Organic compounds -- part of the class 532-570 series – Organic compounds – Heavy metal containing
Reexamination Certificate
2000-08-08
2001-05-08
Bell, Mark L. (Department: 1755)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heavy metal containing
C556S186000, C556S187000, C556S189000, C556S190000
Reexamination Certificate
active
06229034
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the compositions of matter useful as a catalyst system, to a method for preparing these catalyst systems and to a method for polymerization utilizing the catalyst system.
The use of soluble Ziegler-Natta type catalysts in the polymerization of olefins is well known in the prior art. In general, such systems include a Group IV-B metal compound and a metal or metalloid alkyl cocatalyst, such as aluminum alkyl cocatalyst. More broadly, it may be said to include a mixture of a Group I-III metal alkyl and a transition metal complex from Group IVB-VB metals, particularly titanium, zirconium, or hafnium with aluminum alkyl cocatalysts.
First generation cocatalyst systems for homogeneous metallocene Ziegler-Natta olefin polymerization, alkylaluminum chlorides (AlR
2
Cl), exhibit low ethylene polymerization activity levels and no propylene polymerization activity. Second generation cocatalyst systems, utilizing methyl aluminoxane (MAO), raise activities by several orders of magnitude. In practice however, a large stoichiometric excess of MAO over catalyst ranging from several hundred to ten thousand must be employed to have good activities and stereoselectivities. Moreover, it has not been possible to isolate characterizable metallocene active species using MAO. The third generation of cocatalyst, B(C
6
F
5
)
3
, proves to be far more efficient while utilizing a 1:1 catalyst-cocatalyst ratio. Although active catalyst species generated with B(C
6
F
5
)
3
are isolable and characterizable, the anion MeB(C
6
F
5
)
3
⊖
formed after Me
⊖
abstraction from metallocene dimethyl complexes is weakly coordinated to the electron-deficient metal center, thus resulting in a decrease of certain catalytic activities. The recently developed B(C
6
F
5
)
4
⊖
type of non-coordinating anion exhibits some of the highest reported catalytic activities, but such catalysts have proven difficult to obtain in the pure state due to poor thermal stability and poor crystallizability, which is crucial for long-lived catalysts and for understanding the role of true catalytic species in the catalysis for the future catalyst design. Synthetically, it also takes two more steps to prepare such an anion than for the neutral organo-Lewis acid.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the subject invention to prepare and utilize a new class of olefin polymerization catalytic system.
A further object of the subject invention is a catalytic system which permits better control over molecular weight, molecular distribution, stereoselectivity, and comonomer incorporation.
Another object ofthe subject invention is a Ziegler-Natta type catalytic system which reduces the use of excess cocatalyst and activates previously unresponsive metallocenes.
These and other objects are attained by the subject invention whereby in one embodiment, a salt of a strong organo-Lewis acid, such as a (perfluoroaryl)aluminate anion and in particular tris(2,2′,2″-nonafluorobiphenyl)fluoroaluminate (PBA
⊖
) is utilized as a highly efficient cocatalyst for metallocene-mediated olefin polymerization. PBA
⊖
exhibits higher catalytic activities and can activate previously unresponsive metallocenes. The synthesis of the stable perfluoroaryl aluminum anion, tris(2,2′,2″-nonafluorobiphenyl)fluoroaluminate (PBA
⊖
) is accomplished with the use of sterically encumbered perfluorobiphenyl ligand.
In one embodiment of the subject invention a salt of a strong organo-Lewis acid, such as a fluoroaryl metal compound, is utilized to synthesize stoichiometrically precise, isolable/crystallographically characterizable, highly active “cation-like” metallocene polymerization catalysts.
In the subject application, “Cp” represents a cyclopentadienyl radical which may be substituted or unsubstituted, and: (Cp)(Cp′) or Cp-A-Cp′ and Cp and Cp′ are the same or different cyclopentadienyl ring substituted with zero to five substituent groups &bgr; and each substituent group &bgr; is, independently, a radical which can be hydrocarbyl, substituted-hydrocarbyl, halocarbyl, substituted-halocarbyl, hydrocarbyl-substituted organometalloid, halocarbyl-substituted organometalloid, or halogen radicals (the size of the radicals need not be limited to maintain catalytic activity; however, generally the radical will be a C
1
to C
20
radical) or Cp and Cp′ are a cyclopentadienyl ring in which any two adjacent R groups are joined forming a C
4
to C
20
ring to give a saturated or unsaturated polycyclic cyclopentadienyl ligand such as indenyl, tetrahydroindenyl, fluorenyl, or octahydrofluorenyl and A is a bridging group which restricts rotation of the two Cp-groups.
Each carbon atom in the cyclopentadienyl radical (“Cp”) may be, independently, unsubstituted or substituted with the same or different radical group which is a hydrocarbyl, substituted-hydrocarbyl, halocarbyl, substituted-halocarbyl hydrocarbyl radicals in which adjacent substituents are joined to form a ring of 4 to 10 or more carbon atoms, hydrocarbyl- and halocarbyl-substituted organometalloid radicals and halogen radicals.
More specifically, a fluoroaryl metal compound such as ER′R″R′″F
⊖
reacts with early transition metal or actinide alkyls to yield highly reactive cationic complexes:
CpCp′MR
2
+Ph
3
C
⊕
(ER′R″R′″F)
⊖
→[CpCp′MR]
⊕
[ER′R″R′″F]
⊖
+Ph
3
CR (1)
where CpCp′=cyclopentadienyl, cyclopentadienyl substituted or bridged cyclopentadienyl ligands such as CpACp′, indenyl Cp, allyl Cp, benzyl Cp; substituted indenyl Cp; substituted allyl Cp; substituted benzyl Cp; &eegr;
5
-1,2-Me
2
C
5
H
3
; &eegr;
5
-1,3-(SiMe
3
)
2
C
5
H
3
; &eegr;
5
-C
5
Me
5
; (
t
BuN)Me
2
Si(&eegr;
5
-Me
4
C
5
)
M=early transition metal or actinide, e.g., Ti, Zr, Hf, Th, U
R=PhCH
2
, alkyl or aryl group (C≦20), hydride
R′, R″, R′″=fluorinated phenyls, fluorinated biphenyl or fluorinated polycyclic fused ring groups
E=Al, Ga, In
As a specific example of the above, the reaction of PBA
⊖
with a variety of zirconocene dimethyl complexes proceeds rapidly and quantitatively to yield, after recrystallization from hydrocarbon solvents, in the catalytic complex set forth in Eq. 2.
CpCp′MR
2
+Ph
3
C
⊕
(ER′R″R′″F)
⊖
→CpCp′MR
⊕
(ER′R′R′″F)
⊖
+Ph
3
CR (2)
Such catalytic complexes have been found to be active homogeneous catalysts for &agr;-olefin polymerization.
The cocatalyst of the subject invention may be referred to as ER
F
′R
F
″R
F
′″F
⊖
; where R′, R″, and R′″ represent at least one and maybe more fluorinated biphenyls or other fluorinated polycyclic groups, such as naphthyl. Two of the biphenyls may be substituted with a phenyl or other aryl group. Both the biphenyls and the phenyl groups should be highly fluorinated, preferably with only one or two hydrogens on a group, and most preferably, as in PBA
⊖
with no hydrogens and all fluorines. E represents Al, Ga or In.
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patent: 555477
Chen You-Xian
Marks Tobin J.
Bell Mark L.
Northwestern University
Pasterczyk J.
Sieberth & Patty L.L.C.
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