Boron compounds and other compounds of group IIIa

Details Boron compounds and other compounds of group IIIa Boron compounds and other compounds of group IIIa

1997-06-02

2001-07-03

Vollano, Jean F (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Boron containing

C568S006000, C556S170000

Reexamination Certificate

active

06255531

ABSTRACT:

DESCRIPTION
The present invention relates to a chemical compound which can have an uncharged or ionic structure. In combination with a metallocene, this can form a novel catalyst system which is advantageously used for the polymerization of olefins. Here, the use of aluminoxanes such as methylaluminoxane (MAO) as cocatalyst can be omitted and high catalyst activities can nevertheless be achieved.
The role of cationic complexes in Ziegler-Natta polymerization using metallocenes is generally recognized (M. Bochmann, Nachr. Chem. Lab. Techn. 1993, 41, 1220). MAO as hitherto most effective cocatalyst has the disadvantage of being used in a high excess. The preparation of cationic alkyl complexes opens up the route to MAO-free catalysts having comparable activity.
The synthesis of cationic alkyl complexes is achieved by
a) protolysis of metallocene compounds using, for example, weakly acid ammonium salts of the very stable, nonbasic tetra(pentafluorophenyl)borate anion (e.g. [PhMe
2
NH]
+
[B(C
6
F
5
)
4
]
−
),
b) abstraction of an alkyl group from metallocene compounds with the aid of strong Lewis acids, where the Lewis acids employed can be either salts of the formula (Ph
3
C
+
BR
4
−
) or strong, uncharged Lewis acids such as B(C
6
F
5
)
3
or by
c) oxidation of dialkylmetallocene complexes using, for example, AgBPh
4
or [Cp
2
Fe][BPh
4
].
The synthesis of “cation-like” metallocene polymerization catalysts is described in J. Am. Chem. Soc. 1991, 113, 3623. In this reference, the alkyl abstraction from an alkyl metallocene compound is carried out by means of tris(pentafluorophenyl)borane. EP 427 697 claims this synthetic principle and a corresponding catalyst system comprising a neutral metallocene species (e.g. Cp
2
ZrMe
2
), a Lewis acid (e.g. B(C
6
F
5
)
3
) and aluminum alkyls. A process for preparing salts of the formula LMX
+
XA
−
according to the above-described principle is claimed in EP 520 732.
EP 558 158 describes zwitterionic catalyst systems which are prepared from metallocene dialkyl compounds and salts of the formula [R
3
NH]
+
[BPh
4
]
−
. The reaction of such a salt with, for example, Cp
2
*ZrMe
2
leads to the intermediate formation of a methylzirconocene cation by protolysis with elimination of methane. This reacts via C—H-activation to form the zwitterion Cp
2
*Zr
+
-(m-C
6
H
4
)-BPh
3
−
. In this, the Zr atom is covalently bonded to a carbon atom of the phenyl ring and is stabilized via an agostic hydrogen bond.
According to this reaction principle, the protolysis of a dialkylmetallocene species using a perfluorinated [R
3
NH]
+
[B(C
6
F
5
)
4
]
−
salt in the first step likewise gives a cationic species, but the subsequent reaction (C—H-activation) to give zwitterionic complexes is not possible. Salts of the formula [Cp
2
Zr-R-RH]
+
[B(C
6
F
5
)
4
]
−
are thus formed. U.S. Pat. No. 5,348,299 claims corresponding systems in which dimethylanilinium salts having perfluorinated tetraphenylborate anions are used.
A disadvantage of the systems described is that the protolysis results in formation of an amine from the ammonium salts and this coordinates to the strongly Lewis-acid cation and is thus not polymerization-active.
EP 426 637 describes a process in which the Lewis-acid CPh
3
+
cation is used. B(C
6
F
5
)
4
−
functions as weakly coordinating anion. This offers the advantage that after abstraction of a CH
3
group the resulting CH
3
CPh
3
no longer has coordinated properties. In this way, cationic complexes of sterically unhindered metal centers can also be prepared.
WO 95/14044 describes carboboranes as constituents of catalyst systems.
Diboranes which are bridged by a hydrogen atom and an alkyl group are described in WO 95/24269. These systems have the disadvantage that the H-acid functions present therein do not rule out an interaction with the cationic system.
