Synthetic and structural investigations on double- and single-butterfly Fe/E (E = S, Se) cluster complexes containing diselenolate ligands

Article abstract of DOI:10.1021/om060238h

The first examples of diselenolate ligand-containing butterfly Fe/E (E = S, Se) complexes are now reported. When ca. 1 equiv of dilithium reagent 4-LiC₆H₄C₆H₄Li-4′ containing n-BuBr (prepared from 1 equiv of 4,4′-dibromobiphenyl and n-BuLi) was treated with 2 equiv of elemental selenium and Fe₃-(CO)₁₂ followed by treatment with excess CS₂ and Mel, both double-butterfly complex (4-μ-SeC₆H₄C₄H₄-Se-μ- 4′)[(μ-S=CSMe)Fe₂(CO)₆]₂ (4) and single-butterfly complex (4-n-BuSeC₆H₄C₆H ₄Se-μ-4′)[(μ-S= CSMe)Fe₂(CO)₆] (4*) were produced in 11% and 20% yields, respectively. However, when ca. 1 equiv of dilithium reagent 4-LiC₆H₄C₆H ₄Li-4′ without n-BuBr (n-BuBr was removed by evaporation of the initially prepared dilithium reagent containing n-BuBr) reacted with 2 equiv of elemental selenium and Fe₃(CO)₁₂ followed by treatment with excess CS₂ and Mel, only the double-butterfly complex 4 was obtained in a higher yield (21%) without any single-butterfly complex being isolated. Other double-butterfly complexes, such as (4-μ-SeC ₆H₄C₆H₄Se-μ-4′)[(μ-S= CSR)Fe₂(CO)₆]₂ (5, R = Et; 6, PhCH₂; 7, PhC=NPh; 8, Cp(CO)₂Fe), (4-μ-SeC₆H ₄C₆H₄Se-μ-4′)[(μ-SePh)Fe ₂(CO)₆]₂ (9), and (4-μ-SeC₆H ₄C₆H₄Se-μ-4′)[(μ-CH ₂SMe)Fe₂(CO)₆]₂ (10), could be similarly prepared via the latter method by using electrophiles CS ₂/EtBr, CS₂/PhCH₂Br, CS₂/PhC(Cl)= NPh, CS₂/Cp(CO)₂FeI, PhSeBr, and MeSCH₂Cl instead of CS₂/MeI, respectively. A possible pathway for production of the double- and single-butterfly complexes 4-10 and 4* has been proposed, in which the versatile two-μ-CO-containing double-butterfly dianion (4-μ-SeC₆H₄C₆H₄Se-μ-4′) [(μ-CO)Fe₂(CO)₆]₂^2- (3) and the one-μ-CO-containing single-butterfly monoanion (4-n-BuSeC₆H ₄C₆H₄Se-μ-4′)[(μ-CO)Fe ₂(CO)₆]^- (3*) are involved. All the new complexes were fully characterized by elemental analysis and spectroscopy, as well as by X-ray crystallography for 4* and 10.

Full text of DOI:10.1021/om060238h

3468
Organometallics 2006, 25, 3468-3473
Synthetic and Structural Investigations on Double- and
Single-Butterfly Fe/E (E ) S, Se) Cluster Complexes Containing
Diselenolate Ligands
Li-Cheng Song,* Guang-Huai Zeng, Shu-Zhen Mei, Shao-Xia Lou, and Qing-Mei Hu
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai UniVersity,
Tianjin 300071, China
ReceiVed March 15, 2006
The first examples of diselenolate ligand-containing butterfly Fe/E (E ) S, Se) complexes are now
reported. When ca. 1 equiv of dilithium reagent 4-LiC6H4C6H4Li-4′ containing n-BuBr (prepared from
1 equiv of 4,4′-dibromobiphenyl and n-BuLi) was treated with 2 equiv of elemental selenium and Fe3-
(CO)12 followed by treatment with excess CS2 and MeI, both double-butterfly complex (4-µ-SeC6H4C6H4-
Se-µ-4′)[(µ-SdCSMe)Fe2(CO)6]2 (4) and single-butterfly complex (4-n-BuSeC6H4C6H4Se-µ-4′)[(µ-Sd
CSMe)Fe2(CO)6] (4*) were produced in 11% and 20% yields, respectively. However, when ca. 1 equiv
of dilithium reagent 4-LiC6H4C6H4Li-4′ without n-BuBr (n-BuBr was removed by evaporation of the
initially prepared dilithium reagent containing n-BuBr) reacted with 2 equiv of elemental selenium and
Fe3(CO)12 followed by treatment with excess CS2 and MeI, only the double-butterfly complex 4 was
obtained in a higher yield (21%) without any single-butterfly complex being isolated. Other double-
butterfly complexes, such as (4-µ-SeC6H4C6H4Se-µ-4′)[(µ-SdCSR)Fe2(CO)6]2 (5, R ) Et; 6, PhCH2; 7,
PhCdNPh; 8, Cp(CO)2Fe), (4-µ-SeC6H4C6H4Se-µ-4′)[(µ-SePh)Fe2(CO)6]2 (9), and (4-µ-SeC6H4C6H4Se-
µ-4′)[(µ-CH2SMe)Fe2(CO)6]2 (10), could be similarly prepared via the latter method by using electrophiles
CS2/EtBr, CS2/PhCH2Br, CS2/PhC(Cl)dNPh, CS2/Cp(CO)2FeI, PhSeBr, and MeSCH2Cl instead of CS2/
MeI, respectively. A possible pathway for production of the double- and single-butterfly complexes 4-10
and 4* has been proposed, in which the versatile two-µ-CO-containing double-butterfly dianion (4-µ-
2-
SeC6H4C6H4Se-µ-4′)[(µ-CO)Fe2(CO)6]2 (3) and the one-µ-CO-containing single-butterfly monoanion
(4-n-BuSeC6H4C6H4Se-µ-4′)[(µ-CO)Fe2(CO)6]- (3*) are involved. All the new complexes were fully
characterized by elemental analysis and spectroscopy, as well as by X-ray crystallography for 4* and 10.
