnovers. Gas chromatography showed that the hydrogen
yield is >90%.
According to the above-mentioned electrochemical observa-
tions and the reported similar cases,6,20,22 we might proposed
an ECEC (E ) electrochemical, C ) chemical) mechanism for
this electrocatalytic H2-producing process as shown in Scheme
7. First, 2 is reduced at -1.67 V to give monoanion 2–. Then,
2– is protonated by HOAc to generate the neutral Fe-H species
2H. After 2H is further reduced at –2.13 V, the resulting anionic
Fe-H species can be protonated by HOAc to reproduce 2 with
evolution of H2 to complete the catalytic cycle. It follows that
this ECEC mechanism is different from the EECC mechanism
suggested for reduction of a HOAc proton to H2 catalyzed by
complex B.6 It is evident that the major reason causing such a
difference is that one CO ligand of B had been replaced by
stronger electron-donating Ph3P. In fact, while Ph3P makes the
first reduction of 2 more difficult than that of B (Epc ) -1.67
versus -1.54 V), it can make the one-electron-reduced monoan-
ion 2– more electron-rich than the corresponding B- and thus
be directly protonated by weak acid HOAc to cause the ECEC
mechanism.
Figure 5. Molecular structure of 7 with 30% probability level
ellipsoids.
close to those corresponding to the unsubstituted complexes [(µ-
SCH2)2N(C6H4OMe-p)]Fe2(CO)6 (2.5076 Å),4b [(µ-SCH2)2O]-
Fe2(CO)6 (2.5113 Å),12b (µ-SCH2)2CH2]Fe2(CO)6 (2.5103 Å),16
and [(µ-SCH2)2NMe]Fe2(CO)6 (2.4924 Å).17 It is interesting to
note that the [2Fe2SP] model complex 6 and the [3Fe2SP] model
complex 7 are structurally very similar to the previously reported
[2Fe3S] and [3Fe3S] model complexes, respectively.4a,12b,18
Electrochemistry, Electrocatalysis, and Spectroelectro-
chemistry (SEC) of 2. In order to examine the electrocatalytic
H2-producing ability of the phosphine-containing H-cluster
models,19,20 we initiated a study on electrochemical properties
of 2 by using cyclic voltammetry (CV). As can be seen in Figure
6, in the absence of HOAc, 2 displays one quasi-reversible
reduction event at -1.67 V (its second reduction is beyond
In order to gain more evidence to support the electrocatalytic
mechanism shown in Scheme 7, we further carried out the
spectroelectrochemical study of 2 by using IR SEC techniques22,23
(Figures 8 and 9). In Figure 8, for comparison the IR spectrum
of 2 without HOAc recorded prior to the application of the
potential (Figure 8a) is included. As the electrolysis proceeded,
the three ν(CO) IR bands at 2049, 1990, and 1930 cm-1 of the
(17) Lawrence, J. D.; Li, H.; Rauchfuss, T. B.; Bénard, M.; Rohmer,
M.-M. Angew. Chem., Int. Ed. 2001, 40, 1768.
(21) Zanello, P. Inorganic Electrochemistry. Theory, Practice and
Application; Thomas Graham House: Cambridge, UK, 2003.
(22) Chong, D.; Georgakaki, I. P.; Mejia-Rodriguez, R.; Sanabria-
Chinchilla, J.; Soriaga, M. P.; Darensbourg, M. Y. Dalton Trans. 2003,
4158.
(18) Razavet, M.; Davies, S. C.; Hughes, D. L.; Pickett, C. J. Chem.
Commun. 2001, 847.
(19) Mejia-Rodriguez, R.; Chong, D.; Reibenspies, J. H.; Soriaga, M. P.;
Darensbourg, M. Y. J. Am. Chem. Soc. 2004, 126, 12004.
(20) Gloaguen, F.; Lawrence, J. D.; Rauchfuss, T. B. J. Am. Chem. Soc.
2001, 123, 9476.
