Zwitterionic transition metal compound which contains boron

Details Zwitterionic transition metal compound which contains boron Zwitterionic transition metal compound which contains boron

2000-08-14

2002-11-26

Wu, David W. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S126000, C526S160000, C526S161000, C526S172000, C526S943000, C502S117000, C502S152000, C556S053000

Reexamination Certificate

active

06486277

ABSTRACT:

The present invention describes a zwitterionic neutral transition metal compound which can advantageously be used for the polymerization of olefins. It is thereby possible to dispense with the use of aluminoxanes, such as methylaluminoxane (MAO), as a cocatalyst and nevertheless to achieve a high catalyst activity and good polymer morphology.
The role of cationic complexes in the Ziegler-Natta polymerization with metallocenes is generally recognized (H. H. Brintzinger, D. Fischer, R. Mülhaupt, R. Rieger, R. Waymouth, Angew. Chem. 107, (1995) 1255-1283).
MAO, an effective cocatalyst, has the disadvantage that it has to be used in a large excess. The preparation of cationic alkyl complexes is opening up a route with MAO-free catalysts having comparable activity, it being possible to use the cocatalyst in an approximately stoichiometric amount.
The synthesis of cation-like metallocene polymerization catalysts is described in J. Am. Chem. Soc. 113 1991, 3623. A process for the preparation of salts of the formula LMX
+
XA
−
according to the principle described above is claimed in EP 520 732.
EP 558158 describes zwitterionic catalyst systems which are prepared from metallocenedialkyl compounds and salts of the form [R
3
NH]
+
[B(C
6
H
5
)
4
]
−
. The reaction of such a salt with, for example, Cp
2
ZrMe
2
gives a zirconocenemethyl cation as an intermediate by protolysis with methane elimination. Said cation reacts via C—H activation to give the zwitterion Cp
2
Zr
+
—(m—C
6
H
4
)—BPh
3
−
. The Zr atom is covalently bonded to a carbon atom of the phenyl ring and stabilized via agostic hydrogen bonds.
U.S. Pat. No. 5,348,299 describes zwitterionic catalyst systems which are prepared from metallocenedialkyl compounds and salts of the form [R
3
NH]
+
[B(C
6
F
5
)
4
]
−
by protolysis. The C—H activation as a secondary reaction is absent.
EP 426 637 uses a process in which the Lewis acid CPh
3
+
cation is used for abstracting the methyl group from the metal center. B(C
6
F
5
)
4
−
, too, acts as a weakly coordinating anion. Here, metallocenes with Cp
2
MR
2
in which the alkyl radicals R are cyclically bonded to one another are also used, e.g. Cp
2
Zr(2,3-dimethyl-1,3-butadiene). Salts of the form [Cp
2
Zr—R—RH]
+
[B(C
6
F
5
)
4
]
−
form by protolysis.
EP 0687682 describes specific zwitterionic transition metal catalyst systems which are prepared from metallocenebutadiene compounds and a Lewis acid, such as tris(pentafluorophenyl)borane. These zwitterionic compounds prepared in this manner have polymerization activities comparable with metallocene compounds which are activated by MAO.
The zwitterionic compounds described in EP 0687682 have the disadvantage that they become detached from the support surface in the heterogenization required for the industrial use of metallocene catalysts, during the metering of the catalyst system into the reactor. This leads to a homogeneous polymerization in some cases. In addition, the heterogenization of these catalyst systems leads to low polymerization activity.
It is an object of the present invention to provide a transition metal compound which avoids the disadvantages of the prior art. We have found that this object is achieved by specific zwitterionic transition metal compounds. The present invention therefore relates to a zwitterionic transition metal compound of the formula I
where
L are identical or different &pgr;-ligands or electron donors which may be bonded to one another,
N is 1, 2, 3 or 4,
M is a metal atom of group IIIb, IVb, Vb or VIb of the Periodic Table of the Elements,
X is a heteroatom, an aromatic or nonaromatic heterocyclic structure or a hydrocarbon group of 1-40 carbon atoms,
Y is a C
1
-C
40
