DE10035308A1 - Process for the preparation of plyolefins with a narrow, birnodal molecular weight distribution - Google Patents

Abstract

The invention relates to a method for the production of polyolefins at pressures of from 1 to 4,000 bar and temperatures of from 20 to 350 DEG C in the presence of a catalyst system, comprising an organometallic compound from the group of the metallocenes or the catalytically active iron, cobalt, nickel, or palladium complexes. The organometallic compound comprises a Lewis base functionality which is arranged such that said functionality can co-ordinate intramolecularly to the central metal atom of the organometallic compound. The reaction temperature is adjusted such that the resulting polyolefin has a bimodal molecular weight distribution MW/MN of <5.0, measured by gel permeation chromatography.

Description

The present invention relates to a method for the manufacture position of polyolefins at pressures from 5 to 4,000 bar and Temperatures of 20 to 350 ° C in the presence of a catalyst stems, which is an organometallic compound from the group the metallocenes or the catalytically active iron, cobalt, Includes nickel or palladium complexes, these organometallic has a Lewis base functionality, so is arranged to be intramolecular to the central metal atom can coordinate the organometallic compound.

Monomodal, based on the molecular weight distribution M _w / M _n , means in the present application that the molecular weight distribution has a single maximum.

Bimodal, based on the molecular weight distribution M _w / M _n , means in the present application that the course of the molar mass distribution curve has two turning points on one flank.

Catalyst systems with a uniformly defined active Zen trum, so-called single-site catalysts, win at the Po Lymerization of olefins is becoming increasingly important. This Kataly sator systems lead to polymers with monomodal, narrow moles molecular weight distributions, which results in particularly favorable mechani properties results. Due to the monomodal molecular Weight distribution can be made from polymers produced in this way often difficult to process.

To improve the processing of such polymers, is always attempts are often made to produce polymer blends len. Such blends are generally easier to process and usually have a satisfactory degree of advantage mechanical properties of single site catalyzed Po mers.

Such polymer blend or, more generally, polyme risks with broadened and often bimodal molecular weight ver division, can be obtained in different ways. So can of course two or more polymer granules or polymer granules with each other z. B. homogeneously mixed in an extruder. The  The disadvantage of this method is additional processing cost through the additional processing step.

Another possibility for producing such polymers is the use of a reactor cascade, with two reactors with under different reaction conditions coupled one after the other the. The main disadvantage of such cascade processes is: the additional equipment, but also in the difficulty in maintaining constant reaction conditions.

A third way to make bimodal or multimoda Polymer consists of premixing several catalysts with different polymerization properties. Such Polymerization process using multiple catalysts are z. B. from EP-A 128 045, EP-A 0 619 325 or EP-A 0 516 018 known.

Of the metallocene catalysts, the best known group of the Sin gle-site catalysts, more and more chemical variations known. So z. B. also metallocene compounds with Substi described that carry a Lewis base group. Both Lewis base groups are primarily oxygen or nitrogen functionalities. Unbridged metallocene complexes or metallocene catalysts with Lewis base functionalities z. B. in WO 97/27227, US-A 5 563 284 and DE-A 43 03 647 be wrote. Bridged metallocene catalysts with Lewis base sub substituents are described in EP-A 0 608 054. All of these Be However, what is common is that, as far as polymerizations with described these metallocene complexes, the Po obtained lymerisate narrow and monomodal molecular weight distributions show how they are typical for single-site catalysts. In Angew. Chemie 2000, vol. 112, pages 800-803 become polymers described a broad, bimodal or monomodal molecular weights have distribution.

The object of the method according to the invention was therefore to using only one catalyst complex and without large ap parative effort to get polyolefin polymers, which good Processing properties and a narrow, bimodal molecular weight have weight distribution.

Accordingly, a process for the preparation of polyolefins at pressures of 5 to 4,000 bar and temperatures of 20 to 350 ° C in the presence of a catalyst system which is an organometallic compound from the group of metallocenes or the catalytically active iron, cobalt, nickel or Palladium complexes, wherein this organometallic compound has a Lewis base functionality, which is arranged so that it can coordinate intramolecularly to the central metal atom of the organometallic compound, which method is characterized in that the reaction temperature is adjusted so that that the resulting polyolefin has a bimodal molecular weight distribution M _W / M _N , measured by gel permeation chromatography, of <5.0.

Furthermore, the use of such an organometallic compound for the production of polyolefins with a bimodal molecular weight distribution M _W / M _N , measured by gel permeation chromatography, of <5.0 and the corresponding polyolefins were found.