(23) Borg, S. J.; Behrsing, T.; Best, S. P.; Razavet, M.; Liu, X.; Pickett,
C. J. J. Am. Chem. Soc. 2004, 126, 16988.

ActiVe Site Models of [FeFe]-Hydrogenases
Organometallics, Vol. 27, No. 7, 2008 1413
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 1, 3, and 4
1
Fe(1)-S(1)
2.2904(13)
2.2784(14)
2.5066(9)
2.2640(13)
83.72(4)
56.11(4)
56.85(4)
84.12(5)
Fe(2)-S(2)
2.2866(13)
1.427(6)
1.401(5)
2.2562(13)
56.54(4)
66.78(4)
120.6(4)
104.27(5)
Fe(1)-S(2)
N(1)-C(24)
Fe(1)-Fe(2)
Fe(2)-S(1)
S(1)-Fe(1)-S(2)
S(1)-Fe(1)-Fe(2)
S(2)-Fe(1)-Fe(2)
S(1)-Fe(2)-S(2)Fe(1)-S(1)
N(1)-C(26)
Fe(1)-P(1)
S(2)-Fe(2)-Fe(1)
Fe(2)-S(1)-Fe(1)
C(24)-N(1)-C(26)
P(1)-Fe(1)-S(2)Fe(2)-S(2)2.2822(8)
3
Fe(1)-S(2)
202822(8)
2.2764(9)
2.5003(9)
2.2711(9)
84.29(2)
56.48(3)
56.70(3)
66.61(3)
66.64(3)
Fe(2)-S(2)
2.2755(9)
1.433(3)
1.402(2)
2.2231(8)
56.906(19)
107.81(3)
84.56(3)
112.29(18)
111.29(18)
Fe(1)-S(2)
N(1)-C(6)
Fe(1)-Fe(2)
N(1)-C(8)
Fe(2)-P(1)
S(1)-Fe(2)-Fe(1)
P(1)-Fe(2)-S(1)
S(1)-Fe(2)-S(2)
C(6)-N(1)-C(7)
o(7)-C(14)-C(11)
Fe(2)-S(1)
S(2)-Fe(1)-S(1)
S(1)-Fe(1)-Fe(2)
S(2)-Fe(2)-Fe(1)
Fe(2)-S(1)-Fe(1)Fe(2)-S(2)-Fe(1)Fe(1)-S(1)
Fe(2)-S(1)-Fe(1)Fe(2)-S(2)-Fe(1)Fe(1)-S(1)
4
Fe(1)-S(1)
2.2463(6)
2.2820(6)
2.5511(5)
2.2682(6)
90.67(2)
84.46(2)
106.34(2)
163.22(2)
84.44(2)
Fe(2)-S(2)
2.2615(7)
2.2166(7)
1.838(2)
Fe(1)-S(2)
Fe(1)-P(1)
Fe(1)-Fe(2)
Fe(2)-S(1)
P(1)-Fe(1)-S(1)
S(1)-Fe(2)-S(2)
P(1)-Fe(1)-Fe(2)
P(2)-Fe(2)-S(2)
S(2)-Fe(2)-S(1)
P(1)-C(27)
N(1)-C(5)
S(1)-Fe(1)-Fe(2)
S(1)-Fe(2)-Fe(1)
Fe(1)-S(1)-Fe(2)
C(15)-P(1)-Fe(1)C(5)-N(1)-C(6)
C(5)-N(1)-C(6)
1.435(3)
55.998(18)
55.188(16)
68.814(18)
114.10(8)
112.92(18)
cm-1 appeared in higher frequencies. Such IR shifts toward
higher frequencies might be reasonably ascribed to the formation
of the Fe(II)-H species 2H from protonation of monoanion 2-
by HOAc.15 It follows that the studied results of electrochem-
istry, IR, and EPR spectroelectrochemistry have provided
evidence to support the ECEC mechanism, although more
evidence is still needed for the detailed mechanism.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for 6 and 7
6
Fe(1)-S(1)
2.2556(10) Fe(2)-S(2)
2.2690(11)
1.444(4)
1.614(2)
2.2056(10)
56.24(3)
56.76(3)
Fe(1)-S(2)
2.2821(10) N(1)-C(8)
Fe(1)-Fe(2)
Fe(2)-S(1)
S(2)-Fe(1)-S(1)
S(1)-Fe(2)-Fe(1) 55.92(3)
S(2)-Fe(2)-Fe(1) 56.74(3)
Fe(2)-S(1)-Fe(1) 67.32(3)
Fe(2)-S(1)-Fe(1) 67.02(3)
2.5127(7)
2.2776(10) Fe(1)-P(1)
84.18(3) S(2)-Fe(1)-Fe(2)
P(1)-O(6)
S(1)-Fe(1)-Fe(2)
S(2)-Fe(2)-S(1)
C(6)-N(1)-C(7)
O(6)-P(1)-Fe(1)
83.97(4)
116.9(3)
115.28(9)
Conclusion
The N-functionalized diiron azadithiolate phosphine com-
plexes 1–7 as the new H-cluster models have been prepared
from the corresponding complexes A-E via four different
synthetic methods: (i) Me3NO-promoted CO substitution; (ii)
thermally induced CO substitution; (iii) N-functional transfor-
mation followed by CO substitution; and (iv) functional
transformation of ligand Ph2PH in its coordination sphere.
