Synthetic and structural studies of butterfly Fe/S/P cluster complexes related to the active site of [FeFe]-hydrogenases. Proton reduction to H 2 catalyzed by (η1-Ph2PS-η1) 2Fe2(CO)6

Article abstract of DOI:10.1021/om800077c

The butterfly Fe/S cluster anions (μ-RS)(μ-S^-)Fe ₂(CO)₆ (A, R = Et, p-MeC₆H₄), (μ-S^-)₂Fe₂(CO)₆ (C), [(μ-S^-)Fe₂(CO)₆]₂(4-μ-SC ₆H₄C₆H₄S-μ-4′) (D), and [(μ-S^-)Fe₂(CO)₆]₂[4-μ-SC ₆H₄OCH₂CH₂OC₆H ₄S-μ-4′] (E) (generated in situ via reactions of (μ-S₂)Fe₂(CO)₆ with RMgBr, Et ₃BHLi, 4-LiC₆H₄C₆H ₄Li-4′, and 4-LiC₆H₄OCH ₂CH₂OC₆H₄Li-4′) were found to react with Ph₂PCl to give a series of novel butterfly Fe/S/P cluster complexes. Treatment of monoanions A (R = Et, p-MeC₆H₄) with 1 equiv of Ph₂PCl in THF from - 78°C to room temperature gave the single-butterfly Fe₂S₂P complexes (μ-RS)(η¹-Ph₂PS-η¹)Fe ₂(CO)₆ (7, R = Et; 9, R = p-MeC₆H₄) and (μ-RS)(η¹-Ph₂PS-η¹)Fe ₂(CO)₅(Ph₂PY) (8, R = Et, Y = Cl; 10, R = p-MeC₆H₄, Y = p-MeC₆H₄), whereas dianions C, D, and E reacted with 2 equiv of Ph₂PCl to give single-butterfly Fe₂S₂P₂ complex (η¹-Ph₂PS-η¹)₂Fe ₂(CO)₆ (11) and double-butterfly Fe₄S ₄P₂ complexes [(η¹-Ph₂PS- η¹)Fe₂(CO)₆]₂(4-μ-SC ₆H₄C₆H₄S-μ-4′) (12) and [(η¹-Ph₂PS-η¹)Fe₂(CO) ₆]₂[4-μ-SC₆H₄OCH ₂CH₂OC₆H₄S-μ-4′] (13), respectively. More interestingly, the novel μ₄-S-containing double-butterfly Fe₄S₂P complexes [(μ-RS)Fe ₂(CO)₆](μ₄-S)[(μ-Ph₂P)Fe ₂(CO)₆] (14, R = Me; 15, R = Ph; 16, R = Et) could be prepared by reactions of single-butterfly complexes (μ-RS)(η¹- Ph₂PS-η¹)Fe₂(CO)₆ (1, R = Me; 3, R = Ph; 7 R = Et) with excess Fe₂(CO)₉ in THF at room temperature, whereas the quadruple-butterfly Fe₈S₄P ₂ complexes [(μ-Ph₂P)Fe₂(CO) ₆(μ₄-S)Fe₂(CO)₆] ₂(4-μ-SC₆H₄C₆H ₄S-μ-4′) (17) and [(μ-Ph₂P)Fe ₂(CO)₆(μ₄-S)Fe₂(CO) ₆]₂[4-μ-SC₆H₄OCH ₂CH₂OC₆H₄S-μ-4′] (18) were similarly prepared by reactions of the corresponding double-butterfly complexes 12 and 13 with excess Fe₂(CO)₉, respectively. All the new complexes 7-18 have been characterized by elemental analysis, by spectroscopy, and for 9, 11, and 14 by X-ray crystallography. In view of the structural similarity of these Fe/S/P complexes to the [FeFe]-hydrogenase active site, they might be regarded as H-cluster models. As a representative, model complex 11 was found to be able to catalyze proton reduction to hydrogen under CV conditions.

Full text of DOI:10.1021/om800077c

3714
Organometallics 2008, 27, 3714–3721
Synthetic and Structural Studies of Butterfly Fe/S/P Cluster
Complexes Related to the Active Site of [FeFe]-Hydrogenases.
Proton Reduction to H2 Catalyzed by (η1-Ph2PS-η1)2Fe2(CO)6
Li-Cheng Song,* Guang-Huai Zeng, Shao-Xia Lou, Hui-Ning Zan, Jiang-Bo Ming, and
Qing-Mei Hu
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai UniVersity,
Tianjin 300071, People’s Republic of China
ReceiVed January 29, 2008
The butterfly Fe/S cluster anions (µ-RS)(µ-S-)Fe2(CO)6 (A, R ) Et, p-MeC6H4), (µ-S-)2Fe2(CO)6
(C), [(µ-S-)Fe2(CO)6]2(4-µ-SC6H4C6H4S-µ-4′) (D), and [(µ-S-)Fe2(CO)6]2[4-µ-SC6H4OCH2CH2OC6H4S-
µ-4′] (E) (generated in situ via reactions of (µ-S2)Fe2(CO)6 with RMgBr, Et3BHLi, 4-LiC6H4C6H4Li-4′,
and 4-LiC6H4OCH2CH2OC6H4Li-4′) were found to react with Ph2PCl to give a series of novel butterfly
Fe/S/P cluster complexes. Treatment of monoanions A (R ) Et, p-MeC6H4) with 1 equiv of Ph2PCl in
THF from -78 °C to room temperature gave the single-butterfly Fe2S2P complexes (µ-RS)(η1-Ph2PS-
η1)Fe2(CO)6 (7, R ) Et; 9, R ) p-MeC6H4) and (µ-RS)(η1-Ph2PS-η1)Fe2(CO)5(Ph2PY) (8, R ) Et, Y )
Cl; 10, R ) p-MeC6H4, Y ) p-MeC6H4), whereas dianions C, D, and E reacted with 2 equiv of Ph2PCl
to give single-butterfly Fe2S2P2 complex (η1-Ph2PS-η1)2Fe2(CO)6 (11) and double-butterfly Fe4S4P2
complexes [(η1-Ph2PS-η1)Fe2(CO)6]2(4-µ-SC6H4C6H4S-µ-4′) (12) and [(η1-Ph2PS-η1)Fe2(CO)6]2[4-µ-
SC6H4OCH2CH2OC6H4S-µ-4′] (13), respectively. More interestingly, the novel µ4-S-containing double-
butterfly Fe4S2P complexes [(µ-RS)Fe2(CO)6](µ4-S)[(µ-Ph2P)Fe2(CO)6] (14, R ) Me; 15, R ) Ph; 16, R
) Et) could be prepared by reactions of single-butterfly complexes (µ-RS)(η1-Ph2PS-η1)Fe2(CO)6 (1, R
) Me; 3, R ) Ph; 7 R ) Et) with excess Fe2(CO)9 in THF at room temperature, whereas the quadruple-
butterfly Fe8S4P2 complexes [(µ-Ph2P)Fe2(CO)6(µ4-S)Fe2(CO)6]2(4-µ-SC6H4C6H4S-µ-4′) (17) and [(µ-
Ph2P)Fe2(CO)6(µ4-S)Fe2(CO)6]2[4-µ-SC6H4OCH2CH2OC6H4S-µ-4′] (18) were similarly prepared by
reactions of the corresponding double-butterfly complexes 12 and 13 with excess Fe2(CO)9, respectively.
