Synthesis, structure and formation pathways of new Fe-S complexes containing [Fe2S2]-units in different valences, [Fe2S2(CO)4(PPh3) 2], [Fe3S2(CO)6 (PPh3)3] and [Fe4S2(CO) 10]2-

Article abstract of DOI:10.1016/j.jorganchem.2004.05.036

Novel Fe-S cluster complexes, Fe₂S₂ (CO)₄(PPh₃)₂] (1), [Fe₃ S₂(CO)₆(PPh₃)₃] (2) and [Ph₄P]₂[Fe₄S₂(CO) ₁₀] (3) have been synthesized by the reaction of LiEt₃BH with [Fe₂S₂(CO)₆] in the presence of CuCl-PPh₃, AgNO₃ -PPh₃ and CuClO₃-MeCN, respectively.Structure determination indicated that 1, 2 and 3, respectively, possessed [Fe₂S₂]⁰ core with [Fe₂ S₂]⁰-unit, [Fe₃S₂] ⁰ with [Fe₂S₂]^2- and [Fe₄S₂]^2- core with [Fe₂ S₂]^4- unit, which implied that [Fe₂ S₂(CO)₆]^2-, as a starting material, underwent a disproportionation in the synthetic reaction. Investigating the structure and synthetic reaction, an origin of the different valence[Fe₂S₂]-units and formation pathways of those clusters via disproportionation of the [Fe₂ S₂(CO)₆]^2- following by 'Unit Construction' were proposed and discussed. Elsevier B.V. All rights reserved.

Full text of DOI:10.1016/j.jorganchem.2004.05.036

Journal of Organometallic Chemistry 689 (2004) 2674–2683
www.elsevier.com/locate/jorganchem
Synthesis, structure and formation pathways of new Fe–S
complexes containing [Fe2S2]-units in different valences,
[Fe2S2(CO)4(PPh3)2], [Fe3S2(CO)6(PPh3)3] and [Fe4S2(CO)10]2À
and the origin of the [Fe2S2]-unit in metal–[Fe2S2(CO)6] complexes
*
Botao Zhuang , Jun Chen, Lingjie He, Jiutong Chen, Zhangfeng Zhou, Kechen Wu
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter,
Chinese Academy of Sciences, Fuzhou, Fujian 350002, China
Received 10 March 2004; accepted 28 May 2004
Available online 3 July 2004
Abstract
Novel Fe–S cluster complexes, [Fe2S2(CO)4(PPh3)2] (1), [Fe3S2(CO)6(PPh3)3] (2) and [Ph4P]2[Fe4S2(CO)10] (3) have been
synthesized by the reaction of LiEt3BH with [Fe2S2(CO)6] in the presence of CuCl–PPh3, AgNO3–PPh3 and CuClO3–MeCN, respec-
tively.Structure determination indicated that 1, 2 and 3, respectively, possessed [Fe2S2]0 core with [Fe2S2]0-unit, [Fe3S2]0 with
[Fe2S2]2À and [Fe4S2]2À core with [Fe2S2]4À unit, which implied that [Fe2S2(CO)6]2À, as a starting material, underwent a dispropor-
tionation in the synthetic reaction.Investigating the structure and synthetic reaction, an origin of the different valence[Fe2S2]-units
and formation pathways of those clusters via disproportionation of the [Fe2S2(CO)6]2À following by ꢀUnit Constructionꢀ were pro-
posed and discussed.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Fe–S complex; [Fe2S2]-unit; Synthesis and structure; Formation pathway
1. Introduction
It has been found that the cluster complexes containing
[Fe2S2]-units from the reaction involving [Fe2S2(CO)6] re-
agent may possess two type conformations of [Fe2S2],
Plane type, for example, in [MFe2S2(CO)8dtc]À
(M=Mo, W; dtc=S2CNEt2), [15] and butterfly type, for
instance, in [VFe4S4(CO)12] [16], [MoOFe5S6(CO)12]2À
[3], and [Cu5Fe6S6(CO)18(PPh3)2]À [8], and the valence
of Fe in their [Fe2S2]-units can be 0, +1 and +2. Herein
is reported synthesis and structures of new Fe–S cluster
complexes containing different valence [Fe2S2]-units,
[Fe2S2(CO)4(PPh3)2] (1), [Fe3S2(CO)6(PPh3)3] (2) and
[Ph4P]2[Fe4S2(CO)10] (3), which implies the existence of
[Fe2S2(CO)6]0 and [Fe2S2(CO)6]4À species in the reaction
system involving [Fe2S2(CO)6]2À, the origin of the
{Fe2S2}-unit in metal–[Fe2S2(CO)6] cluster and forma-
tion pathway of the complexes were discussed.
The chemistry of [Fe2S2(CO)6] has greatly interested
chemists and bio-inorganic chemists because the reac-
tion with participation of [Fe2S2(CO)6] or [Fe2S2
(CO)6]2À results in a variety of mixed-metal and mixed
valence cluster complexes containing different [Fe2S2]-
units which are very useful for investigation on the
active center in metal enzymes and synthesis of novel
poly-nuclear metal cluster compounds which possess
novel structural conformation and significant physical
and chemical properties [1–14].
*
Corresponding author. Tel.: +86-591-3792464; fax: +86-591-
3714946.
E-mail address: zbt@fjirsm.ac.cn (B. Zhuang).
0022-328X/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.05.036

B. Zhuang et al. / Journal of Organometallic Chemistry 689 (2004) 2674–2683
2675
Table 1
Selected bond distances (A) and bond angles (ꢁ) of complex 1
2. Results and discussion
˚
2.1. Synthesis
Bond distances
Fe(1)–C(1)
Fe(1)–C(2)
Fe(1)–P(1)
Fe(1)–S(1)
Fe(1)–S(2)
Fe(1)–Fe(2)
Fe(2)–C(3)
Fe(2)–C(4)
1.754(5)
1.758(5)
2.247(1)
2.275 (1)
2.275 (1)
2.5374(8)
1.762(5)
1.768(5)
Fe(2)–P(2)
Fe(2)–S(1)
Fe(2)–S(2)
C(1)–O(1)
C(2)–O(2)
C(3)–O(3)
C(4)–O(4)
2.244 (1)
2.272(1)
2.271(1)
1.149(6)
1.150(6)
1.130(6)
1.144(6)
New Fe–S cluster complexes containing different
valence [Fe2S2]-units, [Fe2S2(CO)4(PPh2)2] (1), [Fe3S2
(CO)6(PPh3)3] (2) and [Ph4P]2[Fe4S2(CO)10] (3) were
synthesized by the reaction of [Fe2S2(CO)6] with
LiEt3BH in the presence of CuClÆPPh3, AgNO3–PPh3
and CuClO3 ÆMeCN, respectively. Complex 2 also was
prepared by reaction of [Fe2S2(CO)6] with LiEt3BH in
the presence of PPh3.
