η1-silolyl-FeCp(CO)2 complexes. Is there a way to sila-ferrocene?

Article abstract of DOI:10.1016/j.jorganchem.2015.09.023

The reaction of 1-chlorosilols (12, 13) and K[Fe(CO)₂Cp] in THF yielded two new η¹-silolyl-FeCp(CO)₂ complexes (15, 16) in good yield. These complexes are the first covalent Fe-Si bonded silolyl complexes reported in the l

Full text of DOI:10.1016/j.jorganchem.2015.09.023

Journal of Organometallic Chemistry 799-800 (2015) 291e298
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h1-silolyl-FeCp(CO) complexes. Is there a way to sila-ferrocene?
2
a
a
b
a
a, *
Csaba Fekete , R eꢀ ka Mokrai , Petra Bombicz , L aꢀ szl oꢀ Nyul aꢀ szi , Ilona Kov aꢀ cs
a
Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Szt. Gell ꢀe rt t ꢀe r 4, Budapest, H-1111, Hungary
Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar Tud oꢀ sok k o€ rútja 2, Budapest, H-1117,
b
Hungary
a r t i c l e i n f o
a b s t r a c t
The reaction of 1-chlorosilols (12, 13) and K[Fe(CO) Cp] in THF yielded two new h1-silolyl-FeCp(CO)2
complexes (15, 16) in good yield. These complexes are the first covalent FeeSi bonded silolyl complexes
reported in the literature, which were structurally proven by single crystal X-ray diffraction and
multinuclear NMR spectroscopy. By temperature dependent NMR spectroscopy a rotational barrier of
Article history:
Received 17 July 2015
Received in revised form
2
11 September 2015
Accepted 19 September 2015
Available online 9 October 2015
14.4 kcal/mol was revealed, in agreement with the calculated 14.9 kcal/mol barrier of the phenyl rotation.
The attempted transformation of these complexes to the corresponding silaferrocene by CO elimination
failed. DFT calculations revealed that the rather high stability of the SieFe comparing to the CeFe bond
might be responsible for the stability of the complexes.
Keywords:
Iron complex
Silacyclopentadiene
X-ray structure
Bissilol
©
2015 Published by Elsevier B.V.
DFT calculations
1
. Introduction
the heterocyclopentadienyl analogue [6,7]. Hafnium (6, 7) and
zirconium (8) complexes with a bent sandwich structure were also
reported (Scheme 2) [8].
While the synthesis of the possible silaferrocene precursors
(9e11) was also carried out, their transformation (by heating or UV
irradiation) to the metallocenes was unsuccessful [9e11] (Scheme
3).
One of the milestones in organometallic chemistry is the syn-
thesis of ferrocene by Kealy and Pauson in 1951 and the determi-
nation of its structure by Wilkinson and Woodward in 1952. These
achievements opened up the way to the use of metallocenes in
applied and material science from polymerization catalysis to UV
fluorescent materials [1]. Nowadays several metallocenes are
known in which not just the central iron atom is replaced by other
transition metals but also the ligands are changed to hetero-
cyclopentadienyl analogues containing other main group elements
such as P, As or Sb [2].
Recently, we studied the substituent effect on the aromaticity of
the silolide anions, and reported that Me
position of the silolyl ring increase the aromaticity of the hetero-
cycle significantly according to NICS and ISE values [12]. Since the
3
Si-substituents on the 2,5
c
stability of the ferrocene might be related to the aromaticity of the
cyclopentadienyl moiety, we envisaged that using 2,5-
Interestingly, the number of known metallocenes possessing
silicon or germanium containing heterocycles is small (Scheme 1).
The first heavy metallocene analogue 1 was synthesized by Tilley
trimethylsilyl-substituted silolyls the corresponding ferrocene an-
1
alogues might be synthesized. Hereby, we report on two new
silolyl-FeCp(CO)
h
-
et al. reacting Cp*[RuCl
4
] with in situ generated Li[Me
4
C
4
GeSi(-
2
complexes, and their attempted transformation
SiMe ] [3], and the ferrocene analogue 2 was also published 9
years later [4]. The synthesis and NMR characterization of the first
metallocene containing a silolyl ring (3) has been reported in 1994
3
)
3
to the metallocenes, completed with DFT calculations for a better
understanding of the experimental results.
[
5]. Sekiguchi et al. synthesized metallocenes containing trisila- (4)
and disilagermacyclopentadienyl (5) units using the appropriate
complex source ([Cp*RuCl] or Cp*Fe(acac)) and the lithium salt of
2
. Results and discussion
4
We reported recently the synthesis of 12, via an amine e chlo-
ride exchange route developed originally by Tamao [13,14]. The
synthesis of 13 was performed in an analogous manner, using
Et
2 2
NSiMeCl as starting material. 14 was synthesized by the reac-
*
Corresponding author.
E-mail address: ikovacs@mail.bme.hu (I. Kov ꢀa cs).
ꢁ
1
tion between 12 and tBuLi in THF at ꢀ50 C. Interestingly the H and
http://dx.doi.org/10.1016/j.jorganchem.2015.09.023
022-328X/© 2015 Published by Elsevier B.V.
