Insertion reactions of CS2, COS, and PhNCS at thiolate-bridged diiron centers

Article abstract of DOI:10.1039/b920144k

Treatment of [Cp*Fe(μ₂-SR)₃FeCp*] (1a, R = Et; 1b, R = Me) with CS₂ obtains the insertion products [Cp*Fe(μ₂-SR)₂(μ-η²-S ₂CSR)FeCp*] (2a, R = Et; 2b, R = Me) with the retained Fe ₂S₂ subunit in excellent yield. 2a and 2b represent the first examples for the CS₂ activation and incorporation at the diiron-SR bond. [Cp*Fe(μ₂-SEt)₂(μ- η²-S₂)FeCp*] (3) is prepared from COS and 1a through the decarbonylation and sulfur coupling reaction of COS resulting in the formation of S₂^2- ligand. Addition of PhNCS into 1a affords a mononuclear complex [Cp*Fe(SEt)(η²-SC(SEt)NPh)] (4). 1a is found to be unreactive towards CO₂. The spectral characterization, X-ray diffraction analysis, and electrochemistry of the insertion products have also been described.

Full text of DOI:10.1039/b920144k

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www.rsc.org/dalton | Dalton Transactions
Insertion reactions of CS2, COS, and PhNCS at thiolate-bridged diiron
centers†
Yanhui Chen, Ying Peng, Pingping Chen, Jinfeng Zhao, Litao Liu, Yang Li, Shuoyi Chen and Jingping Qu*
Received 30th September 2009, Accepted 16th November 2009
First published as an Advance Article on the web 23rd December 2009
DOI: 10.1039/b920144k
Treatment of [Cp*Fe(m2-SR)3FeCp*] (1a, R = Et; 1b, R = Me) with CS2 obtains the insertion products
2
[Cp*Fe(m2-SR)2(m-h -S2CSR)FeCp*] (2a, R = Et; 2b, R = Me) with the retained Fe2S2 subunit in
excellent yield. 2a and 2b represent the first examples for the CS2 activation and incorporation at the
2
diiron–SR bond. [Cp*Fe(m2-SEt)2(m-h -S2)FeCp*] (3) is prepared from COS and 1a through the
decarbonylation and sulfur coupling reaction of COS resulting in the formation of S22- ligand. Addition
2
of PhNCS into 1a affords a mononuclear complex [Cp*Fe(SEt)(h -SC(SEt)NPh)] (4). 1a is found to be
unreactive towards CO2. The spectral characterization, X-ray diffraction analysis, and electrochemistry
of the insertion products have also been described.
2
C bond of (h -formaldehyde)zirconocene dimer affording mono-
Introduction
or di-insertion products in h coordination mode.13 But to date,
1
The insertion of heterocumulenes including carbon dioxide (CO2),
carbon disulfide (CS2), carbonyl sulfide (COS), and isothiocyanate
(RNCS) into metal–non-metal bonds such as metal–hydride,
metal–nitrogen, metal–oxygen, metal–carbon, and metal–sulfur
bonds of transition metal fragments and their subsequent func-
tionalization have drawn much attention due to their potential
sources of C1 chemistry for the generation of useful organic
compounds.1,2 The development of practical and effective methods
for the transformations of these small molecules, especially CO2,
an abundant and inexpensive source of carbon, is essential for the
future. Being structurally similar to CO2, the diverse chemistry
of CS2 including coordination, addition, cleavage, and insertion
reactions is currently being intensively investigated, as CS2 is
highly reactive and the transition metal complexes bearing CS2
may be regarded as model compounds for CO2 activation and
transformation.3 Additionally, COS can function as a good
carbonylating agent in the presence of a suitable thiophilic agent,
and RNCS is useful as a source of carbon, nitrogen, and sulfur in
one chemical step.4a
Compared to the numerous insertion reactions with these small
unsaturated molecules at the single transition metal center,4-9
an insertion at the di- or multi-metal centers has still remained
poorly explored, and is just limited to several examples to get
mononuclear insertion products: one is the insertion into nickel(II)
hydroxido complexes,10 another one is about the reaction of
Pt2S(PPh3)3(CO) with CS2 to get a mononuclear Pt complex
(Ph3P)2PtS2CS,11 and the other two reactions are about C–S bond
there is no example on the insertion reaction of CS2, COS and
PhNCS at the diiron–thiolate centers, although a lot of insertion
reactions of heterocumulenes into M–SR bonds (M = Ru, Os, Pt,
W, etc.)5b,6c-6e at the single transition metal site have been reported.