Scheme 1
Introduction
Butterfly Fe/E (E ) S, Se) cluster complexes have received
ever more attention in recent years, largely because of their novel
chemistry1-3 and the close relevance to Fe-only hydrogenases,
a naturally occurring class of enzymes, which mediate the uptake
and production of hydrogen in microorganisms.4-6 Among such
complexes the single-butterfly monoanions [(µ-RE)(µ-CO)Fe2-
(CO)6]- (1, E ) S, Se)2 and the dithiolato-bridged double-
butterfly dianions (µ-SZS-µ)[(µ-CO)Fe2(CO)6]22- (2)7-9 (Scheme
1) are of great interest, since they are easily available and possess
high nucleophilicity toward electrophiles. While the one-µ-CO-
containing monoanions 1 were first prepared 15 years ago by
Seyferth’s group,10,11 we prepared the two-µ-CO-containing
dianions 2 just recently.7,8 Now, these µ-CO-containing butterfly
anions have been demonstrated to be very useful reagents for
synthesizing a wide variety of Fe/E cluster complexes. To further
develop the chemistry of Fe/E cluster complexes, we recently
started to investigate if the first Se analogue of dianions 2,
namely, the diselenolato-bridged double-butterfly dianion (4-
* To whom correspondence should be addressed. Fax: 0086-22-
23504853. E-mail: lcsong@nankai.edu.cn.
(1) Ogino, H.; Inomata, S.; Tobita, H. Chem. ReV. 1998, 98, 2093.
(2) Song, L.-C. In Trends in Organometallic Chemistry; Atwood, J. L.,
Corriu, R., Cowley, A. H., Lappert, M. F., Nakamura, A., Pereyre, M. Eds.;
Research Trends: Trivandrum, India, 1999; Vol. 3, p 1.
(3) Song, L.-C. Acc. Chem. Res. 2005, 38, 21.
2-
µ-SeC6H4C6H4Se-µ-4′)[(µ-CO)Fe2(CO)6]2 (3) (Scheme 1),
(4) Darensbourg, M. Y.; Lyon E. J.; Smee, J. J. Coord. Chem. ReV. 2000,
could be prepared and how its chemical reactivities are toward
electrophiles. Herein we report our results obtained from this
study, which include the formation of dianion 3 and its in situ
reactions with some electrophiles to give a series of double-
206-207, 533.
(5) Rauchfuss, T. B. Inorg. Chem. 2004, 43, 14.
(6) Liu, X.; Ibrahim, S. K.; Tard, C.; Pickett, C. J. Coord. Chem. ReV.
2005, 249, 1641.
(7) Song, L.-C.; Fan, H.-T.; Hu, Q.-M. J. Am. Chem. Soc. 2002, 124,
4566.
(8) Song, L.-C.; Fan, H.-T.; Hu, Q.-M.; Yang, Z.-Y.; Sun, Y.; Gong F.-
H. Chem. Eur. J. 2003, 9, 170.
(9) Song, L.-C.; Gong, F.-H.; Meng T.; Ge, J.-H.; Cui, L.-N.; Hu, Q.-
M. Organometallics 2004, 23, 823.
(10) Seyferth, D.; Womack, G. B.; Dewan, J. C. Organometallics 1985,
4, 398.
(11) Seyferth, D.; Womack, G. B.; Archer, C. M.; Dewan, J. C.
Organometallics 1989, 8, 430.
10.1021/om060238h CCC: $33.50 © 2006 American Chemical Society
Publication on Web 06/06/2006

Butterfly Fe/E (E ) S, Se) Cluster Complexes
Organometallics, Vol. 25, No. 14, 2006 3469
Scheme 2
butterfly Fe/E cluster complexes each containing a diselenolate
ligand 4-µ-SeC6H4C6H4Se-µ-4′. In addition, we also report one
single-butterfly cluster complex, which contains a n-butyl-
substituted diselenolate ligand 4-n-BuSeC6H4C6H4Se-µ-4′, pro-
duced from one of the reactions involved in this study.