Bond angles
C(1)–Fe(1)–C(2)
C(1)–Fe(1)–P(1)
C(2)–Fe(1)–P(1)
C(1)–Fe(1)–S(2)
C(2)–Fe(1)–S(2)
P(1)–Fe(1)–S(2)
C(1)–Fe(1)–S(1)
C(2)–Fe(1)–S(1)
P(1)–Fe(1)–S(1)
S(2)–Fe(1)–S(1)
C(1)–Fe(1)–Fe(2)
C(2)–Fe(1)–Fe(2)
P(1)–Fe(1)–Fe(2)
S(2)–Fe(1)–Fe(2)
S(1)–Fe(1)–Fe(2)
C(3)–Fe(2)–C(4)
C(3)–Fe(2)–P(2)
C(4)–Fe(2)–P(2)
92.6(2)
96.9(2)
C(3)–Fe(2)–S(2)
C(4)–Fe(2)–S(2)
P(2)–Fe(2)–S(2)
C(3)–Fe(2)–S(1)
C(4)–Fe(2)–S(1)
P(2)–Fe(2)–S(1)
Fe(2)–S(1)–Fe(1)
Fe(2)–S(2)–Fe(1)
S(2)–Fe(2)–S(1)
C(3)–Fe(2)–Fe(1)
C(4)–Fe(2)–Fe(1)
P(1)–Fe(2)–Fe(1)
S(2)–Fe(2)–Fe(1)
S(1)–Fe(2)–Fe(1)
O(1)–C(1)–Fe(1)
O(2)–C(2)–Fe(1)
O(3)–C(3)–Fe(2)
O(4)–C(4)–Fe(2)
87.0(2)
157.9(2)
102.45(5)
160.0(2)
92.7(2)
Ph P
3
PPh
3
100.6(2)
87.2(2)
S
PPh
S
S
3
Fe(CO)
(OC) Fe
2
2
Fe(CO)
(OC) Fe
2
S
2
155.7(2)
103.51(4)
161.9(2)
90.6(2)
98.62(5)
67.83(4)
67.86(4)
82.81(5)
104.0(2)
103.5(2)
146.04(4)
56.14(3)
56.15(3)
179.3(5)
177.8(4)
179.0(4)
178.6(5)
Ph P
3
Ph P
3
Fe
(CO)
(1)
2
100.03(4)
82.66(5)
105.9(2)
101.0(2)
147.57(4)
56.00(3)
56.02(3)
90.3(2)
(2)
S
(OC) Fe
2
Fe(CO)
3
[Ph P]
4
2
(OC) Fe
3
Fe(CO)
2
100.4(2)
99.6(2)
S
(3)
It is remarkable that complexes 1, 2 and 3 do not pos-
sess any other metal atoms but iron atoms. This implies
that the synthetic reaction of complexes 1, 2 and 3 does
not have the participation of CuCl, AgNO3 and Cu-
ClO3. The formation pathways of these complexes will
be discussed later.
2.2. The crystal structure of [Fe2S2(CO)4(PPh3)2] (1)
The selected bond distances and bond angles of
complex 1 are listed in Table 1 and the molecular
structure of complex 1 was depicted in Fig. 1. As shown
in Table 1 and Fig. 1, complex 1 contains a ꢀbutterflyꢁ
type [Fe2S2]0 core with FeII. Around each iron of the
core there are two carbonyls and a PPh3- ligand
resulting in six coordination of the iron atom if con-
sidering the Fe–Fe bonding. Fe–Fe bond length is
Fig. 1. The structure of compound [Fe2S2(CO)4(PPh3)2] (1).
of [Fe2S2(CO)6]2À [15] in the synthetic reaction
system.