All the new complexes 7-18 have been characterized by elemental analysis, by spectroscopy, and for 9,
11, and 14 by X-ray crystallography. In view of the structural similarity of these Fe/S/P complexes to
the [FeFe]-hydrogenase active site, they might be regarded as H-cluster models. As a representative,
model complex 11 was found to be able to catalyze proton reduction to hydrogen under CV conditions.
butterfly Fe2S2 cluster core and four unusual ligands: CO, CN-,
Introduction
[Fe4S4(SCys)4], and a dithiolate (Figure 1).5 So far, a great
Although Reihlen prepared the first dinuclear Fe/S cluster
complex (µ-RS)2Fe2(CO)6 (R ) Et) as early as 1928,1 the
butterfly-shaped Fe2S2 structures of such complexes were
confirmed only in 1963 by means of X-ray crystal diffraction
techniques.2 In view of their unique structures and the potentially
novel reactivities, Seyferth and co-workers began in the 1970s
to systematically study the chemistry of such butterfly Fe/S
cluster complexes, which was then thought to be nearly mature
at the end of the 1990s.3,4 However, just around this period of
time research interest in butterfly Fe/S cluster complexes was
extensively revived. This is due to the realization that the active
site of [FeFe]-hydrogenases (so-called H-clusters) resembles the
archetypal (µ-RS)2Fe2(CO)6 derivatives, which consist of a
variety of butterfly Fe/S cluster complexes that act as structural
and functional models of the H-cluster have been prepared and
characterized, which has considerably promoted our understand-
ing of the natural enzymes.6,7 Recently, we published a
(4) (a) Seyferth, D.; Henderson, R. S. J. Am. Chem. Soc. 1979, 101,
508. (b) Nametkin, N. S.; Tyurin, V. D.; Kukina, M. A. J. Organomet.
Chem. 1978, 149, 355. (c) Seyferth, D.; Song, L.-C.; Henderson, R. S. J. Am.
Chem. Soc. 1981, 103, 5103. (d) Seyferth, D.; Henderson, R. S.; Song,
L.-C. Organometallics 1982, 1, 125. (e) Winter, A.; Zsolnai, L.; Huttner,
C. Z. Naturforsch. 1982, 37b, 1430. (f) Bose, K. S.; Sinn, E.; Averill, B. A.
Organometallics 1984, 3, 1126. (g) Seyferth, D.; Ruschke, D. P.; Davis,
W. M.; Cowie, M.; Hunter, A. D. Organometallics 1994, 13, 3834. (h)
Song, L.-C.; Yan, C.-G.; Hu, Q.-M.; Wu, B.-M.; Mak, T. C. W.
Organometallics 1997, 16, 632. (i) Seyferth, D.; Kiwan, A. M.; Sinn., E. J.
Organomet. Chem. 1985, 281, 111. (j) Song, L.-C.; Lu, G.-L.; Hu, Q.-M.;
Fan, H.-T.; Chen, Y.; Sun, J. Organometallics 1999, 18, 3258. (k) Song,
L.-C.; Lu, G.-L.; Hu, Q.-M.; Sun, J. Organometallics 1999, 18, 5429.
(5) (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,
C. E.; Fontecilla-Camps, J. C. Structure 1999, 7, 13.
(6) (a) For reviews, see for example: 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. (d) Vignais, P. M.; Billoud, B. Chem. ReV. 2007, 107, 4206. (e)
Fontecilla-Camps, J. C.; Volbeda, A.; Cavazza, C.; Nicolet, Y. Chem. ReV.
2007, 107, 4273. (f) Siegbahn, P. E. M.; Tye, J. W.; Hall, M. B. Chem.
ReV. 2007, 107, 4414.
* To whom correspondence should be addressed. Fax: 0086-22-
23504853. E-mail: lcsong@nankai.edu.cn.
(1) Reihlen, H.; von Friedolsheim, A.; Oswald, W. J. Liebigs Ann. Chem.
1928, 465, 72.
(2) Dahl, L. F.; Wei, C. H. Inorg. Chem. 1963, 2, 328.
(3) (a) For reviews, see for example: Marko´, L.; Marko´-Monostory, B.
In The Organic Chemistry of Iron; von Gustorf, E. A. K., Grevels, F.-W.,
Fischer, I., Eds.; Academic Press: New York, 1981; pp 283-332. (b) Ogino,
H.; Inomata, S.; Tobita, H. Chem. ReV. 1998, 98, 2093. (c) Song, L.-C. In
AdVances in Organometallic Chemistry; Huang, Y., QianY., Eds.; Chemical
Industry Press: Beijing, 1987; pp 181-204. (d) Song, L.-C. Trends
Organomet. Chem. 1999, 3, 1–20.
10.1021/om800077c CCC: $40.75
2008 American Chemical Society
Publication on Web 07/15/2008

Butterfly Fe/S/P Cluster Complexes
Organometallics, Vol. 27, No. 15, 2008 3715
1-48 should apply to the formation of 7-10 since both cases
involve the same type of highly nucleophilic S-centered
monoanions A and give the same type of products. As shown
in Scheme 2, the nucleophilic substitution between monoanions
A and Ph2PCl will first give the butterfly Fe/S cluster phosphines
M1. Then, major products 7 and 9 can be produced from M1
by nucleophilic attack of its P atom at the neighboring iron atom
accompanied by displacement of mercaptide from it.10 The
minor products 8 and 10 can be produced by further CO
substitution of 7 or 9 with unreacted Ph2PCl or Ph2PC6H4Me-p
(formed in situ from Ph2PCl and the Grignard reagent
p-MeC6H4MgBr present in the reaction system), respectively.
The single-butterfly Fe2S2P2 complex 11 and double-butterfly
Fe4S4P2 complexes 12 and 13 could also be prepared from
Ph2PCl and the corresponding dianions C, D, and E, respec-
tively. Treatment of 1 equiv of the dilithium salt of dianion C
(generated in situ from (µ-S2)Fe2(CO)6 and 2 equiv of
Et3BHLi)11 with 2 equiv of Ph2PCl in THF from -78 °C to
room temperature afforded the single-butterfly complex 11
(Scheme 3), whereas treatment of 2 equiv of Ph2PCl with ca. 1
equiv of the dilithium salt of dianion D (formed by reaction of
1 equiv of 4,4′-dibromodiphenyl with 2 equiv of n-BuLi
followed by treatment of the intermediate 4-LiC6H4C6H4Li-4′12
with (µ-S2)Fe2(CO)6)13 or treatment of 2 equiv of Ph2PCl with
ca. 1 equiv of the dilithium salts of dianions E (generated
similarly by reaction of 1 equiv of the ether chain-bridged 4,4′-
dibromodiphenyls with 2 equiv of n-BuLi followed by treatment
of the intermediate 4-LiC6H4OCH2CH2OC6H4Li-4′12 with (µ-
S2)Fe2(CO)6)13 gave rise to the double-butterfly complexes 12
(Scheme 4) and 13 (Scheme 5), respectively.