Particularly interesting are methods iii and iv, since they can
provide simple and convenient routes leading to novel model
complexes 6 and 7, which structurally resemble the [2Fe3S]
7
Fe(1)-S(1)
2.2607(10) Fe(2)-S(2)
2.2706(10)
2.2905(10)
2.3355(10)
1.442(4)
56.14(3)
67.79(3)
Fe(1)-S(2)
2.2662(10) Fe(1)-P(1)
Fe(1)-Fe(2)
Fe(2)-S(1)
S(2)-Fe(1)-S(1)
S(2)-Fe(1)-Fe(2) 56.30(3)
S(1)-Fe(1)-Fe(2) 56.14(3)
S(1)-Fe(2)-S(2)
S(1)-Fe(2)-Fe(1) 56.07(3)
2.5224(7)
2.2626(10) N(1)-C(25)
84.29(3) S(2)-Fe(2)-Fe(1)
Fe(3)-P(1)
Fe(2)-S(1)-Fe(1)
Fe(1)-S(2)-Fe(2)
Fe(1)-P(1)-Fe(3)
67.56(3)
116.70(4)
84.15(3)
C(26)-N(1)-C(25) 114.6(2)
initial 2 decreased in their intensities with the growth of new
bands at lower frequencies. When the electrolysis was completed
(ca. 1.1 equiv electron passed), the IR spectrum showed three
new ν(CO) bands at 2013, 1972, and 1906 cm-1 (Figure 8b).
These bands were shifted toward lower frequencies relative to
the original ones by an average of 26 cm-1 and could be
reasonably attributed to the formation of monoanion 2-.15 The
EPR spectrum of the catholyte of 2 was recorded at 120 K,
which displayed a strong signal with g ) 2.064 and a weak
signal with g| ) 1.994, indicating the odd-electron species
(FeIFe0) generated by bulk electrolysis of 2.22 The IR spectrum
of 2 with HOAc recorded prior to the electrolysis (Figure 9a)
is essentially the same as that of 2 without HOAc (Figure 8a).
This means that 2 cannot be directly protonated by the weak
acid HOAc. As can be seen in Figure 9b, when the electrolysis
of 2 with HOAc was finished (ca. 1.1 equiv electron passed),
five new ν(CO) bands at 2076, 2036, 1996, 1976, and 1932
Figure 6. Cyclic voltammogram of 2 (1.0 mM) without HOAc in
0.1 M n-Bu4NPF6/MeCN at a scan rate of 100 mV s-1
.

1414 Organometallics, Vol. 27, No. 7, 2008
Song et al.
Figure 9. IR spectra in the CO region recorded during the
electrolysis of 5 mM 2 with 50 mM HOAc in CO-saturated MeCN
solution (0.1 M n-Bu4NPF6) at -1.82 V: (a) prior to the application
of the potential; (b) electrolysis for 2 h.
