Controlled synthesis of mono-substituted diphosphine iron thiocarboxylate complexes CpFe(CO)(Ph2P(CH2)nPPh 2)SCOR [n = 1 (dppm), n = 2 (dppe)]. X-ray crystal structure of CpFe(CO)(dppm-S)SCO-3,5-(NO2)

Article abstract of DOI:10.1016/j.poly.2003.08.005

Controlled photolytic CO-substitution reaction of the organoiron thiocarboxylate complexes CpFe(CO)₂SCOR (R = CH₃, 2-NO₂C₆H₄, 4-NO₂C₆H ₄, 3,5-(NO₂)₂

Full text of DOI:10.1016/j.poly.2003.08.005

Polyhedron 22 (2003) 3445–3449
www.elsevier.com/locate/poly
Controlled synthesis of mono-substituted diphosphine iron
thiocarboxylate complexes CpFe(CO)(Ph2P(CH2)nPPh2)SCOR
[n ¼ 1 (dppm), n ¼ 2 (dppe)]. X-ray crystal structure of
CpFe(CO)(dppm-S)SCO-3,5-(NO2)2C6H3
a,
b,
a
c
Mohammad El-khateeb *, Ibrahim Jibril *, Hisham Barakat , Gerd Rheinwald ,
c
Heinrich Lang
a
Chemistry Department, Faculty of Science, Jordan University of Science and Technology, P.O. Box 3030, Irbid 22110, Jordan
b
Department of Chemistry, Yarmouk University, Irbid, Jordan
Institut f€ur Chemie, TU Chemnitz, Strasse der Nationen 62, Chemnitz D-09107, Germany
c
Received 28 May 2003; accepted 21 August 2003
Abstract
Controlled photolytic CO-substitution reaction of the organoiron thiocarboxylate complexes CpFe(CO)2SCOR (R ¼ CH3, 2-
NO2C6H4, 4-NO2C6H4, 3,5-(NO2)2C6H3) with diphosphines (Ph2P(CH2)nPPh2) [n ¼ 1 (dppm), n ¼ 2 (dppe)] at 0 °C using 1:1
(metal:ligand) molar ratio afforded exclusively the monosubstituted complexes CpFe(CO)(Ph2P(CH2)nPPh2)SCOR. The complex
CpFe(CO)(Ph2PCH2P ¼ S(Ph)2)SCO-3,5-(NO2)2C6H3 has been prepared and its X-ray structure was determined.
Ó 2003 Elsevier Ltd. All rights reserved.
Keywords: Substitution; Iron; Thiocarboxylate; Bisphosphine ligands; Structure
1. Introduction
ratios. Complexes such as [CpFe(CO)2ER3]X (X ¼ ha-
lide), CpFe(CO)(ER3)COCH3, [CpFe(PR3)3]X (X ¼ I,
Br) and Cp0 Fe(CO)(EPh3) SCOR (Cp0 ¼ C5H5, But
C5H4, 1,3-But2C5H3) are among the important products
of such reactions [2–9]. Moreover, diphosphines (R2P
(CH2)nPR2) are useful ligands in forming both chelate
and/or bridged binuclear complexes depending on the
chelating ability of the diphosphine. In forming chelate
complexes, the optimum ring size is five, thus
Ph2P(CH2)2PPh2 (dppe) is an excellent chelate ligand.
Ph2PCH2PPh2 (dppm) can chelate but the four mem-
bered ring formed is so strained and the ligand has a
greater tendency to act as a bridging bidentate ligand.
The chelating ability decreases as the chain length in-
creases. A particularly good example is seen in complexes
RhCl(CO)(Ph2P(CH2)nPPh2) which are dimers when
n ¼ 1; 3; 4 but monomers when n ¼ 2 [10,11].