Figure 1. Basic structure of the H-cluster obtained from protein
crystallography.
communication8 that describes the unexpected formation of the
Fe/S/P cluster complexes 1-6 from reactions of the butterfly
Fe/S cluster anions A (R ) Me, Ph) and B (R ) n-Bu, Ph)
with Ph2PCl (Scheme 1). Since these Fe/S/P complexes contain
a butterfly Fe2S2 or Fe2S2P cluster core that carries a given
amount of CO ligands, they might be regarded as the structural
analogues of the active site of [FeFe]-hydrogenases.5 In order
to show the generality of such new reactions that produce the
interesting Fe/S/P complexes, we further carried out the reactions
of Ph2PCl with other butterfly Fe/S cluster anions, such as (µ-
RS)(µ-S-)Fe2(CO)6 (A, R ) Et, p-MeC6H4), (µ-S-)2Fe2(CO)6
(C), [(µ-S-)Fe2(CO)6]2(4-µ-SC6H4C6H4S-µ-4′) (D), and [(µ-
S-)Fe2(CO)6]2[4-µ-SC6H4OCH2CH2OC6H4S-µ-4′] (E). As a
result, the reactions afforded a series of expected single- and
double-butterfly Fe/S/P cluster complexes. Particularly, when
such single- and double-butterfly complexes were further treated
with Fe2(CO)9, another series of novel µ4-S-containing double-
and quadruple-butterfly Fe/S/P complexes were unexpectedly
produced. In addition, the single-butterfly Fe/S/P complex (η1-
Ph2PS-η1)2Fe2(CO)6 has been found to be a catalyst for proton
reduction to H2 under electrochemical conditions. Herein we
report these interesting results.
Complexes 7-13 are air-stable solids, which have been
1
characterized by elemental analysis and IR, H NMR, and 31P
NMR spectroscopies. For example, the IR spectra of 8 and 10
displayed four absorption bands in the range 2040-1934 cm-1
for their terminal carbonyls, whereas those of 7, 9, and 11-13
exhibited four to six absorption bands in the region 2070-1958
cm-1 for their terminal carbonyls. Compared to the highest νCt
Results and Discussion
O
frequencies of 7, 9, and 11-13, those of 8 and 10 are shifted
by ca. 30 cm-1 toward lower values due to the stronger electron-
donating effects of Ph2P(C6H4Me-p) and Ph2PCl than CO.14 In
addition, the 31P NMR spectra of 8 and 10 each showed two
singlets at ca. 71 and 151 and ca. 58 and 70 ppm, respectively,
for P atoms in their Ph2PS, Ph2PCl, and Ph2P(C6H4Me-p)
ligands, whereas those of 7, 9, and 11-13 all displayed one
singlet in the range 44-67 ppm for P atoms in their Ph2PS
ligands.
In order to unequivocally confirm the butterfly Fe2S2P cluster
cores present in complexes 7-10, 12, and 13, as well as the
butterfly Fe2S2P2 cluster core present in complex 11, we
determined the crystal structures of complexes 9 and 11 by
X-ray diffraction techniques. ORTEP plots of 9 and 11 are
presented in Figures 2 and 3, whereas Table 1 shows selected
bond lengths and angles. As can be seen in Figure 2, complex
9 is actually isostructural with the previously reported complex
1,8 which contains a butterfly Fe(1)Fe(2)S(1)P(1)S(2) cluster
Synthesis and Characterization of Single-Butterfly Fe2S2P/
Fe2S2P2 Complexes 7-11 and Double-Butterfly Fe4S4P2
Complexes 12 and 13. As mentioned above, the single- and
double-butterfly complexes 1-6 can be prepared by reactions
of the BrMg salts of monoanions A (R ) Me, Ph) and the
lithium salts of monoanions B (R ) n-Bu, Ph) with Ph2PCl,
respectively (Scheme 1).8 Similarly, we could further prepare
the single-butterfly Fe2S2P complexes 7-10 by treatment of the
BrMg salts of monoanions A (R ) Et, p-MeC6H4) (prepared in
situ from 1 equiv of (µ-S2)Fe2(CO)6 and 1 equiv of the Grignard
reagents RMgBr)9 with 1 equiv of Ph2PCl in THF from -78
°C to room temperature (Scheme 2).
Although the mechanism for formation of 7-10 is not clear
to date, the previously suggested mechanism for formation of
(7) (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) Lawrence, J. D.; Li, H.; Rauchfuss, T. B. Chem. Commun.
2001, 1482. (e) Song, L.-C.; Ge, J.-H.; Zhang, X.-G.; Liu, Y.; Hu, Q.-M.
Eur. J. Inorg. Chem. 2006, 3204. (f) Song, L.-C.; Yang, Z.-Y.; Hua, Y.-J.;
Wang, H.-T.; Liu, Y.; Hu, Q.-M. Organometallics 2007, 26, 2106. (g)
Morvan, D.; Capon, J.-F.; Gloaguen, F.; Le Goff, A.; Marchivie, M.;
Michaud, F.; Schollhammer, P.; Talarmin, J.; Yaouanc, J.-J. Organometallics
2007, 26, 2042.
(10) Seyferth, D.; Womack, G. B.; Song, L.-C.; Cowie, M.; Hames,
B. W. Organometallics 1983, 2, 928.
(11) Seyferth, D.; Henderson, R. S.; Song, L.-C. J. Organomet. Chem.
1980, 192, C1.
(12) Baldwin, R. A.; Cheng, M. T. J. Org. Chem. 1967, 32, 1572.
(13) (a) Seyferth, D.; Song, L.-C.; Henderson, R. S. J. Am. Chem. Soc.
1981, 103, 5103. (b) Seyferth, D.; Henderson, R. S. J. Am. Chem. Soc.
1979, 101, 508.
(14) Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principles
and Applications of Organotransition Metal Chemistry, 2nd ed.; California
University Science Books: Mill Valley, 1987.
(8) Song, L.-C.; Zeng, G.-H.; Hu, Q.-M.; Ge, J.-H.; Lou, S.-X.
Organometallics 2005, 24, 16.
(9) Seyferth, D.; Henderson, R. S.; Song, L.-C.; Womack, G. B. J.
Organomet. Chem. 1985, 292, C9.

3716 Organometallics, Vol. 27, No. 15, 2008
Song et al.
Scheme 1
Scheme 2
Scheme 4
Scheme 3
Scheme 5
core that carries two phenyl groups, one p-MeC6H4 group, and
six terminal carbonyls. The X-ray crystallographic study
revealed that the dihedral angle of 9 between its triangular wing
Fe(1)Fe(2)S(2) and tetragonal wing Fe(1)Fe(2)P(1)S(1) is 90.3°,
which is almost the same as the corresponding one of 1 (89.1°).
In addition, the S(2) atom of 9 is attached to the substituent
p-MeC6H4 group by an equatorial bond in order to avoid the
strong steric repulsion with one of the two phenyl groups
attached to P(1).15 The X-ray crystallographic study of complex
11 (Figure 3) indicated that it consists of a butterfly Fe(1)Fe(2)-
P(1)S(1)P(2)S(2) cluster core in which the P(1)/P(2) atoms each
carry two phenyl groups and the Fe(1)/Fe(2) atoms are each
attached to three terminal carbonyls. The dihedral angle of 11
between its two tetragonal wings Fe(1)Fe(2)P(1)S(1) and
Fe(1)Fe(2)P(2)S(2) is 87.4°. The Fe-Fe bond length of 11
(2.7790 Å) is much longer than the corresponding bond lengths
of 1 (2.6431 Å)8 and particularly (µ-EtS)2Fe2(CO)6 (2.537 Å).2
This is obviously because the Fe-Fe bond of 11 is bridged by
two diatom (P, S) units, that of 1 by one diatom (P, S) unit and
one monoatom (S) unit and that of (µ-EtS)2Fe2(CO)6 by two
monoatom (S, S) units. It is worth pointing out that 11 is the
first butterfly Fe/S/P complex with two tetragonal wings,
although some butterfly Fe/S/P complexes are known to have
one triangular wing and one tetragonal wing, such as the
previously reported 1-4, or to have two triangular wings such
(15) Shaver, A.; Fitzpatrick, P. J.; Steliou, K.; Butler, I. S. J. Am. Chem.
