1,1,1,3,3,3-Hexamethyltrisilanylene-bridged bis(cyclopentadienyl)tetracarbonyldiiron and its derivatives: Synthesis, properties and molecular structures

Article abstract of DOI:10.1016/j.poly.2006.10.026

The title ring-bridged bis(cyclopentadienyl)diiron complexes [η⁵,η⁵-C₅H₄-Si(SiMe₃)₂-C₅H₄]Fe₂(CO)L(μ-CO)₂ [L = CO (1), P(OPh)₃ (2), P(O

Full text of DOI:10.1016/j.poly.2006.10.026

Polyhedron 26 (2007) 1211–1216
www.elsevier.com/locate/poly
1,1,1,3,3,3-Hexamethyltrisilanylene-bridged
bis(cyclopentadienyl)tetracarbonyldiiron and its derivatives:
Synthesis, properties and molecular structures
*
Huai-Lin Sun , Zhen-Sheng Zhang
Department of Chemistry, Nankai University, 94 Weijin Road, Tianjin 300071, PR China
Received 5 March 2006; accepted 12 October 2006
Available online 21 October 2006
Abstract
The title ring-bridged bis(cyclopentadienyl)diiron complexes [g5,g5-C5H4–Si(SiMe3)2–C5H4]Fe2(CO)L(l-CO)2 [L = CO (1), P(OPh)3
(2), P(OMe)3 (3), PPh3 (4), PMe3 (5)] that contain exocyclic Si–Si bonds attached to the bridging silicon atom have been synthesized. The
Si–Si bonds were found to be stable to the intramolecular iron centers under both thermal and photochemical conditions, in sharp con-
trast to the facile cleavage of the Si–Si bond in 1,1,2,2-tetramethyldisilanylene-bridged analogous complexes. The stability of the Si–Si
bonds in the present cases may be attributed to the fact that these Si–Si bonds are spatially unapproachable by the intramolecular coord-
inatively unsaturated iron centers. Molecular structures of 1 and 2 have been determined by X-ray diffraction methods. An obvious con-
formational change due to substitution of CO for P(OPh)3 was observed.
ꢀ 2006 Elsevier Ltd. All rights reserved.
Keywords: Silicon; Iron; Cyclopentadienyl; Phosphorus; Carbonyl; X-ray diffraction
CO
1. Introduction
Me2
Si
Me2
Si
Me2
Si
L
Fe
heat
Ring-bridged bis(cyclopentadienyl)tetracarbonyldiiron
complexes (g5,g5-C5H4–X–C5H4)Fe2(CO)2(l-CO)2, in
which the bridging group –X– can be either carbon- or
silicon-containing segments (e.g., –CH2– [1], –CMe2– [2],
–CH2CH2– [3], –CMe2CMe2– [4], –(CHNMe2CHNMe2)–
[5], –(CH2)3– [6], –SiMe2– [7,8], –Me2SiCH2CH2SiMe2–
[9] and –Me2SiOSiPh2OSiMe2– [10]) have been extensively
studied owing to their unique structural and reactive prop-
erties in the past. Of particular interest is the introduction
of the Si–Si bond-containing group –Me2SiSiMe2– as the
bridge, which has resulted in the unexpected discovery of
a novel rearrangement reaction involving metathesis of
the intramolecular Si–Si and Fe–Fe bonds under thermal
conditions (Eq. (1)) [11–23].
ð1Þ
Fe
CO
Si
Me2
Fe
Fe
OC
OC
L
OC
CO
L = CO or PR3
Since the first report of this rearrangement by us in 1993
[11], much effort has been devoted to explore its scope and
mechanistic details [12–23]. It was not until very recently,
however, that the nature of this reaction has been recog-
nized to involve activation of the Si–Si bond via oxidative
addition to an intramolecular coordinatively unsaturated
iron center (i.e. the ‘‘oxidative addition mechanism’’)
[13,15] rather than through interaction with iron-centered
free radicals (i.e. the ‘‘free radical mechanism’’) [24].