The present invention is based on the observation that when using special single-site catalyst systems, namely those which have a Lewis base functionality which is able to coordinate to the central metal atom of the complex, at certain temperatures bimodal molecular weight distribution occurs with a molecular weight distribution M _w / M _n of <5, so that a suitable bimodal adjustment of the molecular weight distribution in the direction of the desired polymer properties is possible by suitable temperature control using only one catalyst complex.

The method according to the invention is principally for the production very different polyolefins. So you can invent according to z. B. ethylene, propylene or higher α-olefins alone or polymerize in a mixture of these monomers or copoly polymerize. Especially with catalyst systems based on metal organic compounds of the Villa group of the Periodic Table be rest, polar comonomers such as vinyl can also advantageously be used acetate, acrylic acid or methacrylic acid ester or these acids copolymerize itself with ethylene or α-olefins. Also for The production of vinyl aromatic polymers is ge suitable.

Propylene is preferably homopolymerized or copoly merized with higher α-olefins and / or vinyl aromatic compounds. Highly suitable higher α-olefins are C ₂ -C ₁₀ -alk-1-enes such as ethylene, 1-butene, 1-hexene, 1-octene; well-suited vinyl aromatic compounds are styrene and styrene derivatives.

Preferred bimodal propylene copolymers with M _w / M _n <5 are those which contain at least 50 mol% of propylene. Such copolymers, which have isotactic and / or he miisotactic propylene sequences, are particularly preferred.

Preferred bimodal propylene homopolymers with M _w / M _n <5 are isotactic and hemiisotactic propylene homopolymers.

The method according to the invention can be in a pressure range of 5 up to 4,000 bar. The method can be used in the usual polymerization plants known to those skilled in the art and operate according to the usual polymerization processes. To call are z. B. polymerization processes in gas phase reactors, esp especially in gas phase fluidized bed reactors, polymerizations in Solution or suspension polymerization process. The above Processes are usually carried out at pressures between 1 and 50 bar, operated in particular between 5 and 40 bar. The fiction moderate process is carried out at a reaction temperature, those in a molecular weight distribution of <5.0, preferably <4.0 results. Suitable reaction temperatures are from 20 up to 120 ° C, particularly preferably 60 to 100 ° C. The invention Processes can also be carried out in high pressure polymerization processes z. B. carry out in a stirred autoclave or in tubular reactors, whereby pressures of 500 to 4000 bar, preferably 1000 to 3000 bar and temperatures from 160 ° C to 350 ° C, preferably 200 ° C up to 240 ° C.

The reaction temperature of the process according to the invention depends on the one hand from the catalytically active metal organic compound and on the other hand of the desired molecular weight distribution and the bimodal curve shape of the GPC-Chromato from the polymer. The appropriate polymerization temperature tur can be easily determined by a few preliminary tests.

There is an important feature of the method according to the invention in that the organometallic compounds, the constituent of the catalyst system, have a Lewis base functionality point, which is arranged so that it intramolecularly to the zen coordinate the central metal atom of the organometallic compound can. This feature can be achieved through a variety of possible chemi structures and arrangements as well as a variety of Substitution patterns can be achieved. So less is critical the nature of the substitution or the chemical nature of the Lewis base Ligands rather than the possibility of the aforementioned coordination onsfähigkeit. When choosing suitable organometallic ver bindings can e.g. B. in a simple manner with the help of molecular mo dimples are checked whether a certain catalyst complex  Requirement that namely the Lewis base functionality to the Can coordinate metal atom is fulfilled.

The catalyst systems used in the process according to the invention can contain various organometallic compounds as the catalytically active compound. A preferred embodiment of the method is characterized in that a metallocene complex of the general formula I is used as the organometallic compound

in which the substituents and indices have the following meaning:
M titanium, zirconium, hafnium or vanadium,
R ¹ to R ^{5 are} hydrogen, C ₁ to C ₁₀ alkyl, 5- to 7-membered cycloalkyl, which in turn can carry a C ₁ to C ₁₀ aryl as a substituent, C ₆ to C ₁₅ aryl or ary lalkyl, where optionally also two adjacent radicals together can represent cyclic groups having 4 to 15 carbon atoms, Si (R ⁶ ) ₃ , a group with Lewis base functionality or together with a radical X ¹ to X ⁴ Bridge to the metal atom M,
R ⁶ C ₁ to C ₁₀ alkyl, C ₆ to C ₁₅ aryl or C ₃ to C ₁₀ cycloalkyl,
X ¹ to X ⁴ fluorine, chlorine, bromine, iodine, hydrogen, C ₁ - to C ₁₀ -alkyl, C ₆ - to C ₁₅ -aryl, alkylaryl with 1 to 10 C-atoms in the alkyl radical and 6 to 20 C atoms in the aryl radical, -OR ¹² , -NR ¹² R ¹³ or

