Synthesis and characterization of cyclopentadienyl titanium trichloride and indenyltitanium trichloride; monocyclictitanium trihalide complexes

Article abstract of DOI:10.1080/15533170600862481

CpTiCl₃ and IndTiCl₃ are homogeneous metallocene catalysts that are produced under highly controlled conditions. Syndiotactic polymerization of styrene is carried out using these catalysts while methylaluminoxane (MAO) is used as a cocatalyst. In the present paper synthesis of CpTiCl₃ was examined at first by reacting TiCl₄ with CpNa, this reaction just led to formation of Cp₂TiCl₂ so CpNa was not a suitable Cp donor compound, therefore CpSiMe₃ was used instead of CpNa. Reaction of CpSiMe₃ with TiCl₄, produced CpTiCl₃ immediately. IndTiCl₃ was synthesized by reacting IndSiMe₃ and TiCl₄ as well. At the end two synthetic catalysts were characterized by FTIR and ¹H-NMR spectrometers. Copyright

Full text of DOI:10.1080/15533170600862481

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Synthesis and Characterization of Cyclopentadienyl
Titanium Trichloride and Indenyltitanium Trichloride;
Monocyclictitanium Trihalide Complexes
a
a
a
a
Mitra Masnadi , Roghieh Jamjah , Saeed Ahmadjo & Mehdi Nekoomanesh
a
Catalysis Group, Iran Polymer and Petrochemical Institute, Tehran, Iran
Version of record first published: 15 Feb 2007.
To cite this article: Mitra Masnadi, Roghieh Jamjah, Saeed Ahmadjo & Mehdi Nekoomanesh (2006): Synthesis and
Characterization of Cyclopentadienyl Titanium Trichloride and Indenyltitanium Trichloride; Monocyclictitanium Trihalide
Complexes, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 36:7, 543-547
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Synthesis and Reactivity in Inorganic, Metal-Organic and Nano-Metal Chemistry, 36:543–547, 2006
Copyright # 2006 Taylor & Francis Group, LLC
ISSN: 0094-5714 print/1532-2440 online
DOI: 10.1080/15533170600862481
Synthesis and Characterization of Cyclopentadienyl Titanium
Trichloride and Indenyltitanium Trichloride;
Monocyclictitanium Trihalide Complexes
Mitra Masnadi, Roghieh Jamjah, Saeed Ahmadjo, and Mehdi Nekoomanesh
Catalysis Group, Iran Polymer and Petrochemical Institute, Tehran, Iran
In 1986 Ishihara found that cyclopentadienyltitanium tri-
[7–9]
CpTiCl and IndTiCl are homogeneous metallocene catalysts chloride (CpTiCl ) as half-sandwich catalyst produce sPS.
3
3
3
that are produced under highly controlled conditions. Syndiotactic
polymerization of styrene is carried out using these catalysts while
methylaluminoxane (MAO) is used as a cocatalyst. In the present
paper synthesis of CpTiCl3 was examined at first by reacting
It is worth noting that biscyclopentadienyltitanium dichloride
does not promote syndiospecific polymerization of
[10]
styrene.
sPS catalyst containing indenyl and found that the (h -
so CpNa was not a suitable Cp donor compound, therefore indenyl)TiCl –MAO system catalyzed the polymerization of
In 1993, Rausch and coworkers reported the first
5
TiCl
4
with CpNa, this reaction just led to formation of Cp
2
TiCl
2
3
CpSiMe
3
was used instead of CpNa. Reaction of CpSiMe
3
TiCl , produced CpTiCl immediately. IndTiCl was synthesized
with
styrene over a wide range of polymerization temperature
[1]
more effectively than CpTiCl - MAO.
4
3
3
3
by reacting IndSiMe as well. At the end two synthetic
catalysts were characterized by FTIR and H-NMR spectrometers.
3
and TiCl
4
1
Indenyltrichloro titanium activated with MAO is a
[9,11]
catalyst exceedingly high in both activity and specificity
and which is relatively insensitive to polymerization
[11,12]
conditions.
Keywords monocyclic, synthesis, sodium cyclopentadienide,
trimethylsilylcyclopentadiene, cyclopentadienyltitanium
trichloride, indenyltitanium trichloride
Greater activity for IndTiCl may be attributed to the higher
3
propagation rate due to the greater electron-donating ability of
[
11]
the indenyl group ring relative to the Cp moiety.
reports two different synthesis methods of simple single-ring
This paper
cyclopentadienyltitanium trichloride and
synthesis of indenyltitanium trichloride.
a method for
INTRODUCTION
Since the discovery of the Ziegler–Natta catalyst systems in
the early 1950s, the metallocene complexes of group IVB
metals have become an important class of homogeneous cata-
lysts for the polymerization of a-olefins. Metallocene catalysts
have become increasingly important as part of potentially new
generation of Ziegler-Natta (ZN) catalyst. As an advantage
over the conventional ZN catalyst, metallocene or single site
catalyst have the capability of better control of polymer tacti-
EXPERIMENTAL
CpTiCl and IndTiCl catalysts were prepared according to
methods obtained from literature and developed in Polymer
3
3
[9]
and Petrochemical Institute of Iran (IPPI). All operations
were performed under pure N atmosphere using a dry box
2
equipped with gas driers such as KOH, silica gel and molecular
˚
sieve 4 A.
[1–4]
city, molecular weight, and molecular weight distribution.
The use of TiCl -methylalumoxane (MAO) system in the first
4
preparation of syndiotactic polystyrene by Ishihara has led scien-
0
Materials
tists to observe that titanium compounds of the type Cp TiX3
0
Commercially available titanium tetrachloride (Merck),
trimethylsiliylindene (Aldrich), 2 M solution of sodium cyclo-
pentadienide in THF (Aldrich) and dichloromethane (Aldrich)
were used without further purification. n-Hexane (Iran Pet-
roleum Co.) was distilled over calcium hydride. Toluene, tetra-
hydrofurane and benzene (Merck) were refluxed over metallic
sodium and benzophenone as an indicator. Reactants were
introduced to the degassed flasks under nitrogen (99.999%).
(
or alkyl groups) are among the most effective catalysts for
Cp ¼ C H , C Me , C Me H or C H ; X ¼ halide, alkoxides
5
5
5
5
5
4
9 7
[
5,6]
preparation of syndiotactic polystyrene (sPS).
Received 27 March 2006; accepted 15 May 2006.
Address correspondence to Mitra Masnadi, Catalysis Group, Iran
Polymer and Petrochemical Institute, P.O. Box 14965/115, Tehran,
I.R., Iran. E-mail: mitramasnadi@gmail.com
543