0

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C. Fekete et al. / Journal of Organometallic Chemistry 799-800 (2015) 291e298
Scheme 1. Metallocenes containing group 14 metallols.
reported chemical shift of 10 (
indicates that while the variation of the substituents directly at
d
¼ 47.59 ppm) [10]. This behaviour
silicon has a significant impact on the chemical shielding, changes
2
9
at the
a carbon atoms have only a small influence on the Si NMR
13
chemical shift values of the Si atom in the five membered ring.
C
NMR chemical shifts of complex 15 and 16 indicated similar
restricted rotation of the phenyl groups as mentioned before in the
13
case of 13 and 14. The C NMR chemical shift of the Cp carbons in
5 ( ¼ 85.1 ppm) is somewhat downfielded
¼ 85.2 ppm) and 16 (
with respect to 10 (
¼ 84.2 ppm) [10]. IR bands of the carbonyl
groups of 15 and 16 (15: 2011, 1957 cm ; 16: 1999, 1948 cm
were measured in nujol film and are in the region of the previously
1
d
d
d
ꢀ
1
ꢀ1
)
Scheme 2. Bent sandwich complexes.
1
synthesized
h
-silolyl-FeCp(CO)
960 cm in CH Cl
1955 cm in cyclohexane [9e11]).
2
complexes (Scheme 3: 9: 2010,
; 10: 1995, 1943 cm in benzene; 11: 2015,
ꢀ1
ꢀ1
1
2
2
13C NMR spectra of 13 and 14 show that the signals connected to the
orto-and meta-hydrogens and carbons of the phenyl groups on the
carbons of the silolyl ring show splitting or become broad at room
ꢀ1
ꢁ
Recrystallization of 15 and 16 from hexane at ꢀ30 C resulted in
single crystals suitable for X-ray diffraction study; the structures
are shown in Figs. 1 and 2.
b
temperature indicating a restricted rotation of the phenyl moiety.
13
1
From temperature dependent C and H NMR measurements
temperature range 233e333 K, solvent CDCl ) a coalescence
temperature T
¼ 313 K was determined for 14 (F. S1), allowing to
calculate a rotational barrier of
rot ¼ 14.4 kcal/mol. This value is
in excellent agreement with the DFT calculated phenyl rotation
barrier (
15 and 16 crystallizes in the monoclinic crystal system P2
1
/c and
(
3
P2 /n, respectively. Crystal data and details of the structure deter-
1
mination and refinement are listed in Tables S3eS13. There is one
molecule in the asymmetric unit, and no molecular symmetry
could be found in the compounds. The molecular conformation
around the Fe centre is presented in Table S5. The silolyl rings are
slightly twisted [16] on Si1 (0.0732(14) Å) and C8 (ꢀ0.081(3)) in 15
and on Si1 (ꢀ0.0590(9) Å) and C5 (0.0553(19)) in 16. Typical bond
lengths and endocyclic bond angles can be found in the silolyl rings
of 15 and 16 (Table S6) [17]. The silicon centre has distorted tetra-
hedral geometry (Table S7). The endocyclic CeSieC angles are
c
D
G
DG
rot ¼ 14.9 kcal/mol B3LYP/6-311 þ G*). The optimized
transition structure of the phenyl rotation is shown in Fig. S2.
While 1-chlorosilols (12, 13) provided complexes 15, 16 in good
ꢁ
yield when reacted with K[Fe(CO)
2
Cp] in THF at ꢀ30 C, 14 failed to
give the expected 17 even when the mixture was heated to reflux
temperature, probably due to the steric hindrance of the bulky tBu-
substituent on the silicon (Scheme 4). Likewise, the attempted re-
o
o
94.40(13) in 15 and 93.10(8) in 16 due to the constraints imposed
by the five member ring, while in spite of the chemical difference
actions with K[W(CO)
3
Cp] aiming to form a tungsten complex
o
failed even in THF at reflux temperature. Complexes 15 and 16 were
the Cl1eSi1eFe1 angle (112.86(4) ) in 15 is very close to the
C1eSi1eFe1 angle (112.67(6) ) in 16. The molecular conformations
identified by 1H, C, and Si NMR. The ring Si NMR chemical
13
29
29
o
shift of 15 ( ¼ 82.6 ppm) is in the same region as that of CpFe(-
CO) SiMe Cl (
shift of the ring silicon atom in 16 (
d
are stabilized by CeH …
Me Si group and the neighbouring phenyl ring. The Cp CeH gets
close to the silolyl ring in 16 (2.53 Å), while it does not happen in 15
p intramolecular interactions between the
2
9
2
2
d
¼ 86.36 ppm) [15]. Similarly, the Si NMR chemical
¼ 55.5 ppm) is close to the
3
d
Scheme 3. h1-silolyl-FeCp(CO)
complexes.
2

C. Fekete et al. / Journal of Organometallic Chemistry 799-800 (2015) 291e298
293
Scheme 4. Synthesis of h1-silolyl-FeCp(CO)
complexes 15 and 16.