With
R ¹² and R ^{13 are} C ₁ to C ₁₀ alkyl, C ₆ to C ₁₅ aryl, alkylaryl, arylalkyl, fluoroalkyl or fluoroaryl each having 1 to 10 C atoms in the alkyl radical and 6 to 20 C atoms in the aryl radical .
R ⁷ to R ^{11 are} hydrogen, C ₁ to C ₁₀ alkyl, 5 to 7-membered cycloalkyl, which in turn can carry a C ₁ to C ₁₀ alkyl as a substituent, C ₆ to C ₁₅ aryl or arylalkyl , where appropriate also two adjacent radicals together can represent cyclic groups having 4 to 15 carbon atoms, Si (R ¹⁴ ) ₃ , a group with Lewis base functionality or together with a radical R ¹ to R ⁵ a bridge member between the cyclopentadienyl systems,
With
R ¹⁴ C ₁ to C ₁₀ alkyl, C ₆ to C ₁₅ aryl or C ₃ to C ₁₀ cycloalkyl,
and
o, p, q, r integers in the range 0 to 4, the sum o + p + q + r + 1 corresponding to the valency of M,
with the condition that either at least one of the radicals R ¹ to R ⁵ or R ⁷ to R ^{11 is} a group with Lewis base functionality, or the bridge between the cyclopentadienyl systems or between a cyclopentadienyl system and the metal atom M is such a group with Lewis base functionality.
Preferred metals M are titanium and zirconium, in particular zirconium.

In addition to hydrogen, in particular C ₁ to C ₆ alkyl groups, very particularly suitable substituents R ¹ to R ⁵ are methyl, ethyl, propyl, n-butyl, isobutyl and tert-butyl. The cyclopentadienyl nucleus can be substituted one or more times, preferably once or twice, with such alkyl groups. In addition to these alkyl-substituted cyclopentadienyl radicals, cyclopentadienyl systems are particularly suitable, in which two adjacent radicals R ¹ to R ⁵ are linked to form cyclic groups, which in turn can in turn carry substituents. Examples include substituted and unsubstituted indenyl, tetrahy droindenyl, benzindenyl and fluorenyl radicals. In addition to the substituents mentioned, there may also be a substituent with a Lewis base group.

As a rule, one of the ligands X ¹ to X ⁴ is also a cyclopentadienyl system, so that a biscyclopentadienyl complex is present. Furthermore, one of the radicals X ¹ to X ⁴ can also represent a bridge member which is connected to the cyclopentadienyl nucleus formed in formula I, so that a monocyclopentadienyl complex is present. The further radicals X ¹ to X ⁴ are preferably halogen, in particular chlorine, or C ₁ - to C ₄ -alkyl, chlorine being particularly advantageous as a ligand, especially for precursors of the catalytically active complex.

For the radicals R ⁷ to R ¹¹ , the same radicals are preferred as were mentioned for the radicals R ¹ to R ⁵ .

For use in the method according to the invention, be especially such organometallic compounds as advantageous meadows that have a bridged metallocene complex. Under bridged metallocene complexes should be understood to mean such be either a bridge between a cyclopentadienyl rest and the central metal atom, or those in which the bridge link two cyclopentadienyl residues together combines.

A particularly advantageous embodiment of the invention The process is characterized in that the metallocene complex of formula I a bridge member between two cyclopentadienyl systems.

A further particularly advantageous embodiment consists in a process which is characterized in that the bridge member between two cyclopentadienyl systems has the structure of the general formula II

in which
R ¹⁵ and R ^{16 are} a C ₁ - to C ₂₀ -hydrocarbyl radical with at least one oxygen, sulfur, nitrogen or phosphorus-containing substituent.