˚
2.5374(8) A indicating the interaction between Fe
and Fe atoms. Fe–S bond distances are 2.275(1),
˚
2.275(1), 2.271(1) and 2.272(1) A. The dihedral angle
2.3. The structure of [Fe3S2(CO)6(PPh3)3] (2)
between the plane Fe1S2Fe2 and Fe1S1Fe2 is 74.42ꢁ
indicating that the core [Fe2S2] is in butterfly type
configuration. Evidently, complex 1 should come from
a [FeII2S2(CO)6]0-specie which undergoes substitution
of carbonyl by PPh3-ligand. Thus, the isolation of
complex 1 strongly verified the existence of the species
[FeII2S2(CO)6]0 which results from disproportionation
In the crystals of complex 2, [Fe3S2(CO)6(PPh3)3] com-
plexes and H2O molecules salvation are present. Selected
bond distances and bond angles of complex 2 are listed in
Table 2 and the molecular structure of complex 2 is de
picted in Fig. 2. As is shown in Table 2 and Fig. 2,
complex 2, [Fe3S2(CO)6(PPh3)3], contains a distorted
squre-pyramid [Fe3S2]-core with
a
pseudo-planar

2676
B. Zhuang et al. / Journal of Organometallic Chemistry 689 (2004) 2674–2683
Table 2
˚
Selected bond distances (A) and bond angles (ꢁ) of complex 2Æ1/2H2O
Bond distances
Fe(1)–C(2)
Fe(1)–C(1)
Fe(1)–P(1)
Fe(1)–S(1)
Fe(1)–S(2)
Fe(1)–Fe(2)
Fe(1)–Fe(3)
Fe(2)–C(4)
Fe(2)–C(3)
Fe(2)–S(2)
Fe(2)–S(1)
Fe(2)–P(2)
1.771(6)
1.785(6)
2.245(1)
2.261(2)
2.266(1)
2.608(1)
2.653(1)
1.750(6)
1.769(6)
2.231(1)
2.274(2)
2.281(2)
Fe(3)–C(6)
Fe(3)–C(5)
Fe(3)–P(3)
Fe(3)–S(1)
Fe(3)–S(2)
O(1)–C(1)
O(2)–C(2)
O(3)–C(3)
O(4)–C(4)
O(5)–C(5)
O(6)–C(6)
1.763(6)
1.794(6)
2.233(1)
2.246(1)
2.256(2)
1.129(6)
1.153(7)
1.159(7)
1.151(6)
1.135(6)
1.151(6)
Bond angles
C(2)–Fe(1)–C(1)
C(2)–Fe(1)–P(1)
C(1)–Fe(1)–P(1)
C(2)–Fe(1)–S(1)
C(1)–Fe(1)–S(1)
P(1)–Fe(1)–S(1)
C(2)–Fe(1)–S(2)
C(1)–Fe(1)–S(2)
P(1)–Fe(1)–S(2)
S(1)–Fe(1)–S(2)
C(2)–Fe(1)–Fe(2)
C(1)–Fe(1)–Fe(2)
P(1)–Fe(1)–Fe(2)
S(1)–Fe(1)–Fe(2)
S(2)–Fe(1)–Fe(2)
C(2)–Fe(1)–Fe(3)
C(1)–Fe(1)–Fe(3)
P(1)–Fe(1)–Fe(3)
S(1)–Fe(1)–Fe(3)
S(2)–Fe(1)–Fe(3)
Fe(2)–Fe(1)–Fe(3)
C(4)–Fe(2)–C(3)
C(4)–Fe(2)–S(2)
C(3)–Fe(2)–S(2)
C(4)–Fe(2)–S(1)
C(3)–Fe(2)–S(1)
S(2)–Fe(2)–S(1)
C(4)–Fe(2)–P(2)
C(3)–Fe(2)–P(2)
S(2)–Fe(2)–P(2)
S(1)–Fe(2)–P(2)
99.6(3)
89.1(2)
91.9(2)
C(4)–Fe(2)–Fe(1)
C(3)–Fe(2)–Fe(1)
S(2)–Fe(2)–Fe(1)
S(1)–Fe(2)–Fe(1)
P(2)–Fe(2)–Fe(1)
C(6)–Fe(3)–C(5)
C(6)–Fe(3)–P(3)
C(5)–Fe(3)–P(3)
C(6)–Fe(3)–S(1)
C(5)–Fe(3)–S(1)
P(3)–Fe(3)–S(1)
C(6)–Fe(3)–S(2)
C(5)–Fe(3)–S(2)
P(3)–Fe(3)–S(2)
S(1)–Fe(3)–S(2)
C(6)–Fe(3)–Fe(1)
C(5)–Fe(3)–Fe(1)
P(3)–Fe(3)–Fe(1)
S(1)–Fe(3)–Fe(1)
S(2)–Fe(3)–Fe(1)
Fe(3)–S(1)–Fe(1)
Fe(3)–S(1)–Fe(2)
Fe(1)–S(1)–Fe(2)
Fe(2)–S(2)–Fe(3)
Fe(2)–S(2)–Fe(1)
Fe(3)–S(2)–Fe(1)
O(1)–C(1)–Fe(1)
O(2)–C(2)–Fe(1)
O(3)–C(3)–Fe(2)
O(4)–C(4)–Fe(2)
O(5)–C(5)–Fe(3)
O(6)–C(6)–Fe(3)
149.5(2)
100.1(2)
55.18(4)
54.67(4)
113.65(5)
92.8(2)
111.9(2)
147.8(2)
95.37(5)
109.4(2)
85.3(2)
94.0(2)
92.7(2)
Fig. 2. The structure of compound [Fe3S2(CO)6(PPh3)3] (2).
161.49(6)
77.96(5)
75.3(2)
149.7(2)
88.0(2)
116.21(6)
96.5(2)
dination for Fe(2) and Fe(3) if considering the Fe–Fe
bonding. It is worth pointing out that the two PPh3 lig-
ands on the Fe atoms of the base in complex 2 adopted
equatorial-axial coordination mode which was the same
as that observed in [Fe3Te2(CO)7 (PPh3)2 [17], [Ru3Te2
(CO)6(PPh3)3] [18] and Fe3S2(CO)7(PiPr3)2 [19] and dif-
ferent from the equatorial-equatorial coordination
scheme observed in selenido-analog [Fe3Se2(CO)7
(PPh3)2] [20]. Complex 2 contains 50 skeleton electrons
and possesses two Fe–Fe bonds indicating that its struc-
ture precisely obeys the 2(9NÀL) (N=number of metal
atoms and L=number of metal–metal bonds)rule [21].
To our knowledge, the iron–chalcogen–carbonyl analogs
reported so far, for example, [Fe3S2(CO)9] [22], [Fe3Se2
(CO)9] [23], [Fe3Te2(CO)9] [24], [Fe3S2(CO)8 PCl2SPh]
[25], [Fe3S2(CO)8PPh3] [26], [Fe3Te2(CO)9 (PPh3)] [24b],
[Fe3S2(CO)8P(SPh3)] [27], [Fe3S2 (CO)7(Pi Pr3)2] [19],
[Fe3Se2(CO)7(PPh2C2H4 PPh2)] [28], [Fe3Se2(CO)7
(PPh3)2] [20] and [Fe3Te2(CO)7(PPh3)2] [17] are unsubsti-
tuted, mono-substituted and di-substituted cluster com-
plexes, trisubstituted one like complex 2 containing
three substituting PPh3-ligands has not been seen in the
literature.