2
because the Cp moiety turns with an edge of the pentagon to the
silolyl ring. There is no interaction in 15, while intermolec-
ular interaction is found between the Cp rings in the crystal
1.7425(19), 1.750(2) Å). Our results also agree with the known s-
donor behaviour of Si in FeeSi bond [20].
p
…
p
p
…
p
The attempt to transform 15 and 16 to the desired silaferrocene
was carried out similar way as published in the case of the carbon
analogue [21]. Refluxing the toluene solution of 15 and 16 did not
result in any change even after 1 week. UV irradiation of 16 using a
high-pressure mercury lamp in a hexane solution did not result
again in the desired silaferrocene, however, the dimeric iron com-
lattice of 16 with the distance of 3.8862(14) Å.
Further comparing the structural features of 15 and 16 it is
noteworthy that the FeeSi bond is longer by 0.0597(9) Ǻ in 16 than
in 15, indicating that the presence of chlorine substituent at Si
strengthens the FeeSi bond. Clearly, the doubly filled Fe d orbital(s)
interact in a negative hyperconjugation with the
s
* orbital at Si, and
plex ([FeCp(CO
Interestingly a similar reaction occurred during the irradiation of
the mixture of FpSiPh ) yielding
and FpMe (Fp ¼ CpFe(CO)
MeSiPh and [FeCp(CO , however in this reaction no disilane
2 2
)] ) and bissilol (18) has been formed in low yield.
the interaction is much stronger in the SiCl than in the SiMe case
based on NBOdel calculations on model systems (See Supplemen-
tary information S2) [18]. This negative hyperconjugative effect was
3
2
3
2 2
)]
already assumed in the case of CpFe(CO)
bond length was shorter than expected from the covalent radii
d(FeeSi) ¼ 2.21 Å) [19]. In accordance the -donor ability of the
central Fe in 15 is smaller than in 16, resulting in a reduction of the
-back bonding. This strengthens the CO bond of the carbonyl li-
gands, as indicated by the increasing wavenumber of the CO
stretching frequency as was already noted above. Also the tendency
of slight increase of the FeeC bond length in 15 compared to 16
confirms this explanation (d(FeeCO) ¼ 15: 1.744(3), 1.755(3) Å 16:
2
SiCl
3
where the FeeSi
formation was detected [15]. In the case of 15 the decomposition of
the silolyl ring was observed during the irradiation (likewise,
decomposition was reported in case of 11 [11]). The different
behaviour of 15 and 16 (Scheme 5) might be related to the above
discussed increased stability of the SieFe bond in case of 15
blocking the decomposition pathway, which leads to the formation
of the radicals yielding easily the dimeric products. Interestingly
(
p
p
during the MS measurements of the methyl-derivate (16) the silolyl
þ
fragment [Ph
2
(SiMe
3
)
2
C
4
SiMe] was detected as the base peak,
Fig. 1. ORTEP diagram of 15 at 50% probability level (hydrogen atoms are omitted for
clarity). Selected bond lengths (Å) and angles ( ): Fe(1)eSi(1) 2.3064(8), Si(1)eCl(1)
Fig. 2. ORTEP diagram of 16 at 50% probability level (hydrogen atoms are omitted for
clarity). Selected bond lengths (Å) and angles ( ): Fe(1)eSi(1) 2.3660(5), Si(1)eC(1)
o
o
2
1
1
1
.1043(10), Fe(1)eC(1) 1.755(3), Fe(1)eC(2) 1.745(3), C(1)eO(1) 1.148(4), C(2)eO(2)
.164(4), Si(1)eC(8) 1.886(3), Si(1)eC(11) 1.883(3), C(8)eC(9) 1.362(4), C(9)eC(10)
.516(4), C(10)eC(11) 1.359(4); C(11)eSi(1)eC(8) 94.40(12), C(11)eSi(1)eCl(1)
06.86(9), C(8)eSi(1)eCl(1) 108.84(9), C(11)eSi(1)eFe(1) 117.46(9), C(8)eSi(1)eFe(1)
14.73(9), Cl(1)eSi(1)eFe(1) 112.85(4).
1.8815(18), Fe(1)eC(6) 1.742(2), Fe(1)eC(7) 1.750(2), C(6)eO(2) 1.161(2), C(7)eO(1)
1.154(2), Si(1)eC(2) 1.9022(18), Si(1)eC(5) 1.8945(18), C(2)eC(3) 1.359(2), C(3)eC(4)
1.512(2), C(4)eC(5) 1.363(2); C(5)eSi(1)eC(2) 93.10(8), C(1)eSi(1)eC(5) 113.74(8),
C(1)eSi(1)eC(2) 110.44(8), C(1)eSi(1)eFe(1) 112.67(6), C(5)eSi(1)eFe(1) 110.84(6),
C(2)eSi(1)eFe(1) 114.66(6).
1

294
C. Fekete et al. / Journal of Organometallic Chemistry 799-800 (2015) 291e298
Scheme 5. UV Irradiation of 15 and 16.
which might be related to the cleavage of the FeeSi bond, while in
case of 15 there was no sign of a similar fragmentation route.
