Novel μ-CO-containing butterfly Fe/S cluster anions generated from tetrathiols, Fe3(CO)12, and et3N: Their reactions with electrophiles to give neutral butterfly Fe/S cluster complexes

Article abstract of DOI:10.1021/om800225y

Tetrathiol 1,2,4,5-(HSCH₂)₄C₆H₂ reacted with Fe₃(CO)₁₂ and Et₃N followed by treatment of the intermediate μ-CO-containing tetraanion {[(μ-CO)Fe ₂(CO)₆]₄[1,2,4,5-(μ-SCH₂)4C ₆H₂]}^4- (7) with 2-furancarbonyl chloride to give quadruple-butterfly complex [μ-σ,π-C₄H ₃O)Fe₂(CO)₆]₄ [1,2,4,5-(μ- SCH₂)₄C₆H₂] (9), whereas triple-butterfly complex [(μ-Ph₂P)Fe₂(CO) ₆]₂[Fe₂(CO)₆] [1,2,4,5-(μ- SCH₂)₄C₆H₂] (11) could be produced by reaction of Ph₂PCl with the μ-CO-containing dianion {[(μ-CO)Fe₂(CO)₆]₂[Fe₂(CO) ₆][1,2,4,5-μ-SCH₂)₄C₆H ₂]}^2- (10) generated in situ from the initially formed tetraanion 7. Similarly, the triplebutterfly complexes [(μ-Ph ₂P)Fe₂(CO)₆]₂[Fe₂(CO) ₆][(μ-SCH₂)₄C] (14) and [(μ-σ,π- CH₂CH=CH₂)Fe₂(CO)₆] ₂-[Fe₂(CO)₆] [μ-SCH₂) ₄C] (16) were produced by reaction of Ph₂PCl or CH ₂=CHCH₂Br with the μ-CO-containing dianion {[(μ-CO)Fe₂(CO)₆MFe₂(CO)₆] [(μ-SCH₂)₄C]}^2- (13) formed in situ from tetraanion {[μ-CO)Fe₂(CO)₆]₄[μ-SCH ₂)₄C]}^4- (12) generated initially by reaction of tetrathiol C(CH₂SH)₄ with Fe₃(CO) ₁₂ and Et₃N. The double-butterfly complex [Fe ₂(CO)₆]₂[(μ-SCH₂)₄C] (15) derived in situ from dianion 13 was also isolated as a minor product along with major products 14 and 15. All the new complexes 9, 11, and 14-16 were characterized by elemental analysis and IR and NMR spectroscopy, as well as by X-ray crystallography for 9, 11, 14, and 15.

Full text of DOI:10.1021/om800225y

Organometallics 2008, 27, 3225–3231
3225
Novel µ-CO-Containing Butterfly Fe/S Cluster Anions Generated
from Tetrathiols, Fe3(CO)12, and Et3N: Their Reactions with
Electrophiles To Give Neutral Butterfly Fe/S Cluster Complexes
Li-Cheng Song,* Xiao-Niu Fang,† Chang-Gong Li, Jing Yan, Hai-Lin Bao, and
Qing-Mei Hu
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai UniVersity,
Tianjin 300071, People’s Republic of China
ReceiVed March 10, 2008
Tetrathiol 1,2,4,5-(HSCH2)4C6H2 reacted with Fe3(CO)12 and Et3N followed by treatment of the
intermediate µ-CO-containing tetraanion {[(µ-CO)Fe2(CO)6]4[1,2,4,5-(µ-SCH2)4C6H2]}4- (7) with 2-furan-
carbonyl chloride to give quadruple-butterfly complex [(µ-σ,π-C4H3O)Fe2(CO)6]4[1,2,4,5-(µ-SCH2)4C6H2]
(9), whereas triple-butterfly complex [(µ-Ph2P)Fe2(CO)6]2[Fe2(CO)6][1,2,4,5-(µ-SCH2)4C6H2] (11) could
be produced by reaction of Ph2PCl with the µ-CO-containing dianion {[(µ-CO)Fe2(CO)6]2[Fe2(CO)6][1,2,4,5-
(µ-SCH2)4C6H2]}2- (10) generated in situ from the initially formed tetraanion 7. Similarly, the triple-
butterfly complexes [(µ-Ph2P)Fe2(CO)6]2[Fe2(CO)6][(µ-SCH2)4C] (14) and [(µ-σ,π-CH2CHdCH2)Fe2(CO)6]2-
[Fe2(CO)6][(µ-SCH2)4C] (16) were produced by reaction of Ph2PCl or CH2dCHCH2Br with the µ-CO-
containing dianion {[(µ-CO)Fe2(CO)6]2[Fe2(CO)6][(µ-SCH2)4C]}2- (13) formed in situ from tetraanion
{[(µ-CO)Fe2(CO)6]4[(µ-SCH2)4C]}4- (12) generated initially by reaction of tetrathiol C(CH2SH)4 with
Fe3(CO)12 and Et3N. The double-butterfly complex [Fe2(CO)6]2[(µ-SCH2)4C] (15) derived in situ from
dianion 13 was also isolated as a minor product along with major products 14 and 15. All the new
complexes 9, 11, and 14-16 were characterized by elemental analysis and IR and NMR spectroscopy,
as well as by X-ray crystallography for 9, 11, 14, and 15.