Mono- and diphosphine ligands have played a major
role in coordination chemistry [1]. In addition to their
facile syntheses, their electronic and steric properties can
be varied systematically by varying the substituents on
the phosphorous and by varying the backbone length
of the diphosphines. Photolytic and thermal reactions of
the half-sandwich complexes CpFe(CO)2X (X ¼ halide,
alkyl, SiR3, SnR3, SR) with EPh3 (E ¼ P, As, Sb) were
commonly utilized to prepare CO-substituted complexes.
The type of the product formed in these reactions is de-
termined by the nature of X, the type of ER3, the solvent,
the irradiation time, the temperature and the M:L molar
* Corresponding authors. Tel.: +962-02-7211111x2824; fax: +962-02-
7247983 (I. Jibril), Tel.: +962-02-7201000x23644; fax: +962-2-7095014
(M. El-khateeb).
It was recently reported that the photolytic reaction of
the alkynyl dicarbonyl derivatives CpFe(CO)2(CBCR)
with dppm in THF afforded exclusively the disubstituted
E-mail
addresses:
kateeb@just.edu.jo
(M.
El-khateeb),
iajibril@hotmail.com (I. Jibril).
0277-5387/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2003.08.005

3446
M. El-khateeb et al. / Polyhedron 22 (2003) 3445–3449
derivatives CpFe(dppm)(CBCR). The ‘‘dangling’’ com-
plexes CpFe(CO)(dppm)(CBCR) were never isolated but
they were detected as an intermediates by 31P NMR [12].
Organoiron thiocarboxylate complexes, Cp0 Fe (CO)2
SCOR (Cp0 ¼ C5H5, ButC5H4, 1,3-Bu2t C5H3, R ¼ alkyl,
aryl) appear to be interesting systems especially in their
behavior towards photolytic CO-substitution reactions
with tertiary phosphine ligands. It was found that the
photolytic CO-substitution reactions of Cp0 Fe(CO)2
SCOR with EPh3 (E ¼ P, As, Sb) afforded exclusively the
mono-substituted derivatives Cp0 Fe (CO)(EPh3)SCOR
irrespective of the reaction conditions [9]. On the other
hand, photolytic CO-substitution reactions of CpFe(-
CO)2SCOR with diphosphine ligands seem to be
strongly dependent on the reaction conditions (reaction
temperature, the irradiation time, the metal:ligand molar
ratio, the backbone length of the diphosphine ligand and
the nature of the R group of the thiocarboxylate moiety).
The photolytic CO-substitution reaction of CpFe(-
CO)2SCOR with diphosphine ligands Ph2P(CH2)nPPh2
(n ¼ 1–6) afforded the disubstituted derivatives CpFe
(Ph2P(CH2)nPPh2)SCOR when n ¼ 1; 2; 3 and the mono-
substituted derivatives CpFe(CO)(Ph2P (CH2)nPPh2)SC
OR when n ¼ 4; 5; 6 [13].
diated at 0 °C. The reaction was monitored by IR spec-
troscopy and irradiation was continued until the
disappearance of the two strong terminal carbonyl bands
in the ranges 2025–2040 and 1980–1995 cmꢀ1 and the
appearance of a new band in the range 1940–1970 cmꢀ1
.
The solvent was removed under vacuum and the residue
was dissolved in a minimum amount of CH2Cl2 and
transferred to a silica gel column made up in hexane.
Elution with hexane removes the excess diphosphine li-
gand. The red band of the product was eluted with
CH2Cl2/hexane solution (1:1 volume ratio). Evaporation
of the solvent under vacuum and recrystallization from
CH2Cl2–hexane mixture afforded the monosubstituted
complexes CpFe(CO)(Ph2P(CH2)n PPh2) SCOR (1–4).