We succeeded in growing a single crystal from 18, allowing its
structural characterization (Fig. 3). 18 crystallizes in the triclinic
crystal system, the space group is P-1. In the lack of strong sec-
ondary interactions in the crystal lattice of 18 the crystal quality
was low. Crystal data and details of the structure determination and
refinement are listed in Tables S3eS13. There is one molecule in the
asymmetric unit. The planar silolyl rings have the angle of
52.64(14) (Table S4). A trimethylsilyl CeH gets close to the silolyl
ring in 18 with the distance of 2.85 Å contributing to the stability of
o
the curved shape of the molecule. The structural features are
similar to the other silols. Comparing the SiꢀC
a
, C
a
ꢀC
b
and C
b
ꢀC
b
bond length of the silolyl ring in bissilol 18 with those of 16
revealed that these bond lengths change only slightly when the
iron centre is connected to the Si. The relatively long C
in the complexes 15, 16 and in 18 can be attributed to the repulsion
of the neighbouring phenyl groups in the position. We have
b b
ꢀC bonds
b
shown the effectiveness of this interaction in case of the silolid
dianion [13]. The other effect which might be responsible for the
increased C
b
ꢀC
b
bond length in silols compared to phosphole is
ꢁ
that the C eSieC
a
a
angle about the tetrahedral silicon (109.47 ) is
ꢁ
much wider than the near 90 bonding angle about phosphorus
[
(
22], which results in an apparent increase of the C
Fig. 3, C(3)eC(4) and C(7)eC(8)). It is noteworthy that the SieSi
b
ꢀC
b
distance
bond in 18 (2.4632(13) Å) is longer than the previously reported for
,1-bissilols (2.354(3)e2.375(1) Å) [23], apparently due to the bulky
trimethylsilyl-substituents at the C carbons. (e.g. SieSi distance is
.433(1) Å in tBu [24], and 2.697(3) Å in tBu
HSiꢀSiHtBu
SieSitBu [25]).
In a further attempt to get silaferrocenes complexes, 15 and 16
were treated with Me NO to eliminate CO groups from the complex
1
a
2
2
2
3-
3
3
but no reaction took place even after stirring the mixture for 3 days
in THF solution at reflux temperature [26]. After all attempts to
eliminate the CO ligands from the complexes 15 and 16 were un-
successful, DFT calculations were carried out to understand the
1
observed stability of the
. Calculations
The energy and Gibbs free energy values (at 293 K, atmospheric
h
-complexes.
3
1
Fig. 3. ORTEP diagram of 18 at 50% probability level (hydrogen atoms are omitted for
clarity). Selected bond lengths (Å) and angles ( ): Si(1)eSi(4) 2.4632(12), Si(1)eC(2)
pressure) of the decomposition of the h -complexes to metal-
o
locenes are given for model compounds in Table 1.
1
1
1
1
.891(3), Si(1)eC(1) 1.881(3), Si(1)eC(5) 1.886(3), C(2)eC(3) 1.369(4), C(3)eC(4)
.519(4), C(4)eC(5) 1.359(4), Si(4)ꢀC(10) 1.870(3), Si(4)eC(6) 1.878(3), Si(4)eC(9)
.885(3), C(6)eC(7) 1.363(4), C(7)eC(8) 1.511(4), C(8)eC(9) 1.366(4); C(1)eSi(1)eC(5)
10.65(14), C(1)eSi(1)eC(2) 111.06(14), C(5)eSi(1)eC(2) 94.40(13), C(1)eSi(1)eSi(4)
10.46(11), C(5)eSi(1)eSi(4) 115.15(10), C(2)eSi(1)eSi(4) 114.23(10).
In the case of the carbon analogue the energy difference be-
tween the starting material and the products is positive, but the
Gibbs free energy difference (at 298 K and atmospheric pressure) is
negative due to the formation of two free carbon-monoxid
1

C. Fekete et al. / Journal of Organometallic Chemistry 799-800 (2015) 291e298
295
Table 1
(H
2 4 4
SiC H ) (Fig. 6). Clearly, the facile 1, 5 shift, resulting in a flux-
B3LYP/6-311 þ G* energy and Gibbs free energy values (in kcal/mol) for CO elimi-
1
ional behaviour of
h
2
-cyclopentadienyl-FeCp(CO) (and other
nation reactions.
cyclopentadienyl derivatives) is hindered in the case of the silolyl
derivate [29]. The stability of structure A (Fig. 6) is especially
noteworthy, since the SieH bond is weaker than the CeH.
4. Conclusion
The synthesis of the new silols (13, 14) and h1-silolyl-FeCp(CO)
2
complexes (15, 16) were carried out. 15 and 16 are the first FeeSi
X
D
E
DG
covalent bonded silolyl complexes reported in the literature, which
1
13
29
C
Si
Ge
7.3
44.8
43.6
ꢀ15.7
21.1
20.3
are characterized by H, C, and Si NMR, IR spectroscopies, as
well as with single crystal X-ray diffraction. Transformation of these
complexes to a ferrocene analogue sandwich complexes were un-
successful using UV irradiation, Me
reason for the increased stability of these carbonyl complexes can
be attributed to the increased -electron donating behaviour of the
3
NO or by simple heating. The
molecules, in agreement with the result of Yates and co-workers
s
1
[27]. The stability of the h -complex is much larger in case of the
silicon to the central Fe, while the aromaticity of the silolyl ligand
silolyl (and also for the germolyl) rings and accordingly even the
Gibbs free energy difference remains positive. The energy of the CO
elimination reaction was also calculated for differently substituted
silols but in no case was the ferrocene analogue significantly sta-
bilized (Table 2).
seems to have less influence. According to our experiences there is
little chance to obtain sandwich complexes from decarbonylation
1
h
2
-silolyl-FeCp(CO) complexes.