the lithium salt of 3* reacts with CS2 to give the lithium salt of
an S-centered monoanion m*, and finally the lithium salt of
m* is alkylated with MeI to give the single-butterfly product
4*. The above suggested pathway for production of 4 and 4* is
mainly speculative, but seems to be reasonable. This is because
(i) the above-mentioned metal-halogen exchange to give
4-LiC6H4C6H4Li-4′ and n-BuBr was previously reported;12 (ii)
the insertion of elemental E (E ) S, Se) into the C-Li bond of
the monolithium reagent RLi to give RELi is a well-known
process;13a-c (iii) the reaction of RSLi with Fe3(CO)12 is one
of the known reactions for preparing the one-µ-CO-containing
monoanion [(µ-RS)(µ-CO)Fe2(CO)6]-;14 and (iv) the above-
described reaction modes regarding dianion 3 and monoanion
3* are well-based on the µ-CO chemistry of the other µ-CO-
containing butterfly cluster anions.2,7-9,15
On the basis of our initially studied results, we thought that
if we had removed n-BuBr from the originally prepared solution
containing dilithium reagent 4-LiC6H4C6H4Li-4′ and the in situ
generated n-BuBr, the sequential reaction described above would
afford only the double-butterfly complex 4 in a higher yield
without any single-butterfly complex 4* being produced. In fact,
this conjecture was proved by our experiments. Thus, treatment
of 1 equiv of 4,4′-dibromobiphenyl in THF with 2 eqiuv of
n-BuLi gave rise to a mixture containing 4-LiC6H4C6H4Li-4′
and n-BuBr. Volatiles including n-BuBr were removed at
reduced pressure to leave an off-white solid 4-LiC6H4C6H4Li-
4′. After redissolving it in THF, 2 equiv of elemental selenium
and Fe3(CO)12 were added to give a brown-red solution. This
solution contains the lithium salt of dianion 3, which showed a
µ-CO medium absorption band at 1742 cm-1 in its IR spectrum.
This is consistent with the other µ-CO-containing butterfly
cluster anions.8,10,15 Further treatment of this solution with excess
Results and Discussion
Rational Synthesis of Double-Butterfly Complexes (4-µ-
SeC6H4C6H4Se-µ-4′)[(µ-SdCSR)Fe2(CO)6]2 (4, R ) Me; 5,
Et; 6, PhCH2; 7, PhCdNPh; 8, Cp(CO)2Fe), (4-µ-SeC6H4-
C6H4Se-µ-4′)[(µ-SePh)Fe2(CO)6]2 (9), and (4-µ-SeC6H4C6H4Se-
µ-4′)[(µ-CH2SMe)Fe2(CO)6]2 (10) and Single-Butterfly Com-
plex (4-n-BuSeC6H4C6H4Se-µ-4′)[(µ-SdCSMe)Fe2(CO)6] (4*).
We initially found that when 1 equiv of 4,4′-dibromobiphenyl
in THF reacted sequentially with 2 equiv of n-BuLi, selenium
powder, and Fe3(CO)12 followed by treatment with excess CS2
and MeI, the double-butterfly complex 4 and single-butterfly
complex 4* were produced in 11% and 20% yields, respectively.
To account for the formation of complexes 4 and 4*, we have
proposed a possible pathway, as shown in Scheme 2. Scheme
2 shows that (i) the metal-halogen exchange between 4,4′-
dibromobiphenyl and n-butyllithium gives dilithium reagent
4-LiC6H4C6H4Li-4′ and n-BuBr; (ii) the insertion reaction of
4-LiC6H4C6H4Li-4′ with elemental selenium produces bis-SeLi
species 4-LiSeC6H4C6H4SeLi-4′; (iii) the bis-SeLi species reacts
with Fe3(CO)12 to generate a lithium salt of the desired double-
butterfly two-µ-CO-containing dianion 3; (iv) the lithium salt
of dianion 3 reacts further with two molecules of CS2 (presum-
ably via nucleophilic attack of the two negatively charged Fe
atoms in 3 at the two molecules of CS2 followed by loss of the
two µ-CO ligands in 3) to give the lithium salt of an S-centered
dianion m; and (v) the lithium salt of dianion m is alkylated by
two molecules of MeI to afford the double-butterfly product 4.
However, in contrast to production of 4, Scheme 2 also shows
that the bis-SeLi species can also react with the in situ formed
n-BuBr to give the mono-SeLi species n-BuSeC6H4C6H4SeLi-
4′. This species reacts further with Fe3(CO)12 to produce the
lithium salt of the one-µ-CO-containing monoanion 3*. Then
(12) Baldwin, R. A.; Cheng, M. T. J. Org. Chem. 1967, 32, 1572.
(13) (a) Haller, W. S.; Irgolic, K. J. J. Organomet. Chem. 1972, 38, 97.
(b) Seebach, D.; Beck, A. K. Chem. Ber. 1975, 108, 314. (c) Henriksen, L.
In The Chemistry of Organic Selenium and Tellurium Compounds; Patai,
S., Ed.; Wiley: New York, 1987; Vol. 2, p 398.
(14) Seyferth, D.; Hoke, J. B.; Dewan, J. C. Organometallics 1987, 6,
895.

3470 Organometallics, Vol. 25, No. 14, 2006
Song et al.
Figure 1. ORTEP view of 10 with 30% probability level ellipsoids.
