WO1997042196A1

WO1997042196A1 - Silicon-functional cyclopentadiene

Info

Publication number: WO1997042196A1
Application number: PCT/NL1997/000224
Authority: WO
Inventors: Gerardus Johannes Maria Gruter; Henricus Johannes Arts; Johannes Antonius Maria Van Beek
Original assignee: Dsm N.V.
Priority date: 1996-05-03
Filing date: 1997-04-25
Publication date: 1997-11-13
Also published as: EP0897388A1; NL1003002C2; AU2410197A; JP2000510831A

Abstract

The invention relates to a process for the functionalization of a substituted cyclopentadiene. The invention is characterized in that the substituted cyclopentadiene is reacted with a Brönsted base, after which the anion obtained is reacted with a dihaloalkylsilicon compound. The invention also relates to silicon-functional cyclopentadienes and to transition metal complexes of a transition metal and one or more ligands on the basis of silicon-functional cyclopentadienes.

Description

SILICON-FUNCTIONAL CYCLOPENTADIENE

The invention relates to a process for the functionalization of a substituted cyclopentadiene; the invention also relates to a silicon-functional cyclopentadiene, as well as to a silicon- and amine- functional cyclopentadiene. The invention further relates to transition metal complexes derived from these and catalyst systems derived from these. A process for the functionalization of a cyclopentadiene, which is either ring-substituted or not, is known from an article by Jutzi et al. in Synthesis, July 1993, pp. 684-6. In that process, first of all a hydrogen atom is abstracted from the cyclopentadiene under the influence of a Brόnsted base, resulting in formation of the corresponding anion. As Brδnsted base can be used hydroxide (such as NaOH, KOH), hydrides (such as KH) , alkylalkali-metal compounds (such as the Li-alkyls, for example n- butyllithium) . The anion thus obtained is subseguently treated with an alkylating agent.

The drawback is that the treatment with the alkylating agent often results in low selectivities. In addition, alkylation of a cyclopentadiene which is already ring-substituted mostly leads to geminal substitution (i.e. the already substituted carbon atom of the cyciopentadienyl ring is substituted once again). The foregoing also occurs in case of alkylation with a silicon-containing agent. There is consequently a need for a process for preparing a silicon-functional cyclopentadiene in a more selective way and in which the occurrence of - -

geminal substitution is eliminated or significantly reduced, when substituted cyclopentadienes are involved.

The process is characterized in that the substituted cyclopentadiene is reacted with a Brδnsted base, after which the anion obtained is reacted with a dihaloalkylsilicon compound of the following formula:

R¹ R³ | |

Hal - (Si)_B - (C)„ - Hal, (I)

I I R² R⁴ where the symbols mean the following:

- Hal = a halogen group

- R¹-R⁴ = each a hydrogen or a substituted or unsubstituted alkyl, aryl or aralkyl group

- m >_ 1 and - n > 1

Such a reaction results in a silicon- functional cyclopentadiene of the formula:

R¹ R³

which is substituted with z substituents Y, the number of z satisfying the relation 1 < z <, 4.

Such a compound (II) is not yet known in the literature.

By reacting compound (II) with an (earth)- alkalimetal amide of the formula:

M(NR⁵R⁶)_p (III) where the symbols mean the following:

M = (earth-)alkali metal chosen from group 1 or 2 of the Periodic System of the Elements R⁵, R⁶ = each a hydrogen or a substituted or unsubstituted alkyl, aryl or aralkyl group - -

p = number of (NR⁵R⁶) groups: p = 1 for M = alkali metal p = 2 for M = earth-alkali metal, it is also possible to prepare a functionalized cyclopentadiene which has both an amine and a silicon functionality in the substituent.

For the Periodic System of the elements see the new IUPAC notation to be found on the inside of the cover of the Handbook of Chemistry and Physics, 70th Edition, 1989/1990.

Surprisingly, it has been found that application of a compound (I) or (II) in which m = n = 1 and the reaction with the (earth)alkalimetal amide result in inversion of the substitution on the cyciopentadienyl ring. This reaction mechanism also occurs when the cyclopentadiene is not substituted. This is represented by the following formula:

>) 'P.