2.1.1. CpFe(CO)(Ph2PCH2PPh2)SCO-3,5-(NO2)2C6H3
(1a)
1
Yield ¼ 50%. m.p. ¼ 138–140 °C. H NMR (CDCl3):
d 3.50 (s, 2H, CH2); 4.43 (s, 5H, Cp); 7.25 (m, 20H,
2PPh2); 9.40 (m, 3H, Ph). IR (KBr, cmꢀ1) mCBO, 1959
(vs); mC@O, 1600 (m); mNO , 1531 (s), 1346 (s). Anal. Calc.
for C38H30FeN2O6P2S: C, 60.14; H, 3.95; N, 3.68; S,
4.21. Found C, 59.85; H, 3.95; N, 3.76; S, 4.33%.
2
In continuation to our efforts in this area, we report
here the controlled syntheses of the monosubstituted
diphosphine derivatives CpFe(CO)(Ph2P(CH2)nPPh2)
SCOR (n ¼ 1; 2).
2.1.2. CpFe(CO)(Ph2P(CH2)2PPh2)SCO-3,5-(NO2)2C6H3
(1b)
1
Yield ¼ 65%. m.p. ¼ 97–99 °C. H NMR (CDCl3): d
2.79 (m, 4H, CH2); 4.49 (s, 5H, Cp); 7.29 (s, 20H,
2PPh2); 9.17 (m, 3H, Ph). IR (KBr, cmꢀ1): mCBO, 1959
(vs); mC@O, 1604 (m); mNO , 1537, 1341 (s). Anal. Calc. for
C39H32FeN2O6P2S: C, 60.48; H, 4.16; N, 3.62; S, 4.14.
Found C, 60.46; H, 4.11; N, 3.49; S, 4.28%.
2
2. Experimental
All reactions were conducted under N2 atmosphere
by Schlenk techniques. The organoiron thiocarboxylate
complexes CpFe(CO)2SCOR were prepared according
to published procedure [14]. Bis(diphenylphosph-
ino)methane (dppm) and bis(diphenylphosphino)ethane
(dppe) were purchased from Aldrich and used as re-
ceived. For column chromatography, silica gel of par-
ticle size 0.0063–0.200 mm (70–230 mesh) was
employed. All photolytic reactions were carried out
using a high-pressure mercury lamp (HANAU, 240–
260 nm). Infrared (IR) spectra were recorded on a
2.1.3. CpFe(CO)(PPh2CH2PPh2)SCO-4-NO2C6H4 (2a)
1
Yield ¼ 40%. m.p. ¼ 120–122 °C. H NMR (CDCl3):
d 3.51 (s, 2H, CH2); 4.52 (s, 5H, Cp); 7.25 (m, 20H,
2PPh2); 8.10 (dd, 4H, Ph). IR (KBr, cmꢀ1): mCBO, 1963
(vs); mC@O, 1586 (s); mNO , 1516, 1335 (s). Anal. Calc. for
C38H31FeNO4P2S: C, 63.79; H, 4.37; N, 1.96; S, 4.48.
Found C, 64.10; H, 4.31; N, 1.88; S, 4.62%.
2
2.1.4. CpFe(CO)(Ph2P(CH2)2PPh2)SCO-4-NO2C6H4
(2b)
1
1
Nicolet-Impact 410 FT-IR spectrometer and H NMR
spectra on a Bruker WP 80 SY spectrometer with TMS
as internal standard. Elemental analyses were per-
Yield ¼ 70%. m.p. ¼ 201–203 °C. H NMR (CDCl3):
d 2.55 (t, 4H, CH2); 4.47 (s, 5H, Cp); 7.23 (m, 20H,
2PPh2); 8.28 (dd, 4H, Ph). IR (KBr, cmꢀ1): mCBO, 1955
ꢀ
ꢀ
formed by Laboratoire dÕAnalyse Elementaire, Uni-
(vs); mC@O, 1606 (m); mNO , 1521, 1349 (s). Anal. Calc. for
C39H33FeNO4P2S: C, 64.21; H, 4.56; N, 1.92; S, 4.40.
Found C, 64.85; H, 4.58; N, 2.01; S, 4.32%.