Figure 7. Cyclic voltammograms of 2 (1.0 mM) with and without
HOAc (0–9 mM) in 0.1 M n-Bu4NPF6/MeCN at a scan rate of 100
mV s-1
.
methodology and biomimetically catalytic function of such
H-cluster models are in progress.
Experimental Section
General Comments. All reactions were performed using stan-
dard Schlenk and vacuum-line techniques under N2. Acetonitrile
was distilled once from P2O5 and then from CaH2 under N2. THF
and xylene were purified by distillation under N2 from sodium/
benzophenone ketyl. While [(µ-SCH2)2NC6H4CHO-p)]Fe2(CO)6
(A),10a [(µ-SCH2)2N(C6H4CO2Me-p)]Fe2(CO)6 (B),6 [(µ-SCH2)2N-
(CH2CH2O2CCH2C10H7-1)]Fe2(CO)6 (C),13 [(µ-SCH2)2NCH2CH2-
OH]Fe2(CO)6 (D),13 [(µ-SCH2)2N(C6H4OMe-p)]Fe2(CO)5(Ph2PH)
(E),4b Ph2PH,24 (η5-Ph2PC5H4)2Fe (dppf),25 and CpFe(CO)2I26 were
prepared according to literature procedures, the other starting
materials were commercially available and used without further
purification. Preparative TLC was carried out on glass plates (26
× 20 × 0.25 cm) coated with silica gel H (10-40 µm). IR spectra
were recorded on a Bio-Rad FTS 6000 spectrophotometer. 1H NMR
and 31P NMR spectra were obtained on a Bruker Avance 300 or a
Varian Mercury Plus 400 spectrometer. A Bruker EMX EPR
spectrometer was used to collect electron paramagnetic resonance
spectra. Elemental analyses were performed on an Elementar Vario
EL analyzer. Melting points were determined on a Yanaco MP-
500 apparatus and were uncorrected.
Figure 8. IR spectra in the CO region recorded during the
electrolysis of 5 mM 2 without HOAc in CO-saturated MeCN (0.1
M n-Bu4NPF6) at -1.82 V: (a) prior to the application of the
potential; (b) electrolysis for 2 h.
Scheme 7
Preparation of [(µ-SCH2)2N(C6H4CHO-p)]Fe2(CO)5(Ph3P)
(1). To a red solution of A (0.140 g, 0.28 mmol) in MeCN (10
mL) was added Me3NO · 2H2O (0.032 g, 0.28 mmol). The mixture
was stirred at room temperature for 20 min to give a brown-black
solution. After Ph3P (0.074 g, 0.28 mmol) was added, the new
mixture was stirred at this temperature for 4 h. Volatiles were
removed under vacuum, and the residue was subjected to TLC using
acetone/petroleum ether (v/v ) 1:3) as eluent. From the main red
band, 1 was obtained as a dark red solid (0.106 g, 52%), mp
206–207 °C. Anal. Calcd for C32H24Fe2NO6PS2: C, 52.99; H, 3.34;
N, 1.93. Found: C, 52.73; H, 3.30; N, 2.13. IR (KBr disk): νCt
O
2047 (vs), 1985 (vs), 1926 (s); νCHO 1695 (m) cm-1
.
1H NMR
(300 MHz, CDCl3): 2.89 (br s, 2H, 2CHHS), 4.12 (br s, 2H, 2CH
HS), 6.63–7.73 (m, 19H, C6H4, 3C6H5), 9.79 (s, 1H, CHO) ppm.
31P NMR (121 MHz, CDCl3, 85% H3PO4): 64.30 (s) ppm.
Preparation of [(µ-SCH2)2N(C6H4CO2Me-p)]Fe2(CO)5(Ph3P)
(2). To a red solution of B (0.130 g, 0.25 mmol) in MeCN (20 mL)
was added Me3NO · 2H2O (0.029 g, 0.25 mmol). The mixture was
models reported by the Rauchfuss and Pickett groups,4a,18 as
well as the [3Fe3S] model previously reported by us,
respectively.12b All the new models 1–7 have been fully
characterized, whereas model 2, the Ph3P-monosubstituted
derivative of B, has been found to be a catalyst for H2 production
under electrochemical conditions. Both electrochemical and
spectroelectrochemical data of 2 strongly support the suggested
ECEC mechanism for the electrochemical H2 production
catalyzed by 2. Further studies concerning the synthetic
(24) Kuchen, W.; Buchwald, H. Chem. Ber. 1958, 91, 2871.