Scheme 3
Spectroscopic Characterization of Double-Butterfly Com-
plexes 4-10 and Single-Butterfly Complex 4*. Crystal
Structures of 10 and 4*. Products 4-10 and 4* are air-stable
solids, which were characterized by elemental analysis and IR
and 1H (77Se) NMR spectroscopy. The IR spectra of 4-10 and
4* showed several strong absorption bands in the range 2067-
1967 cm-1 for their terminal carbonyls, and those of 4-8 and
4* displayed an additional medium band at around 1000 cm-1
for their coordinated CdS double bonds.16-18 The 77Se NMR
spectra of 4-10 and 4* not only indicated the presence of their
Se atoms but also provided some information about their
conformational isomers in terms of different (axial or equatorial)
orientations of the substituents attached to the bridged Se
atoms.19-23 For example, from the 77Se NMR spectra of 4-10
and 4*, we can conclude that 9 exists as an isomeric mixture
and the others exist as only one conformer. This is because 9
displayed five singlets for its bridged Se atoms, whereas the
others each showed only one singlet for their bridged Se atoms.
In the five singlets displayed by 9 two singlets at ca. 278 ppm
and three singlets around 318 ppm can be assigned respectively
to its bridged Se atoms bonded to phenyl and biphenylene
groups, whereas the singlets displayed in the range 357-478
ppm by complexes 4-8, 10, and 4* should be attributed to the
bridged Se atoms attached to their biphenylene groups. Although
we cannot further assign their conformers based on only these
available 77Se NMR data, the structures of conformers 10 and
4* have been successfully established by X-ray diffraction
techniques.
CS2 gave the intermediate m‚Li2+, which reacted with excess
MeI to afford the double-butterfly complex 4 in 21% yield,
indeed without any single-butterfly complex 4* being observed
(Scheme 3). Since our main purpose is to prepare dianion 3
and to study its new chemistry, we continued carrying out the
other reactions of this lithium salt of dianion 3 without n-BuBr.
As a result, when the electrophiles CS2/EtBr, CS2/PhCH2Br,
CS2/PhC(Cl)dNPh, and CS2/Cp(CO)2FeI reacted (instead of
CS2/MeI) with the brown-red solution containing the lithium
salt of dianion 3 in the absence of n-BuBr, the corresponding
double-butterfly complexes 5-8 were similarly produced via
The ORTEP drawings of 10 and 4* are shown in Figures 1
and 2, while Tables 1 and 2 present their selected bond lengths
and angles, respectively. As can be seen intuitively in Figure
1, complex 10 indeed consists of two identical structural units
(µ-CH2SMe)Fe2(CO)6, which are bridged by a diselenolate
4-SeC6H4C6H4Se-4′ ligand to form a double-butterfly Fe/E
cluster complex. The X-ray crystallography revealed that the
biphenylene group in the diselenolate ligand is attached to the
+
the intermediate m‚Li2 (Scheme 3). In addition, when the
electrophile PhSeBr or MeSCH2Cl reacted (instead of the two
electrophiles CS2/MeI) with the lithium salt of dianion 3, the
double-butterfly complexes 9 and 10 were obtained presumably
via nucleophilic attack of the two negatively charged iron atoms
of 3 at two molecules of PhSeBr or MeSCH2Cl followed by
displacement of the two µ-CO ligands in intermediates m1 and
m2, respectively (Scheme 4).
(16) Seyferth, D.; Womack, G. B.; Archer, C. M.; Fackler, J. P., Jr.;
Marler, D. O. Organometallics 1989, 8, 443.
(17) Patin, H.; Mignani, G.; Mahe, C.; Le Marouille, J.-Y.; Southern, T.
G.; Benoit, A.; Grandjean, D. J. Organomet. Chem. 1980, 197, 315.
(18) Song, L.-C.; Yan, C.-G.; Hu, Q.-M.; Wang, R.-J.; Mak, T. C. W.
Organometallics 1995, 14, 5513.
(19) Buchholz, D.; Huttner, G.; Zsolnai, L.; Imhof, W. J. Organomet.
Chem. 1989, 377, 25.
(20) Song, L.-C.; Yan, C.-G.; Hu, Q.-M.; Sun, J,; Mao, X.-A. J. Coord.
Chem. 1996, 39, 147.
(21) Song, L.-C.; Lu, G.-L.; Hu, Q.-M.; Sun, J.Organometallics 1999,
18, 2700.
(22) Shaver, A.; Fitzpatrick, P. J.; Steliou, K.; Butler, I. S. J. Am. Chem.
Soc. 1979, 101, 1313.
It should be noted that the isolated yields of products 4-10
(21-12%) and 4* (20%) were calculated on the basis of starting
material 4,4′-dibromobiphenyl. Therefore, it is apparent that the
multistep (usually 5-6 steps) reactions involved in their
synthesis are the main reason for such low yields. In addition,
some byproducts (not fully separated and identified due to their
very small amounts) were also observed, such as those derived
from n-C4H9SeLi generated by insertion of elemental Se with
unreacted n-C4H9Li.
(15) Song, L.-C.; Cheng, J.; Gong, F.-H.; Hu, Q.-M.; Yan, J. Organo-
metallics 2005, 24, 3764.
(23) Seyferth, D.; Henderson, R. S.; Song, L.-C. Organometallics 1982,
1, 125.

Butterfly Fe/E (E ) S, Se) Cluster Complexes
Organometallics, Vol. 25, No. 14, 2006 3471
Figure 2. ORTEP view of 4* with 30% probability level ellipsoids.