5. Experimental section
Calculations on the model h1-complexes revealed that the
Mulliken charge at Fe is getting somewhat more negative when
replacing the cyclopentadienyl ligand by silolyl (1.69 and 1.62,
respectively), despite the fact that the electronegativity of silicon is
smaller than that of carbon. Also the s character of the Si (28%) in
the SieFe bond is significantly larger than the s character of C (19%)
in the CeFe bond based on NBO calculations. It is noteworthy that a
5.1. General
All reactions were performed in oven-dried glassware under
dried nitrogen or argon using standard Schlenk techniques. Sol-
vents were dried according to well-known procedures (THF, diethyl
ether, dioxane, and C
LiAlH .) and distilled freshly before use. Solids were dried in vac-
uum. CDCl was dried over activated molecular sieves.1.6 M n-butyl
6 6
D over sodium/benzophenone, hexane over
comparative M o€ ssbauer spectral study on CpFe(CO)
3
SiMe and
2
4
CpFe(CO) CH provided similar results [20].
2
3
3
We also studied the energy difference between the isomers
shown in Fig. 4. It was revealed that the most stable isomer is (by
about 40 kcal/mol) where iron is connected to silicon. The stabili-
zation can partly be attributed to the stability of the Fe(þ)ꢀSi bond
energy, which is apparently rather stable in comparison with the
lithium and 1.6 M tert-butyl lithium solution in hexane from Merck
Ltd. were used directly. NMR spectra were recorded on a Bruker
Avance 300 and a Bruker DRX-500 spectrometers (standard:
external TMS, chemical shifts are given in ppm). HMBC, HMQC and
DEPT measurements were carried out to interpret the signals of the
phenyl and silolyl rings. Infrared spectra were recorded using Per-
(þ)
Fe ꢀC bond as shown by the energy difference of the isomers
Cp(CO) FeSiH CH and Cp(CO) FeCH SiH (Fig. 5), although the
2
2
3
2
2
3
ꢀ1
kin Elmer System 2000 FT-IR spectrometer from 4000 to 400 cm
different SieH and CeH bond energies also contribute to the rela-
tive stabilities.
A further stabilizing contribution comes from the ca. 30 kcal/
mol stability difference of the C]C and Si]C double bonds [28], as
shown by the energy difference of the constitution isomers of silol
in nujol film. High-resolution mass spectra were recorded with a
Varian MAT 8200 mass spectrometer. Irradiations with UV light
were carried out using HPK-125W high-pressure mercury vapour
lamp. Elemental analysis was performed with an Elemental vario EL
analyser.
The single crystal of 15, 16 and 18 were mounted on a loop.
Intensity data were collected on a RAXIS-RAPID diffractometer
Table 2
(monochromator; Mo-K
a
radiation,
l
¼ 0.71073 Å) at 93(2) K. The
B3LYP/6-311 þ G* energy and Gibbs free energy values (in kcal/mol) of the CO
structures were solved by direct methods [30] (and subsequent
difference syntheses). Hydrogen atomic positions were calculated
from assumed geometries. Hydrogen atoms were included in
structure factor calculations but they were not refined. The
isotropic displacement parameters of the hydrogen atoms were
approximated from the U(eq) value of the atom they were bonded
to. The molecular graphics were prepared using the software
Mercury [31].
elimination reaction for different substituted silolyl-complexes.
5.2. Calculations
R
1
R
2
D
E
DG
Geometry optimizations and energy calculations for complexes
Cl
Me
OMe
SiH
H
H
H
H
H
H
Cl
OMe
SiH
3
49.5
42.7
48.8
41.2
51.4
56.6
44.6
25.3
19.0
24.1
17.6
25.3
31.0
20.6
were carried out at the B3LYP/6-311 þ G* level with Gaussian09
package [32], followed by calculation of the second derivatives to
ensure that real minima were obtained (Tables 1 and 2). For larger
systems such as complex 15 and 16 generated basis set (supple-
mentary information S9) were applied for B3LYP method. On the
3
H
silolyl ring (SiC
4
) and the Fe(CO)
2
Cp fragment 6-311 þ G*, while on

296
C. Fekete et al. / Journal of Organometallic Chemistry 799-800 (2015) 291e298
2 4 5
Fig. 4. Energy differences of the calculated structures of the different constitution isomers of CpFe(CO) SiC H .
mixture was stirred under argon atmosphere at room temperature
ꢁ
for 4 h. The mixture was cooled to ꢀ78 C and 6.86 g (21.6 mmol)
diethylamino-methyl-bis(phenylethynyl)silane were added drop-
wise to it, and was stirred for 1 h at the same temperature. The
mixture was quenched with 10.33 g (95.2 mmol) trimethyl-
ꢁ
chlorosilane at ꢀ78 C, allowed to warm to room temperature and
condensed under reduced pressure. After the addition of dry hex-
ane the insoluble lithium-chloride were filtered and the solvent
was condensed under reduced pressure, followed by the removal of
ꢁ
the naphthalene by sublimation (at 100 C/0.1 mbar). The residue
was dissolved in 130 mL diethyl ether and dry HCl gas generated
from NH
4
Cl (11.58 g, 0.216 mmol) and H
2
SO
4
(11.5 mL, 0.216 mol)
Fig. 5. Energy difference of the calculated structures of the Cp(CO)
2 2 3
FeSiH CH and
ꢁ
Cp(CO) FeCH SiH
2
2
3
.
was bubbled trough it at ꢀ78 C over 2 h. The mixture was allowed
to warm to room temperature, and was condensed under reduced
pressure. After the addition of dry hexane the insoluble salts were
filtrated and filtrate was condensed under reduced pressure. 13 was
the substituents of the silolyl ring (phenyl rings on C
trimethylsilyl-groups on C
carbons) 6-31 þ G* method were used.