anions {[(µ-CO)Fe2(CO)6]2(µ-SZS-µ)}2- (2: Z ) CH2(CH2-
OCH2)2CH2, CH2(CH2OCH2)3CH2) produced through reaction
of dithiols HSZSH with Fe3(CO)12 and Et3N,6 the triple-butterfly
three-µ-CO-containing trianions {[(µ-CO)Fe2(CO)6]3[(µ-SC-
H2CH2)3N]}3- (3) and {[(µ-CO)Fe2(CO)6]3[1,3,5-(µ-SCH2)3-
C6H3]}3- (4) yielded by reaction of trithiol N(CH2CH2SH)3 or
1,3,5-(HSCH2)3C6H3 with Fe3(CO)12 and Et3N,7 and the triple-
butterfly three-µ-CO-containing trianion {[(µ-CO)Fe2(CO)6]3[(µ-
SCH2)3CMe]}3- (5) and the double-butterfly one-µ-CO-con-
taining monoanion {[(µ-CO)Fe2(CO)6][Fe2(CO)6][(µ-SCH2)2C-
Me]}- (6) generated by reaction of trithiol MeC(CH2SH)3,
Fe3(CO)12, and Et3N8 (Scheme 1). Particularly noteworthy is that
these µ-CO-containing cluster anions have been well applied
to synthesize a great variety of acyclic, macrocyclic, and starlike
Fe/S cluster complexes.5–12
Introduction
Butterfly Fe/S cluster complexes have attracted great interest
in view of their unique structures and varied chemical
reactivities,1,2 and particularly their recent widespread uses to
serve as the structural and functional models for the active site
of [FeFe]-hydrogenases.3,4 In 1985 Seyferth first prepared the
single-butterfly one-µ-CO-containing Fe/S cluster monoanions
[(µ-CO)(µ-RS)Fe2(CO)6]- (1) via reaction of monomercaptan
RSH with Fe3(CO)12 in the presence of Et3N.5 Since then, we
have prepared various butterfly µ-CO-containing Fe/S cluster
anions, such as the double-butterfly two-µ-CO-containing di-
* To whom correspondence should be addressed. Fax: 0086-22-
23504853. E-mail: lcsong@nankai.edu.cn.
† Visiting professor, on leave from the Chemistry and Chemical
Engineering College of Jinggangshan University (China).
Recently, as a continuation of our project regarding the µ-CO-
containing Fe/S cluster anions, we carried out a study on
sequential reactions of tetrathiols C(CH2SH)4 and 1,2,4,5-
(HSCH2)4C6H2 with Fe3(CO)12, Et3N, and electrophiles. Our
initial objective in this study was to examine if the corresponding
(1) For reviews, see for example: (a) Ogino, H.; Inomata, S.; Tobita,
H. Chem. ReV. 1998, 98, 2093. (b) Bruce, M. I. J. Organomet. Chem. 1985,
283, 339. (c) Song, L.-C. Acc. Chem. Res. 2005, 38, 21.
(2) (a) Seyferth, D.; Henderson, R. S.; Song, L.-C. Organometallics
1982, 1, 125. (b) Seyferth, D.; Song, L.-C.; Henderson, R. S. J. Am. Chem.
Soc. 1981, 103, 5103. (c) Seyferth, D.; Anderson, L. L.; Villafane, F.; Cowie,
M.; Hilts, R. W. Organometallics 1992, 11, 3262. (d) Song, L.-C.; Lu, G.-
L.; Hu, Q.-M.; Fan, H.-T.; Chen, Y.; Sun, J. Organometallics 1999, 18,
3258. (e) Nametkin, N. S.; Tyurin, V. D.; Kukina, M. A. J. Organomet.
Chem. 1978, 149, 355. (f) de Beer, J. A.; Haines, R. J. J. Organomet. Chem.
1970, 24, 757. (g) Bose, K. S.; Sinn, E.; Averill, B. A. Organometallics
1984, 3, 1126.
(6) Song, L.-C.; Fan, H.-T.; Hu, Q.-M. J. Am. Chem. Soc. 2002, 124,
4566.
(7) Song, L.-C.; Cheng, J.; Hu, Q.-M.; Gong, F.-H.; Bian, H.-Z.; Wang,
L.-X. Organometallics 2005, 24, 472.
(8) Song, L.-C.; Cheng, J.; Yan, J.; Wang, H.-T.; Liu, X. F.; Hu, Q.-M.
Organometallics 2006, 25, 1544.
(3) For reviews, see for example: (a) Darensbourg, M. Y.; Lyon, E. J.;
Zhao, X.; Georgakaki, I. P. PNAS 2003, 100, 3683. (b) Liu, X.; Ibrahim,
S. K.; Tard, C.; Pickett, C. J. Coord. Chem. ReV. 2005, 249, 1641.
(4) (a) Li, H.; Rauchfuss, T. B. J. Am. Chem. Soc. 2002, 124, 726. (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) Liu, T.; Darensbourg, M. Y.
J. Am. Chem. Soc. 2007, 129, 7008.
(9) Song, L.-C.; Fan, H.-T.; Hu, Q.-M.; Yang, Z.-Y.; Sun, Y.; Gong,
F.-H. Chem.-Eur. J. 2003, 9, 170.
(10) Song, L.-C.; Gong, F.-H.; Meng, T.; Ge, J.-H.; Cui, L.-N.; Hu,
Q.-M. Organometallics 2004, 23, 823.