Our group focuses on the synthesis and reactivity of diiron–
sulfur clusters with Cp* as single ancillary ligands, which can
provide bimetallic reaction sites and simulate biological metallo-
proteins to activate small molecules. In our previous work, we
have reported three new triply thiolate-bridged diiron complexes
5
[Cp*Fe(m2-SR)3FeCp*] (Cp*= h -C5Me5; R = Me, Et, Ph) with
excellent properties including the activation of C–Cl of some
chlorohydrocarbons and the catalytic cleavage of N–N single bond
of hydrazines under ambient conditions.14 As an extension of
this work, herein we report the insertion reactions of [Cp*Fe(m2-
SR)3FeCp*] (1a, R = Et; 1b, R = Me) with CS2, COS, and
PhNCS. The X-ray structures and characterizations of new com-
2
plexes [Cp*Fe(m2-SR)2(m-h -S2CSR)FeCp*] (2a, R = Et; 2b, R =
2
2
Me), [Cp*Fe(m2-SEt)2(m-h -S2)FeCp*] (3), and [Cp*Fe(SEt)(h -
SC(SEt)NPh)] (4), together with the electrochemistry of 2a and
2b, are also discussed in this paper.
Results and discussion
As outlined in Scheme 1, reaction of [Cp*Fe(m2-SEt)3FeCp*] (1a)
with excess CS2 at 40 ◦C affords complex [Cp*Fe(m2-SEt)2(m-
2
h -S2CSEt)FeCp*] (2a) in excellent yield (100%) as a blue-
2
purple microcrystalline powder. Complex [Cp*Fe(m2-SMe)2(m-h -
cleavage of CS2 or PhNCS at the diiron centers and insertion of a
S2CSMe)FeCp*] (2b) is also obtained in high yield (100%) in a
similar way by treatment of [Cp*Fe(m2-SMe)3FeCp*] (1b) with
CS2. Completely different from other insertion reactions on dinu-
clear transition metal complexes affording mononuclear products:
[(N3-mc2)Ni(S2COR)][PF6] (N3-mc2 = 2, 4, 4, 9-tetramethyl-1, 5,
9-triazacyclododec-1-ene, R = Me, Et)10 and (Ph3P)2PtS2CS,11 CS2
molecule is incorporated into Fe–SR bond with binding to two Fe
atoms and one SR ligand in 2a and 2b. Complexes 2a and 2b
12
=
S atom into the Fe C or Fe–C bonds. Another example is the
= =
insertion reactions of CO2, Ph2C C O and Me3CNCO into Zr–
State Key Laboratory of Fine Chemicals, School of Chemical Engineering,
Dalian University of Technology, Dalian, 116012, P. R. China. E-mail:
Qujp@dlut.edu.cn, Qujp@chem.dlut.edu.cn; Fax: +86-411-8363-3080
† Electronic supplementary information (ESI) available: Selected bond
distances and angles; cyclic voltammograms. CCDC reference numbers
737810 and 749168–749170 and 753805. For ESI and crystallographic
data in CIF or other electronic format see DOI: 10.1039/b920144k
1
are paramagnetic at room temperature. The H NMR spectrum
of 2a in C6D6 shows four broad signals at d 1.44, 0.57, -0.79,
3020 | Dalton Trans., 2010, 39, 3020–3025
This journal is
The Royal Society of Chemistry 2010
©

Table 1 Crystal data and structure refinement for complexes 2a, 2b, 3, 4
Complex
Formula
2a
2b
3
4
C27H45Fe2S5
C24H39Fe2S5
C24H40Fe2S4
C21H30FeNS3
Fw
T/K
641.63
293(2)
0.71073
599.55
293(2)
0.71073
568.50
293(2)
0.71073
448.49
293(2)
0.71073
˚
Wavelength/A
Crystal size/mm
Crystal system
Space group
0.33 ¥ 0.32 ¥ 0.28
Monoclinic
P21/n
11.9506(2)
15.2338(2)
16.6540(3)
90
