Activation by the Grignard reagent of the bis(2-phenylindenyl)zirconium dichloride-triisobutylaluminum catalytic system for propene polymerization

Article abstract of DOI:10.1023/A:1013019526063

Polymerization of propylene with the three-component catalytic system bis(2-phenylindenyl)zirconium dichloride-alkyl magnesium chloride-triisobutylaluminum is studied. The annelated zirconocene is alkylated by the Grignard reagent. The three-component system is as good in activity as two-component systems with polymethylalumoxane as a cocatalyst. Stereoblock elastomeric polypropylene with a high molecular weight is formed.

Full text of DOI:10.1023/A:1013019526063

1696
Russian Chemical Bulletin, International Edition, Vol. 50, No. 9, pp. 1696—1698, September, 2001
Activation by the Grignard reagent of the bis(2-phenylindenyl)zirconium
dichloride—triisobutylaluminum catalytic system for propene
polymerization
Z. M. Dzhabieva, N. V. Pokostina, and T. S. Dzhabiev«
Institute of Problems of Chemical Physics, Russian Academy of Sciences,
142432 Chernogolovka, Moscow Region, Russian Federation.
Fax: +7 (096) 515 3588. E-mail: timur@cat.icp.ac.ru
Polymerization of propylene with the three-component catalytic system bis(2-phenyl-
indenyl)zirconium dichloride—alkyl magnesium chloride—triisobutylaluminum is studied.
The annelated zirconocene is alkylated by the Grignard reagent. The three-component system
is as good in activity as two-component systems with polymethylalumoxane as a cocatalyst.
Stereoblock elastomeric polypropylene with a high molecular weight is formed.
Key words: bis(2-phenylindenyl)zirconium dichloride, alkylmagnesium chloride, propy-
lene, elastomeric polypropylene, polymerization catalysts.
(2-cyclo-HexylInd)2ZrCl2 and (2-p-TolylInd)2ZrCl2 were syn-
thesized by known procedures.7,8
Thermoplastic elastomeric polypropylene (PP) has
been found in the products of propylene polymerization
more than forty years ago.1 An interest in new catalysts
for propylene polymerization remains high up to now
due to a great significance of the product.2—5 However,
since the consumption of the cocatalyst (methyl-
alumoxane) is relatively high, its use in catalytic systems
affects noticeably the cost of the target product.5 There-
fore, the replacement of methylalumoxane by other
cocatalysts is an urgent problem.
The kinetics of propylene polymerization was studied on a
UVD-60 high-pressure setup in a 0.2-L reactor. The solvent
and triisobutylaluminum were successively introduced with stir-
ring into the reactor. The reaction began from the moment of
destruction in the reactor of two sealed ampules filled with
(2-PhInd)2ZrCl2 and the Grignard reagent. Polymerization was
performed at a constant propylene pressure. The reaction was
terminated by ethanol containing 10% HCl. The product was
washed with water and ethanol and dried at 60 °C in vacuo to a
constant weight. The macrotacticity index of PP (D998/D973
)
This work is aimed at studying propylene poly-
merization in the new three-component catalytic
system (2-PhInd)2ZrCl2—AlkMgCl—AlBui3, where
Alk = Me or Bu.
was determined on a Perkin Elmer FT-IR 1720X instrument.9
13Ñ NMR spectra of solutions of polymers were recorded at
75 MHz on a Bruker AM-250 instrument in tetrachloroethane
at 100 °C. The molecular weight of the obtained polymer was
determined from the viscosity of a solution of PP in decalin at
135 °C and by GLC on a Waters 150-C instrument.
Experimental
Results and Discussion
Preliminarily purified and refrozen above LiAlH4 hexane,
heptane, toluene, and THF were used for the synthesis of the
catalysts and Grignard reagents. All procedures were carried out
in dry pure argon. The Grignard reagents BunMgCl and MeMgCl
were prepared in THF using known procedures.6 To prepare
(2-PhInd)2ZrCl2, BunLi (1.77 mol L–1, 6.7 mmol, 3.78 mL) in
heptane was added dropwise with continuous stirring at –60 °C
to a suspension of 2-phenylindene (1.29 g, 6.7 mmol) in
toluene (10 mL) with a minor content of THF. The resulting
orange-yellow solution of 2-PhIndLi was slowly heated to
25 °C and stored for 3 h. After this the solution was slowly
added to ZrCl4 (Aldrich, 0.78 g, 3.35 mmol) in toluene at
–20 °C. Then the mixture was heated to 25 °C and stirred for
10 h. The solvent was removed, and (2-PhInd)2ZrCl2 was
multiply extracted with toluene combining the extracts and
concentrating the solution by the removal of a portion of the
solvent, and cooled to –30 °C. The crystals were washed with
hexane, dried, and isolated in 71% yield (1.15 g). Found (%):
Ñ, 66.2; Í, 4.1; Cl, 13.0; Zr, 16.7. C30H22Cl2Zr. Calcu-
lated (%): C, 66.16; H, 4.07; Cl, 13.02; Zr, 16.75. Compounds
A double excess (with respect to (2-PhInd)2ZrCl2)
of BunMgCl or MeMgCl was introduced directly into
the reaction mixture to replace the chlorine ions in
(2-PhInd)2ZrCl2 by the alkyl groups. However, active
sites of polymerization are not formed in the two-
component L2ZrCl2—RMgCl systems. The addition of
the third component (AlBui3) to them gives an active
catalytic system (Fig. 1). Triisobutylaluminum itself is
an efficient alkylating reagent, however, active sites of
polymerization are not formed either in the two-compo-
nent (2-PhInd)2ZrCl2—AlBui3 system (without RMgCl).
In the presence of the (2-PhInd)2ZrCl2—
BunMgCl—AlBui3 catalytic system, the rate of propy-
lene polymerization is maximum in the very beginning
of the reaction. Then it decreases during the process
(Fig. 1), and the rate of deactivation of the active sites
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1615—1617, September, 2001.
1066-5285/01/5009-1696 $25.00 ©ꢀ2001 Plenum Publishing Corporation