-hydrocarbon radical which may be halogenated, preferably perhalogenated, with halogens, such as fluorine, chlorine, bromine or iodine, in particular a halogenated, especially perhalogenated, C
1
-C
30
-alkyl group, such as trifluoromethyl, pentachloroethyl, heptafluoroisopropyl or monofluoroisobutyl, or a halogenated C
6
-C
30
-aryl group, such as pentafluorophenyl, 2,4,6-trifluorophenyl, heptachloronaphthyl, heptafluoronaphthyl, heptafluorotolyl, 3,5-bis(trifluoromethyl)phenyl, 2,4,6-tris(trifluoromethyl)phenyl, nonafluorobiphenyl or 4-trifluoromethyl)phenyl; Y is also preferably a radical such as phenyl, naphthyl, anisyl, methyl, ethyl, isopropyl, butyl, tolyl, biphenyl, 2,3-dimethylphenyl or an allyl radical of at least 3 carbon atoms;
f is 0 or 1,
A is a metal atom of group Ib, IIb, IIIa, IVa, Va, VIb, VIIb or VIIIb of the Periodic Table of the Elements,
R
1
is a C
1
-C
40
-hydrocarbon radical which may be halogenated, preferably perhalogenated, with halogens, such as fluorine, chlorine, bromine or iodine, in particular a halogenated, especially perhalogenated, C
1
-C
30
-alkyl group, such as trifluoromethyl, pentachloroethyl, heptafluoroisopropyl or monofluoroisobutyl, or a halogenated C
6
-C
30
-aryl group, such as pentafluorophenyl, 2,4,6-trifluorophenyl, heptachloronaphthyl, heptafluoronaphthyl, heptafluorotolyl, 3,5-bis(trifluoromethyl)phenyl, 2,4,6-tris(trifluoromethyl)phenyl, nonafluorobiphenyl or 4-(trifluoromethyl)phenyl; R
1
is also preferably a radical such as phenyl, naphthyl, anisyl, methyl, ethyl, isopropyl, butyl, tolyl, biphenyl or 2,3-dimethylphenyl;
m is 1, 2, 3, 4 or 5.
The metal atoms M
1
and A are linked to one another by a covalent or coordinate bond via the structural element X.
Where Y is an allyl unit, the bond from Y to the metal atom M may be a &sgr;-allyl or a-allyl bond, an additional bridging is effected via the structural element X which links the metal atoms M
1
and A to one another by a covalent or coordinate bond. This structural element X is preferably a heteroatom, a heterocyclic structure or a hydrocarbon group of 1-40 carbon atoms. If X is a heterocyclic structure containing double bonds, the bond from X to the metal atom M may be a coordinate bond.
Preferred &pgr;-ligands are unsubstituted or substituted cyclopentadienyl groups which are identical or different and constitute a substituted or unsubstituted cyclopentadienyl, indenyl or fluorenyl group, where two radicals L may be linked to one another via a bridge Z.
A heteroatom is understood as meaning any atom of the Periodic Table of the Elements, with the exception of carbon and hydrogen. O, S and N are preferred.
Heterocyclic structures may be, inter alia, substituted or unsubstituted pyrrolidines, pyrroles, indoles, imidazoles, isoindoles or benzimidazoles.
Hydrocarbon groups X may be saturated or unsaturated, linear or branched, e.g. C
4
-C
12
-heteroaryl, C
1
-C
20
-heteroalkyl, C
1
-C
20
-alkyl, C
6
-C
14
-aryl, C
2
-C
10
-alkenyl, C
7
-C
40
-arylalkyl, C
7
-C
40
-alkylaryl or C
8
-C
40
-arylalkyl. Unsubstituted and substituted heteroaryl and heteroalkyl groups which may also have aromatic structural elements are preferred.
n may preferably be from 1 to 4.
Particularly preferred compounds of the formula I are those in which
M is a metal atom of group IVb of the Periodic Table of the Elements, such as titanium, zirconium or hafnium,
n is 2 or 3,
L is a preferably substituted cyclopentadienyl ring, in particular substituted in the 1, 3-, 1, 2-, or 1, 2, 4-position by C
1
-C
20
-carbon-containing groups, such as C
1
-C
10
-alkyl or C
6
-C
20
-aryl, or a preferably substituted indenyl ring, in particular substituted in the 2, 4-, 2, 4, 5-, 2, 4, 6-, 2, 4, 7- or 2, 4, 5, 6-position by C
1
-C
20
-carbon-containing groups, such as C
1
-C
10
-alkyl or C
6
-C
20
-aryl, it also being possible for two or more substituents of the indenyl ring together to form a ring system; these cyclopentadienyl and indenyl ring may be unbridged or bridged by Z; bridging by two radicals L in the 1-position is particularly preferred;
Z are bridging groups of the formula M
2
R
2
R
3
, where M
2
is carbon, silicon, germanium or tin and R
2
and R
3
are identical or different C
1
-C
20
-hydrocarbon-containing groups, such as C
1
-C

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