Half sandwich iron S-bonded mono-thiocarbonate complexes: Structure of CpFe(CO)2SCO2Et

Article abstract of DOI:10.1016/S0277-5387(03)00465-0

The synthesis and characterization of mononuclear iron complexes containing mono-thiocarbonate ligands are described. The new compounds of general formula CpFe(CO)₂SCO₂R [R = Et (1), iso-Bu (2), Ph (3), 4-C₆H₄NO

Full text of DOI:10.1016/S0277-5387(03)00465-0

Polyhedron 22 (2003) 3105–3108
www.elsevier.com/locate/poly
Half sandwich iron S-bonded mono-thiocarbonate
complexes: structure of CpFe(CO)2SCO2Et
*
Mohammad El-khateeb , Khalil J. Asali, Anas Lataifeh
Chemistry Department, Faculty of Science, Jordan University of Science and Technology, P.O. Box 3030, Irbid 22110, Jordan
Received 3 April 2003; accepted 27 June 2003
Abstract
The synthesis and characterization of mononuclear iron complexes containing mono-thiocarbonate ligands are described. The
new compounds of general formula CpFe(CO)2SCO2R [R ¼ Et (1), iso-Bu (2), Ph (3), 4-C6H4NO2 (4), Me (5)] were prepared by
reacting the iron sulfides (l-Sx)[CpFe(CO)2]2 (x ¼ 2, 3) with the corresponding chloroformates (ROCOCl). These new complexes
have been characterized by elemental analyses and spectroscopic methods. The crystal structure of CpFe(CO)2SCO2Et, 1, has been
determined by single crystal X-ray diffraction analysis.
Ó 2003 Elsevier Ltd. All rights reserved.
Keywords: Thiocarbonate complexes; Iron; X-ray structure; Carbonyl; Sulfur-ligands
1. Introduction
plexes were reported to undergo CS2 elimination to give
the dimeric (l-SR)2[CpFe(CO)]2 complexes [20].
Thiocarbonate, dithiocarbonate and trithiocarbonate
ligands provide a variety of transition and main group
metal complexes [1–10]. These complexes were found to
have important chemical [11] and biological [12] prop-
erties. Trithiocarbonate ligands, known as thioxanth-
ates, are the most common ligands among all these
carbonate ligands [6,13–18]. Complexes containing thi-
oxanthate ligands are generally prepared by insertion of
carbon disulfide into the metal–sulfur bond of metal–
thiolate complexes [13–18]. Accordingly, the complexes
CpRu(PPh3)S2CSR [13,14], CpW(CO)2S2CSR [6] and
(PPh3)Pt(SR)(S2CSR) [19] containing bidentate thiox-
anthate ligands were reported. Complexes with
monodentate thioxanthate ligands, such as (PP3)RhS2
CSMe (PP3 ¼ tris(2-diphenylphosphino-ethyl)phosphine)
[4] and CpFe(CO)2S2CSR [20] were also reported in the
literature. The later complexes, CpFe(CO)2S2CSR, were
prepared from the reaction of the iron halide,
CpFe(CO)2X (X ¼ Cl, I) with the corresponding thi-
oxanthate anions [20]. These iron thioxanthate com-
Our studies on the synthesis and reactivities of iron–
sulfur complexes have demonstrated that the iron sul-
fides, (l-Sx)[CpFe(CO)2]2, can serve as precursors to a
variety of iron complexes containing sulfur donor ligands
[17–20]. Iron thiocarboxylate complexes Cp0Fe(CO)2-
SCOR (Cp0 ¼ C5H5, ButC5H4, 1,3-(But)2C5H3) were
prepared from the corresponding iron sulfide precursors
[21–24]. Recently, it has also been found that these iron
sulfides react with sulfonyl chlorides to give the iron
thiosulfonate complexes CpFe(CO)2SSO2R [25].
Although, trithiocarbonate complexes are very com-
mon in the literature, mono-thiocarbonate complexes of
transition metals are rare [26]. In this paper, the iron
precursors (l-Sx)[CpFe(CO)2]2 are used to prepare iron
monothiocarbonate complexes. The preparation and
characterization of CpFe(CO)2SCO2R are discussed.
2. Results and discussion
2.1. Synthesis and characterization
* Corresponding author. Tel.: +962-2-7201000/23644; fax: +962-2-
7095014.
E-mail address: kateeb@just.edu.jo (M. El-khateeb).
A series of cyclopentadienyldicarbonyliron mono-
thiocarbonate complexes, CpFe(CO)2SCO2R (1–5),
0277-5387/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/S0277-5387(03)00465-0