131.7(2)
135.10(5)
55.14(4)
53.93(4)
157.5(2)
94.2(2)
165.7(2)
97.56(5)
78.48(5)
98.5(2)
113.6(2)
150.14(5)
54.20(4)
54.24(4)
72.12(5)
99.90(5)
70.20(5)
100.95(6)
70.90(4)
71.87(4)
178.0(5)
173.3(5)
173.3(7)
174.9(5)
177.0(5)
177.1(5)
108.26(5)
53.68(4)
53.89(4)
82.25(3)
94.5(3)
110.4(2)
154.4(2)
98.3(2)
92.5(2)
78.40(5)
90.6(2)
97.3(2)
88.58(5)
166.14(6)
Fe(2)S(1)Fe(3)S(2) rhombus with dihedral angle of 17.7ꢁ
as the base and Fe(1) atom on the apex. In the base, the
Fe–S bond distances are 2.231(2), 2.246(2), 2.256(2)
˚
and 2.274(2) A, and the Fe(2)Á Á ÁFe(3) bond distance is
A butterfly type [Fe2S2]-unit with Fe–Fe bond of
˚
[Fe2S2]2À-unit of [Fe2S2(CO)6] (Fe–Fe, 2.59 A and
˚
3.460 A indicating non-metal–metal bonding. In the rest,
the Fe(1)–S(1) and Fe(1)–S(2) are 2.261(2) and 2.266(1)
˚
2.60 A and Fe–S of 2.57 A comparable with the
˚
˚
A, respectively, and the Fe(1)–Fe(2) and Fe(1)–Fe(3)
˚
bond distances are 2.608(1) and 2.653(1) A, respectively.
˚
Fe–S, 2.28 A) [1,2] in complex 2.
The core structure also could be considered as two butter-
fly type [Fe2S2]-unit sharing three atoms (S(1), S(2) and
Fe(1)). There are two terminal carbonyls and a PPh3-lig-
and connecting to each iron atom of the core forming the
iron atoms in seven coordination for Fe(1) and six coor-
2.4. The structure of [Ph4P]2[Fe4S2(CO)10] (3)
Selected bond distances and bond angles of com-
pound 3 are listed in Table 3 and the molecular struc-
ture of the anion of compound 3 is depicted in Fig. 3.

B. Zhuang et al. / Journal of Organometallic Chemistry 689 (2004) 2674–2683
2677
Table 3
˚
Selected bond distances (A) and bond angles (ꢁ) of complex 3
Bond distances
Fe(1)–C(1)
Fe(1)–C(2)
Fe(1)–S#
1.756(4)
1.764(4)
2.213(1)
2.213(1)
Fe(2)–S#
2.173(1)
2.6121(6)
2.173(1)
2.213(1)
1.160(5)
1.160(5)
1.147(5)
1.145(4)
1.138(4)
Fe(2)–Fe(1)#
S–Fe(2)#
S–Fe(1)#
Fe(1)–S
Fe(1)–Fe(1)#
Fe(1)–Fe(2)
Fe(1)–Fe(2)#
Fe(2)–C(4)
Fe(2)–C(5)
Fe(2)–C(3)
2.5250(9) C(1)–O(1)
2.6075(6) C(2)–O(2)
2.6121(6) C(3)–O(3)
1.771(4)
1.784(4)
1.792(4)
C(4)–O(4)
C(5)–O(5)
Bond angles
C(1)–Fe(1)–C(2)
C(1)–Fe(1)–S#
C(2)–Fe(1)–S#
C(1)–Fe(1)–S
93.8(2)
99.6(2)
C(4)–Fe(2)–C(5)
C(4)–Fe(2)–C(3)
C(5)–Fe(2)–C(3)
C(4)–Fe(2)–S#
C(5)–Fe(2)–S#
99.4(2)
98.5(2)
100.3(2)
103.2(1)
99.8(1)
147.4(1)
99.4(1)
150.9(1)
98.6(1)
54.23(3)
153.8(1)
97.7(1)
97.8(1)
53.16(3)
125.6(1)
128.0(1)
101.2(1)
Fig. 3. The structure of the anion of compound [Ph4P]2[Fe4S2(CO)10] (3).
C(2)–Fe(1)–S
S#–Fe(1)–S
110.42(3) C(3)–Fe(2)–S#
Fe(1)–S–Fe(1)–S# plane are zero and the rest Fe atoms
˚
with shorter Fe–S bond distances (2.173 A) at both sides
C(1)–Fe(1)–Fe(1)#
C(2)–Fe(1)–Fe(1)#
S#–Fe(1)–Fe(1)#
S–Fe(1)–Fe(1)#
C(1)–Fe(1)–Fe(2)
C(2)–Fe(1)–Fe(2)
S#–Fe(1)–Fe(2)
S–Fe(1)–Fe(2)
133.3(2)
132.9(2)
55.23(3)
55.21(3)
138.3(1)
83.3(1)
C(4)–Fe(2)–Fe(1)
C(5)–Fe(2)–Fe(1)
C(3)–Fe(2)–Fe(1)
S#–Fe(2)–Fe(1)
of Fe(1)–S–Fe(1)#–S# plane are +1. The skeleton elec-
tron number of compound 3 is 62 and five Fe–Fe bonds
were observed in 3. This shows that structure of 3 com-
plied with the 2(9NÀL) (N=number of metal atoms
and L=number of metal–metal bonds) rule [21]. Com-
plex 3 is a novel cluster compound completely different
from the reported neutral iron–chalcogen–carbonyl tet-
ra-nuclear cluster, [Fe4(CO)10(l4-E)2(l-CO)] (E=S
[29], Se [30] and Te [31], which consists of a planar ar-
rangement of four iron atoms with quadruply bridging
S (or Se or Te) atoms on each side of the Fe4-unit, a
bridging carbonyl and two semi-bridging carbonyls.
It is worth noting that a new [Fe2S2]-unit with Fe0,
[Fe2S2]4À, is found in compound 3 and this may evi-
dence the existence of an another species, [Fe2S2-
(CO)6]4À, which results from the disproportionation
of [Fe2S2(CO)6]2À [15] in the synthetic reaction
system.