C3H6 polymerization with zirconocene catalyst
Russ.Chem.Bull., Int.Ed., Vol. 50, No. 9, September, 2001 1697
–1
W/mmol h
initial rates, are approximately equal (2528 and
2147 kg PP (mole Zr h) , see Table 1, entries 4 and
–1
200
12). As can be seen in Table 1, the efficiency increases
with an increase in the propylene pressure and a de-
crease in the reaction temperature. When the partial
pressure of propylene increases from 3 to 7 atm, the
efficiency increases by ∼3 times (entries 1—4), whereas
the initial rate increases by ∼30 times. The molecular
weights of PP are rather high and range from 155000 to
590000 (entries 1—11). Polydispersity of the polymers
obtained (Mw/Mn) is somewhat lower than that of simi-
lar samples obtained previously in the presence
of the (2-PhInd)2ZrCl2—methylalumoxane system
(Mw/Mn = 3.5—4.0)3 and is virtually independent of
the propylene concentration and temperature of the
process.
150
1
100
2
50
0
10
20
30
40
50
t/min
Fig. 1. Rate of propylene polymerization in the three-compo-
nent systems with n-butyl- (1) and methylmagnesium chlo-
ride (2). Reaction conditions: –2 °C; [(2-PhInd)2ZrCl2] =
–5
2.7•10
mol L–1, molar ratios Al/Zr = 150, Mg/Zr = 2;
Analysis of the structure of the PP samples by IR
and 13Ñ NMR spectroscopy indicates the formation of
stereoblock PP. The polymers possess a low stereoregu-
volume of a solution 100 cm3 (of them 60 cm3 toluene); partial
pressure of propylene 5.0 atm.
larity. The isotacticity index of the polymer (D998/D973
)
depends on the experimental conditions. The process
rate in the three-component system involving MeMgCl
differs from that in the system with BunMgCl (Fig. 1).
In this case, the initial polymerization rate is ∼20-fold
lower, however, further it increases gradually, and the
maximum rate, which is achieved in 17 min, becomes
comparable with the polymerization rate in the system
with BunMgCl (Fig. 1, curve 2).
changes from 0.15 to 0.32 (entries 1—9). It is seen that
a decrease in the reaction temperature and molar ratio
Al/Zr increases the stereoregularity and molecular weight
of the polymer. The pentad composition (mmmm) of our
PP (entry 6) agrees with the stereocomposition of the
elastomer obtained previously.2 The 36% content of
isotactic pentads can be achieved (entry 9) by changing
the Al/Zr ratio. For comparison Table 1 contains
the properties of PP obtained in the presence of
(2-cyclo-HexylInd)2Cl2 and (2-p-TolylInd)2ZrCl2 with
other ligands (entries 15 and 16).
The main experimental results of the work are pre-
sented in Table 1. The efficiencies of two sys-
tems containing BunMgCl and MeMgCl, unlike their
Table 1. Influence of polymerization conditions on the catalyst efficiency and properties of polypropylene obtained in the presence
of (2-PhInd)2ZrCl2 and AlBui3 (molar ratio Mg/Zr = 2, solvent toluene, 60 cm3, reaction duration 1 h)
–3
b
c
d
Entry
(2-PhInd)2ZrCl2
Al/Zr
RMgCl
p
T
/°C
Aa
Mw•10
Mw/Mn
mmmm
(%)
m
/µmol
/atm
(%)
1
2
3
4
5
6
7
8
2.35
2.61
2.65
2.69
2.44
2.46
2.78
2.7
2.81
3.13
2.69
3.05
3.0
200
200
200
200
150
150
150
150
100
200
200
200
200
300
300
300
Bu
Bu
Bu
Bu
Bu
Bu
Me
Me
Bu
Bu
Bu
Me
Me
Bu
Bu
Bu
3.1
5.0
6.0
7.1
5.0
5.0
5.0
5.0
7.1
7.1
7.1
7.1
7.1
7.25
7.25
7.25
–3
–3
–3
–3
25
–2
–2
25
–3
25
–3
–3
25
808
1037
1780
2528
602
1057
849
474
2341
1757
2528
2147
1663
1782
770
155
255
320
389
139
425
194
109
416
207
590
317
228
290
132
231
22
24
26
27
65
66
68
70
3.0
2.51
2.58
2.45
2.63
2.5
2.45
2.95
2.95
2.72
2.9
32
36
73
69
9
10
11
12
13
14
15
16
e
3.4
3.6
3.1
18
18
18
24
13
25
66
59
74
f
g
1219
3.35
a Efficiency À in kg PP/(mole Zr h).
b Mw is the weighted-mean molecular weight, and Mn is the numerical-mean molecular weight.
c mmmm is the content of isotactic pentads.
d m is the content of isotactic diads.
e Reaction duration 2 h.
f (2-cyclo-HexylInd)2ZrCl2.
g (2-p-TolylInd)2ZrCl2.