Soc. 1979, 101, 1313.

Butterfly Fe/S/P Cluster Complexes
Organometallics, Vol. 27, No. 15, 2008 3717
Scheme 6
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 9, 11, and 14
9
Fe(1)-S(2)
Fe (1)-S(1)
Fe(2)-P(1)
P(1)-C(14)
2.2424(14)
2.3655(14)
2.2772(13)
1.824(4)
Fe(2)-S(2)
P(1)-S(1)
S(2)-C(7)
Fe(1)-Fe(2)
2.2767(13)
2.0336(15)
1.789 (4)
Figure 2. Molecular structure of 9 with 30% probability level
ellipsoids.
2.6327(9)
S(2)-Fe(1)-S(1)
S(2)-Fe(1)-Fe(2)
S(1)-Fe(1)-Fe(2)
S(2)-Fe(2)-P(1)
83.22(4)
54.98(3)
86.12(4)
87.47(5)
P(1)-Fe(2)-Fe(1)
S(1)-P(1)-Fe(2)
Fe(1)-S(2)-Fe(2)
S(2)-Fe(2)-Fe(1)
77.35(4)
104.77(6)
71.26(4)
53.77(4)
11
Fe(1)-P(1)
Fe(1)-S(2)
Fe(2)-P(2)
Fe(2)-S(1)
2.2576(16)
2.3487(17)
2.2602(16)
2.3469(17)
P(1)-C(7)
P(1)-S(1)
S(2)-P(2)
Fe(1)-Fe(2)
1.830(5)
2.027(2)
2.032(2)
2.7790(13)
S(2)-Fe(1)-P(1)
S(2)-P(2)-Fe(2)
P(1)-S(1)-Fe(2)
P(2)-S(2)-Fe(1)
86.12(6)
106.36(8)
90.55(7)
89.76(7)
S(2)-Fe(1)-Fe(2)
S(1)-Fe(2)-Fe(1)
P(2)-Fe(2)-S(1)
P(2)-Fe(2)-Fe(1)
83.78(5)
83.50(5)
87.20(6)
75.13(5)
14
Fe(1)-P(1)
Fe(1)-S(1)
Fe(2)-P(1)
Fe(2)-S(1)
2.223(2)
2.263(2)
2.223(2)
2.229(2)
Fe(3)-Fe(4)
Fe(1)-Fe(2)
Fe(3)-S(1)
Fe(4)-S(1)
2.5118(17)
2.5889(17)
2.260(2)
2.275(2)
Figure 3. Molecular structure of 11 with 30% probability level
ellipsoids.
P(1)-Fe(1)-S(1)
S(1)-Fe(1)-Fe(2)
P(1)-Fe(2)-Fe(1)
S(1)-Fe(2)-Fe(1)
80.79(8)
54.20(6)
54.40(7)
55.42(6)
Fe(1)-P(1)-Fe(2)
Fe(2)-S(1)-Fe(3)
Fe(3)-S(1)-Fe(4)
Fe(4)-S(2)-Fe(3)
71.22(8)
139.25(10)
67.27(7)
67.49(7)
as (µ-Ph2P)(µ-RS)Fe2(CO)6 (R ) Ph,16 Et,17 C6H1118), (µ-
PhPCl)(µ-t-BuS)Fe2(CO)6,19 and (µ-Me2P)(µ-t-BuS)Fe2(CO)6.20
Synthesis and Characterization of Double-Butterfly
Fe4S2P Complexes 14-16 and Quadruple-Butterfly Fe8S4P2
Complexes 17 and 18. In order to examine the chemical
reactivities of the above-prepared Fe/S/P cluster complexes, we
chose some of the prepared complexes such as 1, 3, 7, 12, and
13 to react with Fe2(CO)9 to see if the higher nuclearity Fe/S/P
cluster complexes could be obtained. The higher nuclearity
double-butterfly Fe4S2P complexes 14-16 were prepared upon
treatment of single-butterfly Fe2S2P complexes 1, 3, and 7 with
excess Fe2(CO)9 in THF at room temperature (Scheme 6),
whereas the higher nuclearity quadruple-butterfly Fe8S4P2
complexes 17 and 18 could be obtained by reactions of double-
butterfly Fe4S4P2 complexes 12 and 13 with excess Fe2(CO)9
under similar conditions (Scheme 7).
is not completely understood, a possible transformation pathway
(Scheme 8) might be proposed according to the following facts:
(i) Fe2(CO)9 in THF solution at room temperature is known to
give the intermediate Fe(CO)4(THF), from which the heteroatom
nitrogen donors can displace the THF,21 and (ii) the coordination
unsaturated species, such as Cr(CO)5, can readily add to a metal-
attached S atom to give the nuclearity increased metal cluster.22
The pathway includes the following steps: (i) the heteroatom S
in the tetragonal Fe2SP wing of the single-butterfly Fe2S2P
cluster m1 attacks the Fe atom of one molecule of Fe(CO)4(THF)
(generated in situ from Fe2(CO)9 and THF) to give intermediate
m2; (ii) further intramolecular attack of the same S atom at its
neighboring Fe atom with displacement of Ph2P from it affords
intermediate m3 (the favored isomerization from tetragonal
Fe2SP wing to triangular Fe2S wing is presumably due to
coordination of the S atom with Fe(CO)4); (iii) the pendant Ph2P
group of m3 displaces THF of another molecule of
Fe(CO)4(THF) to produce intermediate m4; and finally (iv) the
double-butterfly Fe4S2P cluster m5 is formed by steps such as
loss of two CO ligands from the two Fe(CO)4 units and
formation of the new Fe-Fe, Fe-S, and Fe-P bonds followed
by cleavage of the old P-S bond. It should be noted that this
butterfly cluster transformation mechanism for formation of
It is apparent that the formation of 14-18 is actually the
consequence of the transformation of each Ph2-substituted
tetragonal Fe2SP wing in the starting butterfly Fe/S/P complexes
to the (µ-Ph2P)Fe2(CO)6-substituted Fe2S triangular wing.
Although the mechanism regarding this type of transformation
(16) Job, B. E.; Mclean, R. A. N.; Thompson, D. T. J. Chem. Soc.,
Chem. Commun. 1966, 895.
(17) Seyferth, D.; Womack, G. B.; Dewan, J. C. Organometallics 1985,
4, 398.
(18) Winter, A.; Zsolnai, L.; Huttner, G. J. Organomet. Chem. 1983,
250, 409.
(19) Song, L.-C.; Wang, R.-J.; Li, Y.; Wang, H.-G.; Wang, J.-T. Chin.
J. Org. Chem 1989, 9, 512.
(20) Song, L.-C.; Hu, Q.-M.; Zhou, Z.-Y.; Hu, G.-Z. Chin. J. Org. Chem
1991, 11, 533.