C(4)–Fe(2)–Fe(1)#
C(5)–Fe(2)–Fe(1)#
C(3)–Fe(2)–Fe(1)#
S#–Fe(2)–Fe(1)#
52.81(3)
93.10(3)
Fe(1)#–Fe(1)–Fe(2) 61.16(2)
Fe(1)–Fe(2)–Fe(1)# 57.86(3)
C(1)–Fe(1)–Fe(2)#
C(2)–Fe(1)–Fe(2)#
S#–Fe(1)–Fe(2)#
S–Fe(1)–Fe(2)#
85.3(1)
Fe(2)#–S–Fe(1)#
O(2)–C(2)–Fe(1)
O(3)–C(3)–Fe(2)
O(4)–C(4)–Fe(2)
O(5)–C(5)–Fe(2)
72.96(3)
176.0(4)
178.6(4)
179.5(4)
178.3(3)
140.8(1)
92.98(4)
52.73(3)
Fe(1)–Fe(1)–Fe(2)# 60.98(3)
Fe(2)–Fe(1)–Fe(2)# 122.14(2)
Compound 3 comprises two cations, [Ph4P]+, and a di-
anion [Fe4S2(CO)10]2À. As shown in Table 3 and Fig.
3, the anion of compound 3 possesses a [Fe4S2]2À core
which consists of bi-distorted tetrahedron sharing an
edge (Fe(1)–Fe(1)#) in trans arrangement. It can be
found that there are two rhombic planes, Fe(1)–S–
˚
Fe(1)#–S#, with Fe–S bond distance of 2.213(1) A
2.5. Fe2S2]0-, [Fe2S2]2À-, [Fe2S2]4À-units and dispro-
portionation of [Fe2S2(CO)6]2À
˚
and Fe–Fe bond length of 2.5250(9) A and Fe(1)–
Fe(2)–Fe(1)#–Fe(2)# with Fe–Fe bond lengths of
˚
2.6075(6) and 2.6121(6) A. The dihedral angle between
this two planes is 62.71ꢁ. Each Fe atom in Fe(1)–S–
Fe(1)#–S# plane is coordinated by two carbonyl groups
resulting in seven coordination geometry including three
Fe–Fe bonding. Each of the rest Fe atoms is connected
with three carbonyl ligands resulting in six coordination
geometry including two Fe–Fe bonding. Two sulfur at-
oms are l3-S and all carbonyls are terminal carbonyls.
The fact that two kinds of iron atoms in different coor-
dinating environments and two different Fe–S bond dis-
Summarizing the structures of complex 1, 2 and 3
mentioned above, there exist three kinds of [Fe2S2]-
units, [Fe2S2]0 with FeII atoms in compound 1, [Fe2S2]2À
with FeI atoms in compound 2 and [Fe2S2]4À with Fe0
atoms in compound 3, and several kinds of [Fe-
(CO)3 À nLn]z+ (L=PPh3, n=1, z=2 (in 2); n=0, z=1
(in 3)) fragments in these complexes. Noteworthily, the
structures of complexes 1, 2 and 3 do not have any other
metal atom but iron atoms although their syntheses
were carried out in the presence of CuCl or CuClO4 or
AgNO3. This indicates that the formation of complexes
1, 2 and 3 only result from a change of the [Fe2S2-
(CO)6]2À itself, which is derived from the reaction of
[Fe2S2(CO)6] with reduction reagent LiEt3BH. [2] In
˚
tances (2.213 and 2.173 A) exist in compound 3 implies
that there are two kinds of oxidation states for the iron
atoms in compound 3. According to the electric charge
balance of the compound 3, the oxidation states of the
˚
Fe atoms with longer Fe–S bond length (2.213 A) in

2678
B. Zhuang et al. / Journal of Organometallic Chemistry 689 (2004) 2674–2683
fact, compound 2 can also be obtained from the synthet-
ic reaction without AgNO3 (see Section 3.3b).
tion of [Fe2S2(CO)6]2À and the decomposition of the dis-
proportionation products [Fe2S2(CO)6]0, 2À, 4À occur in
Taking account into the three oxidation states of
[Fe2S2]-units, [Fe2S2]0, [Fe2S2]2À and [Fe2S2]4À, observed
in compound 1, 2 and 3, it is undoubted that in the
synthetic reaction system, there should exist three diiron-
disulfide carbonyl species, [Fe2S2(CO)6]0, [Fe2S2(CO)6]2À
and [Fe2S2(CO)6]4À, which are able to generate the
[Fe2S2]0, [Fe2S2]2À and [Fe2S2]4À-units and provide the
iron carbonyl fragments, [Fe(CO)3]+, [Fe(CO)3]2+ and
[Fe(CO)3]0, when they undergo decomposition. Interest-
ingly, the three species, [Fe2S2(CO)6]0, [Fe2S2(CO)6]2À
and [Fe2S2(CO)6]4À, are just the disproportionation
products of [Fe2S2(CO)6]2À. Therefore, the isolation of
the complexes 1 with [Fe2S2]0, 2 with [Fe2S2]2À and 3 with
[Fe2S2]4-units evidences that the disproportionation reac-
the reaction system involving the reagent [Fe2S2(CO)6]2À
.
It is apparent that the [Fe2S2]-units in M–[Fe2S2
(CO)6] cluster complexes should result from the prod-
ucts of the disproportionation of [Fe2S2(CO)6]2À and
the M–[Fe2S2(CO)6] cluster complexes may form via
unit construction of the species from disproportiona-
tion of [Fe2S2(CO)6]2À and metal compound including
iron carbonyl fragments from decomposition of the
disproportionation products. Thus, in the synthetic re-
action system involving with Fe2S2(CO)6 reagent, the
self-change of [Fe2S2(CO)6] and formation of M–
[Fe2S2(CO)6]-cluster compounds via an unit construc-
tion of reactive fragment or species can be described
as following Scheme 1.
LiEt3BH
[Fe2S2(CO)6]2-
[Fe2S2(CO)6]
Disproportionation
[Fe2S2(CO)6]4-
2 [Fe2S2(CO)6]2-
[Fe2S2(CO)6]0
+
Decomposition
Decomposition
Decomposition
[Fe(CO)3]0
[Fe(CO)3]2+
[Fe(CO)3]+
+
2
,
+
1
,
0
]
)
O
C
(
3
e
F
[
Fe-S Cluster
[Fe2S2(CO)6]0, 2- ,4-
M
M-Fe-S Cluster
Scheme 1.