NBO calculations were carried out on the optimized geometries
33]. Tables with the calculated geometries are given in the Sup-
2
carbons and
1
ꢁ
obtained by distillation at reduced pressure (160e180 C/
0.01 mbar) and was purified by recrystallization from hexane so-
[
ꢁ
lution at ꢀ30 C, yielded 6.02 g (65%) colourless crystals. M.p.
plementary materials. For the visualization of the structures the
Molden program was used [34].
ꢁ
9
7e98 C. Anal. Calcd. for C23
H
31ClSi
3
(427.21): C, 64.66; H, 7.31.
1
Found: C, 63.96; H, 7.64. H NMR (CDCl
3
):
d
¼ ꢀ0.06 (s, 18H, SiMe
3
),
¼ 0.4
3
),126.6 (pPh),127.0 (o/mPh),128.4 (o/mPh),139.7
1
3
1
0
.82 (s, 3H, Me), 6.7e7.1 (m,10H, ArH). C{ H} NMR (CDCl
(SiMe ), 0.9 (SiCH
(C ), 141.4 (iPh), 169.7 (C
ring), ꢀ8.7 (SiMe ). HRMS (EI): m/z (%) 426.1412 (calc. for
3
): d
5.3. 1,1-Dichloro-3,4-diphenyl-2,5-bis(trimethylsilyl)-1-
3
2
9
1
silacyclopentadiene (12)
a
b
). Si{ H} NMR (C
6
D
6
):
d
¼ 30.4 (Si-
3
3
5
37
The synthesis was carried out according to Tamao's produce
C
23
H
31ClSi
3
426.1417) (45.8), 428.1377 (calc. for
C
23
H
31ClSi
3
13
29
þ
35
[
13,14] The 1H, C, and Si NMR data of the product were in
428.1387) (21.5) [M ], 411.1177 (calc. for C22
(33.4), 413.1142 (calc. for C22
H
28ClSi
3
411.1187)
ꢁ
1
H
3
7
ClSi 413.1158) (15.4) [M eMe].
þ
agreement with the previously reported results. M.p. 78e81 C. H
28
3
13
NMR (CDCl
{
3
):
H} NMR (CDCl
36.2 (C ), 140.4 (iPh), 169.8 (C
ring), ꢀ7.9 (SiMe ).
d
¼ 0.22 (s,r 18H, SiMe
3
), 6.67e6.96 (m, 10H, ArH). C
1
3
): ), 127.0 (pPh),127.5, 128.4 (o/mPh),
d
¼ 0.3 (SiMe
3
5.5. 1-Chloro-1-tert-buthyl-3,4-diphenyl-2,5-bis(trimethylsilyl)-1-
2
9
1
1
a
b
). Si{ H} NMR (C
6
D
6
):
d
¼ 19.3 (Si-
silacyclopentadiene (14)
3
3
.97 g (8.88 mmol) 12 was dissolved in 80 mL THF and cooled
ꢁ
5.4. 1-Chloro-1-methyl-3,4-diphenyl-2,5-bis(trimethylsilyl)-1-
to ꢀ50 C and tBuLi (1.51 M in hexane, 5.9 mL, 8.88 mmol) was
added dropwise to this solution. The resulting brownish green
mixture was stirred for another 1 h at the same temperature. After
that the reaction mixture was allowed to warm to room tempera-
ture and was stirred overnight. The solvents were removed at
reduced pressure resulting in a red residue. After addition of 20 mL
hexane the mixture was filtered, and the pure compound was
silacyclopentadiene (13)
Synthesis was carried out by a similar way as Tamao's route
[
13,14] using MeSi(NEt
Si(NEt Cl . 0.606 g (86.6 mmol) lithium was added to a THF
200 mL) solution of 11.25 g (86.6 mmol) naphthalene and the
2 2
)Cl as starting material instead of
2
)
2
2
(
Fig. 6. Energy differences of the calculated structures of the different silols.