(25) Bishop, J. J.; Davison, A.; Katcher, M. L.; Lichtenberg, D. W.;
Merrill, R. E.; Smart, J. C. J. Organomet. Chem. 1971, 27, 241.
(26) King, R. B. Organometallic Syntheses, Transition-Metal Com-
pounds; Academic Press: New York, 1965; Vol. I, p 175.

ActiVe Site Models of [FeFe]-Hydrogenases
Organometallics, Vol. 27, No. 7, 2008 1415
Table 3. Crystal Data and Structure Refinement Details for 1, 3, and 4
1
3
4
mol formula
C32H24Fe2NO6PS2
CH2Cl2
27H22Fe2NO7PS2
C40H35Fe2NO6P2S2
mol wt
cryst syst
space group
a /Å
b /Å
c /Å
810.24
monoclinic
P2(1)/c
12.753(3)
17.823(4)
15.462(4)
90
90.205(4)
90
3514.4(14)
4
1.531
1.186
1648
679.25
863.45
triclinic
monoclinic
P2(1)/n
9.3759(13)
19.560(3)
21.756(3)
90
94.719(2)
90
3976.4(10)
4
j
P1
9.679(3)
12.785(5)
12.908(4)
71.734(11)
68.835(13)
77.581(13)
1405.1(8)
2
R /deg
ꢀ /deg
γ /deg
V/Å3
Z
Dc/g cm-3
abs coeff/mm-1
F(000)
1.605
1.285
692
1.442
0.962
1776
index ranges
-14 e h e 16
-22 e k e 19
-19 e l e 18
19 802
-12 e h e 12
-16 e k e 16
-16 e l e 16
16 487
-12 e h e 12
-25 e k e 25
-28 e l e 28
48 732
no. of rflns
no. of indep rflns
7187
6667
9465
2θmax/deg
R
51.04
0.0480
55.74
0.0354
55.74
0.0404
Rw
0.1014
0.0744
0.0990
goodness of fit
1.005
0.687/-0.509
1.043
0.473/-0.349
1.091
0.404/-0.361
largest diff peak and hole/e Å-3
Table 4. Crystal Data and Structure Refinement Details for 6 and 7
and MeCN (20 mL), 3 was obtained as a red solid (0.159 g, 94%),
mp 144–145 °C. Anal. Calcd for C27H22Fe2NO7PS2: C, 47.74; H,
3.26; N, 2.06. Found: C, 47.99; H, 3.27; N, 1.98. IR (KBr disk):
νCt O 2041 (vs), 1957 (vs), 1926 (vs); νCdO 1704 (s) cm-1. 1H NMR
(300 MHz, CDCl3): 3.88 (s, 3H, OCH3), 4.14 (d, J ) 13.2 Hz, 2H,
2CHHS), 4.23 (d, J ) 13.2 Hz, 2H, 2CHHS), 6.24 (d, JPH ) 350
Hz, 1H, PH), 6.62, 6.65, 7.90, 7.93 (AB quartet, 4H, C6H4),
7.42–7.68 (m, 10H, 2C6H5) ppm. 31P NMR (121 MHz, CDCl3, 85%
H3PO4): 47.20 (d, JPH ) 350 Hz) ppm.