[Fe2S2(CO)6]0
LiEt3BH
[Fe2S2(CO)6]2-
Disproportionation
[Fe2S2(CO)6]4-
[Fe2S2(CO)6]0
[Fe2S2(CO)6]2-
2 [Fe(CO)3]+
2 PPh3
2 PPh3
[Fe4S2(CO)10]2-
[Fe2S2(CO)4(PPh3)2]2-
[Fe2S2(CO)4(PPh3)2]
1
[Fe(CO)2PPh3]2+
2 [Ph4P]+
[Fe3S2(CO)6(PPh3)3]
[Ph4P]2[Fe4S2(CO)10]
3
2
Scheme 2.

B. Zhuang et al. / Journal of Organometallic Chemistry 689 (2004) 2674–2683
2679
2.6. Formation pathways of complexes 1, 2 and 3
LiEt3BH and this di-anion underwent disproportiona-
tion resulting in three species, [Fe2S2(CO)6]0, [Fe2S2-
As is discussed above, the synthetic reaction and for-
mation pathways of complexes 1, 2 and 3 could be fig-
ured out in Scheme 2 and more clearly described as
Figs. 4–6. As is shown in Scheme 2, in the synthetic re-
action system, the starting material [Fe2S2(CO)6] was re-
duced to its di-anion [Fe2S2(CO)6]2À by reducing reagent
(CO)6]2À and [Fe2S2(CO)6]4À
.
Two PPh3-ligand replace the carbonyls of the neutral
species [Fe2S2(CO)6]0 containing FeII to obtain com-
pound 1 (Fig. 4) and the [Fe2S2]0 in compound 1 came
from the [Fe2S2(CO)6]0 species. Like compound 1, the
di-anionic species [Fe2S2(CO)6]2À reacts with PPh3 to
[Fe2S2(CO)6]0
2 PPh3
+
CO
OC
CO
CO
CO
Fe
S
[Fe2S2(CO)6]4- + 2 [Fe(CO)3]+
Fe
OC
CO
CO
OC
Fe
OC
S
Fe
CO
CO
Ph3P
OC
S
OC OC
Fe
Fe
OC
S
PPh3
OC
CO
CO
OC
2-
- 2 CO
Fe
S
CO
Fe
-2 CO
OC
OC
OC
CO
CO
Fe
S
Fe
CO
OC
OC
CO
S
Fe
Ph3P
Fe
2 Ph4P+
PPh3
S
CO
OC
[Ph4P]2[Fe4S2(CO)10] (3)
(1)
Fig. 4. Formation pathway of compound 1.
Fig. 6. Formation pathway of compound 3.
CO
Fe
PPh3
OC
[Fe2S2(CO)6]2-
2 PPh
+
CO
3
Ph3P
Fe
CO
OC
S
S
OC
2-
CO
- 2 CO
OC
Ph3P
OC
Fe
PPh3
Fe
CO
CO
Fe
S
PPh3
CO
S
OC
Fe
Ph3P
OC
2+
S
+ [Fe(CO) (PPh )]
S
2
3
Fe
OC
OC
PPh3
CO
OC
Ph3P
OC
Fe
PPh3
Fe
CO
(2)
S
S
Fe++
CO
PPh3
OC
Fig. 5. Formation pathway of compound 2.

2680
B. Zhuang et al. / Journal of Organometallic Chemistry 689 (2004) 2674–2683
give a PPh3-substituting FeI–S–CO compound with but-
terfly type [Fe2S2]2À-unit, [Fe2S2(CO)4(PPh3)2]2À, and
when the [Fe2S2(CO)4(PPh3)2]2À further reacts with
collected beside the compound 3 in the synthetic reaction
of compound 3. [Fe6S6(CO)12]2À possesses a [Fe2S2]2+
-
unit with FeIII, which is more positive than Fe+. The
negative [Fe2S2(CO)6]2À species tend to react with
[Fe2S2]2+-unit resulting in [Fe6S6(CO)12]2À (see Section
3.4) The [Fe2S2]2+-unit may be derived from a species,
[Fe2S2- (CO)6]2+, whichÀmight be a oxidation product of
PPh3-substituting
iron-carbonyl
fragment
[Fe-
(CO)2PPh3]2+, the lone pair electrons on the S atoms
of [Fe2S2(CO)4(PPh3)2]2À coordinated to the Fe atom
of [Fe(CO)2PPh3]2+ accompanied with establishment of
a Fe–Fe bond between the Fe atom of [Fe(CO)2PPh3]2+
and one of the Fe atoms of [Fe2S2(CO)4(PPh3)2]2À af-
fording tri-nuclear cluster [Fe3S2(CO)6(PPh3)3] (2).
(Fig. 4) The butterfly type [Fe2S2]2À-unit in compound
2 is obviously derived from the di-anionic species
[Fe2S2(CO)6]2À and the pseudo plane [Fe2S2]-unit with-
out Fe–Fe bonding in 2 took shape after the reaction
of [Fe2S2(CO)4(PPh3)2]2À with [Fe(CO)2PPh3]2+. When
the tetra-anionic species [Fe2S2(CO)6]4À reacted with
[Fe(CO)3]+ fragments, two S atoms of the tetra-anionic
species [Fe2S2(CO)6]4À, respectively, coordinated to the
Fe atoms of two [Fe(CO)3]+ fragments from both sides
of the planar [Fe2S2]-unit of the tetra-anionic species
[Fe2S2(CO)6]4À accompanied with creation of four Fe–
Fe bonds between the Fe atom of tetra-anionic species
[Fe2S2(CO)6]4À and the Fe atom of [Fe(CO)3]+ frag-
ments resulting in tetra-nuclear cluster [Fe4S2(CO)10]2À
which was collected as Ph4P+-salt, [Ph4P]2[Fe4S2(CO)10]
(3). (Fig. 6) It is evident that the [Fe2S2]4À-unit came
[Fe2S2- (CO)6]0 by ClO4
.
3. Experimental
3.1. Materials and methods
CH3CN, CH2Cl2 and THF were distilled with CaH2,
P2O5 and LiAlH4, respectively, CH3OH and iPrOH were
dried by distillation with Mg(OMe)2. PPh3, Fe(CO)5
and LiEt3BH in THF were purchased from Fluka. CuCl
and AgNO3were products of Shanghai Chemical Com-
pany. [Fe2S2(CO)6] were prepared by reaction of
Fe(CO)5 with Na2S5 and KOH in MeOH [1,2].