(11) Song, L.-C.; Cheng, J.; Gong, F.-H.; Hu, Q.-M.; Yan, J. Organo-
metallics 2005, 24, 3764.
(5) Seyferth, D.; Womack, G. B.; Dewan, J. C. Organometallics 1985,
4, 398.
(12) Seyferth, D.; Womack, G. B.; Archer, C. M.; Fackler, J. P., Jr.;
Marler, D. O. Organometallics 1989, 8, 443.
10.1021/om800225y CCC: $40.75
2008 American Chemical Society
Publication on Web 06/11/2008

3226 Organometallics, Vol. 27, No. 13, 2008
Song et al.
Scheme 1
Figure 1. Molecular structure of 9 with 30% probability level
ellipsoids.
four µ-CO-containing quadruple-butterfly tetraanions could be
initially formed and if they could further react in situ with
electrophiles to give the expected neutral butterfly Fe/S cluster
complexes. Interestingly, from this study we have prepared a
series of unexpected neutral butterfly Fe/S cluster complexes
from the initially formed four-µ-CO-containing quadruple-
butterfly tetraanions and the corresponding two-µ-CO-containing
triple-butterfly dianions generated in situ from the initially
formed tetraanions. Herein we report the results obtained from
this study.
Results and Discussion
Reactions of Tetrathiol System 1,2,4,5-(HSCH2)4C6H2/
Fe3(CO)12/Et3N with Electrophiles. Synthesis and Charac-
terization of Quadruple- and Triple-Butterfly Complexes [(µ-
σ,π-C4H3O)Fe2(CO)6]4[1,2,4,5-(µ-SCH2)4C6H2](9)and[(µ-Ph2P)-
Fe2(CO)6]2[Fe2(CO)6][1,2,4,5-(µ-SCH2)4C6H2] (11). We found that
the benzene ring-centralized tetrathiol 1,2,4,5-(HSCH2)4C6H2
could react with Fe3(CO)12 and Et3N in a 1:4:4 molar ratio in
THF at room temperature to give a brown-red solution that
containsthe[Et3NH]4saltoftetraanion{[(µ-CO)Fe2(CO)6]4[1,2,4,5-
(µ-SCH2)4C6H2]}4- (7) (Scheme 2). The IR spectrum of 7 in
solution displayed a medium absorption band at 1734 cm-1 for
its µ-CO ligands, which is very similar to those reported for
the other µ-CO-containing anions, such as monoanion 1 (R )
Et),5 dianion 2 (Z ) CH2(CH2OCH2)3CH2),9 and trianions 3
and 4.11 Further treatment of the [Et3NH]4 salt of tetraanion 7
with 2-furancarbonyl chloride resulted in formation of the
unexpected quadruple-butterfly complex 9 in 16% yield (Scheme
2). According to the well-known reaction manners of the µ-CO-
containing Fe/S cluster anions with acyl chlorides,5,9 as well as
the easy extrusion of µ-acyl CO in the R,ꢀ-unsaturated acyl
Fe/S complexes,13 we might suggest that the formation of the
starlike complex 9 is most likely via loss of the four µ-acyl
carbonyls of the expected quadruple-butterfly complex 8 (gener-
ated by nucleophilic attack of the four negatively charged Fe
Figure 2. Molecular structure of 11 with 30% probability level
ellipsoids.
atoms in 7 at the leaving group (Cl-)-attached C atoms in four
molecules of furancarbonyl chloride followed by displacement
of the four µ-CO ligands in 7) and subsequent σ,π-coordination
of the four CdC double bonds in four furan rings of 8 (Scheme
2).
It was further found that when the above-mentioned tetrathiol
system 1,2,4,5-(HSCH2)4C6H2/Fe3(CO)12/Et3N was treated with
electrophile Ph2PCl under the same conditions, the expected
quadruple-butterfly complex was not isolated, but instead, the
triple-butterfly starlike complex 11 was obtained in 20% yield
(Scheme 3). At present, we are not clear about the mechanism
for formation of complex 11. However, if considering the
previously reported transformation from trianion 5 to monoanion
6,8 we might propose a pathway to explain how product 11was
produced. The proposed pathway (Scheme 3) involves dianion
10 derived in situ from tetraanion 7 via formal loss of its two
(µ-CO)Fe(CO)3 units with their negative charges from the
neighboring two butterfly clusters of 7 followed by dimerization
of the remaining two (µ-SCH2)Fe(CO)3 units.8,14 Then, dianion
10 reacts further with electrophile Ph2PCl (through nucleophilic
attack of the negatively charged two Fe atoms in 10 at the two
(13) (a) Song, L.-C.; Liu, J.-T.; Liu, R.-G.; Wang, J.-T. Chem. J. Chin.
UniV. 1988, 9, 802. (b) Song, L.-C.; Liu, J.-T.; Wang, J.-T. Chin. J. Org.
Chem. 1989, 9, 51. (c) Song, L.-C.; Wang, R.-J.; Hu, Q.-M.; Wang, H.-G.
Chin. J. Struct. Chem. 1989, 8, 115. (d) Song, L.-C.; Liu, J.-T.; Wang,
J.-T. Acta Chim. Sin. 1990, 48, 110.