R ¹⁵ and R ¹⁶ are chemically very different C ₁ to C ₂₀ hydrocarbyl groups. Examples include alkoxyphenyl radicals which are connected to the silicon atom via an alkylene group. Alkylamino or alkoxy groups which are linked to the silicon via alkylene radicals having a length of 1 to 10 carbon atoms are also suitable. Also to be mentioned are residues in which the Lewis base functionality is based in a thioether or ester group. Examples include C ₁ - to C ₄ -alkyl esters of carboxylic acid groups, where the carboxylic acid can in turn be bound to the silicon atom via an alkylene radical. In addition to the alkoxy functions, cyclic ethers such as tetrahydrofuranyl groups, which are likewise bonded to the silicon atom via a suitable alkylene radical, are also suitable. In addition to the silyl bridges of the general formula II, analog bridge members with germanium atoms or C ₁ - to C ₃ -alkylene groups, which can be substituted in an analogous manner to the silicon atom, are also suitable.

A further preferred embodiment of the process is characterized in that at least one of the radicals R ¹ to R ⁵ or R ⁷ to R ¹¹ denotes a radical of the general formula IIIa or IIIb

- (CR ¹⁷ R ¹⁸ ) n - YR ¹⁹ R ²⁰ IIIa
- (CR ¹⁷ R ¹⁸ ) n - ZR ¹⁹ IIIb

in which the variables have the following meaning:
R ¹⁷ and R ^{18 are} hydrogen, C ₁ to C ₁₀ alkyl, C ₆ to C ₁₅ aryl or C ₃ to C ₁₀ cycloalkyl,
R ¹⁹ and R ^{20 are} C ₁ to C ₁₀ alkyl, C ₆ to C ₁₅ aryl or C ₃ to C ₁₀ cycloalkyl,
n is an integer in the range from 0 to 10
Y nitrogen or phosphorus and
Z oxygen or sulfur.

The radicals R ¹⁷ and R ¹⁸ are preferably hydrogen or lower alkyl such as methyl or ethyl, the radicals R ¹⁹ and R ²⁰ are preferably short alkyl groups such as methyl, ethyl, propyl or butyl. n is preferably a number between 2 and 6, in particular 2 or 4. y is preferably nitrogen, z is preferably oxygen.

As particularly advantageous for use in the invention Processes have proven metallocene complexes, in which one the cyclopentadienyl system is a substituted or unsubsti is fluorenyl system.

In addition to the metallocene complexes, other organometallic compounds can also be used in the process according to the invention. In principle, all single-site catalysts known to the person skilled in the art, such as are described, for example, in WO 96/23010, WO 98/27124 or WO 96/23004, are suitable, provided that they are used in a suitable manner with a substituent with Lewis base radio functionality. A further embodiment of the process according to the invention is therefore characterized in that a compound of the general formula IV is used as the organometallic compound

where the variables have the following meaning:
R ²¹ to R ^{32 are} hydrogen, C ₁ to C ₁₀ alkyl, 5- to 7-membered cycloalkyl, which in turn can carry a C ₁ to C ₁₀ alkyl as a substituent, C ₆ to C ₁₅ aryl or ary lalkyl, where optionally also two adjacent radicals together can represent cyclic groups having 4 to 15 carbon atoms, Si (R ⁶ ) ₃ or a group with Lewis base functionality, at least one radical R ²¹ to R ^{32 being} one such a group with Le wis base functionality must be R ³³ and R ³⁴ fluorine, chlorine, bromine, iodine, hydrogen, C ₁ - to C ₁₀ -alkyl, C ₆ - to C ₁₅ -aryl, alkylaryl with 1 to 10 C atoms in the alkyl radical and 6 to 20 C atoms in the aryl radical, -OR ¹² or -NR ¹² R ¹³ , and
M 'a metal from the Villa group of the Periodic Table.

In addition to hydrogen, radicals R ²¹ to R ³² are in particular never alkyl groups such as methyl, ethyl, propyl or butyl, the aromatic ring systems preferably being substituted one to three times with such alkyl groups. For the structure of the group with Lewis base functionality, this already applies to the corresponding metallocene complexes. Preferably, at least one of the radicals R ²¹ to R ^{32 represents} a radical of the general formula IIIa or IIIb.

According to the invention, the use of an organometallic compound, as described above, for the production of polyolefins with a molecular weight distribution M _W / M _n , measured by gel permeation chromatography, of <5.0, preferably <4.

The preparation of the catalyst complexes can according to the usual Methods known to those skilled in the art are carried out. Manufacturing instructions of metallocene complexes, for example from WO 97/27227 will hold.

To develop catalytic polymerization activity, the mentioned organometallic complexes usually by a co- catalyst activated. The methods to activate the Catalyst complexes are well known and do not form Be peculiarity of this invention. For example, the Metal loce complexes in a known manner with alumoxanes, in particular with Methylalumoxane, or with ionizing compounds that are in the Are capable of a metallocenium cation in a non-coordinating manner complex to be activated.