Scheme 4
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 10
Se(1) atom to the two Fe atoms of the (µ-SdCSMe)Fe2(CO)6
structural unit to consititute a single-butterfly Fe/E cluster
complex. Similar to the biphenylene group in 10, the biphen-
ylene group in 4* is bound to the bridged Se(1) atom in an
equatorial orientation ( C(7)‚‚‚Se(1)-C(9) ) 159.9°, S(1)‚‚‚
Se(1)-C(9) ) 152.3°) to give the most stable conformational
isomer, since its methyl group attached to the S(2) atom is an
exo-methyl group.23 In addition, the dihedral angle between two
benzene rings of its biphenylene group is 35.2°, which is
remarkably different from the corresponding dihedral angle (0°)
in 10. It is worthy of note that the thiocarbonyl C(7)dS(1) in
the S(2)-C(7)dS(1) moiety is bridged to Fe(2) through a σ
bond (Fe(2)-C(7) ) 2.000(5) Å) and to Fe(1) via the donation
of an unshared electron pair from S(1) (Fe(1)-S(1) ) 2.304-
(2) Å). Compared to the CdS double bond in free CS2 (1.554
Å),24 the bond length of the double bond C(7)dS(1) extends to
1.692(6) Å, but is still shorter than that of the single bond C(8)-
S(2) (1.825(6) Å). It follows that the structural feature of 4* in
this respect resembles that of the single-butterfly complex (µ-
SePh)(µ-SdCSCH2Ph)Fe2(CO)6.18
Fe(1)-C(1)
Fe(1)-Se(1)
Fe(1)-Fe(2)
Fe(2)-Se(1)
1.78(2)
Fe(2)-S(1)
S(1)-C(7)
S(1)-C(8)
Fe(1)-C(7)
2.278(5)
1.78(2)
1.82(2)
2.04(2)
2.299(3)
2.628(3)
2.419(2)
C(7)-Fe(1)-Se(1)
C(7)-Fe(1)-Fe(2)
Se(1)-Fe(1)-Fe(2)
S(1)-Fe(2)-Se(1)
S(1)-Fe(2)-Fe(1)
83.2(7)
81.5(6)
58.35(7)
86.89(15)
74.82(17)
Se(1)-Fe(2)-Fe(1)
C(7)-S(1)-C(8)
C(7)-S(1)-Fe(2)
S(1)-C(7)-Fe(1)
Fe(1)-Se(1)-Fe(2)
54.01(7)
106.4(13)
97.9(6)
103.1(11)
67.64(8)
Table 2. Selected Bond Lengths (Å) and Angles (deg) for 4*
Fe(1)-S(1)
Fe(1)-Se(1)
Fe(1)-Fe(2)
Fe(2)-Se(1)
2.304(2)
Se(1)-C(9)
S(1)-C(7)
Se(2)-C(21)
Se(2)-C(18)
1.946(5)
1.692(6)
1.755(8)
1.921(6)
2.3796(19)
2.6572(17)
2.3900(16)
S(1)-Fe(1)-Se(1)
S(1)-Fe(1)-Fe(2)
Se(1)-Fe(1)-Fe(2)
83.12(6) S(2)-C(7)-Fe(2)
75.82(5) S(1)-C(7)-Fe(2)
56.33(4) C(7)-Fe(2)-Fe(1)
123.3(3)
111.8(3)
77.75(17)
55.96(5)
67.71(4)
C(21)-Se(2)-C(18) 104.4(4)
S(2)-C(7)-S(1) 124.8(3)
Se(1)-Fe(2)-Fe(1)
Fe(1)-Se(1)-Fe(2)
two bridged Se atoms in equatorial orientations (the calculated
C(7)‚‚‚Se(1)-C(9) ) 161.0°, S(1)‚‚‚Se(1)-C(9) ) 153.2°).
Actually, such a conformer is quite stable since it avoids the
strong steric repulsion between the axially bonded biphenylene
group and the endo-methyl groups attached to S(1) and S(1A)
atoms.23 In addition, it should be noted that all 12 carbonyls
attached to the four Fe atoms are terminal and the whole
molecule is centrosymmetric. However, in contrast to 10,
complex 4* (Figure 2) contains a n-butyl-substituted diselenolate
4-n-BuSeC6H4C6H4Se-4′ ligand, which is bridged through its
In summary, we have synthsized the first diselenolate ligand-
containing double- and single-butterfly Fe/E (E ) S, Se) cluster
complexes 4-10 and 4* by two synthetic methods, which
involve using a dilithium reagent 4-LiC6H4C6H4Li-4′ containing
the in situ generated n-BuBr or without n-BuBr. When the
dilithium reagent containing n-BuBr is used, both the two-µ-
CO-containing dianion 3 and the one-µ-CO-containing mono-
anion 3* are formed, which react further with electrophiles CS2/
(24) Butler, I. S.; Fenster, A. E. J. Organomet. Chem. 1974, 66, 161.

3472 Organometallics, Vol. 25, No. 14, 2006
Song et al.