3106
M. El-khateeb et al. / Polyhedron 22 (2003) 3105–3108
were prepared by the reaction of (l-Sx)[CpFe(CO)2]2
with the corresponding chloroformates ROCOCl [R ¼
Et (1), iso-Bu (2), Ph (3), 4-C6H4NO2 (4), Me (5)] as
shown in Eq. (1). The chloro-derivative CpFe(CO)2Cl,
was also obtained as a side product of Eq. (1). These two
products were easily separated by column chromatog-
raphy.
ligands are excellent bidentate ligands, the monothio-
carbonate ligands are not. All attempts to prepare the
bidentate complexes CpFe(CO)SCO2R, in which the
thiocarbonate ligands is bonded to the iron through
both S and O-atoms, were unsuccessful. Irradiating of a
THF solution of the complexes 1–5 with UV-light or
heating of these solutions under reflux resulted in ex-
cessive decomposition of the starting complexes.
CO
CO
O
O
2.2. Crystal structure
R
Fe
R
Fe Sx
OC
Fe
Fe
+
+
Cl
O
OC
OC
S
O
OC
OC
OC
Cl
1-5
The molecular structure of CpFe(CO)2SCO2Et, 1,
and the atom numbering scheme are shown in Fig. 1. It
can be seen that the thiocarbonate ligand is bonded to
the iron atom in a monodentate fashion through the
sulfur atom. Compound 1 possesses a Fe–S bond dis-
ð1Þ
The thiocarbonate complexes (1–5) are air stable as
solids and are air sensitive in solutions. They are soluble in
most common polar organic solvents but insoluble in
hydrocarbons. The structures of these complexes were
established by elemental analysis, IR and 1H NMR
spectroscopy. The IR spectra of 1–5 showed two strong
bands in the ranges 2044–2045 and 1997–1999 cmꢀ1 at-
tributed to the stretching frequencies of the two terminal
carbonyl groups bonded to the iron center. These bands
are within the same range observed for the thiocarboxy-
late analogues CpFe(CO)2SCOR (2027–2060 and 1998–
1984 cmꢀ1) [22] and lower than those of thiosulfonates,
ꢀ
tance of 2.2675(10) A, which is similar to that observed
ꢀ
for CpFe(CO)2SCO–2-C6H4NO2 (2.266(1) A) [22], and
a Fe–S–C(1) angle of 108.25(12)°. The C(1)–O(1) bond
length of 1.197(4) A is also similar to that obtained for
ꢀ
ꢀ
CpFe(CO)2SCO–2-C6H4NO2 (1.209(5) A) [22]. The S–
C(1)–O(2) bond angle of 108.2(2)° is smaller than the S–
CO–R bond in CpFe(CO)2SCO–2-C6H4NO2 (114.7(3)°)
and similar to those obtained for Ph2Ge(SCO2R)2 and
Ph3GeSCO2R (average 107°). The C(1)–O(2)–C(3) angle
(116.7(3)°) is consistent with less p-bond character in the
C–O bond involved in the C(1)–O(2)–C(3) connection
compared to the S–C(1)–O(1) core, in accordance with
reported systems [26].
CpFe(CO)2SSO2R (2047–2064 and 1991–1998 cmꢀ1
)
[25]. The spectra also contain a band with medium in-
tensity in the range 1655–1677 cmꢀ1 for the ketonic car-
bonyl group of the thiocarbonate ligand. This band is
lower than that observed for Ph2Ge(SCO2R)2 and
Ph3GeSCO2R (1691–1702 cmꢀ1) [26]. This shift is due to
higher electron density on iron in 1–5 compared to that of
germanium. The frequency of this ketonic band is also
higher than that of the corresponding thiocarboxylate
complexes (1595–1605 cmꢀ1) [22], which may be attrib-
uted to more p-bond character in the S–C bond compared
3. Experimental
3.1. General
Manipulations were performed under a nitrogen at-
mosphere using Schlenk techniques. Diethyl ether, hex-
ane and benzene were purified by reflux over sodium
and distillation under nitrogen. Dichloromethane was
heated under reflux over P2O5 and distilled under ni-
trogen. Chloroformates, iron dimer, elemental sulfur
were obtained from Acros and were used as received.
The iron sulfides were prepared using literature proce-
dures [28].
1
to that of the C–OR bond (vide infra) [26,27]. The H
NMR data of these new complexes are collected in Sec-
tion 3 and exhibit a singlet peak for the five Cp-protons in
the range 4.98–5.12 ppm. These peaks are similar to those
observed for the thiocarboxylates, CpFe(CO)2SCOR
(4.98–5.13 ppm) and lower than those observed for the
thiosulfonate complexes, CpFe(CO)2SSO2R (5.21–5.28
ppm) [25]. The IR and NMR data reflect a relatively
higher electron density around the iron-center in com-
plexes 1–5 compared to those of the thiosulfonates and
similar to those of the thiocarboxylates. The chemical
shifts for the protons of the thiocarbonate ligands are
observed in the expected ranges and the signals have the
expected multiplicity.
IR and 1H NMR spectra were recorded on a Nicolat-
Impact 410 FT-IR spectrometer and a Bruker AS-200
MHz spectrometer, respectively. Elemental analyses
ꢁ
were done in the Laboratoire DÕAnalyse Elementaire
ꢁ
ꢁ
ꢁ
Universite de Montreal, Montreal, Quebec, Canada.
Melting points were reported on a Staurt Melting point
apparatus (SMP3) and are uncorrected.
The reactivity of the iron sulfides toward the chlo-
roformates is due to the presence of lone pairs of elec-
trons on the sulfur atoms of the sulfide-bridge ligand. In
contrast to the sulfonyl chlorides [25], all chloroformates
used in this study reacted with the iron sulfides to give
mono-thiocarbonate complexes. Although thioxanthate
3.2. General procedure for the preparation of
CpFe(CO)2SCO2R, 1–5
A 100 ml Schlenk flask was charged with the iron
sulfides (l-Sx)[CpFe(CO)2]2 (0.45 g, 1.00 mmol) and 50