µ-CO-Containing Butterfly Fe/S Cluster Anions
Organometallics, Vol. 27, No. 13, 2008 3227
Scheme 2
Scheme 3
P atoms in two molecules of Ph2PCl) followed by displacement
of the two µ-CO ligands in 10 to give 11.
its methylene protons, respectively. The 31P NMR spectrum of
11 displayed a singlet at 141.51 ppm for P atoms in its Ph2P
groups. The molecular structures of 9 and 11 were confirmed
by X-ray diffraction analysis. Their ORTEP plots are shown in
Figures 1 and 2, whereas Table 1 lists their selected bond lengths
and angles. As can be seen in Figure 1, complex 9 contains
four identical butterfly cluster [(µ-C4H3O)Fe2(CO)6(µ-S)]4 moi-
eties, which are connected through their µ-S atoms to each R-C
atom of the central benzene ring by equatorial bonds, in order
to avoid the strong steric repulsions between these bulky
cluster moieties.2a,11 It is worthy to note that one of the CdC
double bonds in each of the bridged furan rings is coordinated
to two Fe atoms in a σ,π-manner. The bond lengths involved
in each of the coordinated furan rings are, for example,
C13-Fe1 ) 2.166 Å, C14-Fe1 ) 2.322 Å, C13-Fe2 )
1.969 Å, and C13-C14 ) 1.423 Å, which are close to those
corresponding to the reported σ,π-vinyl-coordinated diiron
complexes.15This molecule possesses a symmetric center, i.e.,
the center of the benzene ring. To our knowledge, 9 is the
first starlike quadruple-butterfly Fe/S cluster complex, al-
Starlike complexes 9 and 11 are air-stable red solids, which
have been fully characterized by elemental analysis, spectros-
copy, and X-ray diffraction techniques. The IR spectra of 9 and
11 showed three to four absorption bands in the range
1
2074-1985 cm-1 for their terminal carbonyls. The H NMR
spectrum of 9 displayed a singlet at 7.0 ppm for its benzene
ring protons, a singlet at 3.65 ppm for its methylene protons,
and three singlets in the region 4.96-7.86 ppm for its furan
ring protons, respectively. The 1H NMR spectrum of 11
exhibited a singlet at 6.91 ppm for its benzene ring protons, a
multiplet in the range 7.20-7.58 ppm for its Ph2P protons, and
one singlet and two doublets in the region 3.08-3.79 ppm for
(14) (a) Seyferth, D.; Hoke, J. B.; Womack, G. B. Organometallics 1990,
9, 2662. Similar intermolecular processes are known, by which the [Et3NH]
salts of monoanions [(µ-RE)(µ-CO)Fe2(CO)6]- (E ) S, Se) can be converted
to dimers (µ-RE)2Fe2(CO)6; see for example: (b) Song, L.-C.; Lu, G.-L.;
Hu, Q.-M.; Fan, H.-T.; Chen, J.; Sun, J.; Huang, X.-Y. J. Organomet. Chem.
2001, 627, 255.

3228 Organometallics, Vol. 27, No. 13, 2008
Song et al.
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 9, 11, 14,
and 15
9
Fe(1)-S(1)
2.298(2)
Fe(4)-S(2)
2.275(2)
Fe(2)-S(1)
Fe(1)-Fe(2)
Fe(3)-S(2)
2.261(2)
2.551(2)
2.287(2)
56.11(5)
Fe(3)-Fe(4)
2.559(2)
2.166(6)
2.322(7)
68.24(6)
55.65(4)
77.9(2)
Fe(1)-C(13)
Fe(1)-C(14)
S(2)-Fe(4)-Fe(3)
Fe(4)-S(2)-Fe(3)
S(2)-Fe(3)-Fe(4)
S(1)-Fe(1)-C(14)
S(2)-Fe(3)-C(23)
Fe(2)-C(13)-Fe(1)
C(17)-S(1)-Fe(1) 115.5(2)
Fe(2)-S(1)-Fe(1)
68.04(5)
C(21)-S(2)-Fe(3) 113.6(2)
78.6(2)
76.0(2)
S(1)-Fe(1)-Fe(2)
55.29(4)
11
Fe(1)-S(1)
2.262(2)
2.257(2)
2.522(2)
Fe(3)-S(4)
Fe(3)-Fe(4)
Fe(4)-P(1)
2.276(2)
2.549(2)
2.227(2)
2.256(2)
68.44(5)
100.7(2)
75.10(6)
54.91(5)
69.48(6)
Fe(1)-S(2)
Fe(1)-Fe(2)
Fe(3)-P(1)
S(2)-Fe(1)-S(1)
S(2)-Fe(1)-Fe(2)
S(1)-Fe(1)-Fe(2)
C(10)-S(1)-Fe(1) 114.3(2)
Fe(1)-S(1)-Fe(2)
2.24524(2) Fe(4)-S(4)
87.37(6)
55.99(4)
56.27(4)
Fe(4)-S(4)-Fe(3)
C(35)-P(1)-C(41)
P(1)-Fe(3)-S(4)
P(1)-Fe(3)-Fe(4)
Fe(4)-P(1)-Fe(3)
67.66(5)
Figure 3. Molecular structure of 14 with 30% probability level
ellipsoids.