Preparation of [(µ-SCH2)2N(C6H4CO2Me-p)]Fe2(CO)4(dppe)
(4). A red solution of B (0.092 g, 0.18 mmol) and Ph2PC2H4PPh2
(dppe, 0.080 g, 0.20 mmol) in xylene (20 mL) was refluxed for
2 h. The same workup as that for the preparation of 2 using CH2Cl2/
petroleum ether (v/v ) 4:1) as eluent gave 4 as a red solid (0.102
g, 67%), mp 122–123 °C. Anal. Calcd for C40H35Fe2NO6P2S2: C,
55.64; H, 4.09; N, 1.62. Found: C, 55.85; H, 4.35; N, 1.59. IR
6
7
mol formula
mol wt
cryst syst
space group
a/Å
C21H18Fe2NO6PS2 C33H26Fe3NO8PS2
587.15
827.19
monoclinic
P2(1)/n
12.519(2)
17.022(3)
12.706(2)
90
119.186(3)
90
2363.8(7)
4
triclinic
P1
j
11.090(2)
12.673(3)
14.953(3)
89.762(4)
69.865(3)
64.380(3)
1752.9(6)
2
b/Å
c/Å
R/deg
ꢀ/deg
γ/deg
V/Å3
Z
Dc/g cm-3
abs coeff/mm-1
F(000)
1.650
1.567
1.510
1.440
1192
840
index ranges
-15 e h e 15
-21 e k e 21
-8 e l e 15
13 169
4799
52.66
-13 e h e 13
-15 e k e 10
-18 e l e 15
9981
7071
52.80
(KBr disk): νCt 1990 (s), 1955 (vs), 1923 (s); νCdO 1706 (m)
O
cm-1. 1H NMR (400 MHz, CDCl3): 2.30 (br s, 2H, 2PCH2), 3.86
(s, 3H, OCH3), 4.33 (s, 2H, 2CHHS), 4.51 (s, 2H, 2CHHS),
7.39–7.81 (m, 20H, 4C6H5), 6.77, 6.80, 7.98, 8.01 (AB quartet,
4H C6H4) ppm. 31P NMR (121 MHz, CDCl3, 85% H3PO4): 60.80
(s) ppm.
no. of rflns
no. of indep rflns
2θmax/deg
R
0.0404
0.0380
Rw
0.0750
0.0842
Preparation of [(µ-SCH2)2N(CH2CH2O2CCH2C10H7-1)Fe2-
(CO)5]2(dppf) (5). To a red solution of C (0.142 g, 0.24 mmol) in
MeCN (10 mL) was added Me3NO · 2H2O (0.026 g, 0.24 mmol),
and then the mixture was stirred at room temperature for 20 min.
After dppf (0.066 g, 0.12 mmol) was added, the new mixture was
stirred at room temperature for 4 h. The same workup as that for
the preparation of 2 using acetone/petroleum ether (v/v ) 1:4) as
eluent produced 5 as a red solid (0.060 g, 30%), mp 78–80 °C.
Anal. Calcd for C76H62Fe5N2O14P2S4: C, 53.80; H, 3.68; N, 1.65.
Found: C, 54.06; H, 3.89; N, 1.84. IR (KBr disk): νCt O 2042 (vs),
goodness of fit
1.054
1.013
0.409/-0.374
largest diff peak and hole/e Å-3 0.636/-0.328
stirred at room temperature for 20 min, and then Ph3P (0.065 g,
0.25 mmol) was added. After the new mixture was stirred at this
temperature for 3 h, volatiles were removed under vacuum and the
residue was subjected to TLC using CH2Cl2/petroleum ether (v/v
) 1:2) as eluent. From the main red band, 2 was obtained as a
dark red solid (0.144 g, 76%), mp 172 °C (dec). Anal. Calcd for
C33H26Fe2NO7PS2: C, 52.47; H, 3.47; N, 1.85. Found: C, 52.05;
1
1980 (vs), 1926 (s); νCdO 1735 (s), cm-1. H NMR (400 MHz,
H, 3.75; N, 2.01. IR (KBr disk): νCt 2046 (vs), 1987 (vs), 1933
O
(s); νCdO 1713 (s) cm-1. H NMR (300 MHz, CDCl3): 2.95 (d, J
1
CDCl3): 2.24–2.28 (m, 8H, 4CHHS, 2NCH2CH2O), 2.59 (d, 4H, J
) 11.2 Hz, 4CHHS), 3.65 (s, 4H, 2NCH2CH2O), 3.98 (s, 4H,
2CH2C10H7), 4.16–4.25 (m, 8H, 2C5H4), 7.26–7.89 (m, 34H, 4C6H5,
2C10H7) ppm. 31P NMR (162 MHz, CDCl3, 85% H3PO4): 56.46
(s) ppm.
