Organic compounds -- part of the class 532-570 series – Organic compounds – Heavy metal containing
Reexamination Certificate
2000-04-20
2002-02-12
Shaver, Paul F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heavy metal containing
Reexamination Certificate
active
06346635
ABSTRACT:
The present invention relates to a simple process for the industrial preparation of silyl-bridged fluorenyl-cyclopentadienyl ligands and also to a process for preparing silyl-bridged fluorenyl-cyclopentadienyl metallocenes.
The metallocenes of transition group IV of the Periodic Table, i.e. the metallocenes of titanium, zirconium and hafnium, have in recent years proven to be an important consitutent of a significant new class of polyolefin catalysts (H.-H. Brintzinger, D. Fischer, R. Mülhaupt, B. Rieger and R. Waymouth, Angew. Chem. Int. Ed. Engl., 34 (1995) 1143; M. Aulbach and F. Küber, Chiuz, 28 (1994) 197). The metallocenes are, if appropriate in combination with one or more cocatalysts, used as catalyst component for the polymerization and copolymerization of olefins. Bridged metallocenes, known as ansa metallocenes, play an important role in, for example, the stereoselective preparation of polypropylene. Thus, for example, syndiotactic polypropylene can be prepared using bridged fluorenyl-cyclopentadienyl metallocenes (J. A. Ewen, R. L. Jones and A. Razavi, J. Am. Chem. Soc., 110 (1988) 6255).
The synthesis of silicon-bridged fluorenyl-cyclopentadienyl metallocenes and the use of these compounds in the polymerization of olefins is known (K. Patsidis, H. G. Alt, W. Milius and S. J. Palackal, J. Organomet. Chem., 509 (1996) 63-71; W. Spaleck, M. Aulbach, B. Bachmann, F. Kuber and A. Winter, Macromol. Symp. 89 (1995) 237-247; U.S. Pat. No. 5401817; U.S. Pat No. 5393911; EP 0628577). The synthesis of the silicon-bridged fluorenyl-cyclopentadienyl metallocenes is carried out as shown in the scheme below using a zirconocene as an example:
where R
1
, R
2
are identical or different alkyl or aryl radicals and M can be Li, Na, MgCl or MgBr and Cp is cyclopentadiene.
A disadvantage of the syntheses described in the literature with regard to transfer to the production scale is the use of critical solvents such as diethyl ether (highly flammable) or hexamethylphosphoramide (carcinogenic). Furthermore, the isolation of fluorenyl lithium or the isolation of the dilithium salt of the silyl-bridged fluorenyl-cyclopentadienyl ligand is a complicated step in process engineering terms.
Chromatographic purification of intermediates is also a great disadvantage on the industrial scale.
It is an object of the present invention to find methods for steps 1 to 3 in Scheme 1 which avoid the abovementioned disadvantages and can be carried out without problems under industrial conditions.
We have found that this object is achieved by carrying out steps 1-3 of the above scheme (Scheme 1) using particular solvents or solvent mixtures and a particular reaction methodology, thus enabling the steps to be carried out under conditions which are feasible in process engineering terms and are acceptable in terms of safety.
The present invention accordingly provides a process for preparing compounds of the formula (IV)
wherein
R
1
, R
2
are identical or different C
1
-C
20
-hydrocarbon radicals, preferably C
1
-C
10
-alkyl or C
6
-C
14
-aryl radicals, particularly preferably methyl, ethyl, tert-butyl or phenyl,
R
3
, R
4
, R
5
, R
6
, R
7
, R
8
, R
9
, R
10
are identical or different and are each hydrogen, halogen or a C
1
-C
20
-hydrocarbon radical, preferably hydrogen, C
1
-C
10
-alkyl, C
1
-C
10
-alkenyl, C
6
-C
14
-aryl, C
7
-C
12
-alkylaryl or C
7
-C
12
-arylalkyl, particularly preferably hydrogen, methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, amyl, hexyl, heptyl, octyl or phenyl, where preferably at least R
4
, R
7
, R
9
and R
10
are hydrogen,
R
11
, R
12
, R
13
, R
14
are identical or different and are each hydrogen or a C
1
-C
20
-hydrocarbon radical, preferably hydrogen, C
1
-C
10
-alkyl, C
1
-C
10
-alkenyl, C
6
-Cl
14
-aryl, C
7
-C
12
-alkylaryl or C
7
-C
19
-arylalkyl, particularly preferably hydrogen, methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, amyl, hexyl, heptyl, octyl, trimethylsilyl, triphenyl-methyl, 2-methyl-2-phenylpropyl, 2,2-diphenylpropyl, 2,2-diphenylethyl or phenyl, where preferably at least two of the radicals R