14
Fe(3)-Fe(4)
Fe(1)-P(1)
2406(12)
2.5646(8)
2.2499(12)
2.2541(12)
2.5129(10)
83.70(4)
55.59(3)
56.65(3)
83.64(4)
Fe(1)-S(1)
2.2786(11) Fe(5)-S(3)
2.2259(12) Fe(5)-S(4)
Fe(2)-P(1)
Fe(1)-Fe(2)
P(1)-Fe(1)-S(1)
P(1)-Fe(1)-Fe(2)
S(1)-Fe(1)-Fe(2)
Fe(2)-P(1)-Fe(1)
Fe(2)-S(1)-Fe(1)
2.5730(8)
77.16(4)
54.56(3)
55.29(3)
70.35(4)
68.96(3)
Fe(5)-Fe(6)
S(3)-Fe(5)-S(4)
S(3)-Fe(5)-Fe(6)
S(4)-Fe(5)-Fe(6)
S(3)-Fe(6)-S(4)
C(45)-C(44)-C(46) 112.83(3)
15
Fe(1)-S(1)
2.319(3)
2.283(3)
1.847(11)
2.270(4)
56.02(8)
83.50(12)
55.98(10)
66.72(9)
83.04(11)
Fe(1)-Fe(2)
2.532(2)
2.286(3)
1.845(11)
1.543(14)
56.44(9)
57.26(10)
118.8(4)
67.58(9)
111.2(6)
Fe(2)-S(2)
Fe(2)-S(1)
S(1)-C(7)
Fe(1)-S(2)
S(1)-Fe(1)-Fe(2)
S(2)-Fe(2)-S(1)
S(2)-Fe(2)-Fe(1)
Fe(2)-S(1)-Fe(1)
S(2)-Fe(1)-S(1)
S(2)-C(9)
C(7)-C(8)
S(2)-Fe(1)-Fe(2)
S(1)-Fe(2)-Fe(1)
C(7)-S(1)-Fe(1)
Fe(1)-S(2)-Fe(2)
C(7)-C(8)-C(9)
knowledge, the first heterotriple-butterfly Fe/S cluster complex
reported so far.
Reactions of Tetrathiol System C(CH2SH)4/Fe3(CO)12/
Et3N with Electrophiles. Synthesis and Characterization
of Triple- and Double-Butterfly Complexes [(µ-Ph2P)Fe2-
(CO)6]2[Fe2(CO)6][(µ-SCH2)4C] (14), [Fe2(CO)6]2[(µ-SCH2)4C]
(15), and [(µ-σ,π-CH2CHdCH2)Fe2(CO)6]2[Fe2(CO)6][(µ-SC-
H2)4C] (16). The quaternary carbon atom-centralized tetrathiol
C(CH2SH)4 was found to react similarly with Fe3(CO)12 and
Et3N in a 1:4:4 molar ratio in THF at room temperature to afford
the [Et3NH]4 salt of tetraanion {[(µ-CO)Fe2(CO)6]4[(µ-
SCH2)4C]}4- (12) (Scheme 4). The IR spectrum of 12 in
solution showed a medium absorption band at 1745 cm-1 for
its µ-CO ligands, which is very similar to those corresponding
to tetraanion 7 and the other µ-CO-containing Fe/S cluster
anions.5,9,11 Similar to the above-mentioned reaction of the
tetrathiol system 1,2,4,5-(HSCH2)4C6H2/Fe3(CO)12/Et3N with
Ph2PCl, when the tetrathiol system C(CH2SH)4/Fe3(CO)12/Et3N
was treated with excess electrophile Ph2PCl or CH2dCHCH2Br,
we did not isolate the corresponding quadruple-butterfly com-
plexes, but instead, the triple-butterfly starlike complex 14 (20%)
and double-butterfly complex 15 (3%), or the corresponding
complexes 16 (21%) and 15 (5%) were isolated, respectively
(Scheme 5).
Figure 4. Molecular structure of 15 with 30% probability level
ellipsoids.
though several starlike complexes terminated with three-
butterfly Fe/S clusters are known.11
Figure 2 shows that complex 11 is different from complex
9, which includes one butterfly cluster [Fe2(CO)6(µ-S)2] unit
and two identical butterfly cluster [(µ-Ph2P)Fe2(CO)6(µ-S)]2
moieties. The former moiety is connected via its two µ-S atoms
to the two neighboring R-C atoms of the central benzene ring
by axial bonds, whereas the latter two moieties are attached to
another two neighboring R-C atoms via their µ-S atoms by
equatorial bonds.2a,11 The metal-metal bond length of Fe1-Fe2
(2.522 Å) is slightly shorter than that of Fe3-Fe4 (2.549 Å) or
Fe5-Fe6 (2.544 Å), which is obviously due to the Fe1-Fe2
bond being involved in a closed and axially bridged butterfly
Fe2S2 cluster moiety. Although the homotriple-butterfly starlike
complexes were previously reported,7,11 complex 11 is, to our
(15) (a) Song, L.-C.; Wang, R.-J.; Liu, J.-T.; Wang, H.-G.; Wang, J.-T.
Acta Chim. Sin. 1990, 48, 1141. (b) Song, L.-C.; Hu, Q.-M.; Zhou, Z.-Y.;
Liu, L. Chin. J. Struct. Chem. 1989, 8, 197.