99.659(1)
90
2988.93(8)
4
1.426
1.335
1356
2.29 to 27.50
-15 ≤ h ≤ 15
-19 ≤ k ≤ 19
-21 ≤ l ≤ 21
22845
6380
0.0290
0.35 ¥ 0.33 ¥ 0.25
Monoclinic
C2/c
31.2295(12)
11.3352(4)
16.2519(6)
90
97.191 (2)
90
5707.8(4)
8
1.395
1.393
2520
1.91 to 25.00
-37 ≤ h ≤ 37
-13 ≤ k ≤ 12
-18 ≤ l ≤ 19
22282
5025
0.0249
0.43 ¥ 0.31 ¥ 0.26
Monoclinic
C2/c
18.9893(6)
12.8536(6)
11.2639(5)
90
92.964(4)
90
2745.6(2)
4
1.375
1.371
1200
2.60 to 24.98
-22 ≤ h ≤ 21
-13 ≤ k ≤ 15
-13 ≤ l ≤ 12
11074
2420
0.0236
0.16 ¥ 0.13 ¥ 0.11
Monoclinic
P21/c
9.5932(15)
15.484(2)
15.385(2)
90
90.014(12)
90
2285.4(6)
4
1.303
0.939
948
1.87 to 25.00
-11 ≤ h ≤ 11
-15 ≤ k ≤ 18
-18 ≤ l ≤ 18
12379
4027
0.0636
˚
a/A
˚
b/A
˚
c/A
a/◦
b/◦
g /◦
3
˚
V/A
Z
rc/g cm-3
m/mm-1
F(000)
q/◦
Limiting indices
Reflns collected
Reflns unique
Rint
GOF(F2)
1.034
1.079
1.062
1.026
R1, awR2 b[I > 2s(I)]
0.0346/0.0877
0.0429/0.0916
0.518. -0.656
0.0325/0.0896
0.0393/0.0929
0.599, -0.407
0.0270/0.0796
0.0321/0.0832
0.231, -0.244
0.0595/0.1305
0.0803/0.1398
0.580, -0.280
R1, awR2 b(all data)
-3
˚
Largest diff. peak and hole/e A
ꢀ
ꢀ
ꢀ
ꢀ
a R1 = ꢀFo| - |Fcꢀ/ |Fo|. b wR2 = { [w(Fo - Fc2)2]/ [w(Fo2)2]}
.
2
1/2
-2.64, and -9.33 ppm assigned to the protons of CH2 in S2CSEt
group, CH2 in SEt, CH3 in S2CSEt, CH3 in SEt, and the protons
1
of two Cp* ligands, respectively. The H NMR spectrum of 2b
exhibits three resonances at d 12.44, -6.43, -8.84 ppm attributed
to the protons of CH3 in SMe group, CH3 in S2CSMe and CH3
in two equivalent Cp* ligands, respectively. Both 2a and 2b are
unambiguously characterized by single-crystal X-ray diffraction
analysis, and their spectral features are fully consistent with their
crystal structures. Crystallographic data are listed in Table 1.
Complex 2a crystallizes in the monoclinic space group P21/n
with four asymmetric molecules per unit cell. An ORTEP drawing
of 2a is shown in Fig. 1. The overall structure consists of two
Cp*Fe units bridged by two syn-axial SEt ligands, in which the
˚
long Fe ◊ ◊ ◊ Fe distance of 3.141(4) A is indicative of the absence of
a bonding interaction between the two Fe atoms.14a,15 The Fe2S2
ring is substantially puckered with a dihedral angle of 156◦ and
two Cp* ligands are overlapped by each other along Fe1 ◊ ◊ ◊ Fe2
vector. The remaining sites of two Fe atoms are occupied by two
S atoms from the S2CSEt group resulting in the formation of
tetrahedral coordination geometry of the iron center. There are no
significant differences in the coordination geometry between two
Fe atoms. Two Cp* ligands are in mutually cis orientation, and
the dihedral angle between the Cp* rings in 2a (62◦) is apparently
wider than that in the precursor 1a (4.3◦),14a which may be a
consequence of the incorporation of the larger S2CSEt ligand
in place of the SEt ligand. Fe1Fe2S3S4C25 are nearly coplanar
with the deviation being 0.02◦, whose dihedral angles with two
Cp* rings are 90.3◦ and 86.9◦, respectively. All the Fe–C bond
Scheme 1 The insertion reactions of heterocumulenes at thiolate-bridged
diiron centers.