11
, R
12
, R
13
and R
14
are hydrogen and
L is zirconium, hafnium or titanium,
comprising the measures:
a) deprotonation of the compound of the formula (I)
using a base,
b) reaction of the deprotonated compound from step a) with R
1
R
2
SiCl
2
to give the compound of the formula (II)
where R
1
, R
2
, R
3
, R
4
, R
5
, R
6
, R
7
, R
8
, R
9
and R
10
are as defined above,
c) reaction of the compound of the formula (II) obtained as described in step b) with
M
+
Cp
−
to form the compound of the formula (III)
where R
1
, R
2
, R
3
, R
4
, R
5
, R
6
, R
7
, R
8
, R
9
, R
10
, R
11
, R
12
, R
13
and R
14
are as defined above,
M is Li, Na, K, MgCl or MgBr and
Cp is a substituted or unsubstituted cyclopentadienyl radical,
d) reaction of the compound of the formula (III) with a base and addition of LCl
4
, where L is zirconium, titanium or hafnium, to form the compound of the formula (IV),
wherein
i. the deprotonation of step a) is carried out in a mixture of one or more aromatic, aliphatic hydrocarbons and &agr;,&bgr;-dialkoxyalkanes or &agr;,&bgr;-dialkoxyaromatics,
ii. an alkane is added after deprotonation is complete and before the reaction with the organochlorosilane as described in step b),
iii.the reaction of step d) is carried out in a mixture of one or more aromatic, aliphatic hydrocarbons and a polar aprotic solvent, with the exception of diethyl ether.
In step a), the compound of the formula (I), for example fluorene, is deprotonated in an inert solvent mixture by means of a strong base, for example butyllithium, and the metal salt formed is subsequently, after addition of an alkane having from 5 to 30 carbon atoms, reacted directly without further isolation with a silicon dichloride reagent R
1
R
2
SiCl
2
to give the compound (II), with the compound (II) preferably being added to the metal salt (single-vessel process).
As fluorenyl compound of the formula (I), it is possible to use unsubstituted fluorene itself or monosubstituted and polysubstituted fluorenes, as described, for example, in EP 0528 287 A. Examples are 1-methylfluorene, 4-methylfluorene, 1-tert-butylfluorene, 2-ethylfluorene, 2-tert-butylfluorene, 4-tert-butylfluorene, 4-phenylfluorene, 2,7-di-tert-butyl-fluorene, 2,7-di-tert-butyl-4-methylfluorene and 2,7-di-tert-butyl-4-phenylfluorene. Furthermore, instead of substituted fluorenes, it is also possible to use the fluorene-analogous heteroatom-substituted tricyclic compounds described in WO 98/22486. Preference is given to using fluorene, 4-methyl-fluorene, 2-tert-butylfluorene, 4-tert-butylfluorene, 4-phenyl-fluorene and 2,7-di-tert-butylfluorene; very particularly preferably unsubstituted fluorene and 2,7-di-tert-butylfluorene.
In the deprotonation of step a), use is made of an inert solvent mixture of one or more hydrocarbons and one or more &agr;,&bgr;-dialkoxyalkanes or &agr;,&bgr;-dialkoxyaromatics.
In the process of the present invention, up to one mol of &agr;,&bgr;-dialkoxyalkanes or &agr;,&bgr;-dialkoxyaromatics is added per mol of fluorene, preferably less than half a mol.
The &agr;,&bgr;-dialkoxyalkanes or &agr;,&bgr;-dialkoxyaromatics used according to the present invention are preferably 1,2-dimethoxyethane (DME), 2,3-dimethoxybutane, 1,2-diethoxyethane, dioxane, diethylene glycol dimethyl ether, 1,2-dimethoxybenzene, 1,2-diethoxybenzene and 2-ethoxyanisole, in particular 1,2-dimethoxyethane (DME).
The hydrocarbons are aromatic and aliphatic hydrocarbons such as pentane, hexane and its isomers, heptane, ®Exxsol DSP 100-120, toluene, ethylbenzene, xylene or tetrahydronaphthalene, preferably toluene and heptane.
To suppress the formation of silyl-bridged bisfluorenylene, the silicon dichloride reagent R
1
R
2
SiCl
2
is used in excess over the metal fluorenyl salt, with the molar ratio being from 1.1:1.0 to 3.5:1, preferably from 1.25:1 to 2.5:1. The excess silicon reagent can be removed, for example by distillation or by crystallization, before addition of the M
+
Cp
−
.
The deprot
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Basell Polyolefine GmbH
Shaver Paul F.
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