One of the significant features of this rearrangement is
the regiospecific cleavage of the bridging Si–Si bond in
the cyclic structure. This has been demonstrated previously
with complexes containing additional non-bridging Si–Si
*
Corresponding author. Tel.: +86 22 2349 8132; fax: +86 22 2350 2458.
E-mail address: sunhl@nankai.edu.cn (H.-L. Sun).
0277-5387/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2006.10.026

1212
H.-L. Sun, Z.-S. Zhang / Polyhedron 26 (2007) 1211–1216
25 mmol) of n-butyllithium at ꢀ78 ꢁC. The mixture was
(CO)2
Fe
SiMe3
Si
stirred at room temperature for 1 h, then, 3.0 g (12 mmol)
of Me3SiSiCl2SiMe3 was added dropwise at ꢀ78 ꢁC. The
mixture was allowed to warm to room temperature, stirred
at this temperature overnight and then refluxed for 2 h.
After cooling to room temperature, the mixture was hydro-
lyzed with a saturated solution of NH4Cl, extracted with
ether, washed with water and dried over anhydrous magne-
sium sulfate. Evaporation of the solvent under reduced
pressure gave Me3SiSi(C5H5)2SiMe3 as an oil, which was
used directly, without further purification, for the next step
of reaction.
Fe
(CO)2
Me3Si
Fig. 1. Iron-centered free radicals from Fe–Fe bond homolysis of 1.
bonds attached to the Cp rings [16,17], which furnished
strong evidence to rule out the stepwise pathway of the free
radical mechanism [24]. To further examine the regiospec-
ific feature, a study on systems containing non-bridging Si–
Si bonds attached to other positions, such as at the bridge,
is desirable. In this aspect, we have in a recent study [25]
occasionally isolated the silicon-bridged complex [g5,g5-
C5H4–Si(Me)(SiMePh2)–C5H4]Fe2(CO)2(l-CO)2 that con-
tains a non-bridging exocyclic Si–Si bond at the silicon
bridge. Unfortunately, the complex has been obtained as
a by-product in a too small amount to study its chemistry.
In this paper, we report the first designed synthesis of
such complexes by choosing the 1,1,1,3,3,3-hexamethyltri-
To a flask containing the oil product obtained above
and 50 ml of p-xylene was added 4.9 g of Fe(CO)5
(25 mmol). The mixture was refluxed with stirring over-
night. The solvent was removed under reduced pressure
(unreacted Fe(CO)5 should be collected in a liquid nitrogen
trap) to give a solid residue, which was separated through a
neutral alumina column. Elution with petroleum ether/
dichloromethane (4:1) gave a red band, from which 1.2 g
of 1 (28% yield) was obtained as a dark-red crystalline
solid, m.p. 220 ꢁC (dec). Anal. Calc. for C20H26O4Fe2Si3:
1
silanylene-bridged
complex
[g5,g5-C5H4–Si(SiMe3)2–
C, 45.63; H, 4.94. Found: C, 45.64; H, 5.00%. H NMR
C5H4]Fe2(CO)2(l-CO)2 (1) and its CO ligand substitution
derivatives [g5,g5-C5H4–Si(SiMe3)2–C5H4]Fe2(CO)L(l-CO)2
[L = P(OPh)3 (2), P(OMe)3 (3), PPh3 (4), PMe3 (5)] that
contain two exocyclic Si–Si bonds at the silicon bridge as
the target molecules. Examination of the chemical properties
of these complexes under various conditions demonstrated
that these Si–Si bonds could not be cleaved by the intramo-
lecular iron centers, providing further evidence to rule out
the possibility of activation of Si–Si bonds by the iron-cen-
tered free radicals from homolysis of the Fe–Fe bond
(Fig. 1). On the contrary, the inertness of the Si–Si bonds
towards the metal centers could be rationally explained in
terms of the oxidative addition mechanism of activation of
Si–Si bonds [26,27].