µ-CO-Containing Butterfly Fe/S Cluster Anions
Organometallics, Vol. 27, No. 13, 2008 3229
Scheme 4
Scheme 5
Although the mechanisms for formation of complexes 14-16
are not completely understood, the possible pathways (which
are similar to that suggested for formation of complex 11) could
be proposed (Scheme 5). That is, the initially formed tetraanion
12 is first converted to dianion 13 through formal loss of its
two (µ-CO)Fe(CO)3 units with their negative charges followed
by dimerization of the remaining two (µ-SCH2)2Fe(CO)3
moieties.8,14 Then, the resulting dianion 13 reacts further with
electrophile Ph2PCl or CH2dCHCH2Br via the processes similar
to that mentioned above for formation of 11 to give products
14 and 16. The common double-butterfly complex 15 is
produced via a process similar to that suggested for formation
of dianion 13 from tetraanion 12.8,14
similar to those spectra of complex 11 and the previously
reported single-,5,16 double-,9 and triple11-butterfly Fe2PS cluster
complexes.
The molecular structures of 14 and 15 have been unequivo-
cally confirmed by X-ray diffraction techniques. While their
ORTEP drawings are depicted in Figures 3 and 4, the selected
bond lengths and angles are given in Table 1. Figure 3 shows
that starlike complex 14 consists of one butterfly Fe2S2 moiety
[Fe2(CO)6(µ-S)2] and two identical butterfly Fe2SP units [(µ-
Ph2P)Fe2(CO)6(µ-S)]2. While the former is connected via its two
µ-S atoms to the two methylene C atoms of the centralized
“pentaerythrityl” group by the axial bonds, the latter two
moieties are bound to another two methylene C atoms through
their µ-S atoms by equatorial bonds.2a,11 The bond length of
Fe5-Fe6 (2.5129 Å) in the closed cluster is shorter than those
of Fe1-Fe2 (2.5730 Å) and Fe3-Fe4 (2.5646 Å) in the two
open clusters. It follows that starlike complex 14 is virtually
isostructural with complex 11, except that they have different
central parts, that is, for 14 a quaternary C atom-centralized
organic group, but for 11 a benzene ring-centralized group. It
can be seen in Figure 4 that complex 15 is centrosymmetric
Complexes 14-16 are also air-stable red solids and charac-
terized by elemental analysis and spectroscopy. The IR spectra
of 14-16 displayed four absorption bands in the range
1
2076-1980 cm-1 for their terminal carbonyls. The H NMR
spectra of 14-16 exhibited a singlet in the range 2.18-2.52
ppm for their µ-SCH2 groups, and that of 16 showed two
additional doublets at ca. 0.6 and ca. 2 ppm for the anti and
syn protons of the CH2 groups in its two allyl ligands. The 31
P
(16) Winter, A.; Zsolnai, Z.; Huttner, G. J. Organomet. Chem. 1983,
250, 409.
NMR spectrum of 14 (showing a singlet at 141.29 ppm) is very

3230 Organometallics, Vol. 27, No. 13, 2008
Song et al.
Table 2. Crystal Data and Structure Refinement Details for 9, 11, 14, and 15
9
11
14
15
C8.5H4Fe2O6S2
mol formula
C50H22Fe8O28S4 ·
2CHCl3
1884.45
monoclinic
P2(1)/c
C52H30Fe6O18P2S4
C47H28Fe6O18P2S4
mol wt
cryst syst
space group
a/Å
b/Å
c/Å
1468.04
triclinic
1405.97
monoclinic
C2/c
377.94
orthorhombic
lba2
j
P1
13.241(6)
26.387(12)
11.576(5)
90
115.037(7)
90
3665(3)
2
1.708
1.945
1868
-16 e h e 16
-19 e k e 32
-14 e l e 13
20 611
12.876(1)
14.861(2)
17.022(2)
103.426(1)
94.687(1)
108.111(1)
2969.2(4)
2
1.642
1.690
1472
-15 e h e 15
-17 e k e 17
-20 e l e 20
17 871
13.7796(17)
20.849(3)
40.694(5)
90
94.807(2)
90
11650(3)
8
1.603
1.719
5712
-17 e h e 17
-26 e k e 20
-50 e l e 47
32 686
11.825(10)
17.627(15)
12.708(12)
90
90
90
2649(4)
8
1.895
2.519
1496
R/deg
ꢀ/deg
γ/deg
V/Å3
Z
Dc/g cm-3
abs coeff/mm-1
F(000)
index ranges
-8 e h e 14
-19 e k e 20
-12 e l e 15
5949
no. of rflns
no. of indep rflns
7456
9664
11 909
2076
2θmax/deg
R
52.90
0.0515
50.00
0.0482
52.76
0.0465
50.02
0.0723
Rw
0.1299
0.0707
0.0919
0.1806
goodness of fit
1.017
0.990/-0.871
1.051
0.419/-0.369
0.940
0.398/-0.351
1.037
1.467/-1.016
largest diff peak and hole/e Å-3
Na/benzophenone ketyl under nitrogen. Fe3(CO)12,17 1,2,4,5-
(HSCH2)4C6H2,18 C(CH2SH)4,19 and furancarbonyl chloride C4H3-
OC(O)Cl20 were prepared according to literature procedures. Et3N,
Ph2PCl, and CH2dCHCH2Br were of commercial origin and used
without further purification. Preparative TLC was carried out on
glass plates (25 × 15 × 0.25) coated with silica gel G (10-40
µm). IR spectra were recorded on a Bio-Rad FTS 135 infrared
spectrophotometer. 1H (31P) NMR spectra were taken on a Bruker
Avance 300 NMR spectrometer. Elemental analyses were performed
with an Elementar Vario EL analyzer. Melting points were
determined on a Yanaco MP-500 apparatus and were uncorrected.
with respect to atom C8 and consists of two identical butterfly
Fe2S2 clusters [Fe2(CO)6(µ-S)2]2 joined together through the four
methylene C atoms of the “pentaerythrityl” bridge by axial
bonds C7-S1, C9-S2, C7A-S1A, and C9A-S2A. The
metal-metal bond lengths of Fe1-Fe2 ) Fe1A-Fe2A (2.532
Å) are very close to those corresponding to the closed Fe2S2
butterfly clusters of starlike complexes 11 and 14.