IR spectra were recorded on Nicolet Magno 750 and
elemental analysis were performed on Carlo Erba In-
strumentation Elemental Analyzer-MOD 1106.
All reaction procedures were carried out under N2 at-
mosphere by using Schlenk technique and all solvents
and reagents were degassed before use.
from the tetra-anionic species [Fe2S2(CO)6]4À
.
It must be pointed out that there are other possible
formation pathways for complex 2: an unsubstituted
[Fe2S2(CO)6]2À species reacts with [Fe(CO)3]2+ fragment
to form [Fe3S2(CO)9] cluster compound which under-
goes PPh3-substitution resulting in complex 2 or a
[Fe4S2(CO)11], generated from the reaction system, re-
acts with PPh3 to give complex 2 like Ru-analog
[Ru3S2(CO)6(PPh3)3] [18], but taking notice of the fact
that no [Fe3S2(CO)9], [Fe4S2(CO)11], [Fe3S2(CO)8PPh3]
and [Fe3S2(CO)7(PPh3)2] have been isolated from the
synthetic reaction system of complex 2, these two forma-
tion pathways for complex 2 may be excluded.
Finally, it should be pointed out that the Cu(Ag)–
[Fe2S2(CO)6] complexes have not been isolated although
the synthetic reactions were carried out in the presence
of Cu+ and Ag+. This is due to the larger electronegativi-
ties of Cu (1.9)and Ag (1.9) than Fe (1.8) [32], thus, the
Cu+ and Ag+ are less positive than Fe+ or Fe++, and the
negative species [Fe2S2(CO)6]nÀ (n=0, 2 and 4) tend to re-
act with Fe+ or Fe++. As a matter of fact, the M–[Fe2S2
(CO)6] complexes (M‚Mo0 [15], Mov [3], W0 [15], VVI
[16], MnII [16], CrII [16],) have been obtained because
the electronegativities of Mo, W, V, Mn and Cr are less
than or equal to that of Fe. So, it will be possible to obtain
a new Metal–[Fe2S2(CO)6] cluster compound if the metal
ion with less electronegativity than Fe+ or Fe++ and prop-
er reaction condition such as reactant ratio, precipitate re-
agent, reaction temperature and so on are used. In fact, a
FeIII–[Fe2S2(CO)6] compound [Fe6S6(CO)12]2À [33] was
3.2. Synthesis of [Fe2S2(CO)4(PPh3)2] (1)
To a red solution of [Fe2S2(CO)6] (0.25 g, 0.73 mmol)
in 20 ml THF was dropped slowly 1.5 ml 1 M LiEt3BH–
THF at À78 ꢁC under stirring resulting in green solu-
tion, and, then, to this green solution was added a
mixture of CuCl (0.072 g, 0.72 mmol), PPh3 (0.38 g,
1.45 mmol) and Et4NCl (0.12 g, 0.73 mmol) in 20 ml
MeCN. After the temperature rose to room temperature
by removing the cold-bath, the reaction mixture was
stirred at room temperature for 24 h. Filtering off small
amount of solid, the brown filtrate was concentrated to
15 ml, and 8 ml of isopropanol was added. After filtering
off a small amount of precipitate again, the resulting fil-
trate was cooled at 4 ꢁC for three months. 0.13 g of red
brown crystalline [Fe2S2(CO)4(PPh3)2] (1) was obtained
by filtration, washed with isopropanol and dried in vac-
uum. Yield: 21.9% (base on [Fe2S2(CO)6] used). Anal.
Calc. for C40H30Fe2O4P2S2: C, 59.1; H, 3.7; P, 7.6; Fe,
13.8. Found: C, 58.9; H, 3.4; P, 7.2; Fe, 13.5%. IR
(KBr pellet): 1994, 1952, 1932, 1909 cmÀ1 (mCO).
3.3. Synthesis of [Fe3(CO)6(PPh3)3] (2)
(a) To a red solution of [Fe2S2(CO)6] (0.25 g, 0.73
mmol) in 20 ml THF was dropped 1.5 ml 1M LiEt3BH
in THF at À78 ꢁC under stirring resulting in a green so-
lution and then AgNO3(PPh3)2 (0.5 g, 0.61 mmol) in 20

B. Zhuang et al. / Journal of Organometallic Chemistry 689 (2004) 2674–2683
2681
ml MeCN was added into this green solution. After the
temperature rose to room temperature by removing the
cold bath, the resulting reaction mixture was stirred at
room temperature overnight, 0.12 g (0.73 mmol) of
Et4NCL was added and the reaction mixture was stirred
for another 16 h resulting in brown solution with some
solid in it. After filtering off small amount of solid, the
brown filtrate was concentrated to dryness. The residue
was dissolved in 20 ml MeCN and 9 ml isopropanol was
added. Filtering off a little bit precipitate, the filtrate was
cooled at 4 ꢁC for a month. 0.2 g of crystalline [Fe3S2
(CO)6(PPh3)3] (2) was collected by filtration, washed
with isopropanol and dried in vacuum. Yield: 34%
(based on [Fe2S2(CO)6] used) Anal. Calc. for
C60H45Fe3O6P3S2: C, 60.7; H, 3.8; Fe, 14.2; S, 5.4; P,
7.8. Found: C, 59.8; H, 3.9; Fe, 13.8; S, 5.3; P, 7.4%.
IR (KBr pellet): 1996, 1973, 1954, 1934, 1911, 1900
cmÀ1 (mCO).
ing in green solution. After filtering (no precipitate was
found), the green filtrate was concentrated to dryness by
vacuum and the residue was dissolved in 15 ml MeCN
and then 8 ml isopropanol was added. After filtering,
the resulting filtrate was cooled at 4 ꢁC for several
months crystalline 2 was obtained.