5
44
M. MASNADI ET AL.
Anhydrous MgSO (Scharloo) was used to dry a compound SYNTHESIS OF INDENYLTITANIUM TRICHLORIDE
4
during the synthesis. Two different methods to synthesis of
CpTiCl were used.
3
SYNTHESIS OF CYCLOPENTADIENYLTITANIUM
TRICHLORIDE
Synthesis of CpTiCl with CpNa
3
First, 26.4 mmol of TiCl4 was dissolved in 70 mL of
dichloromethane in a 250 mL flask, equipped with magnetic
stirrer and an addition funnel. Then 31.2 mmol of trimethylsi-
lylindene that was dissolved in 30 mL of dichloromethane, was
added drop wise, while the temperature was maintained at
Sixty-one mL of 2 M solution of sodium cyclopentadienide
in tetrahydrofurane containing 0.12 mol CpNa was added drop
wise at 0 8C to 0.12 mol of TiCl that was dissolved in 200 mL
4
of toluene. The reaction mixture was allowed to stand over-
night at room temperature then it was filtered. The filtrate
was stored at refrigerator for a few days and some red
0
8C. The initially yellow solution slowly turned deep-red.
[
13]
The mixture stirred overnight at room temperature before the
solvent was removed under vacuum. To the dark-red residue,
crystals appeared in the solution.
The compound (1a) was
1
characterized by its H-NMR and FTIR spectra.
100 mL of hexane was added and the resultant suspension
was cooled to 230 8C for several hours. A dark-violet precipi-
tate formed which was collected by filtration, washed with
Trimethylsilylcyclopentadiene was prepared by treating cold hexane, and dried under vacuum. The compound was
3
Synthesis of CpTiCl with CpSiMe3
1
sodium cyclopentadienide (1 mol) with chlorotrimethylsilane characterized by its H-NMR spectrum.
(
CpTiCl as Equation (1).
1 mol). Then CpSiMe3 was reacted with TiCl4 to form
[
14]
3
CHARACTERIZATION
The synthetic catalysts were characterized by BRUKER,
IFS48 infrared spectrometer and the BRUKER 400 MHz
AVANCE 400 nuclear magnetic resonance spectrometer and
Elementar Analysensysteme GmbH VarioEL.
Preparation of Trimethylsilylcyclopentadiene
To a solution of 0.2 mol of sodium cyclopentadiene in
00 mL of dry THF was added drop wise 0.2 mol of chlorotri-
1
RESULT AND DISCUSSION
methylsilane in 50 mL of dry THF at 0 8C with stirring under
N atmosphere. After the addition was completed the resulting
2
Infrared Spectra
The infrared absorption spectra of 1a and 1b (Figures 1 and
reaction mixture was stirred for 1 h at room temperature. The
reaction mixture was poured into a large amount of water;
the organic phase was separated and dried over MgSO , and
2) were compared with reference spectra and it was found that
4
1a was Cp TiCl and 1b was CpTiCl . The characteristic peaks
are 833, 935, 1017, 1433, 3107 cm for CpTiCl
2
2
3
21
then concentrated to leave a residue. The residue was distilled
under reduced pressure to give trimethylsilylcyclpentadiene as
an isomeric mixture: colorless liquid; bp. 50–55 8C/
[18]
and 820,
3
21
66, 1016, 1439, 3099 cm for Cp TiCl .
[19]
8
2 2
[
8,14–16]
1
0 mmHg.
H-NMR spectrum.
The compound was characterized by its
1
Reaction of Trimethylsilylcyclopentadiene with Titanium
Tetrachloride
To 66 mmol titanium tetrachloride in 40 mL of benzene was
slowly added 66 mmol of trimethylsilylcyclopentadiene with
stirring. The reaction was rather violent with evolution of
heat and precipitation of a yellow solid was virtually immedi-
ate. The reaction mixture was stirred for a further 30 minute.
The product was filtered off. Washed with two 20 mL
[
14,16]
portion of benzene and dried under vacuum.
1
The
compound (1b) was characterized by its H-NMR and FTIR
[17]
spectra. Anal. Calcd. for CpTiCl (%): C, 27.37; H, 2.30
3
.
Found: C, 27.68; H, 2.11.
4
FIG. 1. FTIR spectrum of 1a, the product of the reaction of CpNa with TiCl .