(21) Cotton, F. A.; Troup, J. M. J. Am. Chem. Soc. 1974, 96, 3438.
(22) Richter, F.; Vahrenkamp, H. Angew. Chem., Int. Ed. Engl. 1978,
17, 444.

3718 Organometallics, Vol. 27, No. 15, 2008
Song et al.
Scheme 7
Scheme 8
attached to C(14) and C(20) of the two phenyl groups by an
equatorial and an axial bond,13 respectively. In addition, each
of the three carbonyls attached to Fe(1), Fe(2), Fe(3), and Fe(4)
are terminal. In butterfly subcluster Fe(1)Fe(2)S(1)P(1) the
dihedral angle between its two triangular wings is 105.9°, which
is obviously larger than the corresponding dihedral angle
(96.81°) in subcluster Fe(3)Fe(4)S(1)S(2). In addition, the
Fe(1)-Fe(2) bond length (2.5889 Å) is slightly longer than the
Fe(3)-Fe(4) bond length (2.5118 Å). It should be noted that
complexes 14-18 are the first butterfly Fe/S/P complexes with
two different subclusters, Fe2S2 and Fe2SP, joined together
through a common µ4-S atom, although numerous µ4-E (E )
S, Se)-containing butterfly cluster complexes are known, such
as[(µ-RS)Fe2(CO)6]2(µ4-S)(R)Me,25 Et26),[(µ-EtS)Fe2(CO)6][(µ-
PhCt CS)Fe2(CO)6](µ4-S),27 [(µ-EtS)Fe2(CO)6]2(µ4-Se),28 and
[(µ-EtTe)Fe2(CO)6]2(µ4-S).29
Electrochemistry of Complex 11. The electrochemical
properties of 11 were studied by cyclic voltammetry (CV) in
MeCN solution under an atmosphere of N2. As shown in Figure
5, the cyclic voltammogram of 11 shows two irreversible one-
electron reductions at Epc) -1.32 and - 2.09 V and one
irreversible one-electron oxidation at Epa ) + 0.74 V, which
could be ascribed to the FeIFe1/Fe1Fe0, FeIFe0/Fe0Fe0, and
FeIFeI/FeIFeII couples, respectively. The one-electron assign-
ments for these redox processes were supported by the calculated
value of 0.95 faraday/equiv (obtained through study of bulk
electrolysis of a MeCN solution of 11) and the calculated value
of (ip/ν1/2)/(it1/2) ) 3.3 (obtained through study of CV and
chronoamperometry (CA) of 11).30 The cyclic voltammograms
of 11 with HOAc and without HOAc (for comparative purposes)
are presented in Figure 6. Interestingly, as shown in Figure 6,
when the first 2 mM HOAc was added to the MeCN solution
of 11, the original first reduction peak at -1.32 V did not
change, but the second reduction peak at - 2.09 V considerably
increased and continued to grow up with sequential addition of
the acid. Apparently, these observations are characteristic of
an electrocatalytic proton reduction process.31–33 More interest-
14-18 seems to be reasonable, but it is mainly speculative. So,
more work needs to be done in the future.
Complexes 14-18 are also air-stable solids, which were
characterized by elemental analysis and various spectroscopies.
For example, the IR spectra of 14-18 showed four to six
absorption bands in the region 2079-1943 cm-1 for their
1
terminal carbonyls. The H NMR spectra of 14 and 16 each
displayed a singlet at 2.07 and 1.33 ppm for CH3 protons in
their MeS and EtS groups, whereas the spectrum of 18 exhibited
an AB quartet in the range 6.7-7.2 ppm for its two phenylene
groups. In addition, the 31P NMR spectra of 14-18 displayed
a singlet at ca. 145 ppm for P atoms in their Ph2P groups, very
close to those displayed by P atoms in complexes (µ-Ph2P)(µ-
RS)Fe2(CO)6 (R ) C6H11,18 R ) n-Pr, i-Pr, t-Bu23) and [(µ-
Ph2P)Fe2(CO)6]2[µ-SCH2(CH2OCH2)2CH2S-µ].24
To further confirm the µ4-S-containing double-butterfly
Fe4S2P cluster cores present in complexes 14-18, X-ray
diffraction analysis for the representative complex 14 was
undertaken. The molecular structure of 14 is depicted in Figure
4, whereas selected bond lengths and angles are listed in Table
1. Complex 14 is composed of two butterfly subclusters,
Fe(1)Fe(2)S(1)P(1) and Fe(3)Fe(4)S(1)S(2), joined to a pyran
type of µ4-S(1) atom. While the S(2) atom is attached to C(13)
of the methyl group by an equatorial bond, the P(1) atom is
(23) Song, L.-C.; Li, Y.; Hu, Q.-M.; Wang, J.-T.; Zhao, W.-J.; Fan,
Y.-Q.; Zhang, S.-J.; Li, X.-Q.; Li, G.-W. Chem. J. Chin. UniV. 1990, 11,
154.
(24) Song, L.-C.; Fan, H.-T.; Hu, Q.-M.; Yang, Z.-Y.; Sun, Y.; Gong,
F.-H. Chem.-Eur. J. 2003, 9, 170.
(25) Coleman, J. M.; Wojcicki, A.; Pollick, P. J.; Dahl, L. F. Inorg.
Chem. 1967, 6, 1236.
(26) Seyferth, D.; Kiwan, A. M. J. Organomet. Chem. 1985, 286, 219.
(27) Song, L.-C.; Qin, X.-D.; Hu, Q.-M.; Huang, X.-Y. Organometallics
1998, 17, 5437.
(28) Song, L.-C.; Yan, C.-G.; Hu, Q.-M.; Wang, R.-J.; Mak, T. C. W.;
Huang, X.-Y. Organometallics 1996, 15, 1535.
(29) Song, L.-C.; Hu, Q.-M.; Sun, B.-W.; Tang, M.-Y.; Yang, J; Hua,
Y.-J. Organometallics 2002, 21, 1627.
(30) Zanello, P. Inorganic Electrochemistry. Theory, Practice and
Application; Thomas Graham House: Cambridge, UK, 2003.
(31) Bhugun, I.; Lexa, D.; Saveant, J.-M. J. Am. Chem. Soc. 1996, 118,
3982.
Figure 4. Molecular structure of 14 with 30% probability level
ellipsoids.

Butterfly Fe/S/P Cluster Complexes
Organometallics, Vol. 27, No. 15, 2008 3719
complexes 14-18 could be prepared by another novel type of
reactions of complexes 1, 3, 7, 12, and 13 with Fe2(CO)9,
respectively. That is, the first type of reactions can accomplish
the conversion from the S-centered triangular Fe2S wings in
anions A, C, D, and E to the tetragonal Fe2SP wings in
complexes 7-13, whereas the second type of reactions can
achieve the conversion from the Ph2-substituted tetragonal Fe2SP
wings in complexes 1, 3, 7, 12, and 13 to the (µ-Ph2P)Fe2(CO)6-
substituted Fe2S triangular wings in complexes 14-18, respec-
tively. Considering the structural similarity of complexes 7-18
to the active site of [FeFe]-hydrogenases, as well as the H2
production catalyzed by complex 11, these butterfly Fe/S/P
complexes might be regarded as H-cluster models. Further
studies regarding the formation mechanism for such butterfly
Fe/S/P complexes and the electrocatalytic mechanism for proton
reduction catalyzed by such complexes are underway.