3.4. Synthesis of [Ph4P]2[Fe4S2(CO)10] (3)
To a red solution of [Fe2S2(CO)6] (0.25 g, 0.73 mmol)
in 20 ml THF was dropped slowly 1.5 ml 1M LiEt3BH in
THF at À78 ꢁC under stirring and then a solution of Cu-
ClO4 ÆMeCN (0.15 g, 0.73 mmol) in 20 ml CH3CN was
added. After removing cold bath, the reaction tempera-
ture rose to room temperature and the reaction mixture
was stirred at room temperature for 3 h. Ph4PBr (0.3 g,
0.72 mmol) was added and the resulting mixture was con-
tinued to stir overnight. After filtering off a small amount
of black precipitate, the brown filtrate was concentrated
to dryness. The residue was dissolved in 25 ml CH2Cl2,
and after filtering off some gray solid the brown filtrate
was concentrated again to dryness. The residue was dis-
solved in 17 ml CH3CN and 8 ml isopropanol was added.
After filtering, the filtrate was cooled at 4 ꢁC for more
than two months. 0.1 g crystalline [Ph4P]2[Fe4S2(CO)10]
(b) To the solution of [Fe2S2(CO)6] (0.3 g, 0.87 mmol)
in 25 ml THF was dropped slowly 1.8 ml 1 M LiEt3BH
in THF at À78 ꢁC under stirring resulting in green solu-
tion and PPh3 (0.48 g, 1.83 mmol) in 70 ml MeCN was
added. After the reaction temperature was raised to
room temperature by removing cold bath, the reaction
mixture was stirred at room temperature for 24 h result-
Table 4
Crystal data and collection and refinement details for 1, 2ÆH2O and 3
Compounds
1
2ÆH2O
3
Empirical formula
Formula weight
Temperature (K)
Crystal system
C40H30Fe2O4P2S2
812.40
293
C60H46Fe3O6.5P3S2
1195.55
293
C29H20Fe2O5PS
623.18
293
Monoclinic
P21/n
Monoclinic
P21/n
Monoclinic
P21/n
Space group
Unit cell dimensions
˚
a (A)
10.2905(2)
22.411(4)
17.1882(3)
90
17.262(3)
14.985(4)
21.442(4)
90
10.8238(2)
14.8907(1)
17.2887(3)
90
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
96.265(1)
90
96.67(1)
90
5509(2)
90.4460(1)
90
3
˚
V (A )
3940.2(1)
4
1.369
2786.40(7)
4
1.486
Z
4
1.442
0.994
Dcalc (mg cmÀ3
)
k (mmÀ1
)
0.962
1.210
Crystal size (mm3)
0.45·0.3·0.2
1.50–25.08
À126h612
À216k626
À126l620
15,798
0.45·0.2·0.2
1.66–23.27
À196h617
À126k616
À226l623
24,585
0.4·0.25·0.2
1.80–25.15
À126h612
À176k612
À206l616
13,947
h Range (ꢁ)
Index ranges
Reflections collected
Independent reflections
No. observations with I>2r(I)
Data/restrains/parameters
Goodness-of-fit
6921
5653
7849
6455
4958
4892
6913/0/451
1.158
7849/0/671
1.040
4956/0/343
1.134
R1, wR2 (I>2r(I)
R1, wR2 (I>2r (I)
Largest difference peak and hole (e A
0.0505, 0.1605
0.0649, 0.1793
1.676/À0.440
0.0512, 0.1346
0.0660, 0.1475
1.291/À0.365
0.0413, 0.1095
0.0595, 0.1262
0.467/À0.756
À3
˚
)

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B. Zhuang et al. / Journal of Organometallic Chemistry 689 (2004) 2674–2683
(3) was collected by filtration, washed with isopropanol
and dried in vacuum. Yield: 22% (based on [Fe2S2(CO)6]
used). Anal. Calc. for C29H20Fe2O5PS: C, 55.8; H, 3.2;
Fe, 18.0; P, 5.0; S, 5.1. Found: C, 55.2; H, 3.1; Fe, 17.6;
P, 4.9; S, 5.0%. IR (KBr pellet): 1994, 1952, 1932, 1909
cmÀ1 (mCO).
1EZ, UK (fax: +44-1233-336033; e-mail: deposit@
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
Acknowledgement
The mother liquid was continued to stand at 4 ꢁC for
several days. A known product [Ph4P]2[Fe6S6(CO)12]
[26] was obtained.
We are grateful to the National Natural Science
Foundation of China and State Key Laboratory of
Structural Chemistry for financial support in this
research.
3.5. X-ray crystal structure determination
References
A crystal samples of compound 1, 2Æ1/2H2O and 3
wrapped with glue were mounted on Siemems Smart
CCD diffractometer equipped with a graphite mono-
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˚
chromator (Mo Ka radiation k=0.71073A) for data col-
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(1982) 125.
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details are listed in Table 4. All calculations were per-
formed on a Silicon Graphics computer station by using
the SHELXTL program system.
[3] K.S. Bose, P.E. Lamberty, J.A. Kouacs, E. Sinn, B.A. Averill,
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Data were corrected for Lorentz and polarization ef-
fects and absorption effects by SADABS [34]. The struc-
ture was solved by directed methods (SHELXTL) and
were refined by the full-matrix least-squares on all F2 da-
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4. Summary
[10] M.D. Curits, P.D. Williams, W.M. Butler, Inorg. Chem. 27 (1988)
2853.
New di-, tri- and tetra-nuclear Fe–S carbonyl complex-
es, [Fe2S2(CO)4(PPh3)2](1), [Fe3S2(CO)6(PPh3)3] (2), and
[Ph4P]2[Fe4S2(CO)10] (3) have been isolated from the reac-
[11] M. Cowie, R.L. Dekock, T.R. Wagenmaker, D. Seyferth, R.S.
Henderson, M.K. Gallager, Organometallics 8 (1989) 119.
[12] N.S. Nametkin, V.D. Tyurin, M.A. Kukina, Russ. Chem. Rev. 55
(1986) 439.
tion involving with [Fe2S2(CO)6] and [Fe2S2(CO)6]2À
.
Crystal structure determination indicated that 1, 2 and 3
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5. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC nos. 197026, 197027 and 197028
for compounds 1, 2, and 3, respectively. Copies of this
information may be obtained free of charge from The
Director, CCDC, 12, Union Road, Cambridge CB2
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