Conclusions
Preparation of [(µ-σ,π-C4H3O)Fe2(CO)6]4[1,2,4,5-(µ-SCH2)4C6H2]
(9). A mixture of 1,2,4,5-(HSCH2)4C6H2 (0.100 g, 0.38 mmol),
Fe3(CO)12 (0.75 g, 1.49 mmol), Et3N (0.21 mL, 1.50 mmol), and
THF (20 mL) was stirred at room temperature for 0.5 h to give a
brown-red solution. To this solution was added C4H3C(O)Cl (0.15
mL, 1.50 mmol), and the new mixture was stirred at room
temperature for 24 h. After solvent was removed at reduced
pressure, the residue was subjected to TLC using petroleum ether/
CH2Cl2 (3:1 v/v) as eluent to develop a major red band with many
tiny bands such as the purple, green, and orange bands. From the
major red band, 9 (0.096 g, 16%) was obtained as a red solid, mp
171 °C (dec). Anal. Calcd for C50H22Fe8O28S4: C, 36.49 H, 1.35.
The sequential reactions of tetrathiols with Fe3(CO)12 and
Et3N followed by treatment with electrophiles are first inves-
tigated. It has been found that (i) tetrathiol 1,2,4,5-
(HSCH2)4C6H2 or C(CH2SH)4 reacts with Fe3(CO)12 and Et3N
in a molar ratio of 1:4:4 to give the µ-CO-containing quadruple-
butterfly tetraanions 7 and 12, (ii) quadruple-butterfly complex
9 can be produced by direct reaction of tetraanion 7 with
furancarbonyl chloride followed by CO extrusion and CdC
double bond coordination of the thermodynamically unstable
complex 8, (iii) tetraanions 7 and 12 can be in situ converted
to the µ-CO-containing triple-butterfly dianions 10 and 13,
respectively, (iv) while dianion 10 reacts with Ph2PCl to give
triple-butterfly complex 11, reaction of dianion 13 with Ph2PCl
or CH2dCHCH2Br affords triple-butterfly complexes 14 and
16, respectively, and (v) double-butterfly complex 15 derived
in situ from dianion 13 can be isolated as a minor product along
with major products 14 and 16. Further studies on the proposed
pathways for formation of products 9, 11, and 14-16, and
particularly on the chemical reactivities of the µ-CO-containing
anions 7, 10, 12, and 13 involved in the suggested pathways,
are in progress in our laboratory.
Found: 36.21; H, 1.39. IR (KBr disk) νCt 2073 (s), 2035 (vs),
O
1995 (vs) cm-1. 1H NMR (300 MHz, CDCl3): 3.65 (s, 8H, 4CH2S),
4.96 (s, 4H, 4CHFe), 6.25 (s, 4H, 4CHCHO), 7.01 (s, 2H, C6H2),
7.86 (s, 4H, 4CHO) ppm.
Preparation of [(µ-Ph2P)Fe2(CO)6]2[Fe2(CO)6][1,2,4,5-(µ-SCH2)4-
6H2] (11). The same procedure was followed as for 9, but Ph2PCl
C
(0.27 mL, 1.50 mmol) was used instead of C4H3C(O)Cl. From the
major red band, 11 (0.110 g, 20%) was obtained as a red solid, mp
183 °C (dec). Anal. Calcd for C52H30Fe6O18P2S4: C, 42.54; H, 2.06.
Found: 42.30; H, 2.16. IR (KBr disk): νCt 2074 (s), 2059 (s),
O
1
2021 (vs), 1985 (vs) cm-1. H NMR (300 MHz, CDCl3): 3.59 (s,
Experimental Section
(17) King, R. B. Organometallic Syntheses, Transition-Metal Com-
pounds; Academic Press: New York, 1965; Vol. I, p 95.
(18) Vinod, T.; Hart, H. J. Org. Chem. 1990, 55, 881.
(19) Shostakovskii, M. F.; Atavin, A. S.; Mirskova, A. M. Zh. Obshch.
Khim. 1965, 35, 807.
General Comments. All reactions were carried out under an
atmosphere of prepurified nitrogen by using standard Schlenk and
vacuum-line techniques. Tetrahydrofuran (THF) was distilled from

µ-CO-Containing Butterfly Fe/S Cluster Anions
Organometallics, Vol. 27, No. 13, 2008 3231
4H, 2CH2SFe2P), 3.08, 3.79 (2d, J ) 12.0 Hz, 4H, 2CH2SFe2),
6.91 (s, 2H, C6H2), 7.20-7.58 (m, 20H, 4C6H5) ppm. 31P NMR
(121.48 MHz, CDCl3, 85% H3PO4): 141.51 (s) ppm.
hexane solutions at about 4 and -20 °C, respectively. A single
crystal of 9, 14, or 15 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.21 The structures were solved
by direct methods using the SHELXS-97 program22 and refined
by full-matrix least-squares techniques (SHELXL-97)23 on F2.