Examples

The following conditions were used for the GPC examinations selected according to DIN 55672: solvent: 1,2,4-trichlorobenzene, Flow: 1 mL / min, temperature: 140 ° C, calibration: PE standards, Ge advises: Waters 150C.

Isopropylidene [3- (N; N; diethalaminoethyl) cyclopentadienyl fluo ren-9-yl) zirconocene dichloride (1).  

(1) was as in Eur. J. Inorg. Chem 1998, 663-674, manufactured.

Polymerization of propylene

General procedure for the polymerization of propylene:

A previously carefully heated 11 Büchi laboratory autoclave (2 h under high vacuum at 90 ° C), equipped with mass flow, 1 pressure and temperature regulator, was m counter argon flow with the Solvent toluene and part of the MAO solution (see respective test instructions). The total volume during the Polymerization was 200 ml. The content was adjusted to the desired one Brought temperature and 5 bar propylene were injected; The Propylene pressure was applied over the entire polymerization period kept constant. The pre-activated catalyst solution was introduced into the autoclave using a pressure burette. The Polymerization was abge by adding 20 ml of isopropanol broken.

General procedure for working up the polymerization reaction:

The polymerization of propylene with (1) / MAO occurred Propylene polymer that is soluble in toluene. The polymer-containing Solution therefore became a solution after the polymerization process from 200 ml of methanol, 200 ml of water and 50 ml of conc. HCl solution ge give and stir for 18 h. Then the organic Phase separated and concentrated to about 5 ml. Subsequently acetone (approx. 20 ml) was added, the polypropylene as colorless, elastic and elastic solid was obtained.

example 1

Catalyst system: (1) / MAO
Preactivation: (1) (16.0 mg, 3.0 × 10 ^-5

mol),
10.00 ml MAO (16.7 mmol Al)
Autoclave content: 182 ml toluene, 8.0 ml MAO (13.3 mmol)
Mole ratio Zr: Al: 1: 1000
Polymerization temperature: T = 50 ° C
Propylene pressure: p = 5 bar
Polymerization time: t = 1.5 h
Yield of polymer: 1.9 g
Activity of the catalyst: 8.4 kg PP / (mol Zr. H. Bar)
GPC analysis of the polymer: M _W

: 20466, M _n

: 5300; M _w

/ M _n

; 3.94

Example 2

Preactivation: (1) (26.6 mg, 5.0 × 10'5 mol),
16.7 ml MAO (16.7 mmol Al)
Autoclave content: 170 ml toluene, 20 ml MAO (33.3 mmol)
Mole ratio Zr: Al: 1: 1000
Polymerization temperature: T = 25 ° C
Propylene pressure: p = 5 bar
Polymerization time: t = 2.0 h
Yield of polymer: 4.1 g
Activity of the catalyst: 10.9 kg PP / (mol Zr.h.bar)
GPC analysis of the polymer: M _W

: 58265, M _n

: 11784; M _w

/ M _n

; 4.94

Claims (10)