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 3020–3025 | 3021
©

Fig. 2 Molecular structure of 2b. Hydrogen atoms are omitted for clarity
˚
Fig. 1 Molecular structure of 2a. Hydrogen atoms and one disor-
(30% probability thermal ellipsoids). Selected bond lengths (A) and angles
(◦): Fe(1) ◊ ◊ ◊ Fe(2) 3.350(1), Fe(1)–S(1) 2.273(1), Fe(1)–S(2) 2.253(1),
Fe(1)–S(3) 2.179(1), Fe(2)–S(1) 2.264(1), Fe(2)–S(2) 2.255(1), Fe(2)–S(4)
2.162(1), S(3)–C(23) 1.704(3), S(4)–C(23) 1.677(3), S(5)–C(23) 1.764(2),
S(3)–Fe(1)–S(2) 98.3(1), S(3)–Fe(1)–S(1) 99.0(1), S(2)–Fe(1)–S(1) 79.7(1),
S(4)–Fe(2)–S(2) 97.9(1), S(4)–Fe(2)–S(1) 98.9(1), S(2)–Fe(2)–S(1) 79.9(1),
Fe(2)–S(1)–Fe(1) 95.2(1), Fe(1)–S(2)–Fe(2) 96.0(1), S(4)–C(23)–S(3)
129.4(1), S(4)–C(23)–S(5) 119.5(1), S(3)–C(23)–S(5) 111.3(1).
dered SEt ligand are omitted for clarity (30% probability thermal
◦
˚
ellipsoids). Selected bond lengths (A) and angles ( ): Fe(1) ◊ ◊ ◊ Fe(2)
3.141(1), Fe(1)–S(1) 2.311(2), Fe(1)–S(2) 2.269(1), Fe(1)–S(3) 2.184(1),
Fe(2)–S(1) 2.304(2), Fe(2)–S(2) 2.260(1), Fe(2)–S(4) 2.193(1), S(4)–C(25)
1.694(2), S(5)–C(25) 1.768(2), S(5)–C(26) 1.813(2), S(3)–C(25) 1.687(2),
S(2)–Fe(1)–S(3) 97.0(1), S(2)–Fe(1)–S(1) 91.4(1), S(3)–Fe(1)–S(1) 92.1(1),
S(4)–Fe(2)–S(2) 96.3(1), S(4)–Fe(2)–S(1) 92.4(1), S(2)–Fe(2)–S(1) 92.5(1),
Fe(2)–S(2)–Fe(1) 87.8(1), Fe(2)–S(1)–Fe(1) 85.8(1), S(3)–C(25)–S(4)
129.3(1), S(3)–C(25)–S(5) 112.1(1), S(4)–C(25)–S(5) 118.8(1).
Being structurally very similar to CS2 and CO2, the reaction
of COS with the triply thiolate-bridged diiron complex 1a is
also investigated. Treatment of 1a with 2.0 eq. COS in THF at
˚
distances (2.101(3)~2.143(2) A) fall in the normal range for Fe–
C single bonds. The Fe–S (S atoms are from the SEt ligands)
bond lengths (2.260(1)~2.311(1) A) are obviously longer than
those (2.184(1)~2.193(1) A) of S atoms from the S2CSEt group.
In the S2CSEt group, we can see that the S3–C25 and S4–C25
◦
2
˚
50 C for 12 h affords complex [Cp*Fe(m2-SEt)2(m-h -S2)FeCp*]
(3) as a red-brown crystalline solid in 37% yield (Scheme 1)
and some unidentified complexes containing a CO ligand proved
˚
1
˚
bond distances are almost equal (1.687(1), 1.694(1) A), and are
by IR. Complex 3 is diamagnetic at room temperature. The H
intermediate between single- and double-bond distances,16 which
shows that the electrons are delocalized over the S–C–S unit.