TRIHALIDE COMPLEX SYNTHESIS
545
FIG. 2. FTIR spectrum of 1b, the product of the reaction of CpSiMe
3
with
TiCl
4
.
[20]
Moffitt characterized the cyclopentadienyl radical in bis-
cyclopentadienyl titanium dibromide as a five membered
aromatic ring bonded to the central metal atom through the p
orbitals. The evidences suggest that such a structure exists
also in Cp TiCl and CpTiCl . For both CpTiCl and
1
2 2
FIG. 3. H-NMR spectrum of Cp TiCl in DMSO.
2
2
3
3
Cp TiCl the presence of a single band in the C-H stretch being at room temperature for about half an hour before
2
2
2
1
1
3107 and 3099 cm ) and C-H bend regions (1433 and taking H-NMR spectrum.
(
2
439 cm ) and the absence of peaks in the C 55 C stretch
1
1
Two singlet peaks of H-NMR spectrum of CpTiCl
1
in
3
2
1
region (1575–1700 cm ) suggest for the ring a resonance CHCl
structure in which there are no formal double bonds. The Cp TiCl
postulated by Sloan and ring does not settle symmetrically on the Ti element in
(Figure 5), at 6.9 and 7.03 ppm indicate that unlike
3
1
that has a single peak in H-NMR spectrum; C H
2 5 5
2
2
1
strong infrared band at 770 cm
[
20]
[26]
Barber
is absent so it is in agreement with the results obtained by Reid
to be characteristic of mono-ring titanium trihalides CpTiCl , so two separate sharp peaks appeared.
3
1
In the H-NMR spectrum of IndTiCl in benzene (Figure 6),
3
[18]
and Wailes.
it can be seen that there are four groups of hydrogen with the
Proton Magnetic Resonance Spectra
1
The H-NMR spectrum obtained for solution of Cp TiCl in
2
2
[
18]
DMSO (Figure 3) shows one very sharp peak at 6.6 ppm.
This data is consistent with a structure in which all the
protons are equivalent. It can be concluded that in this
compound two C H rings are similarly p-bonded. A
5
5
p-bonded structure results in five equivalent hydrogen atom
positions.
[21]
1
In the H-NMR spectrum of CpSiMe in benzene (Figure 4),
3
there are two doublets at 6.6 and 6.8 ppm that are related to the
four vinylic protons of the Cp ring and there is a single peak
3
at 3.3 ppm, which is related to the nonvinylic sP proton of
the Cp ring. It has been reported that 1-trimethylsilylcyclopen-
tadien converts to 2-trimethylsilyl cyclopentadiene and then to
3
and also with the time of storage as Scheme 1.
-trimethylsilylcyclopentadiene with increasing temperature
[
22–25]
Because of weaker intensity of the peak that is at the lower
magnetic field of the spectrum, it can be concluded that some
portion of the 1-trimethylsilylcyclopentadien has been con-
verted to the 2-trimethylsilylcyclopentadiene because of
1
FIG. 4. H-NMR spectrum of CpSiMe
3
in benzene.