(CDCl3): d 0.26 (s, 9H, SiMe), 4.99 (t, J = 2.1 Hz, 2H,
Cp), 5.46 (t, J = 2.1 Hz, 2H, Cp). 13C NMR (CDCl3): d
0.64 (SiMe), 86.45, 86.83, 101.38 (Cp), 209.83 (terminal
CO), 272.65 (bridging CO). IR (KBr, cmꢀ1): mco 1993 (s),
1949 (s), 1774 (s).
2.3. Synthesis of complexes 2–5
2.3.1. Thermal reactions of 1 with P(OPh)3 and P(OMe)3
To a flask charged with 100 mg (0.19 mmol) of 1 and
10 ml of p-xylene was added 92 mg (0.74 mmol) of
P(OPh)3. The mixture was refluxed for 16 h with magnetic
stirring. The solvent was removed under reduced pressure.
The residue was separated through a neutral alumina col-
umn. Elution with petroleum ether/dichloromethane (4:1)
developed a green band, from which 46 mg (36% yield) of
2 was afforded as black crystals. In a similar fashion, 3
was prepared (32% yield) from 1 and P(OMe)3 after reflux-
ing for 24 h.
2. Experimental
2.1. General
All the reactions were carried out under a nitrogen or
argon atmosphere by using vacuum line and Schlenk tech-
niques. THF, p-xylene and hexane were dried and distilled
from sodium/benzophenone. IR spectra were recorded
For 2: m.p. 210 ꢁC (dec). Anal. Calc. for
C37H41O6Fe2PSi3: C, 54.95; H, 5.07. Found: C, 54.88; H,
5.08%. H NMR (CDCl3): d 0.23 (s, 18H, SiMe), 4.29,
4.49, 4.97, 5.41 (br s, 2H:2H:2H:2H, Cp), 7.16–7.33 (m,
15H, Ph). 13C NMR (CDCl3): d 0.69 (SiMe); 83.56,
85.68, 86.34, 88.32, 98.09, 99.82 (Cp); 121.75 (d, J =
3.6 Hz, Ph), 124.70 (Ph), 129.59 (Ph), 151.51 (d,
J = 9.9 Hz, Ph), 213.96 (terminal CO), 278.62 (d,
J = 21.5 Hz, bridging CO). IR (KBr, cmꢀ1): mco 1993 (s),
1964 (s), 1777 (s), 1746 (s).
1
1
with a Bio-Rad FTS 135 spectrometer. H and 13C NMR
spectra were recorded with a Varian UNITY Plus-400 or
a Bruker AC-P200 spectrometer. Elemental analysis was
performed using an Elementar Vario EL instrument.
(Me3Si)2SiCl2 was prepared according to the literature pro-
cedures [28].
For 3: m.p. 208 ꢁC (dec). Anal. Calc. for C22H35O6Fe2-
1
2.2. Synthesis of complex 1
Si3P: C, 42.44; H, 5.63. Found: C, 42.48; H, 5.61%. H
NMR (CDCl3):
d 0.26 (s, 18H, SiMe3), 3.55 (d,
To a flask containing 1.9 g (29 mmol) of cyclopentadi-
ene and 50 ml of THF was added 14 ml (1.77 M in hexane,
J = 11.1 Hz, 9H, OCH3), 4.81, 4.90, 4.91, 5.32 (br s,
2H:2H:2H:2H, Cp). 13C NMR (CDCl3): d 0.75 (SiMe),

H.-L. Sun, Z.-S. Zhang / Polyhedron 26 (2007) 1211–1216
1213
52.06 (d, J = 4.93 Hz, OCH3), 82.63, 85.40, 85.76, 87.13,
99.11, 100.28 (Cp), 214.51 (terminal CO), 281.90 (d,
J = 24.65 Hz, bridging CO). IR (KBr, cmꢀ1): mco 1995 (s),
1963 (s), 1774 (s), 1730 (s).
2H:2H:2H:2H, Cp). 13C NMR (CDCl3): d 0.76 (SiMe),
18.78 (d, J = 28.2 Hz, CH3); 80.89, 85.60, 85.81, 88.57,
99.24 (Cp); 217.20 (terminal CO), 283.80 (d, J = 16.0 Hz,
bridging CO). IR (KBr, cmꢀ1): mco 1933 (s), 1767 (s),
1729 (s).