Complex 2b crystallizes in the monoclinic space group C2/c
with eight asymmetric molecules per unit cell. The molecular
structure of 2b (Fig. 2) resembles that of 2a. There is no interaction
NMR spectrum of 3 exhibits a signal at 1.43 ppm corresponding
to the protons of two Cp* ligands, and the resonances at 1.14
and 0.79 ppm are ascribed to the protons of CH2 and CH3 in
SEt ligands. The molecular structure of 3 is confirmed by X-ray
diffraction analysis, and its spectral features are fully in accordance
with the crystal structure. 3 crystallizes in the monoclinic space
group C2/c with eight asymmetric molecules per unit cell. As
shown in Fig. 3, there is a planar Fe–S–S–Fe bridge and the ethyl
sulfide ligands also bridge the two irons while each is bonded to a
Cp* group. There is no metal–metal interaction between the two Fe
˚
between the two Fe atoms (Fe ◊ ◊ ◊ Fe distance: 3.350(1) A). The
dihedral angle between the two Cp* rings is 57◦ and smaller
than that of 2a (62◦), while the dihedral angle of the butterfly-
shaped Fe1S1Fe2S2 (34◦) is significantly larger than that of 2a
(14◦) along the Fe1 ◊ ◊ ◊ Fe2 vector. There is also an expected pattern
of delocalization among S3, C23, and S4 atoms from the S2CSMe
˚
atoms, and the Fe ◊ ◊ ◊ Fe distance is 3.328(1) A. The S–Fe–S angles
ligand, where the S–C bond distances (1.704(3) A, 1.677(3) A) are
vary between 77◦ and 94◦. The dihedral angle of the two Cp*
˚
˚
◦
˚
comparable to those in 2a, and shorter than the S5–C23 single
rings is 32 . The Fe–S bond distances (2.296(1), 2.135(1) A) are
in the normal range of Fe–S single bonds. The S–S bond distance
˚
bond (1.764(2) A).
2-
˚
The formation of S2CSR (R = Et, Me) in the insertion products
2a and 2b shows that the linear CS2 molecule can be activated
at the diiron centers. The process may be via the loss of the SR
ligand and precoordination of CS2 to the iron atoms,6b followed
by electrophilic attack through the CS2 ligand on the sulfur atom
of the thiolate ligand to get a S2CSR (R = Et, Me) group as
in the S2 ligand is 2.033(1) A. All these structural parameters of
3 are comparable to the analogous diiron sulfur cluster [CpFe(m2-
2
SEt)2(m-h -S2)FeCp] (Cp = C5H5) reported by L. W. Reeves
and R. Rivest.17 Unlike the COS insertion into the Fe–H bond
of monomer cis-Fe(dmpe)2H2 (dmpe = Me2PCH2CH2PMe2)
1
yielding h -SCHO coordination to the Fe atom,5a an unexpected
2
2-
a consequence. Such coordination mode of a m-h -S2CSR (R =
bridging S2 ligand is formed in 3. Such formation shows that
Et, Me) group between two iron atoms represents a new type of
heterocumulenes activation at the dinuclear metal centers.
decarbonylation occurs when COS is inserted at the diiron centers,
with the cleavage of the C–S bond from COS to get S and CO,
3022 | Dalton Trans., 2010, 39, 3020–3025
This journal is
The Royal Society of Chemistry 2010
©

Fig. 3 Molecular structure of 3. Hydrogen atoms and one disor-
dered Cp* ligand attached to Fe1 atom are omitted for clarity (30%
˚
probability thermal ellipsoids). Selected bond lengths (A) and angles
Fig. 4 Molecular structure of 4. Hydrogen atoms are omitted for
clarity (30% probability thermal ellipsoids). Selected bond lengths (A)
(◦): Fe(1) ◊ ◊ ◊ Fe(1)#1 3.328(1), Fe(1)–S(2) 2.135(1), S(1)–Fe(1)#1 2.296(1),
S(2)–S(2)#1 2.033(1), S(2)–Fe(1)–S(1) 93.6(1), Fe(1)–S(1)–Fe(1)#1 93.0(1),
S(2)#1–S(2)–Fe(1) 107.7(1), S(1)–Fe(1)–S(1)#1 76.6(1).
˚
and angles (◦): Fe(1)–N(1) 1.989(5), Fe(1)–S(2) 2.192(1), Fe(1)–S(3)
2.327(2), S(1)–C(19) 1.760(5), S(1)–C(21) 1.821(7), C(19)–N(1) 1.309(7),
C(11)–N(1) 1.417(8), C(19)–S(3) 1.711(6), N(1)–Fe(1)–S(2) 96.4(1),
N(1)–Fe(1)–S(3) 70.2(1), S(2)–Fe(1)–S(3) 99.3(1), C(19)–S(1)–C(21)
103.2(3), C(19)–S(3)–Fe(1) 77.8(2), N(1)–C(19)–S(3) 110.7(4),
N(1)–C(19)–S(1) 124.5(4), S(3)–C(19)–S(1) 124.7(3), C(19)–N(1)–Fe(1)
101.0(4).