M. El-khateeb et al. / Polyhedron 22 (2003) 3105–3108
3107
ꢀ
Fig. 1. ORTEP drawing of CpFe(CO)2SCO2Et (1). Selected bond lengths (A) and angles (°): Fe–S ¼ 2.2675(10), Fe–C11 ¼ 1.768(4), Fe–
C12 ¼ 1.780(4), Fe–C31 ¼ 2.081(4), Fe–C32 ¼ 2.088(4), Fe–C33 ¼ 2.103(4), Fe–C34 ¼ 2.092(4), Fe–C35 ¼ 2.090(4), S–C1 ¼ 1.748(3), C1–
O1 ¼ 1.97(4), C1–O2 ¼ 1.346(4), C11–O11 ¼ 1.137(4), C12–O12 ¼ 1.125(4), C11–Fe–C12 ¼ 93.80(17), C11–Fe–S ¼ 89.83(12), C12–Fe–S ¼ 93.55(11),
C1–S–Fe ¼ 108.25(12), O1–C1–O2 ¼ 123.8(3), O1–C1–S ¼ 123.8(3), O2–C1–S ¼ 108.2(2), C1–O2–C3 ¼ 116.7(3).
ml of diethyl ether. The chloroformate (1.20 mmol) was
added via syringe. The resulting solution was stirred
overnight. The volatiles were removed under vacuum
and the resulting solid was redissolved in a minimum
amount of dichloromethane and introduced to a silica
gel column made up in hexane. Elution with hexane
eliminated the unreacted chloroformates. Elution with
hexane/dichloromethane solution (1:1 v:v ratio) gave an
orange band which was collected and identified as
CpFe(CO)2SCO2R, followed by a red band which was
also collected and identified as CpFe(CO)2Cl. The
CpFe(CO)2SCO2R were recrystallized from dichlorom-
ethane/hexane.
H, 3.05; S, 9.71%. IR (CH2Cl2, cmꢀ1): 2045 s, 1999 s
1
(mCBO), 1677 w (mC@O). H NMR (CDCl3, d ppm):
5.12 (s, 5H, C5H5), 7.22 (m, 3H, C6H5), 7.41 (m, 2H,
C6H5).
3.2.4. CpFe(CO)2SCO2–4-C6H4NO2 (4)
Yield, 80%. M.p., 59–60 °C. Anal. Found: C, 43.90;
H, 2.35; S, 7.85, N, 3.51. Required for C14H9FeNO6S:
C, 44.80; H, 2.42; S, 8.55; N, 3.73%. IR (CH2Cl2, cmꢀ1):
2044 s, 1998 s (mCBO), 1670 w (mC@O). 1H NMR
(CDCl3, d ppm): 5.08 (s, 5H, C5H5), 6.94 (d, 2H, C6H4),
8.22 (d, 2H, C6H4).
3.2.5. CpFe(CO)2SCO2Me (5)
3.2.1. CpFe(CO)2SCO2Et (1)
Yield, 65%. M.p., 101–102 °C. Anal. Found: C, 39.51;
H, 2.48; S, 11.19. Required for C9H8FeO4S: C, 40.33; H,
3.10; S, 11.96%. IR (CH2Cl2, cmꢀ1): 2044 s, 1999 s
(mCBO), 1662 w (mC@O). H NMR (CDCl3, d ppm):
3.73 (s, 3H, CH3), 5.00 (s, 5H, C5H5).
Yield, 75%. M.p., 109–110 °C. Anal. Found: C, 42.35;
H, 3.33; S, 11.95. Required for C10H10FeO4S: C, 42.58;
H, 3.57; S, 11.37%. IR (CH2Cl2, cmꢀ1): 2044 s, 1997 s
1
1
(mCBO), 1655 w (mC@O). H NMR (CDCl3, d ppm):
1.15 (t, 3H, CH3), 4.12 (q, 2H, CH2), 5.05 (s, 5H, C5H5).
3.3. Crystallographic analysis
3.2.2. CpFe(CO)2SCO2CH2CH(CH3)2 (2)
Yield, 65%. M.p., 69–70 °C. Anal. Found: C, 45.95;
H, 4.64; S, 10.51. Required for C12H14FeO4S: C, 46.49;
H, 4.55; S, 10.34%. IR (CH2Cl2, cmꢀ1): 2044 s, 1997 s
(mCBO), 1657 w (mC@O). H NMR (CDCl3, d ppm):
0.95 (d, 6H, CH3), 1.90 (m, 1H, CH), 3.80 (d, 2H, CH2),
4.98 (s, 5H, C5H5).
Single crystals suitable for X-ray were obtained by
recrystallization of 1 from dichloromethane/hexane
mixture. The crystallographic data are shown in Table 1.
Cell parameters were determined from 7978 reflections
(2:92° < h < 72:88°). There were 2277 independent re-
flections with 1638 observed reflections (>2rðIÞ). The
structure was solved by direct methods using SHELXS-97
[29] and DIFMAP synthesis using SHELXL-96 [30]. All
non-hydrogen atoms are anisotropic. Hydrogen atoms
are isotropic.
1
3.2.3. CpFe(CO)2SCO2Ph (3)
Yield, 72%. M.p., 98–99 °C. Anal. Found: C, 50.28;
H, 3.17; S, 10.19. Required for C14H10FeO4S: C, 50.94;