2
ꢀ
ꢀ
ꢀ
versite de Montreal, Montreal, Canada. Melting points
were measured on an electrothermal melting point
apparatus and are uncorrected.
2.1.5. CpFe(CO)(Ph2P(CH2)2PPh2)SCO-2-NO2C6H4
(3b)
2.1. General procedure for the preparation of CpFe
(CO)(Ph2P(CH2)nPPh2)SCOR
1
Yield ¼ 62%. m.p. ¼ 185–187 °C. H NMR (CDCl3):
d 2.56 (t, 4H, CH2); 4.56 (s, 5H, Cp); 7.43 (m, 20H,
2PPh2); 7.80 (dd, 4H, Ph). IR (KBr, cmꢀ1): mCBO, 1950
A THF solution (100 ml) of the CpFe(CO)2SCOR
(1.00 mmol) and the diphosphine (1.0 mmol) were irra-
(vs); mC@O, 1605 (m); mNO , 1530, 1340 (s). Anal. Calc. for
2

M. El-khateeb et al. / Polyhedron 22 (2003) 3445–3449
3447
ꢁ
ꢁ
ꢁ
C39H33FeNO4P2S: C, 64.21; H, 4.56; N, 1.92; S, 4.40.
Found C, 64.56; H, 4.61; N, 1.98; S, 4.71%.
12:860ð3Þ A, b ¼ 11:052ð2Þ A, c ¼ 29:955ð6Þ A and
b ¼ 98:667ð5Þ°; V ¼ 4208:8ð15Þ A ; dcalc: ¼ 1:251 g/cm3,
3
ꢁ
Z ¼ 4; l ¼ 0:576 mmꢀ1
.
The cell constants and reflections were measured at
a temperature of 173(2) K on a Bruker Smart 1K
CCD detector with a graphite monochromator, k(Mo
2.1.6. CpFe(CO)(PPh2P(CH2)2PPh2)SCOCH3 (4b)
Yield ¼ 55%. m.p. ¼ 212–214 °C. 1H NMR (CDCl3): d
1.42 (s, 3H, CH3); 2.72 (t, 4H, CH2); 4.58 (s, 5H, Cp);
7.50 (m, 20H, 2PPh2). IR (KBr, cmꢀ1): mCBO, 1950 (vs);
mC@O, 1610 (m). Anal. Calc. for C34H32FeO2P2S: C,
65.60; H, 5.18; S, 5.15. Found C, 65.34; H, 5.22; S, 5.37%.
ꢁ
Ka) ¼ 0.71073 A. An x scan with a scan range 1:65°
6 2h 6 29:26° has been employed. There were 3947
independent significant reflections (I P 2r). The
structure was solved by use of the program SHELX 97
[15] by direct methods. The position of disordered or
not refinable solvent molecule was calculated by the
2.2. Preparation of CpFe(CO)(Ph2PCH2P ¼ S(Ph)2)S-
CO-3,5-(NO2)2C6H3 (1c)
P
LATON [16] integrated SQEEZE [17] procedure and
the corresponding electron density was subtracted
before the final refinement. All non-hydrogen atoms
were refined with anisotropic thermal parameters.
Hydrogen atoms were placed in the calculated posi-
tions. The refinement converged at R1 ¼ 0:0958 and
Rw ¼ 0:1940.
A methylene chloride solution containing 1a (2.0 g,
1.5 mmol) and (l-S3)[CpFe(CO)2]2 (1.1 g, 0.5 mmol) was
stirred at room temperature for 2 h. The solvent was
evaporated under vacuum and the residue was intro-
duced to a chromatography column made up in hexane.