2-
and S atoms coupling to achieve S2 ligand. This phenomenon
also happens at a single metal center,1a for example, the reaction
between decamethylvanadocene and COS.18 The different reaction
results of CS2 and COS with 1a reflects their distinct behaviors
towards metal centers, although COS is structurally related to
1
4a
˚
value (2.321(1) A) in trans-Fe(dmpe)2(h -SCHNPh)2. Similar to
the CS2 insertion of 2a and 2b, substantial electronic delocalization
over the S–C–N unit is found, as the C19–S3 and C19–N1 bond
2
CS2. Usually, the metal-(h -CS2) complexes are much more stable
than the metal-(h -COS) complexes, thus the elimination of sulfur
from metal-(h -CS2) complexes is more difficult than metal-(h -
COS) complexes, as the weakening of the C S bond of COS
on coordination to a metal induced by dp–p* back donation is
apparently sufficient to promote the elimination of sulfur.
Treatment of 1a with 2.0 eq. PhNCS in THF solution at
50 C for 2 h produces complex [Cp*Fe(SEt)(h -SC(SEt)NPh)]
(4) as a red-brown crystalline solid in 46% yield (Scheme 1).
2
˚
lengths in complex 4, 1.711(6) and 1.309(7) A, are between the
2
2
corresponding single and double bond distances.16
=
Electrochemistry
◦
2
The cyclic voltammograms (CV) of 2a and 2b have been measured
in THF–0.1 M [n-Bu4N][PF6]. The CV of 2a shows three quasi-
reversible redox peaks. The process observed at E1/2 = +0.37 V vs.
Fc/Fc+ is assigned to [FeIIFeIII]/[FeIIIFeIII],14a one at E1/2 = -1.01 V
1
Complex 4 is characterized by IR, H NMR, elemental analyses
and X-ray diffraction analysis. In the IR spectrum of 4, the
two strong absorptions at 1490 and 1025 cm-1 can be assigned
to the bidentate CN and CS vibrations in the SC(SEt)NPh
ligand, respectively,19 which shows that this ligand is formed
by the transfer of the SEt group to the PhNCS carbon atom.
Complex 4 is diamagnetic at room temperature. The broad singlet
is ascribed to [FeIIFeII]/[FeIIFeIII], and another one at E1/2
=
-1.92 V results from [FeIFeII]/[FeIIFeII].14a,20 In the case of 2b, three
quasi-reversible redox processes are also observed at E1/2 = +0.35,
-0.97 and -1.90 V, which corresponds to [FeIIFeIII]/[FeIIIFeIII],
[FeIIFeII]/[FeIIFeIII] and [FeIFeII]/[FeIIFeII], respectively. The quite
close redox potentials of 2a and 2b indicate that SEt and SMe
ligands do not have a significant affect on the electrochemistry
of the diiron complexes. Comparison to the electrochemistry of
the precursor [Cp*Fe(m2-SMe)3FeCp*] (1b) with the half-wave
potential being 0, -0.95 and -1.98 V vs. Fc/Fc+ reflects a shift to a
more positive potential in the process of [FeIIFeIII]/[FeIIIFeIII] and
two close redox potentials in the processes of [FeIIFeII]/[FeIIFeIII]
and [FeIFeII]/[FeIIFeII].
1
at 7.34 ppm is attributed to Ph protons in the H NMR of 4,
and the resonances at 6.24, 5.38, and 1.55 ppm correspond to
the protons of CH2, CH3 in the SEt group, and Cp* ligand,
respectively. The spectral features are fully consistent with its
crystal structure. Complex 4 crystallizes in the monoclinic space
group P21/c with four asymmetric molecules per unit cell. As
shown in Fig. 4, complex 4 is a monomeric species in which the
SC(SEt)NPh group is chelating to the four coordinated Fe atom in
2
a h arrangement. While in the incorporation of PhNCS into the
Fe–H bonds of mononuclear complex cis-Fe(dmpe)2H2 (dmpe =
Conclusions
1
Me2PCH2CH2PMe2),4a h S-bound SCHNPh ligands are observed
1
in the insertion product trans-Fe(dmpe)2(h -SCHNPh)2. The Fe1–
Thiolate-bridged diiron complexes [Cp*Fe(m2-SR)3FeCp*] (1a,
R = Et; 1b, R = Me) react readily with small unsaturated molecules
˚
S3 bond distance (2.327(1) A) in 4 is identical to the corresponding
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 3020–3025 | 3023
©

CS2, COS and PhNCS yielding insertion products [Cp*Fe(m2-
2901, 2867, 1426, 1370, 1308, 1289, 1261, 1097, 1019, 976, 945, 900,
844, 800, 685, 427. Anal. Calcd for C24H39Fe2S5: C, 48.00; H, 6.71.