2.3.2. Photochemical reactions of 1 with PPh3 and PMe3
A solution containing 100 mg (0.19 mmol) of 1, 199 mg
(0.76 mmol) of PPh3 and 20 ml benzene in a Pyrex tube was
irradiated with a high-pressure mercury lamp (500 W) for
10 h at room temperature. The solvent was removed under
reduced pressure and the residue was separated through a
column (neutral alumina, petroleum ether/ether, 10:1).
Collection of the dark green band gave black crystals of
4 (90 mg, 62% yield). In a similar fashion, 5 was obtained
by using PMe3 in place of PPh3 as grey crystals in 53%
yield.
For 4: m.p. 220 ꢁC (dec). Anal. Calc. for C37H41-
Fe2O3PSi3: C, 58.42; H, 5.43. Found: C, 58.41; H, 5.40%.
1H NMR (CDCl3): d 0.27 (s, 18H, SiMe), 4.19, 4.90, 4.91,
5.12 (br s, 2H:2H:2H:2H, Cp), 7.24–7.53 (m, 15H, Ph).13C
NMR (CDCl3): d 0.77 (SiMe); 82.00, 86.36, 88.84, 90.00,
97.72, 98.61 (Cp); 128.65 (d, J = 9.9 Hz, Ph), 129.77 (Ph),
134.21 (d, J = 9.2 Hz, Ph), 135.84 (d, J = 41.7 Hz, Ph),
212.88 (terminal CO), 284.11 (d, J = 14.8 Hz, bridging
CO). IR: (KBr, cmꢀ1): mco 1955 (s), 1766 (s), 1730 (s).
For 5: m.p. 230 ꢁC (dec) Anal. Calc. for C22H35-
Fe2O3PSi3: C, 46.0; H, 6.14. Found: C, 45.87; H, 5.90%.
1H NMR (CDCl3): d 0.26 (s, 18H, SiMe), 1.00 (d, J =
9.0 Hz, 9H, CH3), 4.77, 4.88, 4.94, 5.29 (br s,
2.4. X-ray molecular structure determination of 1 and 2
Single crystals of 1 and 2 suitable for X-ray diffraction
analyses were obtained from n-hexane/dichloromethane
solutions. Data collections were performed on a BRUKER
SMART 1000 diffractometer at room temperature using
2h/x
scan
techniques
with
Mo Ka
radiation
˚
(k = 0.71073 A). The structures were solved by direct meth-
ods using the SHELX-90 program and refined by least square
methods on F2. All non-hydrogen atoms were refined
anisotropically. Hydrogen atoms were added theoretically
and included in the refinement processes in an isotropic
manner. Crystal data and selected experimental informa-
tion have been listed in Table 1.
3. Results and discussion
3.1. Synthesis of complexes
Synthesis of complex 1 was accomplished through the
reaction of (Me3Si)2Si(C5H5)2, prepared from (Me3Si)2-
SiCl2 and two equivalents of C5H5Li in THF, with
Fe(CO)5 in refluxing p-xylene in a total yield of 28%
(Scheme 1).