3108
M. El-khateeb et al. / Polyhedron 22 (2003) 3105–3108
Table 1
Selected crystal data and refinement parameters for CpFe(CO)2SCO2Et
(1)
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Dalton Trans. (1989) 233.
Empirical formula
Formula weight
Crystal size (mm)
Crystal system
C10H10FeO4S
282.09
[4] M. Di Varia, D. Rovai, P. Stoppioni, Polyhedron 12 (1993)
13.
0.60 ꢁ 0.14 ꢁ 0.10
orthorhombic
Pbca
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Organomet. Chem. 580 (1999) 137.
Space group
Unit cell dimension
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1900.
ꢀ
a (A)
13.5049(3)
11.3748(3)
15.1179(3)
2322.34(9)
8
[7] Z. Travincek, M. Malon, Z. Sindelar, Trans. Met. Chem. 24
(1999) 156.
ꢀ
b (A)
ꢀ
c (A)
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(1999) 38.
3
ꢀ
V (A )
Z
Index ranges
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44 (1998) 193.
ꢀ16 < h < 15, ꢀ13 < k < 12,
ꢀ17 < l < 17
1.614
[10] L. Contreras, A. Pizzano, L. Sanchez, E. Camona, A. Monge, C.
Ruiz, Organometallics 14 (1995) 58.
Dcalc (Mg mꢀ3
Radiation type
)
Cu Ka
12.088
1.54178
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[12] J. Vicente, M.-T. Chicote, P. Conzalez-Herrero, Inorg. Chem. 36
(1997) 5735.
l (mmꢀ1
)
ꢀ
k (A)
h Range (°)
2.92–72.88
0.0395
0.1166
[13] A. Shaver, P.-Y. Plouffe, P. Bird, E. Livingstone, Inorg. Chem. 29
(1990) 1826.
R½F 2 > 2rðF 2Þꢂ
a
xRðF 2Þ
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6913.
2
a x ¼ 1=½r2ðFo2Þ þ ð0:0693PÞ ꢂ where P ¼ ðFo2 þ 2Fc2Þ=3.
[15] F. Sato, K. Hida, M. Sato, J. Organomet. Chem. 39 (1972)
197.
4. Supplementary materials
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Inorg. Chem. 25 (1986) 4181.
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC No. 208084. Copies of this infor-
mation may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (fax:
+44-1233-336-033; e-mail: deposit@ccdc.cam.ac.uk or
www:http://www.ccdc.cam.ac.uk).
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Acknowledgements
We are grateful to the Deanship of Research, Jordan
University of Science and Technology for financial
support, Grant No. 31/2002. We wish also to thank Mrs.
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ꢁ
F. Belanger-Gariepy (University of Montreal) for de-
termining the X-ray structure.
ꢁ
ꢁ
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