Found: C, 48.22; H, 6.78.
2
SR)2(m-h -S2CSR)FeCp*] (2a, R = Et; 2b, R = Me), [Cp*Fe(m2-
2
2
SEt)2(m-h -S2)FeCp*] (3), and [Cp*Fe(SEt)(h -SC(SEt)NPh)] (4).
The heterocumulenes CS2 and PhNCS are all bound to the metal
iron atoms in a h mode both in the dimer or monomer products.
In the case of COS insertion reaction, decarbonylation and sulfur
[Cp*Fe(l2-SEt)2(l-g2-S2)FeCp*] (3). 2.0 eq. of COS (ca.
52 mL) was added by syringe to a solution of 1a (0.65 g,
1.15 mmol) in 50 mL THF at room temperature. The resulting
2
coupling reaction of COS happens at the diiron centers, obtaining
◦
solution was heated to 50 C and then stirred for 12 h with the
2
S22- ligand coordinating to the two Fe atoms also in h fashion. 2a
color of solution changing from red-purple to red-brown. After
removal of the solvent in vacuo the residue was purified by column
chromatography on neutral alumina with n-hexane as the eluent
to give 3 (0.23 g, 0.43 mmol, 37% yield) as a red-brown solid.
The crystals of 3 suitable for X-ray analysis were obtained in
concentrated n-hexane at -20 ◦C. 3: 1H NMR (400 MHz, C6D6):
d 1.43 (s, 30H, Cp*-CH3), 1.14 (q, 4H, SCH2CH3), 0.79 (t, 6H,
SCH2CH3). IR (KBr, cm-1): 2963, 2907, 2867, 1474, 1447, 1426,
1373, 1261, 1097, 1021, 801. Anal. Calcd for C22H40Fe2S4: C, 48.89;
H, 6.71. Found: C, 48.77; H, 6.68.
and 2b represent the first examples of CS2 activation at thiolate-
bridged diiron centers and insertion into the Fe–SR bond. These
resulting insertion products may be regarded as model compounds
for CO2 activation and transformation at the di- or multi-metal
centers.
Experimental
General procedures
All manipulations, unless otherwise stated, were carried out under
an argon atmosphere using standard Schlenk-line techniques.
All solvents were dried and distilled over an appropriate drying
agent under argon. Complexes [Cp*Fe(m2-SEt)3FeCp*] (1a)14a and
[Cp*Fe(m2-SMe)3FeCp*] (1b)14b were prepared according to the
literature. CO2, CS2 and COS were commercially obtained and
used as received. The 1H NMR spectra were recorded on a Bruker
400 Ultra Shield spectrometer. Infrared spectra were measured
on a NEXVSTM FT-IR spectrometer. Elemental analyses were
performed on a Vario EL analyzer. Electrochemical measurements
were recorded using a BAS-100W electrochemical potentiostat at
a scan rate of 100 mV s-1. Cyclic voltammogram was obtained in a
three-electrode cell under argon in THF-0.1M [n-Bu4N][PF6]. The
working electrode was a glassy carbon disk (diameter 3 mm), the
reference electrode was a non-aqueous Ag/AgNO3 electrode, and
the auxiliary electrode was a platinum wire.
[Cp*Fe(SEt)(g2-SC(SEt)NPh)] (4). 2.0 eq. of PhNCS (0.29 g,
2.12 mmol) was added to a solution of 1a (0.60 g, 1.06 mmol)
in 30 mL THF at room temperature. The resulting solution was
stirred for 2 h after it was warmed to 50 ◦C, and the color of
solution turned from red-purple to red-brown. After removal
of the solvent in vacuo the residue was purified by column
chromatography on neutral alumina with n-hexane as the eluent to
give red-brown solid 4 (0.44 g, 0.96 mmol, 46% yield). The crystals
of 4 suitable for X-ray analysis were obtained in concentrated n-
hexane at -20 ◦C. 4: 1H NMR (400 MHz, C6D6): d 7.40 (br s, 5H,
Ph), 6.24(br s, 2H, SCH2CH3), 5.38 (br s, 3H, SCH2CH3), 1.25–
2.52(br s, 20H). IR(KBr, cm-1): 3048, 2957, 2922, 2865, 1588, 1490,
1464, 1446, 1405, 1375, 1261, 1244, 1201, 1157, 1075, 1049, 1025,
983, 779, 707, 604, 497. Anal. Calcd for C21H30FeNS3: C, 56.24;
H, 6.74. Found: C, 56.27; H, 6.88.