Preparation of [(µ-SCH2)2N(CH2CH2OPPh2-η1)]Fe2(CO)5
(6). Method i: A red solution of D (0.100 g, 0.23 mmol) in THF (5
mL) was cooled to –40 °C, and then n-BuLi (1 M in hexane, 0.23
) 12.9 Hz, 2H, 2C HHS), 3.86 (s, 3H, OCH3), 4.13 (d, J ) 12.9
Hz, 2H, 2CH HS), 6.56, 6.59, 7.87,7.90 (AB quartet, 4H, C6H4),
7.47–7.76 (m, 15H, 3C6H5) ppm. 31P NMR (121 MHz, CDCl3, 85%
H3PO4): 64.41 (s) ppm.
Preparation of [(µ-SCH2)2N(C6H4CO2Me-p)]Fe2(CO)5(Ph2-
PH) (3). Similarly, from complex B (0.130 g, 0.25 mmol),
Me3NO · 2H2O (0.029 g, 0.25 mmol), Ph2PH (0.047 g, 0.25 mmol),

1416 Organometallics, Vol. 27, No. 7, 2008
Song et al.
SMART 1000 diffractometer. Data were collected at room tem-
perature by using a graphite monochromator with Mo KR radiation
(λ ) 0.71073 Å) in the ω-ꢁ scanning mode. Absorption correction
was performed by the SADABS program.27 A single crystal of 3
or 4 was mounted on a Rigaku MM-007 (rotating anode) diffrac-
tometer equipped with Saturn 70CCD. Data were collected at room
temperature, using a confocal monochromator with Mo KR radiation
(λ ) 0.71070 Å) in the ω-ꢁ scanning mode. Data collection,
reduction, and absorption correction were performed by the
CRYSTALCLEAR program.28 All the structures were solved by
direct methods using the SHELXS-97 program29 and refined by
full-matrix least-squares techniques (SHELXL-97)30 on F2. Hy-
drogen atoms were located using the geometric method. Details of
crystal data, data collections, and structure refinements are sum-
marized in Tables 3 and 4, respectively.
Figure 10. EPR spectrum of 2– in MeCN at 120 K.
Electrochemistry and Spectroelectrochemistry (SEC). Ac-
etonitrile (HPLC grade) was used for electrochemistry assays. A
solution of 0.1 M n-Bu4NPF6 in MeCN was used as electrolyte in
all cyclic voltammetric experiments. 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, a platinum counter electrode, and an Ag/
Ag+ (0.01 M AgNO3/0.1 M n-Bu4NPF6 in MeCN) reference
electrode under CO atmosphere. The working electrode was
polished with 0.05 µm alumina paste and sonicated in water for 10
min prior to use. Bulk electrolysis was run on a vitreous carbon
rod (ca. 3 cm2) in a gastight H-type electrochemical cell containing
20 mL of MeCN. All potentials are quoted against the ferrocene/
ferrocenium (Fc/Fc+) potential. Gas chromatography was performed
with a Shimadzu gas chromatograph GC-9A under isothermal
conditions with nitrogen as a carrier gas and a thermal conductivity
detector. Bulk electrolysis for IR SEC study was carried out under
the same conditions as those described above. During the course
of bulk electrolysis a given amount of catholyte was withdrawn at
intervals for determining its IR spectrum on a Bruker FT-IR
Equinox 55 spectrophotometer.