1. A process for the preparation of polyolefins at pressures of 1 to 4,000 bar and temperatures of 20 to 350 ° C in the presence of a catalyst system which comprises an organometallic compound from the group of metallocenes or the catalytically active iron, nickel or palladium complexes, wherein this organometallic compound has a Lewis base functionality which is arranged so that it can coordinate intramolecularly to the central metal atom of the organometallic compound, which process is characterized in that the reaction temperature is adjusted so that the resulting polyolefins have a bimodal molecular weight distribution M _W / M _N , measured by gel permeation chromatography, of <5.0. 2. The method according to claim 1, characterized in that a metal complex of the general formula I is used as the organometallic compound
in which the substituents and indices have the following meaning:
M titanium, zirconium, hafnium or vanadium,
R ¹ to R ^{5 are} hydrogen, C ₁ to C ₁₀ alkyl, 5- to 7-membered cycloalkyl, which in turn can carry a C ₁ to C ₁₀ aryl as a substituent, C ₆ to C ₁₅ aryl or arylalkyl , where appropriate also two adjacent radicals together can represent cyclic groups having 4 to 15 carbon atoms, Si (R ⁶ ) ₃ , a group with Lewis base functionality or together with a radical X ¹ to X ⁴ a bridge member to the metal atom M, R ⁶ C ₁ to C ₁₀ alkyl, C ₆ to C ₁₅ aryl or C ₃ to C ₁₀ cycloalkyl,
X ¹ to X ⁴ fluorine, chlorine, bromine, iodine, hydrogen, C ₁ to C ₁₀ alkyl, C ₆ to C ₁₅ aryl, alkylaryl with 1 to 10 C atoms in the alkyl radical and 6 to 20 C atoms in the aryl radical, -OR ¹² , -NR ¹² R ¹³ or
With
R ¹² and R ^{13 are} C ₁ to C ₁₀ alkyl, C ₆ to C ₁₅ aryl, alkylaryl, arylalkyl, fluoroalkyl or fluoroaryl each having 1 to 10 C atoms in the alkyl radical and 6 to 20 C atoms in the aryl radical.
R ⁷ to R ^{11 are} hydrogen, C ₁ to C ₁₀ alkyl, 5 to 7-membered cycloalkyl, which in turn can carry a C ₁ to C ₁₀ alkyl as a substituent, C ₆ to C ₁₅ aryl or arylalkyl, where appropriate, two adjacent radicals together can represent 4 to 15 carbon atoms pointing to cyclic groups, Si (R ¹⁴ ) ₃ , a group with Lewis base functionalities or together with a radical R ¹ to R ⁵ a bridge member between the cyclopentadienyl systems,
With
R ¹⁴ C ₁ to C ₁₀ alkyl, C ₆ to C ₁₅ aryl or C ₃ to C ₁₀ cycloalkyl,
and
o, p, q, r integers in the range 0 to 4, the sum o + p + q + r + 1 corresponding to the valency of M,
with the condition that either at least one of the radicals R ¹ to R ⁵ or R ⁷ to R ^{11 is} a group with Lewis base functionality or the bridge between the cyclopentadienyl systems or between a cyclopentadienyl system and the metal atom M has such a group Lewis base functionality. 3. The method according to claim 2, characterized in that one a bridged metallocene as an organometallic compound complex. 4. The method according to claims 1 to 3, characterized in that at least one of the radicals R ¹ to R ⁵ or R ⁷ to R ^{11 represents} a radical of the general formula purple or Ilib
- (CR ¹⁷ R ¹⁸ ) n - YR ¹⁹ R ²⁰ IIIa
- (CR ¹⁷ R ¹⁸ ) n - ZR ¹⁹ IIIb
in which the variables have the following meaning:
R ¹⁷ and R ^{18 are} hydrogen, C ₁ to C ₁₀ alkyl, C ₆ to C ₁₅ aryl or C ₃ to C ₁₀ cycloalkyl,
R ¹⁹ and R ^{20 are} C ₁ to C ₁₀ alkyl, C ₆ to C ₁₅ aryl or C ₃ to C ₁₀ cycloalkyl,
n is an integer in the range from 0 to 10
Y nitrogen or phosphorus and
Z oxygen or sulfur. 5. The method according to claim 4, characterized in that one the cyclopentadienyl system is a substituted or unsubsti is fluorenyl system. 6. The method according to claim 1, characterized in that a compound of the general formula IV is used as organometallic compound
where the variables have the following meaning:
R ²¹ to R ^{32 are} hydrogen, C ₁ to C ₁₀ alkyl, 5- to 7-membered cycloalkyl, which in turn can carry a C ₁ to C ₁₀ alkyl as a substituent, C ₆ to C ₁₅ aryl or Arylalkyl, where optionally two adjacent radicals together can represent cyclic groups having 4 to 15 carbon atoms, Si (R ⁶ ) ₃ or a group with Lewis base functionality, at least one radical R ²¹ to R ^{32 being} such a group with Lewis base functionality must be
R ³³ and R ³⁴ fluorine, chlorine, bromine, iodine, hydrogen, C ₁ - to C ₁₀ -alkyl, C ₆ - to C ₁₅ -aryl, alkylaryl with 1 to 10 C-atoms in the alkyl radical and 6 to 20 C-atoms in the aryl radical, -OR ¹² or -NR ¹² R ¹³ and
M 'a metal from the Villa group of the Periodic Table. 7. The method according to claim 6, characterized in that at least one of the radicals R ²¹ to R ^{32 is} a radical of the general formula IIIa or IIIb. 8. The method according to claims 1 to 7, wherein the polyolefins Propylene homopolymers or propylene copolymers with high other α-olefins and / or vinyl aromatic compounds are. 9. Polyolefins obtainable by the process according to claims 1 till 8. 10. Use of an organometallic compound according to claims 1 to 8 for the production of polyolefins with a molecular weight distribution M _W / M _n , measured by gel permeation chromatography, of <5.0.