(IV) (III)

Such a compound (V) has not been described in the literature, nor has such a process been described or suggested. Here such a compound has been synthesized for the first time. In particular, the substituent inversion is an unknown phenomenon in the literature.

The substituents R^L-R⁶ present in formulas (I)-(V) are a hydrogen group or a substituted or unsubstituted alkyl, aryl or aralkyl group. The Hal group in formulas (I), (II) and (III) is a halogen group from group 17 of the Periodic System of the Elements. The Hal group preferably is a Cl group; this enhances the reactivity of compound (II) in subsequent reactions. The cyciopentadienyl group (the -group) represented in formula (II) is ring-substituted with at least one substituent Y. The cyciopentadienyl group in formulas IV and V may also be ring-substituted with 1-4 substituents Y. Suitable substituents here are alkyl, aryl and aralkyl groups. By preference, alkyl groups are present as substituents. Such substituents may also form part of a ring system, such as occurs for instance in cyclopentadiene derivatives derived from indene, tetrahydroindene, fluorene and similar compounds. Examples of substituents are methyl, ethyl, propyl, isopropyl, n-butyl, i-butyl, t-butyl, phenyl, benzyl, cyclohexyl, trimethylsilyl. The cyclopentadiene can also be a heterocyclopentadiene. Here and hereinafter the term heterocyclopentadiene compound refers to a compound which is derived from cyclopentadiene but in which at least one of the C atoms in the 5-ring thereof has been replaced by a hetero atom, while the hetero atom has been selected from group 14, 15 or 16 of the Periodic System of the Elements. If more than one hetero atom is present in the 5-ring, these hetero atoms can be either identical or different. More preferably, the hetero atom is selected from group 15, especially preferably the hetero atom is phosphorus. The conversion of the suibstituted cyclopentadiene started from takes place under the influence of a Brδnsted base, which abstracts a hydrogen atom from the cyclopentadiene and so produces an anion. Preferably a lithiumalkyl compound, more preferably n-butyllithium, is used for this purpose. With these compounds the anion is formed very fast and selectively. The anion is subsequently contacted with the dihaloalkylsilicon compound of formula (I). - -

Both the formation of the anion and the reaction with compound (I) normally take place in a solvent. Suitable solvents are those substances in which both the starting product and the reaction product are soluble. Hydrocarbons, for instance hexane or pentane, or ethers can be used.

More preferably a compound having Lewis base characteristics is chosen; this promotes the H abstraction. Ethers in particular are suitable for this, weak Lewis base ethers (i.e. bases the conjugated acid of which has a pKa value ≤ -2.5, such as dimethoxyethane, diethyl ether and dioxane), as well as, most preferably, strong Lewis base ethers (such as tetrahydrofuran (THF) having a corresponding pKa value of -2.0).

The temperature at which the formation of (II) and (IV) takes place is usually between -40 and +50°C; preferably the reaction temperature is between 10 and 35°C. The pressure at which the reactions are carried out is not critical; atmospheric pressure is already sufficient.

As already indicated in the foregoing, the reaction of a compound of formula (III) with a specific form of compound (II), i.e. in which m = n = 1, results in an unexpected substituent inversion. This process involves a change of the atom that is substituted directly on the cyciopentadienyl group: while in formula (II) this is the Si atom, in the end product (V) there is a C atom on the cyciopentadienyl group.

The present invention is therefore of particular value in relation with those silicon-functional cyclopentadienes which have m = n = 1. It has been found to be of advantage if the substituents R¹ and R² are alkyl groups, in particular methyl groups, and if R³ and R* are H groups; this results in a higher selectivity in the substituent inversion. The silicon-functional cyclopentadienes according to the invention are suitable for a wide variety of applications. They are suitable in particular to be incorporated in a transition metal complex of a transition metal and one or more ligands on the basis of a cyclopentadiene. Suitable cyclopentadiene ligands are one or more of the above- mentioned silicon-functional cyclopentadienes according to the invention. This applies in particular if such a transition metal complex is used as a catalyst in a catalyst system for the polymerization of α-olefins, with the catalyst system also comprising a cocatalyst. In such a situation the transition metal in the complex has been chosen from groups 3-6 of the Periodic System of the Elements.