From the second red band, 4 (0.117 g, 11%) was obtained as a red
solid, mp 130 °C (dec). Anal. Calcd for C28H14Fe4O12S4Se2: C,
31.94; H, 1.33. Found: C, 31.93; H, 1.28. IR (KBr disk): νCtO
MeI to produce both the double-butterfly complex 4 and single-
butterfly complex 4*. However, when the dilithium reagent
without n-BuBr is utilized, only the two-µ-CO-containing
intermediate dianion 3 is formed, which reacts further with the
electrophiles CS2/MeI, CS2/EtBr, CS2/PhCH2Br, CS2/PhC(Cl)d
NPh, CS2/Cp(CO)2FeI, PhSeBr, and MeSCH2Cl to produce only
the double-butterfly complexes 4-10. It can be expected that
dianion 3 and monoanion 3* will play an important role in
development of the chemistry of such butterfly Fe/E cluster
complexes, since they all contain the reactive µ-CO functional-
ity.
1
2067 (vs), 2027 (vs), 2002 (vs); νCdS 1013 (m) cm-1. H NMR
(CDCl3): 2.60 (s, 6H, 2CH3), 7.37, 7.41, 7.46, 7.50 (q, AA′BB′,
8H, 2C6H4) ppm. 77Se NMR (CDCl3): 476.6 (s) ppm.
Preparation of Double-Butterfly Complex (4-µ-SeC6H4C6H4Se-
µ-4′)[(µ-SdCSMe)Fe2(CO)6]2 (4) without Single-Butterfly Com-
plex 4*. In the same equipped flask described above was dissolved
4-BrC6H4C6H4Br-4′ (0.312 g, 1.0 mmol) in THF (20 mL). The
resulting solution was cooled to -65 °C, and then a solution of
n-BuLi (2.0 mmol) in Et2O was slowly added. The mixture was
stirred for an additional 0.5 h from -65 to 0 °C, and then volatiles
including the in situ formed n-BuBr were removed under vacuum
to leave 4-LiC6H4C6H4Li-4′ as an off-white solid. To this solid was
added THF (20 mL) cooled to -5 °C to give an off-white
suspension. After cooling the suspension to -15 °C, selenium
powder (0.158 g, 2.0 mmol) was added. The mixture was stirred
for several minutes at this temperature, and then Fe3(CO)12 (1.00
g, 2.0 mmol) was added. The new mixture was naturally warmed
from -15 °C to room temperature and continued stirring for 45
min to give a brown-red solution. To this solution was added CS2
(0.24 mL, 4.0 mmol). After the mixture was stirred for 1 h, MeI
(0.25 mL, 4.0 mmol) was added, and the new mixture was stirred
for an additional 12 h. Solvent was removed under vacuum, and
the residue was subjected to TLC separation using THF/petroleum
ether (v/v ) 1:20) as eluent. From the main band, 4 (0.221 g, 21%)
was obtained as a red solid.
Experimental Section
General Comments. All reactions were performed using stan-
dard Schlenk and vacuum-line techniques under a prepurified N2
atmosphere. THF was distilled under N2 from sodium/benzophenone
ketyl. n-BuLi,25 Fe3(CO)12,26 PhSeBr,27 MeSCH2Cl,28 and 4,4′-
BrC6H4C6H4Br29 were prepared according to the published methods.
Other reactants were purchased from commercial suppliers and used
as received. 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 Nicolet Magna 560 FTIR or a Bruker
Vector 22 infrared spectrophotometer. 1H NMR spectra were
recorded on a Bruker AC-P200 NMR spectrometer or a Bruker
AC-P 300 NMR spectrometer. 77Se NMR spectra were recorded
on a Bruker AV600 NMR spectrometer with Ph2Se2 as an external
standard, and the chemical shifts were referenced to Me2Se (δ )
0). Elemental analysis was performed on an Elementar Vario EL
analyzer. Melting points were determined on a Yanaco MP-500
apparatus and were uncorrected.
Preparation of Double-Butterfly Complex (4-µ-SeC6H4C6H4Se-
µ-4′)[(µ-SdCSMe)Fe2(CO)6]2 (4) along with Single-Butterfly
Complex (4-n-BuSeC6H4C6H4Se-µ-4′)[(µ-SdCSMe)Fe2(CO)6]
(4*). A 100 mL three-necked flask fitted with a magnetic stir-bar,
a rubber septum, and a nitrogen inlet tube was charged with
4-BrC6H4C6H4Br-4′ (0.312 g, 1.0 mmol) and THF (20 mL). While
stirring, the resulting solution was cooled to -65 °C and then an
Et2O solution of n-BuLi (2.0 mmol) was dropwise added. The
mixture was stirred for an additional 0.5 h from -65 to 0 °C to
give an off-white mixture containing an equimolar amount of
4-LiC6H4C6H4Li-4′ and n-BuBr. The mixture was recooled to -15
°C, and then selenium powder (0.158 g, 2.0 mmol) was added.
After several minutes the mixture turned orange-red and Fe3(CO)12
(1.00 g, 2.0 mmol) was added to cause vigorous gas evolution.
The new mixture was naturally warmed from -15 °C to room
temperature and continued stirring for 45 min to give a brown-red
solution. To this solution was added CS2 (0.24 mL, 4.0 mmol),
and the mixture was stirred for 1 h. After MeI (0.25 mL, 4.0 mmol)
was added, the new mixture was stirred for an additional 12 h.