1698
Russ.Chem.Bull., Int.Ed., Vol. 50, No. 9, September, 2001
Dzhabieva et al.
4. C. D. Tagge, R. L. Kravchenko, T. K. Lal, and R. M.
Waymouth, Organometallics, 1999, 18, 380.
Thus, elastomeric PP can be obtained in the pres-
ence of the new three-component Ziegler—Natta sys-
tem containing no methylalumoxane. Desired alkyl
groups, including labile groups, can be introduced into
zirconocenes using the Grignard reagent. Changing the
conditions of the process allows the purposeful influ-
ence on the properties of the polymeric product (mo-
lecular-weight distribution, stereoregularity, and others,
see Table 1), which makes it possible to vary the
physicomechanical parameters of PP.
5. V. I. Tsvetkova, Vysokomol. Soedin., Ser. Ñ, 2000, 42, 1954
[Polym. Sci. Ser. C, 2000, 42 (Engl. Transl.)].
6. Metody elementoorganicheskoi khimii [Methods of Organo-
element Chemistry], Eds. A. N. Nesmeyanov and K. A.
Kocheshkov, Izd-vo AN SSSR, Moscow, 1963, 20, 27 (in
Russian).
7. L. G. Greifenstein, J. B. Lambert, R. J. Nienhuis, H. E.
Fried, and G. A. Pagani, J. Org. Chem., 1981, 46, 5125.
8. G. Y. Lee, M. Xue, M. S. Kang, O. C. Kwon, J. S. Yoon,
Y. S. Lee, H. S. Kim, H. Lee, and J. M. Lee, J. Organomet.
Chem., 1998, 558, 11.
References
9. Y. V. Kissin, Isospecific Polymerization of Olefins with Het-
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Received November 20, 2001;
in revised form July 27, 2001