A red band of [Fp–Fp] was eluted (CH2Cl2/hexane)
(3:7). The product 1c was eluted with (CH2Cl2/hexane)
(7:3). Recrystallization from CHCl3/hexane afforded a
3. Results and discussion
1
dark-red crystals. Yield ¼ 80%. m.p. ¼ 110–112 °C. H
NMR (CDCl3): d 3.21 (s, 2H, CH2); 4.45 (s, 5H, Cp);
In our study of the photolytic CO-substitution re-
action of CpFe(CO)2SCOR with diphosphine ligands
we observed that the reaction temperature and the
irradiation time are significant in determining the type
of product formed [13]. Thus the monosubstituted
derivatives, CpFe(CO)(Ph2P(CH2)nPPh2)SCOR (n ¼ 1; 2),
could be prepared if the reaction temperature is kept
at 0 °C and the irradiation time is stopped when the
first CO group is substituted (Scheme 1). Small
amount (ca. 5–10%) of a red complexes have been
obtained from these reactions. These complexes were
found to be the dimers of the formula (l-Ph2P(CH2)
nPPh2)[CpFe(CO)SCOR]2. The yield of these products
can be maximized by doing a separate reaction using
2:1 (metal:ligand) ratio. The complex (l-Ph2P (CH2)2
PPh2)[CpFe(CO)SCO-3,5-C6H3(NO2)2]2 has been pre-
pared and characterized by elemental analysis and
spectral data.
The monosubstituted derivatives (1–4) which are
stable in the solid state seem to be novel complexes in
view of the large chelation tendency of such diphosphine
ligands and in view of the unsuccessful attempts to
isolate them in similar systems as CpFe(CO)2(CBCR)
[12]. Moreover, these newly prepared complexes are of
special interest, because they can be considered as a
good precursors for the synthesis of homo and hetero
phosphino-bridged binuclear complexes in which the
two metals are in close proximity that promote catalytic
organometallic reactions.
7.23 (m, 20H, 2PPh2); 9.38 (m, 3H, Ph). IR (KBr, cmꢀ1):
m
CBO, 1960 (vs); mC@O, 1600 (s); mNO , 1534, 1345 (s).
2
Anal. Calc. for C38H30FeN2O6P2S2 ꢁ CHCl3: C, 51.34;
H, 3.40; N, 3.07; S, 7.03. Found C, 51.19; H, 3.52; N,
3.17; S, 7.08%.
2.3. Preparation of the bridging complex (l-Ph2P(CH2)2
PPh2)[CpFe(CO)SCO-3,5-(NO2)2C6H3]2 (5b)
In a procedure similar to that described for 1, solu-
tion of CpFe(CO)2SCO-3,5-C6H3 (NO2)2 (2.47 g, 1.0
mmol) and Ph2P(CH2)2PPh2 (1.24 g, 0.5 mmol) in THF
was irradiated for 30 min. Column chromatography
afforded a dark-red band, which was eluted with
CH2Cl2/hexane (9:1). Removal of the solvent under
vacuum and recrystalization from CH2Cl2/hexane afford
red crystals of the title compound. Yield ¼ 50%.
1
m.p. ¼ 126–128 °C. H NMR (CD2Cl2): d 2.58 (s, 4H,
CH2); 4.50 (s, 10H, Cp); 7.50 (m, 26H, 2PPh2 + C6H4).
IR (KBr, cmꢀ1): mCBO, 1948(vs); mC@O, 1601 (m); mNO
,
2
1534, 1437(s). Anal. Calc. for (C26H30FeN2O6PS): C,
50.66; H, 4.91; N, 4.54; S, 5.20. Found C, 49.79; H, 4.57;
N, 4.43; S, 5.42%.