Solvent was removed under vacuum and the residue was subjected
to TLC separation using THF/petroleum ether (v/v ) 1:20) as
eluent. From the first orange-red band, 4* (0.147 g, 20%) was
obtained as a red solid, mp 108-109 °C. Anal. Calcd for C24H20-
Fe2O6S2Se2: C, 39.02; H, 2.71. Found: C, 38.94; H, 2.85. IR (KBr
Preparation of (4-µ-SeC6H4C6H4Se-µ-4′)[(µ-SdCSEt)Fe2-
(CO)6]2 (5). The same procedure was followed as for the preparation
of 4 without 4*, except that EtBr (0.436 g, 4.0 mmol) was used
instead of MeI and THF/petroleum ether (v/v ) 1:25) as eluent. 5
(0.195 g, 18%) was obtained as a red solid, mp 117-118 °C. Anal.
Calcd for C30H18Fe4O12S4Se2: C, 33.33; H, 1.67. Found: C, 33.50;
H, 1.56. IR (KBr disk): νCtO 2067 (s), 2028 (vs), 2008 (vs), 1986
1
(s); νCdS 998 (m) cm-1. H NMR (CDCl3): 1.28 (t, J ) 7.2 Hz,
6H, 2CH3), 3.14 (q, J ) 7.2 Hz, 4H, 2CH2), 7.37, 7.41, 7.45, 7.49
(q, AA′BB′, 8H, 2C6H4) ppm. 77Se NMR (CDCl3): 477.1 (s) ppm.
Preparation of (4-µ-SeC6H4C6H4Se-µ-4′)[(µ-SdCSCH2Ph)Fe2-
(CO)6]2 (6). When PhCH2Br (0.48 mL, 4.0 mmol) was utilized
instead of MeI and THF/petroleum ether (v/v ) 1:15) as eluent, 6
(0.227 g, 19%) was obtained as a red solid, mp 122-123 °C. Anal.
Calcd for C40H22Fe4O12S4Se2: C, 39.87; H, 1.83. Found: C, 39.86;
H, 1.92. IR (KBr disk): νCtO 2067 (s), 2026 (vs), 2004 (s), 1983
1
(s); νCdS 1011 (m) cm-1. H NMR (CDCl3): 4.35 (s, 4H, 2CH2),
7.23-7.45 (m, 18H, 2C6H5, 2C6H4) ppm. 77Se NMR (CDCl3): 478.0
(s) ppm.
Preparation of (4-µ-SeC6H4C6H4Se-µ-4′)[(µ-SdCSC(Ph)d
NPh)Fe2(CO)6]2 (7). When PhC(Cl)dNPh (0.862 g, 4.0 mmol) was
utilized instead of MeI and THF/petroleum ether (v/v ) 1:4) as
eluent, 7 (0.212 g, 15%) was obtained as a red solid, mp 142 °C
(dec). Anal. Calcd for C52H28Fe4N2O12S4Se2: C, 45.15; H, 2.03,
N, 2.03. Found: C, 44.97; H, 2.06; N, 2.29. IR (KBr disk): νCtO
2051 (s), 2009 (vs), 1967(vs); νCdN 1592 (w); νCdS 1001 (m) cm-1
.
1H NMR (CDCl3): 6.95-7.56 (m, 28H, 4C6H5, 2C6H4) ppm. 77Se
disk): νCtO 2064 (vs), 2026 (vs), 1992 (vs); νCdS 1015 (m) cm-1
.
NMR (CDCl3): 357.4 (s) ppm.
1H NMR (CDCl3): 0.90 (t, J ) 7.2 Hz, 3H, CH2CH3), 1.35-1.52
(m, 2H, CH2CH3), 1.63-1.78 (m, 2H, SeCH2CH2), 2.60 (s, 3H,
SCH3), 2.92 (t, J ) 7.2 Hz, 2H, SeCH2), 7.39-7.52 (m, 8H, 2C6H4)
ppm. 77Se NMR (CDCl3): 286.9 (s, n-BuSe), 477.6 (s, SeFe2) ppm.
Preparation of (4-µ-SeC6H4C6H4Se-µ-4′)[(µ-SdCSFe(CO)2Cp)-
Fe2(CO)6]2 (8). When Cp(CO)2FeI (1.22 g, 4.0 mmol) was
employed instead of MeI and THF/CH2Cl2/petroleum ether (v/v/v
) 1:1:14) as eluent, 8 (0.188 g, 14%) was obtained as a red solid,
mp 120 °C (dec). Anal. Calcd for C40H18Fe6O16S4Se2: C, 34.88;
H, 1.31. Found: C, 34.84; H, 1.37. IR (KBr disk): νCtO 2063 (s),
2020 (vs), 1988 (vs); νCdS 1000 (m) cm-1. 1H NMR (CDCl3): 4.99
(s, 10H, 2C5H5), 7.38-7.46 (m, 8H, 2C6H4) ppm. 77Se NMR
(CDCl3): 462.4 (s) ppm.
(25) Jones, R. G.; Gilman, H. Organic Reactions; John Wiley and
Sons: New York, 1951; Vol. 6, p 352.
(26) King, R. B. Organometallic Syntheses; Transition-Metal Com-
pounds; Academic Press: New York, 1965; Vol. 1, p 95.
(27) Machel, V.; Roger, V. Bull. Soc. Chim. Fr. 1970, 27, 746.