Figure 5. Cyclic voltammogram of 11 (1.0 mM) in 0.1 M
Experimental Section
n-Bu4NPF6/MeCN at a scan rate of 100 mV s-1
.
General Comments. All reactions were carried out under an
atmosphere of prepurified nitrogen using standard Schlenk and
vacuum-line techniques. Tetrahydrofuran (THF) was purified by
distillation under nitrogen from Na/benzophenone ketyl. (µ-
S2)Fe2(CO)6,34 Fe2(CO)9,35 RMgBr (R ) Et, p-MeC6H4),36
Ph2PCl,37 4-BrC6H4C6H4Br-4′,38 4-BrC6H4OCH2CH2OC6H4Br-4′,39
and (µ-RS)(η1-Ph2PS-η1)Fe2(CO)6 (R ) Me, Ph)8 were prepared
according to the published procedures. n-BuLi (1 M in hexane)
and Et3BHLi (1 M in THF) were available commercially. While
products were separated by preparative TLC (25 × 15 × 0.25 cm)
on glass plates coated with silica gel 60 H, samples for analysis
were further purified by recrystallization from common organic
solvents. IR spectra were recorded on a Nicolet Magna 500 FTIR
1
or a Bruker Vector 22 infrared spectrophotometer. H NMR and
31P NMR spectra were taken on a Bruker AC-P200 NMR
spectrometer. C/H analyses were performed with an Elementar
Vario EL analyzer. Melting points were determined on a Yanaco
MP-500 apparatus and are uncorrected.
Preparation of (µ-EtS)(η1-Ph2PS-η1)Fe2(CO)6 (7) and (µ-
EtS)(η1-Ph2PS-η1)Fe2(CO)5(Ph2PCl) (8). A red solution of (µ-
S2)Fe2(CO)6 (0.344 g, 1.0 mmol) in THF (20 mL) was cooled to
-78 °C under stirring by a dry ice/acetone bath. To this solution
was added a diethyl ether solution of EtMgBr (ca. 1 mmol) by
syringe until the mixture turned emerald green. The green mixture
was stirred at this temperature for 15 min, and then Ph2PCl (0.2
mL, 1.0 mmol) was added to cause an immediate color change to
red. The new mixture was allowed to warm to room temperature
and stirred at this temperature for 1 h. Volatiles were removed under
reduced pressure, and the residue was subjected to TLC separation
using CH2Cl2/petroleum ether (1:4 v/v) as eluent. From the first,
orange-red band 7 was obtained as a red solid (0.346 g, 62%). Mp:
120-121 °C. Anal. Calcd for C20H15Fe2O6PS2: C, 43.04; H, 2.71.
Figure 6. Cyclic voltammogram of 11 (1.0 mM) with HOAc (0-10
mM) in 0.1 M n-Bu4NPF6/MeCN at a scan rate of 100 mV s-1
.
ingly, this process was further proved by bulk electrolysis of a
MeCN solution of 11 (0.5 mM) with HOAc (25 mM) at -2.20
V. During 0.5 h of the bulk electrolysis, 10.2 F per mol of 11
was passed, which corresponds to 5.1 turnovers. H2 bubbles
could be seen during the large-scale electrolytic experiment.
GC analysis showed that the hydrogen yield was nearly 100%.
Conclusion
We have synthesized and characterized a series of new
butterfly Fe/S/P cluster complexes, which include (i) complexes
7-10, having one butterfly Fe2S2P cluster core, (ii) complex
11, having one butterfly Fe2S2P2 cluster core, (iii) complexes
12 and 13, having two butterfly Fe2S2P cluster cores, (iv)
complexes 14-16, containing one double-butterfly Fe4S2P core
with a common µ4-S atom, and (v) complexes 17 and 18,
containing two double-butterfly Fe4S2P cluster cores each with
a common µ4-S atom. Interestingly, while 7-13 were synthe-
sized via a novel type of reactions of the S-centered butterfly
anions A (R ) Et, p-MeC6H4), C, D, and E with Ph2PCl,
Found: C, 42.83; H, 2.69. IR (KBr disk): νCt 2066 (vs), 2020
O
(vs), 2007 (vs), 1992 (vs), 1972 (s), 1958 (s) cm-1. 1H NMR (200
MHz, CDCl3): 1.66 (t, J ) 7.2 Hz, 3H, CH3), 2.82 (q, J ) 7.2 Hz,
2H, CH2), 7.24-7.78 (m, 10H, 2C6H5) ppm. 31P NMR (81.0 MHz,
CDCl3, 85% H3PO4): 66.99 (s) ppm. From the second, brown-red
band 8 was obtained as a red solid (0.061 g, 8%). Mp: 151-152
°C. Anal. Calcd for C31H25ClFe2O5P2S2: C, 49.57; H, 3.33. Found:
(34) Seyferth, D.; Henderson, R. S.; Song, L.-C. Organometallics 1982,
1, 125.
(35) King, R. B. Organometallic Syntheses, Transition-Metal Com-
pounds; Academic Press: New York, 1965; Vol. I, p 95.
(36) Gilman, H.; Zoellner, E. A.; Dickey, J. B. J. Am. Chem. Soc. 1929,
51, 1576.
(32) Chong, D.; Georgakaki, I. P.; Mejia-Rodriguez, R.; Sanabria-
Chinchilla, J.; Soriaga, M. P.; Darensbourg, M. Y. Dalton Trans. 2003, 3,
4158.
(37) Horner, L. Chem. Ber. 1961, 94, 21.
(33) Capon, J.-F.; Gloaguen, F.; Schollhammer, P.; Talarmin, J. Coord.
Chem. ReV. 2005, 249, 1664.
(38) Buckles, R. E.; Wheeler, N. G. Org. Synth. 1951, 31, 29.
(39) Tashiro, M.; Sumida, T.; Fukata, G. J. Org. Chem. 1980, 45, 1156.

3720 Organometallics, Vol. 27, No. 15, 2008
Song et al.
Table 2. Crystal Data and Structure Refinement Details for 9, 11, and 14
9
11
14
mol formula
mol wt
cryst syst
space group
a/Å
C25H17Fe2O6PS2
620.18
monoclinic
P2(1)/c
15.333(5)
10.876(3)
17.090(5)
90
112.554(5)
90
2632.2(13)
4
1.565
1.360
1256
C30H20Fe2O6P2S2
714.22
C25H13Fe4O12PS2
823.84
monoclinic
Cc
10.268(4)
15.146(7)
20.165(9)
90
98.215(7)
90
3104(2)
4
1.736
2.077
1640
triclinic
j
P1
9.991(4)
11.558(5)
14.893(6)
71.732(7)
88.952(7)
70.292(7)
1530.1(11)
2
b/Å
c/Å
R/deg
ꢀ/deg
γ/deg
V/Å3
Z
Dc/g cm-3
abs coeff/mm-1
F(000)
1.550
1.231
724
index ranges
-19 e h e 15
-13 e k e 11
-9 e l e 21
12 136
-12 e h e 12
-5 e k e 13
-17 e l e 17
6543
-11 e h e 12
-9 e k e 18
-23 e l e 23
5417
no. of rflns
no. of indep rflns
5374
5530
4895
2θmax/deg
R
52.82
0.0552
50.70
0.0494
50.04
0.0490
Rw
0.0734
0.0945
0.0710
goodness of fit
0.961
0.411/-0.377
0.992
0.469/-0.464
1.043
0.376/-0.349
largest diff peak and hole/e Å-3
C, 49.70; H, 3.48. IR (KBr disk): νCt O 2039 (vs), 1985 (vs), 1953
(vs), 1941 (s) cm-1. 1H NMR (200 MHz, CDCl3): 1.42 (t, J ) 7.2
Hz, 3H, CH3), 2.35-2.50 (m, 2H, CH2), 7.27-7.97 (m, 20H,
4C6H5) ppm. 31P NMR (81.0 MHz, CDCl3, 85% H3PO4): 70.99
(s), 151.04 (s) ppm.