2.4. Crystal structural analysis for CpFe(CO)
(Ph2PCH2P( ¼ S)Ph2)SCO-3,5-(NO2)2C6H3 (1c)
Crystals suitable for the X-ray study were obtained by
recrystallization from CHCl3. Compound 1c (C38H30
N2O6P2S2Fe), molar mass 782.55; crystallizes in the
monoclinic system, space group P21=n with a ¼
Complexes 1–4 were characterized by elemental
analysis, IR and 1H NMR spectral data. Their IR
spectra exhibit one very strong band in the range 1940–
1970 cmꢀ1 corresponding to the carbonyl group bon-

3448
M. El-khateeb et al. / Polyhedron 22 (2003) 3445–3449
Scheme 1.
ded to the iron atom. The C@O stretching band of the
thiocarboxylate moiety appears in the range 1586–1621
cmꢀ1. The assignment of these bands was made on the
bases of the reported results of the organoiron thio-
carboxylate complexes [14]. Their 1H NMR spectra
show the characteristic protons in their expected
chemical shift regions.
In an attempt to test the reactivity of the unbonded
phosphine of the prepared mono-substituted complexes,
the complex CpFe(CO)(Ph2PCH2PPh2)SCO-3,5-C6H3
(NO2)2, 1a, was treated with (l-S3)[CpFe CO)2]2, which
is known to undergo smooth desulfurization with tertiary
phosphines [18]. Indeed, desulfurization took place and
the unbonded phosphine abstracted sulfur forming the
phosphine–sulfide derivative CpFe(CO)(Ph2PCH2P ¼
S(Ph)2)SCO-3,5-(NO2)2C6H3, 1c. The structure of 1c was
determined by X-ray analysis.
ꢁ
Fig. 1. Selected bond lengths (A) and angles (°): Fe–C38 ¼ 1.755(6),
Fe–C33 ¼ 2.102(7), Fe–C34 ¼ 2.085(7), Fe–C35 ¼ 2.058(7), Fe–
3.1. Description of the crystal structure of CpFe
(CO)(Ph2PCH2P ¼ S(Ph2)SCO-3,5-(NO2)2C6H3 (1c)
C36 ¼ 2.107(7),
Fe–C37 ¼ 2.089(6),
Fe–P1 ¼ 2.2092(18),
Fe–
S1 ¼ 2.273(2), P2–S2 ¼ 1.951(3), S1–C1 ¼ 1.760(8), C1–O1 ¼ 1.215(9);
C38–Fe–P1 ¼ 93.5(2), C38–Fe–S1 ¼ 93.5(2), C1–S1–Fe ¼ 106.2(3),
O1–C1–S1 ¼ 125.7(6), P2–C8–P1 ¼ 124.6(3).
The complex consists of a monomeric molecule in
which the Fe-atom is bonded to four different groups
(Fig. 1). The cyclopentadienyl ring is bound to the Fe-
atom in a g5-fashion with Fe–C bond distances
legs C38–Fe–S1 93.5(2)°, C38–Fe–P1 93.5(2)° and S1–Fe–
P1 92.16(7)° are almost equal.
ꢁ
ranging between 2.058(7) and 2.107(7) A. The (dppm-
S) ligand acts as monodentate ligand through the P-
ꢁ
atom with an Fe–P bond distance of 2.209(2) A. The
4. Supplementary data
Fe–S bond distance of the thiocarboxylate moiety is
2.273(3), which is in agreement with that of the Fe–S
thiocarboxylate complexes [14].
The coordination around the Fe-atom of the cyclo-
pentadienyl ring (taken as bound to its centroid), the CO
group, the thiocarboxylate moiety and the dppm-S li-
gand can be described as a three-legged piano stool.
Moreover, the values of the angles involving the three
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Center, CCDC No. 209309. Copies of the infor-
mation may be obtained free of charge from The Di-
rector, CCDC, 12 Union Road, Cambridge, CB2 1EZ,
UK (fax: +44-1223-336033; e-mail: deposit@ccdc.cam.
ac.uk or www: http//www.ccdc.cam.ac.uk).

M. El-khateeb et al. / Polyhedron 22 (2003) 3445–3449
3449
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Acknowledgements
The authors thank the Deanship of Research, Jordan
University of Science & Technology for financial sup-
port, Grant No. 143/99.
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