C. Fekete et al. / Journal of Organometallic Chemistry 799-800 (2015) 291e298
297
ꢁ
obtained by crystallization from hexane at ꢀ30 C, yielded: 2.70 g
5.8. Reaction of 13, 14 with K[W(CO)
3 2
Cp] and 14 with K[Fe(CO) Cp]
ꢁ
(
65%). M.p. 120e122 C. Anal. calcd. for C26
H
37Si
3
Cl (469.29): C,
):
¼ 0.10
1
6
6.54; H, 7.95%. Found: C, 66.23; H, 7.90. H NMR (CDCl
3
d
K[W(CO) Cp] or K[Fe(CO) Cp] was dissolved in THF and the
3
2
1
3
1
ꢁ
(
s, 18H, SiMe
3
), 1.24 (s, 9H, tBu), 6.65e7.1 (m, 10H, ArH). C{ H}
¼ 1.2 (SiMe ), 21.4 (C(CH ), 27.7 (C(CH ), 126.6
), 141.5 (iPh),
¼ 33.9 (Si-ring), ꢀ8.8 (SiMe
solution was cooled to ꢀ40 C. Solution of 13 or 14 in THF was
ꢁ
NMR (CDCl
3
):
d
3
3
)
3
3
)
3
added dropwise to this solution at ꢀ40 C. After stirring for 3 h
ꢁ
(
1
pPh), 126.9, 127.0, 128.5, 129.4 (o/mPh), 138.6 (C
a
at ꢀ40 C the mixture was allowed to warm to room temperature
2
9
1
71.6(C
b
). Si{ H} NMR (C
6
D
6
):
d
3
)
followed by further stirring for 10 h or refluxing for 10 h. The sol-
vent was removed under reduced pressure and 10 mL hexane was
added to the residue. The resulting insoluble salt was filtered out
and the filtrate was condensed at reduced pressure and the light-
coloured solid was identified in all three cases as starting mate-
rials (13, 14) according to NMR spectroscopy.
3
5
HRMS (EI): m/z (%) 468.1886 (calc. for C26
4
for C22
4
H
3
37ClSi 468.1892) (15.8),
3
7
þ
70.1854 (calc. for C26
H
37ClSi
3
470.1862) (7.3) [M ], 411.1169 (calc.
411.1187) (22.8), 413.1140 (calc. for C22
3
5
37
H
28ClSi
3
H
28ClSi
3
þ
13.1158) (13.7) [M etBu].
5.9. UV irradiation reactions
5
.6. (1-Chloro-3,4-diphenyl-2,5-bis(trimethylsilyl)-1-
5
silacyclopentadienyl)-
h
-cyclopentadienyl-dicarbonyl-iron (15)
A 200 mg (0.34 mmol) of 15 were dissolved in 10 mL hexane. After
the solution was irradiated with UV lamp for 30 min. The colour
of the mixture became darker during the irradiation. After that
the solvent was removed under reduced pressure and the res-
idue was dissolved in CDCl and NMR measurements were
3
carried out, but the products could not be identified.
1
0 mL THF was added to 0.23 g (1.05 mmol) K[Fe(CO) Cp] and
2
ꢁ
the resulting mixture was cooled to ꢀ40 C. During the dropwise
addition of 0.47 g (1.05 mmol) 12 in 10 mL THF, the colour of the
mixture first became orange and after the addition was completed
it is turned to brown. The reaction mixture was stirred for an
B 250 mg (0.44 mmol) of 16 was dissolved in 10 mL hexane. After
the solution was irradiated with UV lamp for 30 min. The colour
of the mixture became darker during the irradiation in all cases.
After that the solvent was removed under reduced pressure and
the residue was dissolved in hexane, filtered, and the solution
was concentrated. The resulted colourless crystals were identi-
ꢁ
additional 15 min at ꢀ40 C and was subsequently allowed to warm
to room temperature and was stirred for another 2 h at the same
temperature. The solvent was removed under reduced pressure and
1
5 mL hexane was added to the residue. The resulting insoluble
white salt was filtered out and the brown filtrate was concentrated
ꢁ
under reduced pressure and crystallized at ꢀ30 C to get yellow
ꢁ
fied as 18. Yield: 25 mg (10%), m.p. 224e226 C. Anal. calcd. for
needles. Yield: 0.45 g (73%). Anal. calcd. for C29
H
33Si
3
FeO
2
Cl
):
C
1
C
46
H62Si
6
(783.49): C, 70.52; H, 7.98. Found: C, 70.45; H, 8.46. H
1
(
589.12): C, 59.12; H, 5.65. Found: C, 58.82; H, 5.67. H NMR (C
6
D
6
NMR (CDCl
3
):
d
¼ ꢀ0.01 (s, 18H, SiMe
3
), 0.78 (s, 3H, CH
):
¼ ꢀ0.7 (SiMe),
), 126.1, 126.8, 129.1, 142.8, 147.9, 170.0. Si{ H} NMR
3
),
1
3
d
¼ 0.19 (s, 18H, SiMe
3
), 4.28 (s, 5H, Cp), 6.7e7.0 (m, 10H, Ph).
13
1
6.80e7.15 (m, 10H, Ph). C{ H} NMR (CDCl
3
d
1
{
H} NMR (CDCl
3
):
d
¼ 1.5 (SiMe
3
), 85.1 (Cp), 126.5 (pPh), 127.2,
), 213.9 (CO).
). IR (nujol,
) n(CO) 2011, 1957. HRMS (EI): m/z (%) 588.0828 (calc. for
29
1
1
.7 (SiMe
3
1
a b
28.9, 129.8 (o/mPh), 142.5 (C ), 150.8 (iPh), 162.0 (C
(
7
CDCl
3
):
d
¼ 5.8 (Si-ring), ꢀ9.9 (SiMe
3
). HRMS (EI): m/z (%)
782.3462) (13.5) [M ], 767.3207
2
9
1
Si{ H} NMR (CDCl
3
):
d
¼ 82.6 (Si-ring), ꢀ8.7 (SiMe
3
þ
82.3481 (calc. for C46
H62Si
6
ꢀ
1
cm
þ
(calc. for C45
H59Si
6
767.3227) (5.1) [M eMe], 391.1727 (calc. for
3
5
C
C
C
5
29
H
29
H
27
H
33ClFeO
2
Si
Si
3
588.0826) (76.3), 590.0836
(calc.
for
þ
C
23
H31Si
1
391.1734) (89.3) [1/2 M ].