0.5 h from -65 to 0 °C and then recooled to -78 °C. To this
mixture was added (µ-S2)Fe2(CO)6 (0.688 g, 2.0 mmol), and after
stirring for 15 min, Ph2PCl (0.4 mL, 2.0 mmol) was added. The
new mixture was stirred at -78 °C for 15 min and then allowed to
warm to room temperature. After the mixture continued stirring at
room temperature for 2 h, volatiles were removed and the residue
was subjected to TLC separation using CH2Cl2/petroleum ether (1:2
v/v) as eluent. From the first, orange-red band 12 was obtained as
a red solid (0.278 g, 23%). Mp: 145 °C (dec). Anal. Calcd for
C48H28Fe4O12P2S4: C, 47.65; H, 2.33. Found: C, 47.64; H, 2.78. IR
Preparation of (µ-p-MeC6H4S)(η1-Ph2PS-η1)Fe2(CO)6 (9) and
(µ-p-MeC6H4S)(η1-Ph2PS-η1)Fe2(CO)5(Ph2PC6H4Me-p) (10). The
same procedure was followed as for 7 and 8, except that
p-MeC6H4MgBr was used instead of EtMgBr. Elution with CH2Cl2/
petroleum ether (1:6 v/v) afforded 9 as a red solid (0.397 g, 64%).
Mp: 146-147 °C. Anal. Calcd for C25H17Fe2O6PS2: C, 48.84; H,
(KBr disk): νCt 2070 (vs), 2032 (vs), 2004 (vs), 1970 (s) cm-1
.
O
1H NMR (200 MHz, CDCl3): 7.33-7.85 (m, 28H, 4C6H5, 2C6H4)
ppm. 31P NMR (81.0 MHz, CDCl3, 85% H3PO4): 44.69 (s) ppm.
Preparationof[(η1-Ph2PS-η1)Fe2(CO)6]2(4-µ-SC6H4OCH2CH2-
OC6H4S-µ-4′) (13). The same procedure was followed as for 12,
except that 4-BrC6H4OCH2CH2OC6H4Br-4′ (0.372 g, 1.0 mmol)
and excess n-BuLi (ca. 3 mmol) were used. From the first, orange-
red band 13 was obtained as a red solid (0.523 g, 41%). Mp: 154
°C (dec). Anal. Calcd for C50H32Fe4O14P2S4: C, 47.24; H, 2.52.
2.76. Found: C, 48.69; H, 2.75. IR (KBr disk): νCt 2066 (vs),
O
2028 (vs), 1992 (vs), 1968 (vs) cm-1. 1H NMR (200 MHz, CDCl3):
2.32 (s, 3H, CH3), 7.07-7.80 (m, 14H, 2C6H5, C6H4) ppm. 31P
NMR (81.0 MHz, CDCl3, 85% H3PO4): 44.50 (s) ppm. From the
second, bwown-red band 10 was obtained as a red solid (0.208 g,
24%). Mp: 127-128 °C. Anal. Calcd for C43H34Fe2O5P2S2: C,
59.45; H, 3.92. Found: C, 59.48; H, 4.06. IR (KBr disk): νCt O 2040
(vs), 1974 (vs), 1947 (s), 1934 (s) cm-1 1H NMR (200 MHz,
.
CDCl3): 2.20 (s, 3H, CH3C6H4P), 2.39 (s, 3H, CH3C6H4S),
6.73-7.72 (m, 28H, 4C6H5, 2C6H4) ppm. 31P NMR (81.0 MHz,
CDCl3, 85% H3PO4): 57.99 (s), 70.41 (s) ppm.
Found: C, 47.21; H, 2.55. IR (KBr disk): νCt 2069 (vs), 2031
O
(vs), 2003 (vs), 1985 (s), 1970 (s) cm-1
.
1H NMR (200 MHz,
CDCl3): 4.28 (s, 4H, 2CH2), 6.84-7.83 (m, 28H, 4C6H5, 2C6H4)
ppm. 31P NMR (81.0 MHz, CDCl3, 85% H3PO4): 67.02 (s) ppm.
Preparation of [(µ-MeS)Fe2(CO)6](µ4-S)[(µ-Ph2P)Fe2(CO)6]
(14). A mixture of (µ-MeS)(η1-Ph2PS-η1)Fe2(CO)6 (1, 0.181 g, 0.33
mmol) and Fe2(CO)9 (0.728 g, 2.0 mmol) in THF (20 mL) was
stirred for 6 h at room temperature. After the solvent was removed
under reduced pressure, the residue was subjected to TLC separation
using CH2Cl2/petroleum ether (1:4 v/v) as eluent. From the major,
orange-red band 14 was obtained as a red solid (0.069 g, 25%).
Mp: 182 °C (dec). Anal. Calcd for C25H13Fe4O12PS2: C, 36.41; H,
1.58. Found: C, 36.04; H, 1.70. IR (KBr disk): νCt O 2078 (s), 2054
Preparation of (η1-Ph2PS-η1)2Fe2(CO)6(11). To a stirred solu-
tion of (µ-S2)Fe2(CO)6 (0.344 g, 1.0 mmol) in THF (20 mL) (cooled
to -78 °C) was added a solution of Et3BHLi (2 mL, 2 mmol) by
syringe. At the midpoint of the addition, the solution turned from
red to emerald green; for the rest of the addition it remained green.
The green mixture was stirred at -78 °C for 15 min, and then
Ph2PCl (0.4 mL, 2.0 mmol) was added, causing an immediate color
change back to red. The new mixture was allowed to warm to room
temperature and stirred at this temperature for 1 h. The same workup
as that for 7 and 8 gave 11 as a red solid (0.302 g, 42%). Mp: 132
°C (dec). Anal. Calcd for C30H20Fe2O6P2S2: C, 50.45; H, 2.82.
1
(vs), 2031 (vs), 1990 (vs), 1943 (s) cm-1. H NMR (200 MHz,
Found: C, 50.72; H, 3.08. IR (KBr disk): νCt 2066 (vs), 2029
CDCl3): 2.07 (s, 3H, CH3), 7.24-7.65 (m, 10H, 2C6H5) ppm. 31P
NMR (81.0 MHz, CDCl3, H3PO4): 145.63 (s) ppm.
O
(vs), 2001 (vs), 1967 (s) cm-1
.
1H NMR (200 MHz, CDCl3):
7.25-8.07 (m, 20H, 4C6H5) ppm. 31P NMR (81.0 MHz, CDCl3,
85% H3PO4): 49.71 (s) ppm.