Hydrogen atoms were located by using the geometric method.
Details of crystal data, data collections, and structure refinements
of 9, 14, and 15 are summarized in Table 2.
X-ray Structure Determination of 11. The single crystals of
11 suitable for X-ray diffraction analysis were grown by slow
evaporation of their CHCl3/hexane solutions at about 4 °C and were
mounted on a Bruker APEX-II CCD diffractometer. Data were
collected at 296(2) K, 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.
The structure was solved by direct methods and subsequently refined
by full-matrix least-squares techniques on F2. Hydrogen atoms were
located by using the geometric method, and non-hydrogen atoms
were refined anisotropically. All software programs employed are
from the Bruker AXS APEX2 software package.24 Details of crystal
data, data collection, and structure refinement of 11 are summarized
in Table 2.
Preparation of [(µ-Ph2P)Fe2(CO)6]2[Fe2(CO)6][(µ-SCH2)4C] (14)
and [Fe2(CO)6]2[(µ-SCH2)4C] (15). A mixture of C(CH2SH)4 (0.200
g, 1.0 mmol), Fe3(CO)12 (2.00 g, 4.0 mmol), Et3N (0.55 mL, 4.0
mmol), and THF (60 mL) was stirred at room temperature for 0.5 h
to give a brown-red solution. To this solution was added Ph2PCl
(1.44 mL, 8.0 mmol), and the new mixture was stirred at room
temperature for 24 h. Solvent was removed at reduced pressure
and the residue was subjected to TLC using petroleum ether/CH2Cl2
(4:1 v/v) as eluent to develop a major red band and a small orange
band along with several tiny purple, yellow, orange-red, and brown
bands. From the lower major red band, 14 (0.310 g, 22%) was
obtained as a red solid, mp 101-103 °C. Anal. Calcd for
C47H28Fe6O18P2S4: C, 40.15; H, 2.01. Found: 39.98; H, 2.25. IR
(KBr disk): νCt 2075 (s), 2062 (s), 2024 (vs), 1984 (vs) cm-1
.
O
1H NMR (300 MHz, CDCl3): 2.30 (s, 4H, 2CH2SFe2), 2.51 (s, 4H,
2CH2SFe2P), 7.18-7.55 (m, 20H, 4C6H5) ppm. 31P NMR (121.48
MHz, CDCl3, 85% H3PO4): 141.29 (s) ppm. From the upper small
orange band, 15 (0.024 g, 3%) was obtained as a red solid, mp
180 °C (dec). Anal. Calcd for C17H8Fe4O12S4: C, 27.01; H, 1.07.
Found: C, 27.15; H, 1.23. IR (KBr disk): νCt 2076 (vs), 2038
O
(vs), 1997 (vs), 1980 (vs) cm-1. 1H NMR (300 MHz, CDCl3): 2.18
(s, 8H, 4CH2S) ppm.
Preparation of [(µ-σ,π-CH2CHdCH2)Fe2(CO)6]2[Fe2(CO)6][(µ-
SCH2)4C] (16) and 15. The same procedure was followed as for
14 and 15, but CH2dCHCH2Br (0.70 mL, 8.0 mmol) was utilized
in place of Ph2PCl. From the lower major red band, 16 (0.235 g,
21%) was obtained as a red solid, mp 240 °C (dec). Anal. Calcd
for C29H18Fe6O18S4: C, 31.16; H, 1.62. Found: C, 31.07; H, 1.86.
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.
IR (KBr disk): νCt O 2075 (s), 2065 (s), 2028 (vs), 1981 (vs) cm-1
.
Supporting Information Available: Full tables of crystal data,
atomic coordinates and thermal parameters, and bond lengths and
angles for 9, 11, 14, and 15. This material is available free of charge
via the Internet at http://pubs.acs.org.
1H NMR (300 MHz, CDCl3): 0.58 (d, J ) 13.2 Hz, 4H, 4 anti-
FeC HH), 2.04 (d, J ) 6.9 Hz, 4H, 4 syn-FeCH H), 2.42 (s, 4H,
2CH2SFe2), 2.52 [s, 4H, 2CH2SFe2 (allyl)], 4.85-5.05 (m, 2H,
2CH) ppm. From the upper small orange band, 15 (0.038 g, 5%)
was obtained.
OM800225Y
X-ray Structure Determinations of 9, 14, and 15. While single
crystals of 9 suitable for X-ray diffraction analysis were grown by
slow evaporation of its CHCl3/hexane solution at about 4 °C, those
of 14 and 15 were produced by slow evaporation of their CH2Cl2/
(21) Sheldrick, G. M. SADABS, A Program for Empirical Absorption
Correction of Area Detector Data; University of Go¨ttingen: Germany, 1996.
(22) Sheldrick, G. M. SHELXS-97, A Program for Crystal Structure
Solution; University of Go¨ttingen, Germany, 1997.
(23) Sheldrick, G. M. SHELXL-97, A Program for Crystal Structure
Refinement; University of Go¨ttingen, Germany, 1997.
(24) APEX2 Software Suite, Version 1.22; Bruker AXS: Madison, WI,
2004.
(20) Chadwick, D. J.; McKnight, M. V.; Ngochindo, R. J. Chem. Soc.,
Perkin Trans. 1 1982, 1343.