When 1 was heated in refluxing p-xylene in the presence
of P(OPh)3 or P(OMe)3, CO-substituted derivatives 2 and 3
were obtained, respectively. The CO substitution reaction
with PPh3, which did not occur under thermal conditions
Table 1
Crystallographic data of 1 and 2
1
2
Formula
C
526.38
293(2)
0.20 · 0.16 · 0.10
orthorhombic
Pnma
20H26Fe2O4Si3
C37H41Fe2O6PSi3
808.64
293(2)
0.24 · 0.22 · 0.18
monoclinic
P2(1)/n
13.167(4)
17.500(5)
17.057(5)
90
Formula weight
Temperature (K)
Crystal size (mm)
Crystal system
Space group
Cl
Me3Si Si SiMe3
Cl
C5H5
Me3Si Si SiMe3
C5H5
THF
+ 2 C5H5Li
˚
a (A)
21.295(8)
12.203(4)
9.363(3)
90
90
90
2433.2(15)
4
1.437
Bruker Smart 1000
0.71073
1088
˚
b (A)
˚
c (A)
Me3Si
SiMe3
a (ꢁ)
b (ꢁ)
c (ꢁ)
Si
99.681(5)
90
3874.5(18)
4
2 Fe(CO)5
p-xylene
Fe
3
Fe
˚
OC
V (A )
CO
OC
CO
Z
Dcal (g cmꢀ3
Instrument
)
1.386
1
Bruker Smart 1000
0.71073
1680
˚
Wavelength (A)
F(000)
Me3Si
SiMe3
Si
PR3
h Range (ꢁ)
Ntotal
1.91–26.37
13304
2612
1693
157
1.81–25.00
19358
6714
3131
442
Δ orhν
Fe
Fe
OC
PR3
Nindependent
Nobserved
Parameters
Restrains
Goodness-of-fit
R
OC
CO
2: R = OPh
3: R = OMe
4: R = Ph
8
0
1.036
0.0471
0.0836
0.926
0.0566
0.0819
5: R = Me
Rw
Scheme 1. Synthesis of the complexes.

1214
H.-L. Sun, Z.-S. Zhang / Polyhedron 26 (2007) 1211–1216
due to steric hindrance, could be carried out under photo-
chemical conditions, to provide complex 4. The same kind
of reaction of 1 with PMe3, which is too volatile to be used
at high temperatures, could be effected photochemically at
room temperature to afford complex 5 (Scheme 1).
the present systems. This should be attributed to the fact
that these Si–Si bonds are located in a position such that
they could not be approached by the intramolecular iron
center, due to restriction of the cyclic structure. Such spa-
tial restriction, however, does not exist in the structure of
the iron-centered free radical (Fig. 1), because the cyclic
structure has been opened after breaking the Fe–Fe bond.
Complexes 1–5 were characterized by elemental analyses
1
and spectroscopic methods. The H NMR spectrum of 1
showed a singlet at 0.26 ppm for the SiMe protons and
two sets of pseudotriplets at 4.99 and 5.46 ppm for protons
of the Cp groups. After substitution of CO by a phosphite
or phosphine ligand, the singlet due to the SiMe groups
remained little changed, whereas the signals due to the
Cp protons split into four sets, demonstrating successful
substitution of CO by a phosphorus ligand. Signals due
to PR3 were also observed. The 13C NMR spectrum of 1
exhibited one signal at 0.64 ppm for the SiMe carbons,
three signals at 86.45, 86.83 and 101.38 ppm for Cp car-
bons, and two signals at 209.83 and 272.65 ppm for termi-
nal and bridging CO carbons, respectively. The spectra of
the PR3-substituted derivatives showed generally one signal
for SiMe carbons, six signals due to Cp carbons, a singlet
and a doublet for terminal and bridging CO, respectively,
along with those attributable to the PR3 ligands. The dou-
blet signal for the bridging CO was due to coupling with
the adjacent phosphorus nucleus. IR spectra of these com-
plexes showed absorption bands for both terminal and
bridging CO groups, just as expected.
3.3. Molecular structures
The molecular structures of 1 and 2 have been deter-
mined by X-ray diffraction methods. The molecule of 1
(Fig. 2) contains a disordered Me3Si group that has two
rotational positions (each at 50% occupancy). The overall
molecule has Cs symmetry. The symmetrical plane goes
through three silicon atoms and the center of the Fe–Fe
3.2. Stability of the Si–Si bonds
It was found that the Si–Si bonds of 1 were stable under
the conditions of refluxing in p-xylene. This is in sharp con-
trast to the case of the –Me2SiSiMe2– bridged complexes
[11,12], in which the bridging Si–Si bond could be readily
broken under the same conditions. Moreover, the Si–Si
bonds of 1 were also stable under UV irradiation. The sta-
bility of the Si–Si bonds has allowed the CO substitution
reactions of 1 to be operated under either thermal or pho-
tochemical conditions. The Si–Si bonds in the ligand
substituted derivatives 2–5 were also found to be stable
under both thermal and photochemical conditions. Since
it has been well established that the phosphorus ligands
can considerably accelerate the Si–Si bond activation in
the Si–Si bond-bridged systems [12], the present results
could further strengthen the conclusion that these exocyclic
Si–Si bonds could not be activated by the intramolecular
transition metal centers.