X-Ray data collection and structure refinement
Syntheses
The data for complexes 2a, 2b, 3, and 4 were collected on
a Bruker SMART APEX CCD diffractometer with graphite
[Cp*Fe(l2-SEt)2(l-g2-S2CSEt)FeCp*] (2a). 20 mL CS2 was
added to 1a (0.45 g, 0.80 mmol) at ambient temperature, followed
by refluxing for 2 h. The color of the solution turned from red-
purple to blue-purple. The solvent was removed in vacuo and a
blue-purple crystalline powder 2a (0.51 g, 0.80 mmol, 100% yield)
was obtained. The crystals of 2a suitable for X-ray analysis were
˚
monochromated Mo Ka radiation (l = 0.71073 A). Empiri-
cal absorption corrections were performed using the SADABS
program.21 Structures were solved by direct methods and refined by
full-matrix least-squares based on all data using F2 using SHELX
97.22 All of the non-hydrogen atoms were refined with anisotropic
thermal displacement coefficients. Hydrogen atoms were fitted
geometrically at calculated distances and allowed to ride on the
parent non-hydrogen atoms with the isotropic displacement being
fixed at 1.2 and 1.5 times that of the aromatic and methyl carbon
atoms that attached, respectively. For complex 2a, the sulfur and
carbon atoms of one thiolate ligand (S1C21C22) were refined
disordered with the s.o.f. of the parts being refined using free
variable, and thermal parameters on adjacent atoms in disordered
moieties were restrained to be similar. For complex 3, in order
to assist the refinement, several restrains were applied: (1) the
geometrical constraints of an idealized regular pentagon for one
Cp* ligand bonding to an Fe1 center was used; (2) thermal
parameters on adjacent carbon atoms in disordered moieties were
restrained to be similar. In addition, the carbon atoms of this Cp*
ligand attached to the Fe1 center were refined disordered with
the s.o.f. of the parts being refined using free variable.
1
obtained by benzene solution layered with acetonitrile. 2a: H
NMR (400 MHz, C6D6): d 1.44 (br s, 2H, S2CSCH2CH3), 0.57
(br s, 4H, SCH2CH3), -0.79 (br s, 3H, S2CSCH2CH3), -2.64 (br s,
6H, SCH2CH3), -9.33 (br s, 30H, Cp*-CH3). IR (KBr, cm-1):
2964, 2899, 2860, 1447, 1427, 1371, 1253, 1157, 1069, 1020, 986,
900, 869, 755, 610, 453. Anal. Calcd for C27H45Fe2S5: C, 50.46; H,
7.21. Found: C, 50.42; H, 7.18.
[Cp*Fe(l2-SMe)2(l-g2-S2CSMe)FeCp*] (2b). 20 mL CS2 was
added to 1b (0.35 g, 0.68 mmol) at ambient temperature, followed
by refluxing for 2 h. The color of the resulting solution turned
from red-purple to blue-purple. The solvent was removed in vacuo
and a blue-purple crystalline powder 2b (0.40 g, 0.68 mmol, 100%
yield) was isolated. The crystals of 2b suitable for X-ray analysis
were obtained by benzene solution layered with acetonitrile. 2b:
1H NMR (400 MHz, C6D6): d 12.44 (br s, 6H, SCH3), -6.43 (br s,
3H, S2CSCH3), -8.84 (br s, 30H, Cp*-CH3). IR (KBr, cm-1): 2963,
3024 | Dalton Trans., 2010, 39, 3020–3025
This journal is
The Royal Society of Chemistry 2010
©

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Acknowledgements
The authors thank the National Natural Science Foundation of
China (No. 20972023, No. 20944003) and the Fund for Foreign
Scholars in University Research and Teaching Programs of China
for financial support of this work.
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©