mL) was added to give a brown-black mixture. After the mixture
was stirred at –40 °C for 0.5 h, Ph2PCl (0.05 mL, 0.25 mmol) was
added. The new mixture was warmed to room temperature and
stirred for 12 h. The same workup as that for the preparation of 2
using acetone/ petroleum ether (v/v ) 1:3) as eluent produced 6 as
a red solid (0.014 g, 10%), mp 192 °C (dec). Anal. Calcd for
C21H18Fe2NO6PS2: C, 42.96; H, 3.09; N, 2.39. Found: C, 42.73;
H, 3.11; N, 2.36. IR (KBr disk): νCt 2042 (s), 1979 (s), 1960
O
1
(vs), 1931 (m) cm-1. H NMR (300 MHz, CDCl3): 2.87 (t, 2H, J
) 3.9 Hz, NCH2CH2O), 3.81 (d, J ) 12.5 Hz, 2H, 2CHHS), 3.86
(t, 1H, J ) 3.9 Hz, OCHH), 3.91 (t, 1H, J ) 3.9 Hz, OCHH), 3.99
(d, J ) 12.5 Hz, 2H, 2CHHS), 7.42–7.74 (m, 10H, 2C6H5) ppm.
31P NMR (121 MHz, CDCl3, 85% H3PO4): 172.47 (s) ppm. Method
ii: A red solution of D (0.100 g, 0.23 mmol) in THF (5 mL) was
cooled to 0 °C, and then Ph2PCl (0.05 mL, 0.25 mmol) and Et3N
(0.035 mL, 0.25 mmol) were added. After the new mixture was
warmed to room temperature it was stirred overnight. The same
workup as that for method i afforded 6 (0.072 g, 53%).
Preparation of [(µ-SCH2)2N(C6H4OMe-p)]Fe2(CO)5[Ph2PFe-
(CO)2Cp] (7). To a red solution of E (0.043 g, 0.07 mmol) in THF
(10 mL) cooled to –40 °C was added n-BuLi (1 M in hexane, 0.07
mL). The mixture was stirred at this temperature for 10 min,
resulting in a color change from red to brown-black. After
CpFe(CO)2I (0.022 g, 0.07 mmol) was added, the new mixture was
warmed to room temparature and stirred for 2 h. The same workup
as that for the preparation of 2 gave 7 as a red solid (0.035 g, 60%),
mp 210 °C (dec). Anal. Calcd for C33H26Fe3NO8PS2: C, 47.92; H,
3.17; N, 1.69. Found: C, 47.72; H, 3.12; N, 1.66. IR (KBr disk):
νCt O 2039 (s), 2019 (s), 1974 (vs), 1909 (m) cm-1. 1H NMR (400
MHz, CDCl3): 2.78 (br s, 2H, 2CHHS), 3.71 (br s, 5H, 2CHHS,
OCH3), 4.77 (s, 5H, C5H5), 6.47, 6.48, 6.72, 6.74 (AB quartet, 4H,
C6H4), 7.35–7.96 (m, 10H, 2C6H5) ppm. 31P NMR (121 MHz,
CDCl3, 85% H3PO4): 62.79 (s) ppm.
Acknowledgment. We are grateful to the National Natural
Science Foundation of China and the Research Fund for the
Doctoral Program of Higher Education of China for financial
support.
Supporting Information Available: Full tables of crystal data,
atomic coordinates and thermal parameters, and bond lengths and
angles for 1, 3, 4, 6, and 7 as CIF files. This material is available
free of charge via the Internet at http://pubs.acs.org.
OM700956E
X-ray Structure Determinations of 1, 3, 4, 6, and 7. Single
crystals of 1, 3, 6, and 7 suitable for X-ray diffraction analyses
were grown by slow evaporation of the CH2Cl2/hexane solutions
of 1 and 3 at 4 °C, the CH2Cl2 solution of 6 at –20 °C, and the
THF solution of 7 at –10 °C, respectively, whereas a single crystal
of 4 was grown by slow diffusion of MeOH into its CH2Cl2 solution
at 4 °C. A single crystal of 1, 6, or 7 was mounted on a Bruker
(27) Sheldrick, G. M. SADABS, A Program for Empirical Absorption
Correction of Area Detector Data; University of Göttingen: Germany, 1996.
(28) CRYSTALCLEAR 1.3.6; Rigaku and Rigaku/MSC: The Woodlands,
TX, 2005.
(29) Sheldrick, G. M. SHELXS97, A Program for Crystal Structure
Solution; University of Göttingen: Germany, 1997.
(30) Sheldrick, G. M. SHELXL97, A Program for Crystal Structure
Refinement ; University of Göttingen: Germany, 1997.