Since iron-centered free radicals could easily be pro-
duced under the thermal and photochemical conditions
[29,30], the stableness of the Si–Si bonds means that these
radicals are not able to activate the Si–Si bonds. Also
formed under these conditions could be the coordinatively
unsaturated iron species from dissociation of the appropri-
ate ligands [30–32]. Although these species are believed to
be responsible for activation of the bridging Si–Si bond
as concluded in the previous paper [15], they are apparently
not able to cleave the non-bridging exocyclic Si–Si bonds in
Fig. 2. (a) ORTEP drawing of [g5,g5-C5H4–Si(Me3Si)2–C5H4]Fe2-
(l-CO)2(CO)2 (1). Thermal ellipsoids are at the 30% probability level.
Hydrogen atoms are omitted for clarity. (b) Side view of 1.

H.-L. Sun, Z.-S. Zhang / Polyhedron 26 (2007) 1211–1216
1215
Table 2
bond. The bridging silicon atom, however, is not located
˚
Selected bond lengths (A) and angles (ꢁ) for 1
on the top of the molecule but moves away from the plane
defined by two iron and two bridged-head Cp carbon
Fe(1)–Fe(1A)
Si(1)–Si(2)
Fe(1)–C(4)
2.523(1)
2.361(2)
2.143(4)
1.939(5)
Si(1)–C(4)
Si(1)–Si(3)
Fe(1)–C(3)
Fe(1)–C(1)
1.886(4)
2.362(2)
1.752(5)
1.930(4)
˚
atoms by a distance of 0.58 A (see Fig. 2b). This results
Fe(1)–C(2)
C(4)–Si(1)–C(4A)
C(4)–Si(1)–Si(2)
Si(1)–C(4)–Fe(1)
103.7(2)
111.3(1)
121.2(2)
Si(2)–Si(1)–Si(3)
C(4)–Si(1)–Si(3)
C(4)–Fe(1)–Fe(1A)
110.4(1)
110.0(1)
95.9(1)
Table 3
˚
Selected bond lengths (A) and angles (ꢁ) for 2
Fe(1)–Fe(2)
Si(1)–Si(2)
Si(1)–C(8)
Fe(1)–C(8)
Fe(1)–C(1)
Fe(1)–C(3)
Fe(2)–C(3)
2.531(1)
2.351(2)
1.870(5)
2.146(5)
1.735(7)
1.933(5)
1.906(5)
Fe(2)-P(1)
Si(1)–Si(3)
Si(1)–C(15)
Fe(2)–C(15)
Fe(1)–C(2)
Fe(2)–C(2)
2.123(2)
2.355(2)
1.880(5)
2.138(5)
1.922(6)
1.915(6)
Si(2)–Si(1)–Si(3)
C(8)–Si(1)–Si(2)
C(8)–Si(1)–Si(3)
C(8)–Fe(1)–Fe(2)
P(1)–Fe(2)–Fe(1)
Si(1)–C(8)–Fe(1)
113.0(1)
C(8)–Si(1)–C(15)
C(15)–Si(1)–Si(2)
C(15)–Si(1)–Si(3)
C(15)–Fe(2)–Fe(1)
Si(1)–C(15)–Fe(2)
105.3(2)
109.1(2)
108.6(2)
97.2(1)
105.6(1)
120.2(2)
111.0(2)
109.6(2)
94.9(1)
122.3(2)
in the five-membered ring composed of the bridging silicon,
two iron and two the bridged-head Cp carbon atoms tak-
ing an envelope-like conformation. This type of conforma-
tion has previously been observed in other silicon- and
carbon-bridged complexes [2,7,8]. Interestingly, in complex
2 the bridging silicon atom has moved onto the top of the
molecule (Fig. 3). Thus, the molecule has C1 symmetry in
the crystalline state. The five-membered cyclic skeleton is
˚
basically planar, with a mean deviation of only 0.011 A
(Fig. 3b). This is, to our knowledge, the first example of
a silicon-bridged complexes to have such a conformation.