Preparation of [(µ-PhS)Fe2(CO)6](µ4-S)[(µ-Ph2P)Fe2(CO)6]
(15). The same procedure was followed as for 14, except that (µ-
PhS)(η1-Ph2PS-η1)Fe2(CO)6 (3, 0.202 g, 0.33 mmol) was used
instead of 1. From the major band 15 was obtained as a red solid
(0.032 g, 11%). Mp: 190-191 °C. Anal. Calcd for
C30H15Fe4O12PS2: C, 40.63; H, 1.69. Found: C, 40.42; H, 1.85. IR
Preparation of [(η1-Ph2PS-η1)Fe2(CO)6]2(4-µ-SC6H4C6H4S-
µ-4′) (12). While stirring, a solution of 4-BrC6H4C6H4Br-4′ (0.312
g, 1.0 mmol) in THF (20 mL) was cooled to ca. -65 °C, and then
a hexane solution of n-BuLi (ca. 2 mmol) was dropwise added to
give an off-white mixture. The mixture was stirred for an additional
(KBr disk): νCt 2079 (s), 2052 (vs), 2030 (vs), 1994 (vs) cm-1
.
O

Butterfly Fe/S/P Cluster Complexes
Organometallics, Vol. 27, No. 15, 2008 3721
1H NMR (200 MHz, CDCl3): 7.19-7.74 (m, 15H, 3C6H5) ppm.
31P NMR (81.0 MHz, CDCl3, 85% H3PO4): 145.53 (s) ppm.
Preparation of [(µ-EtS)Fe2(CO)6](µ4-S)[(µ-Ph2P)Fe2(CO)6]
(16). The same procedure was followed as for 14, except that (µ-
EtS)(η1-Ph2PS-η1)Fe2(CO)6 (7, 0.186 g, 0.33 mmol) was employed
in place of 1. From the major band 16 was obtained as a red solid
(0.053 g, 19%). Mp: 173-174 °C. Anal. Calcd for
C26H15Fe4O12PS2: C, 37.23; H, 1.79. Found: C, 37.05; H, 2.24. IR
Bruker SMART 1000 automated diffractometer. Data were collected
at room temperature, using a graphite monochromator with Mo KR
radiation (λ ) 0.71073 Å) in the ω-φ scanning mode. Absorption
correction was performed by the SADABS program.40 The
structures were solved by direct methods using the SHELXS-97
program41 and refined by full-matrix least-squares techniques
(SHELXL-97)42 on F2. Hydrogen atoms were located by using the
geometric method. Details of crystal data, data collections, and
structure refinements are summarized in Table 2.
Electrochemistry. Acetonitrile (Fisher Chemicals, HPLC grade)
was used for electrochemistry assays. A solution of 0.1 M
n-Bu4NPF6 in MeCN was used as electrolyte in all cyclic voltam-
metric 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 N2 atmosphere. The working electrode was polished
with 0.05 µm alumina paste and sonicated in water for at least 10
min prior to use. Bulk electrolysis was run on a vitreous carbon
rod (ca. 3 cm2) in a two-compartment, gastight, H-type electrolysis
cell containing ca. 20 mL of MeCN. All potentials are quoted
against the ferrocene/ferrocenium (Fc/Fc+) potential. Gas chroma-
tography was performed with a Shimadzu GC-9A gas chromato-
graph under isothermal conditions with nitrogen as a carrier gas
and a thermal conductivity detector.
(KBr disk): νCt 2078 (s), 2051 (vs), 2026 (vs), 1993 (vs), 1976
O
1
(vs), 1950 (m) cm-1. H NMR (200 MHz, CDCl3): 1.33 (t, J )
7.2 Hz, 3H, CH3), 2.41 (q, J ) 7.2 Hz, 2H, CH2), 7.31-7.70 (m,
10H, 2C6H5) ppm. 31P NMR (81.0 MHz, CDCl3, 85% H3PO4):
145.78 (s) ppm.
Preparation of [(µ-Ph2P)Fe2(CO)6(µ4-S)Fe2(CO)6]2(4-µ-SC6H4-
C6H4S-µ-4′) (17). A solution of [(η1-Ph2PS-η1)Fe2(CO)6]2[4-µ-
SC6H4C6H4S-µ-4′] (12, 0.204 g, 0.20 mmol) and Fe2(CO)9 (1.092
g, 3.0 mmol) in THF (20 mL) was stirred for 48 h at room
temperature. After the solvent was removed under reduced pressure,
the residue was subjected to TLC separation using THF/petroleum
ether (1:5 v/v) as eluent. From the major, orange-red band 17 was
obtained as a red solid (0.072 g, 20%). Mp: 90 °C (dec). Anal.
Calcd for C60H28Fe8O24P2S4: C, 40.68; H, 1.58. Found: C, 40.81;
H, 1.75. IR (KBr disk): νCt O 2079 (s), 2053 (vs), 2031 (vs), 1994
(vs) cm-1 1H NMR (200 MHz, CDCl3): 7.32-7.80 (m, 28H,
.
4C6H5, 2C6H4) ppm. 31P NMR (81.0 MHz, CDCl3, 85% H3PO4):
145.51 (s) ppm.
Preparation of [(µ-Ph2P)Fe2(CO)6(µ4-S)Fe2(CO)6]2(4-µ-SC6H4-
OCH2 CH2OC6H4S-µ-4′) (18). The same procedure was followed
as for 17, but [(η1-Ph2PS-η1)Fe2(CO)6]2(4-µ-SC6H4OCH2CH2OC6H4S-
µ-4′) (13, 0.254 g, 0.20 mmol) was used in place of 12. Elution of
the major, orange-red band with CH2Cl2/petroleum ether (5:1 v/v)
produced 18 as a red solid (0.092 g, 25%). Mp: 85-87 °C. Anal.
Calcd for C62H32Fe8O26P2S4: C, 40.66; H, 1.75. Found: C, 40.48;
H, 1.88. IR (KBr disk): νCt O 2079 (s), 2052 (vs), 2030 (vs), 1994
(vs) cm-1. 1H NMR (200 MHz, CDCl3): 4.20 (s, 4H, 2CH2), 6.70,
6.74, 7.13, 7.17 (AB quartet, 8H, 2C6H4), 7.30-7.67 (m, 20H,
4C6H5) ppm. 31P NMR (81.0 MHz, CDCl3, 85% H3PO4): 145.60
(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 9, 11, and 14 as CIF files. This material is available free
of charge via the Internet at http://pubs. acs.org.
OM800077C
X-ray Structure Determinations of 9, 11, and 14. Single
crystals of 9, 11, and 14 suitable for X-ray diffraction analyses
were grown by slow evaporation of a hexane solution of 9 and a
hexane/CH2Cl2 solution of 14 at about 4 °C, and by slow diffusion
of hexane into a diethyl ether solution of 11 at about 4 °C,
respectively. A single crystal of 9, 11, or 14 was mounted on a
(40) Sheldrick, G. M. SADABS, A Program for Empirical Absorption
Correction of Area Detector Data; University of Go¨ttingen: Germany, 1996.
(41) Sheldrick, G. M. SHELXS97, A Program for Crystal Structure
Solution; University of Go¨ttingen: Germany, 1997.
(42) Sheldrick, G. M. SHELXL97, A Program for Crystal Structure
Refinement; University of Go¨ttingen: Germany, 1997.