The invention therefore also relates to a process for the polymerization of an α-olefin with the aid of a catalyst system of the type indicated above. The polymerization of α-olefins, for example ethene, propene, butene, hexene, octene and mixtures thereof and combinations with dienes, can be carried out in the presence of the metal complexes with the cyciopentadienyl compounds according to the invention as ligand. Suitable in particular for this purpose are complexes of transition metals which are not in their highest valency state, in which just one of the cyciopentadienyl compounds according to the invention is present as ligand and in which the metal is cationic during the polymerization. Said polymerizations can be carried out in the manner known for the purpose and the use of the metal complexes as catalyst component does not make any essential adaptation of these processes necessary. The known polymerizations are carried out in suspension, solution, emulsion, gas phase or as bulk polymerization. The cocatalyst usually applied is an organometal compound, the metal being chosen from - -

groups 1, 2, 12 or 13 of the Periodic System of the Elements. To be mentioned are for instance trialkylaluminium, alkylaluminium halides, alkylaluminooxanes (such as methylaluminoxanes) , tris(pentafluorophenyl) borate, dimethylanilinium tetra(pentafluorophenyl) borate or mixtures thereof. The polymerizations are carried out at temperatures between -50°C and +350°C, more particularly between 25 and 250°C. The pressures used are generally between atmospheric pressure and 250 MPa, for bulk polymerizations more particularly between 50 and 250 MPa, and for the other polymerization processes between 0.5 and 25 MPa. As dispersants and solvents, use may be made of, for example, hydrocarbons, such as pentane, heptane and mixtures thereof. Aromatic, optionally perfluorinated hydrocarbons, are also suitable. The monomer applied in the polymerization can also be used as dispersant or solvent.

The invention will be elucidated by means of the following examples, without being restricted thereto.

Example I

31,0 g of tetramethylcyclopentadiene (0.24 mol) was dissolved in 500 ml of tetrahydrofuran (THF) and cooled to 2°C in a 1500-ml reactor. Then 160 ml of n-butyllithium (1.6M in hexane, 0.26 mol) was added dropwise. This was followed by 18 hours' stirring by means of a mechanical stirrer at room temperature. The reaction mixture obtained was cooled to -90°C. Then 36.3 g of chlorodimethylsilylchloride (0.28 mol) was added at once. Then the cooling bath was removed; the reaction mixture was allowed to reach room temperature and was stirred for a total of 18 hours. Then 200 ml of water was added. The THF was evaporated in a rotary evaporator and the residue was extracted three times with 200 ml of exthoxyethane. The combined ether layers were dried on sodium sulphate, the sodium sulphate was filtered off and the filtrate boiled down. The residue (58.0 g) had a purity of >98% (determined with GC) of (1,2,3,4-tetramethylcyclopentadien-5-yl)- chloromethyldimethylsilane.

Comparative Experiment A

15.9 g of diphenylphosphine (85 mmol) was dissolved in 100 ml of ether. The solution was cooled to 2°C, after which 53 ml of n-butyllithium (1.6M in hexane, 85 mmol) was added dropwise. This was followed by stirring for 30 minutes at 2°C and subsequently for 18 hours at room temperature (the lithiumdiphenylphosphine was not completely soluble). Then 100 ml of THF was added. This resulted in a dark- red homogeneous solution. This solution was added dropwise to a solution of 19.5 g (85 mmol) of (1,2,3,4- tetramethylcyclopentadien-5-yl)- chloromethyldimethylsilane as obtained in Example I in 150 ml of THF at 2°C. The reaction mixture was stirred at room temperature for 18 hours. Then the THF was evaporated. 200 ml of petroleum ether was added to the residue, the precipitate was filtered off and the filtrate was boiled down. The residue was pure (1,2,3,4-tetramethylcyclopentadien-5-yl)- (diphenylphosphinomethyl) )dimethylsilane.