5
46
M. MASNADI ET AL.
SCH. 1. Temperature and time dependant equilibrium among trimethylsilyl-
cyclopentadiene isomers.
chemical shifts at 6.26 t 1H, 6.38 d 2H, 6.85 did 2H and 7.15 m
[
27]
2
H related to cyclic protons.
CONCLUSION
It was found that the CpTiCl can be obtained in a high yield
3
in a single step reaction, syndiotactic polymerization of styrene
was carried out with this catalyst and optimum conditions
was obtained for polymerization and polymers were
[28]
1
3
FIG. 6. H-NMR spectrum of IndTiCl in benzene.
characterized.
.
Attempt to isolate CpTiCl from the reaction of
3
reaction time; secondly the product is easily separ-
ated by filtration.
The disadvantage of CpSiMe is that it is time and
TiCl with CpNa was unsuccessful.
4
.
The synthesis of CpTiCl by reaction of TiCl and
3
4
.
.
CpSiMe3 as a Cp donor compound instead of
CpNa, lead to the formation of CpTiCl3
immediately.
3
temperature dependent and converts to vinylic
isomers. So it should be consumed just after distilla-
tion to prevent formation of undesirable isomers.
.
The advantage of CpSiMe is that, firstly it doesn’t
3
As well the use of IndSiMe as an indenyl group
3
replace two Cp rings in the TiCl even by unlimited
4
donor in the synthesis of IndTiCl3 by reacting
TiCl with IndSiMe was successful.
4
3
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(
C5Me5)SiMe3 as
a
transfer of the C5Me5 ring: an improved route to
mild and effective reagent for