(28) Bordwell, F. G.; Pitt, M. B. J. Am. Chem. Soc. 1955, 77, 572.
(29) Norman R. Organic Syntheses; John Wiley and Sons. Inc.: New
York, 1963; Collect. Vol. 4, p 256.
Preparation of (4-µ-SeC6H4C6H4Se-µ-4′)[(µ-SePh)Fe2(CO)6]2
(9). The same procedure as for the preparation of 4 without 4*

Butterfly Fe/E (E ) S, Se) Cluster Complexes
Organometallics, Vol. 25, No. 14, 2006 3473
Table 3. Crystal Data and Structural Refinements Details
for 10 and 4*
preparation of 9, but MeSCH2Cl (0.290 g, 3.0 mmol) was employed
in place of PhSeBr. From the major red band, 10 (0.115 g, 12%)
was obtained as a red solid, mp 95 °C (dec). Anal. Calcd for C28H18-
Fe4O12S2Se2: C, 33.87; H, 1.81. Found: C, 33.99; H, 1.92. IR (KBr
disk): νCtO 2061 (s), 2019 (vs), 1989 (vs) cm-1. 1H NMR (CDCl3):
1.18, 1.81 (2d, 4H, 2CH2), 2.09 (s, 6H, 2CH3), 7.46,7.63 (2s, 8H,
2C6H4) ppm. 77Se NMR (CDCl3): 461.7 (s) ppm.
10
4*
mol formula
C28H18Fe4O12S2Se2
‚0.5C4H8O
1027.92
C24H20Fe2O6S2Se2
mol wt
738.14
cryst syst
space group
a/Å
b/Å
c/Å
monoclinic
P2(1)/n
8.609(3)
19.667(6)
13.705(3)
90
90.257(3)
90
2320.4(12)
2
triclinic
P1h
X-ray Structure Determination of 10 and 4*. Single crystals
of 10 and 4* suitable for X-ray diffraction analyses were grown
by slow evaporation of the THF/hexane solution of 10 at about
-20 °C and the CH2Cl2/hexane solution of 4* at about -4 °C,
respectively. A single crystal of 10 or 4* was mounted on a 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.30 The struc-
tures were solved by direct methods using the SHELXS-97
program31 and refined by full-matrix least-squares techniques
(SHELXL-97)32 on F2. Hydrogen atoms were located by using the
geometric method. Details of crystal data, data collections, and
structure refinements are summarized in Table 3.
10.707(7)
11.391(7)
13.432(9)
96.136(12)
97.556(10)
115.678(10)
1438.8(16)
2
R/deg
â/deg
γ/deg
V/Å3
Z
Dc/g cm-3
abs coeff/mm-1
cryst size (mm)
F(000)
1.471
2.931
1.704
3.718
0.22 × 0.20 × 0.18
0.25 × 0.20 × 0.20
1012
728
2θmax/deg
no. of rflns
no. of indep rflns
index ranges
53.02
13 009
4763
-10 e h e 10
-24 e k e 23
-17 e l e 14
1.109
52.74
8278
5772
-13 e h e 12
-12 e k e 14
-13 e l e 16
1.009
goodness of fit
Acknowledgment. We are grateful to the National Natural
Science Foundation of China and the Specialized Research Fund
for the Doctoral Program of Higher Education of China for
financial support of this work.
R
0.0620
0.0507
Rw
0.1887
0.1100
largest diff peak
0.880 and -0.372
1.013 and -0.928
and hole (e Å-3
)
was followed, except that PhSeBr (0.472 g, 2.0 mmol) was used
instead of both electrophiles CS2 and MeI. In addition, after addition
of PhSeBr the mixture was stirred for 3 h and the eluent for TLC
was CH2Cl2/petroleum ether (v/v ) 1:5). From the major orange-
red band, 9 (0.170 g, 14%) was obtained as a red solid, mp 91-93
°C. Anal. Calcd for C36H18Fe4O12Se4: C, 36.55; H, 1.52. Found:
C, 36.57; H, 1.33. IR (KBr disk): νCtO 2066 (s), 2027 (vs), 1992
(vs) cm-1. 1H NMR (CDCl3): 7.14-7.40 (m, 18H, 2C6H5, 2C6H4)
ppm. 77Se NMR (CDCl3): 277.8, 278.4 (2s, PhSe), 316.5, 316.8,
319.8 (3s, SeC6H4C6H4Se) ppm.
Supporting Information Available: Full tables of crystal data,
atomic coordinates and thermal parameters, and bond lengths and
angles for 10 and 4* in CIF format. This material is available free
of charge via the Internet at http://pubs. acs.org.
OM060238H
(30) Sheldrick, G. M. SADABS, A Program for Empirical Absorption
Correction of Area Detector Data; University of Go¨ttingen: Germany, 1996.
(31) Sheldrick, G. M. SHELXS97, A Program for Crystal Structure
Solution; University of Go¨ttingen: Germany, 1997.
(32) Sheldrick, G. M. SHELXL97, A Program for Crystal Structure
Refinement; University of Go¨ttingen: Germany, 1997.
Preparation of (4-µ-SeC6H4C6H4Se-µ-4′)[(µ-CH2SMe)Fe2-
(CO)6]2 (10). The same procedure was followed as for the