3
7
þ
33ClFeO
2
3
590.0797) (17.7) [M ], 532.0931 (calc. for
35
37
33ClFeSi
3
532.0928) (4.1), 534.0920 (calc. for C27
H
33ClFeSi
3
þ
34.0899) (1.9) [M e2CO].
3
5.10. Reactions of 14 or 15 with Me NO
0.54 mmol 14 or 15 dissolved in 3 ml THF was added dropwise to
5
.7. (1-Methyl-3,4-diphenyl-2,5-bis(trimethylsilyl))-1-
the THF solution of 40 mg (0.54 mmol) trimethylamine N-oxide
5
ꢁ
ꢁ
silacyclopentadienyl)-
h
-cyclopentadienyl-dicarbonyl-iron (16)
at ꢀ20 C. The mixture was stirred for 30 min at ꢀ20 C. The re-
action mixture did not show any change, therefore it was allowed to
warm to room temperature and was stirred for another 30 min at
that temperature. The insoluble solid was filtered out, the filtrate
was concentrated under reduced pressure and crystallized
1
.06 g (2.48 mmol) K[Fe(CO) Cp] was dissolved in 10 mL tetra-
2
ꢁ
hydrofuran and cooled to ꢀ40 C. 0.53 g (2.48 mmol) 13 in 10 mL
ꢁ
tetrahydrofuran was added dropwise at ꢀ40 C. The colour of the
ꢁ
mixture became brown during the addition and the mixture was
at ꢀ30 C. The residue was identified as starting material based (12
ꢁ
stirred for 4 h at ꢀ40 C. After that it was allowed to warm to room
or 13) on NMR measurements.
temperature and was stirred overnight. The solvent was removed
under reduced pressure and 20 ml hexane was added to the res-
idue. The resulting insoluble white salt was filtered out and the
brown filtrate was concentrated under reduced pressure and
Acknowledgements
The authors thank the Institut für Anorganische Chemie,
Karlsruher Institut für Technologie (KIT) for the measurements of
NMR spectra, mass spectra and for elemental analysis. Financial
support from the Hungarian Scientific Research Fund OTKA NN
113772, K-100801 and COST CM10302 (SIPS) is gratefully
acknowledged.
ꢁ
crystallized at ꢀ30 C. The pure compound was obtained by
ꢁ
recrystallized from hexane at ꢀ30 C resulting in yellow cubic
crystals. Yield: 1.14 g (90%) Anal. calcd. for C30
H36Si
3
FeO
2
(568.71):
):
¼ 0.11
), 4.26 (s, 5H, Cp), 6.65e7.14 (m, 10H,
¼ 1.7 (SiMe), 1.8 (SiMe ), 85.1 (Cp),
26.2 (pPh), 127.1, 127.2, 129.4, 130.0 (o/mPh), 143.4 (C ), 154.8 (iPh),
1
C, 63.25; H, 6.55. Found: C, 63.37; H, 6.18. H NMR (CDCl
s, 18H, SiMe ), 0.90 (s, 3H, CH
Ph). C{ H} NMR (CDCl ):
3
d
(
3
3
13
1
3
d
3
1
a
Appendix A. Supplementary data
2
9
1
163.3 (C
b
), 215.8 (CO). Si{ H} NMR (CDCl
3
):
d
¼ 55.5 (Si-ring), ꢀ9.7
ꢀ
1
(
SiMe
3
). IR (nujol, cm
)
n
(CO) 1999, 1948. HRMS (EI): m/z (%)
CCDC 1412535 (15), CCDC 1412536 (16) and CCDC 1412537 (18)
contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
þ
5
68.1355 (calc. for C30
36FeSi
H
36FeO
2
Si
3
568.1367) (2.5) [M ], 512.1469
þ
(
calc. for C28
H
3
512.1469) (62.3) [M e2CO], 391.1721(calc. for
þ
C
23
H31Si
3
391.1734) (100.0) [M eFe(CO)
2
Cp].

298
C. Fekete et al. / Journal of Organometallic Chemistry 799-800 (2015) 291e298
[12] C. Fekete, I. Kov
77e387.
13] C. Fekete, I. Kov ꢀa cs, L. Nyul aꢀ szi, Phosphorus, Sulfur, Silicon 189 (2014)
076e1083.
ꢀa cs, L. K o€ ncz o€ l, Z. Benk o} , L. Nyul aꢀ szi, Struct. Chem. 25 (2014)
request/cif.
3
[
Appendix B. Supplementary data
1
[
[
14] R.-Z. Jin, K. Tamao, Organometallics 16 (1997) 2230e2232.
15] S. Fortier, Y. Zhang, H.K. Sharma, K.H. Pannell, Organometallics 29 (2010)
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1041e1044.
[
[
16] A.L. Spek, Acta Cryst. D65 (2009) 148e155.
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