The shift of the bridge onto the top of the molecule is
likely caused by the steric effect of the P(OPh)3 ligand.
Meanwhile, the bulkiness of P(OPh)3 makes the Fe–Fe
˚
˚
bond slightly lengthened from 2.5227 A for 1 to 2.5311 A
for 2. The Cp–Si–Cp angle is also increased from 103.7ꢁ
for 1 to 105.3ꢁ for 2. Interestingly, the bridging Si–Cp
˚
bonds have been slightly shortened from 1.886 A for 1 to
1.870/1.880 A for 2, implying that the original strain that
˚
may exist in the five-membered cyclic structure may have
been released to some extent. The lengths of the Si–Si
˚
˚
bonds are 2.362/2.361 A for 1 and 2.355/2.351 A for 2,
which are rather close to one another. Other selected bond
lengths and angles for 1 and 2 have been listed in Tables 2
and 3, respectively.
4. Summary
According to the results observed above, it seems that
an appropriate position of the Si–Si bonds with respect
to the transition metal centers should be an important
factor that may control the intramolecular Si–Si bond
Fig. 3. (a) ORTEP drawing of [g5,g5-C5H4–Si(Me3Si)2–C5H4]Fe2-
(l-CO)2(CO)P(OPh)3 (2). Thermal ellipsoids are at the 30% probability
level. Hydrogen atoms are omitted for clarity. (b) Side view of 2.

1216
H.-L. Sun, Z.-S. Zhang / Polyhedron 26 (2007) 1211–1216
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activation. Without such a position that is approachable
by the intramolecular coordinatively unsaturated transi-
tion metal centers, the Si–Si bond would remain stable,
although Si–Si bonds should be highly susceptible towards
oxidative addition to intramolecular transition metal cen-
ters [33,34].
Acknowledgements
[11] H. Sun, S. Xu, X. Zhou, H. Wang, X. Yao, J. Organomet. Chem. 444
(1993) C41.
We thank the National Natural Science Foundation of
China for financial support of this work (Project Nos.
29872020, 20372036 and 20421202) and the Natural
Science Foundation of Tianjin (Project No. 05YFJM-
JC06800).
[12] H. Sun, X. Teng, X. Huang, Z. Hu, Y. Pan, J. Organomet. Chem. 595
(2000) 268.
[13] H. Sun, Z. Zhang, Y. Pan, J. Yang, X. Zhou, Inorg. Chem. 42 (2003)
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[14] H. Sun, Z. Zhang, X. Zhou, Chin. J. Chem. 21 (2003) 839.
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Wang, Organometallics 25 (2006) 133.
[16] H. Sun, X. Huang, Z. Hu, Z. Zhang, X. Leng, L. Weng, Inorg. Chim.
Acta 348 (2003) 8.
Appendix A. Supplementary material
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[18] W. Xie, B. Wang, X. Dai, S. Xu, X. Zhou, Organometallics 17 (1998)
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[19] W. Xie, B. Wang, X. Dai, S. Xu, X. Zhou, J. Chem. Soc., Dalton
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CCDC 280002 and 280003 contain the supplementary
crystallographic data for 1 and 2, respectively. These data
can be obtained free of charge via http://www.ccdc.cam.a-
c.uk/conts/retrieving.html, or from the Cambridge Crystal-
lographic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: (+44) 1223-336-033; or e-mail: depos-
it@ccdc.cam.ac.uk. Supplementary data associated with
this article can be found, in the online version, at
doi:10.1016/j.poly.2006.10.026.
[24] X. Zhou, Y. Zhang, W. Xie, S. Xu, J. Sun, Organometallics 16 (1997)
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