It is an object of the invention to find a chemical compound which has a low tendency to coordinate and which avoids the disadvantages of the prior art.
The present invention accordingly provides a chemical compound and a process for preparing this chemical compound. It further provides a catalyst system comprising at least one metallocene and at least one chemical compound of the invention as cocatalyst. In addition, a process for preparing polyolefins is described.
The chemical compound of the invention corresponds to the formula:
where
R are, independently of one another, identical or different and are each a halogen atom or a C
1
-C
40
-group such as a C
1
-C
40
-alkyl, C
1
-C
40
-haloalkyl, C
6
-C
40
-aryl, C
6
-C
40
-haloaryl, C
7
-C
40
-aralkyl or C
7
-C
40
-haloaralkyl group,
X are, independently of one another, identical or different and are each a C
1
-C
40
-group such as a C
1
-C
40
-alkylene, C
1
-C
40
-haloalkylene, C
6
-C
40
-arylene, C
6
-C
40
-haloarylene, C
7
-C
40
-arylalkylene or C
7
-C
40
-haloarylalkylene, C
2
-C
40
-alkynylene, C
2
-C
40
-haloalkynylene, C
2
-C
40
-alkenylene or C
2
-C
40
-haloalkenylene group,
M are, independently of one another, identical or different and are each an element of group IIa, IIIa, IVa or Va of the Periodic Table of the Elements,
a is an integer from 0 to 10, b is an integer from 0 to 10, c is an integer from 0 to 10 and a=b•c,
d is 0 or 1, e is 0 or 1, f is 0 or 1,
g is an integer from 0 to 10, h is an integer from 0 to 10, k is an integer from 0 to 10,
i is an integer from 0 to 1000,
j is an integer from 1 to 6 and
A is a cation of group Ia, IIa, IIIa of the Periodic Table of the Elements, a carbenium, oxonium or sulfonium cation or a quaternary ammonium compound.
When a=0, the formula represents an uncharged chemical compound; when a≧1, the formula represents a negatively charged compound having b cations A
c+
as counterions.
If the chemical compound of the formula I has a plurality of groups MR
j
, these can be identical or different from one another.
The structural unit X connects the elements M to one another by means of covalent bonds. X can have a linear, cyclic or branched carbon skeleton.
R is preferably a C
1
-C
40
-hydrocarbon radical which can be halogenated, preferably perhalogenated, by halogens such as fluorine, chlorine, bromine or iodine, in particular a halogenated, in particular perhalogenated, C
1
-C
30
-alkyl group such as trifluoromethyl, pentachloroethyl, heptafluoroisopropyl or monofluoroisobutyl or a halogenated, in particular perhalogenated, C
6
-C
30
-aryl group such as pentafluorophenyl, heptachloronaphthyl, heptafluoronaphthyl, 1,2,3-trifluorophenyl, 1,3,5-trifluorophenyl, heptafluorotolyl, 3,5-bis(trifluoromethyl)phenyl, 2,4,6-tris(trifluoromethyl)phenyl or 2,2′(octafluoro)biphenyl.
X is preferably a C
6
-C
30
-arylene group, a C
2
-C
30
-alkenylene group or a C
2
-C
30
-alkynylene group, each of which can be halogenated, in particular perhalogenated.
Preferably j=1 or 2 when M is an element of group IIa, j=2 or 3 when M is an element of group IIIa, j=3 or 4 when M is an element of group IVa and j=4 or 5 when M is an element of the group Va. M is particularly preferably boron as an element of group IIIa.
i is preferably an integer from 0 to 6, particularly preferably 0 or 1.
a, b and c are preferably 0, 1 or 2.
g, h and k are preferably 0 or 1.
i, g, h and k are very particularly preferably 0.
As A, preference is given to carbenium ions (R
3
C
+
) or quaternary ammonium ions having an acid H function (R
3
NH
+
). Particular preference is given to quaternary ammonium salts having acid H functions.
If a≧1 and all M are boron, it is preferred that the number of boron atoms is ≦4, particularly preferably 2.
Examples of the chemical compound of the invention are:
In place of the N,N-dimethylanilinium cation [C
6
H
5
N(CH
3
)
2
H]
+
, the cation used can alternatively be CPh
3
+
o is 0 to 20.
The preparation of a chemical compoun

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