Example II

1.22 g of diisopropylamine (12 mmol) was dissolved in 25 ml of THF and cooled to 2°C. Then 7.5 ml of n-butyllithium (1.6M in hexane; 12 mmol) was added dropwise and this was followed by stirring for 30 minutes at room temperature. To the resulting solution, 2.70 g of (1,2,3,4-tetramethylcyclopentadien-5-yl)- chloromethyldimethylsilane as obtained in Example I was added. The reaction mixture was stirred for 18 hours at room temperature. The THF was evaporated and 100 ml of - -

ether was added to the residue, after which the resulting salts were filtered off and the filtrate was boiled down, which yielded 3.0 g of residue. GC analysis showed a conversion of 100% and a purity of >90% of (1,2,3, 4-tetramethylcyclopentadien-5- methylyl ) (N,N-diisopropylamino)dimethylsilane.

Example III

Example II was repeated, starting from 1.75 g (13.5 mmol) of di-n-butylamine and 3.05 g of (1,2, 3,4- tetramethyleyelopentadien-5- yl)chloromethyldimethylsilane (13.3 mmol). GC analysis showed 100% conversion. After evaporation 3.95 g of (1,2,3 ,4-tetramethylcyclopentadien-5-methylyl) ( N,N-di- n-butylamino)dimethylsilane was obtained.

Claims

C L A I M S

Process for the functionalization of a substituted cyclopentadiene, characterized in that the substituted cyclopentadiene is reacted with a Brδnsted base, after which the anion obtained is reacted with a dihaloalkylsilicon compound of the following formula:

R¹ I

Hal - (Si)_m - (C)_n - Hal,

R² R^<

where the symbols mean the following:

- Hal = a halogen group

- R^x-R⁴ = each a hydrogen or a substituted or unsubstituted alkyl, aryl or aralkyl group - m >.1 and n >_.1 2. Process according to Claim 1, characterized in that the anion is reacted with a dihaloalkylsilicon compound of the formula R¹ R³

I I Hal - (Si). - (C)_n - Hal,

I I R² R⁴ after which the reaction product obtained is treated with an (earth-)alkalimetal amide of the formula:

M(NR⁵R⁶)_p where the symbols mean the following: M = (earth-)alkali metal chosen from group 1 or 2 of the Periodic System of the

Elements

R^s, R⁶ = each a hydrogen or a substituted or unsubstituted alkyl, aryl or aralkyl group - -

p = number of (NR⁵R⁶) groups: p = 1 for M = alkali metal p = 2 for M = earth-alkali metal.

3. Process according to any one of Claims 1-2, characterized in that m = n = 1.

4. Process according to any one of Claims 1-3, characterized in that a Li-alkyl compound is used as Brόnsted base.

5. Process according to Claim 4, characterized in that butyllithium is used.

6. Silicon-functional cyclopentadiene of the formula:

in which Y is a substituent and 1 <, z < 4. Silicon-functional cyclopentadiene of the formula:

in which Y is a substituent and 1 <. z < 4. 8. Silicon-functional cyclopentadiene according to any one of Claims 6-7, characterized in that the Hal group is a Cl group. 9. Silicon-functional cyclopentadiene of the formula:

10. Silicon-functional cyclopentadiene according to Claim 8, characterized in that m = n = 1 and R^R⁶ = H.

11. Silicon-functional cyclopentadiene according to any one of Claims 6-10, characterized in that the cyciopentadienyl ring is mono- or disubstituted. 12. Silicon-functional cyclopentadiene according to any one of Claims 6-10, characterized in that the cyciopentadienyl ring is tri- or tetrasubstituted.

13. Silicon-functional cyclopentadiene according to any one of Claims 6-12, characterized in that the cyciopentadienyl ring is derived from indene, fluorene or benzoindene.

14. Transition metal complex of a transition metal and one or more ligands on the basis of a cyclopentadiene, characterized in that at least one ligand is a silicon-functional cyclopentadiene according to any one of Claims 6-13.

15. Catalyst system for the polymerization of an α- olefin, comprising the transition metal complex according to Claim 14 and a cocatalyst, the transition metal in the complex being chosen from groups 3-6 of the Periodic System of the Elements.

16. Process for the polymerization of an α-olefin, characterized in that the polymerization is carried out under the influence of the catalyst system of Claim 15.