Single-site catalysts based on caged diimide ligands

Details Single-site catalysts based on caged diimide ligands Single-site catalysts based on caged diimide ligands

2000-10-18

2002-07-02

Wu, David W. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C502S103000, C502S165000, C502S166000, C502S167000, C502S171000, C526S134000

Reexamination Certificate

active

06414099

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to catalysts useful for polymerizing olefins. In particular, the invention relates to catalysts that contain diimide ligands having multiple carbocyclic rings and a cage-like structure (“caged diimide ligands.”) The caged diimides are particularly valuable for use with late transition metal catalysts.
BACKGROUND OF THE INVENTION
Interest in single-site (metallocene and non-metallocene) catalysts continues to grow rapidly in the polyolefin industry. These catalysts are more reactive than Ziegler-Natta catalysts, and they produce polymers with improved physical properties. The improved properties include narrow molecular weight distribution, reduced low molecular weight extractables, enhanced incorporation of &agr;-olefin comonomers, lower polymer density, controlled content and distribution of long-chain branching, and modified melt rheology and relaxation characteristics.
Traditional metallocenes commonly include one or more cyclopentadienyl groups, but many other ligands have been used. Putting substituents on the cyclopentadienyl ring, for example, changes the geometry and electronic character of the active site. Thus, a catalyst structure can be fine-tuned to give polymers with desirable properties. Other known single-site catalysts replace cyclopentadienyl groups with one or more heteroatomic ring ligands such as boraaryl (see, e.g., U.S. Pat. No. 5,554,775), pyrrolyl, indolyl, (U.S. Pat. No. 5,539,124), or azaborolinyl groups (U.S. Pat. No. 5,902,866).
Single-site catalysts based on “late” transition metals (especially those in Groups 8-10, such as Fe, Ni, Pd, and Co) and diimines or other ligands have recently sparked considerable research activity because of the unusual ability of these catalysts to incorporate functionalized comonomers or to give branched polyethylenes without including a comonomer. See, for example, U.S. Pat. Nos. 5,714,556 and 5,866,663 and PCT international applications WO 96/23010, WO 98/47933, and WO 99/32226. These catalysts are often less active than would otherwise be desirable.
The diimine ligands described above are often called “Brookhart” ligands or “Brookhart-DuPont” ligands because much of the early work in this area was performed by Professor Maurice Brookhart (University of North Carolina at Chapel Hill) and scientists at E.I. du Pont de Nemours and Company (Wilmington, Del.). The vast majority of Brookhart ligands used to date are &agr;-diimines, i.e., they derive from 1,2-diketones (as indicated by the “DAB” acronym used in the references to identify the 1,4-diaza-1,3-butadiene structural subunit). Other diimines derived from alkylene diamines (e.g., 1,3-propanediamine) and simple aldehydes or ketones are also taught (see, e.g., U.S. Pat. No. 5,866,663, formula (XXX), column 3, where n=2 or 3). Diimines derived from primary amines and multicyclic diketones are generally unknown as ligands for olefin polymerization catalysts.
The Diels-Alder reaction is legendary in synthetic organic chemistry because of its phenomenal utility for creating complex carbocyclic compounds with predictable stereospecificity. Simple heating of dienes and dienophiles gives a wide variety of substituted cyclohexenes in a [4+2] cycloaddition reaction. Another synthetically valuable reaction involves the photochemical [2+2] cycloaddition reaction, which converts two proximally oriented olefin groups into a cyclobutane ring. This transformation is accomplished by irradiating two olefins (usually a diolefin) with light of a suitable energy under reaction conditions that favor cyclization. By performing a Diels-Alder reaction in tandem with a photochemical [2+2] cycloaddition, one can create remarkably complex, multicyclic compounds from readily available dienes and dienophiles in two simple steps (see, e.g., G. Mehta, Tetrahedron 37 (1981) 4543). In spite of the availability of the Diels-Alder reaction and photochemical cycloadditions, these reactions have not been exploited to prepare ligands useful for single-site olefin polymerization catalysts.
In sum, there is a continuing need for new ligands and new single-site catalysts for olefin polymerization processes. In particular, there is a need for ligands that can be used with late transition metals to boost activity, improve catalyst solubility, and facilitate polar comonomer incorporation. Ideally, the ligands and catalysts could be made easily from readily available starting materials.
SUMMARY OF THE INVENTION
The invention is catalyst system useful for polymerizing olefins. The catalyst system comprises an organometallic complex and an optional activator. The complex includes a Group 3 to 10 transition, lanthanide or actinide metal and a caged diimide ligand. In a preferred catalyst system of the invention, the catalyst incorporates a “late” transition metal, i.e., a metal from Groups 6 to 8. The invention includes caged diimide ligands prepared by a tandem Diels-Alder and photochemical [2+2] cycloaddition sequence to give a multicyclic dione, followed by condensation with a primary amine. Because a wide variety of caged diimide ligands are easy to prepare from commercially available dienes and dienophiles, the invention enables the preparation of a new family of single-site catalysts. Based on their unique structure and geometry, the catalysts offer polyolefin producers new ways to improve activity, control comonomer incorporation, or regulate polyolefin tacticity.
DETAILED DESCRIPTION OF THE INVENTION
Catalyst systems of the invention comprise an organometallic complex and an optional activator. The complex is “single site” in nature, i.e., it is a distinct chemical species rather than a mixture of different species. Single-site catalysts, which include metallocenes, typically give polyolefins with characteristically narrow molecular weight distributions (Mw/Mn<3) and good, uniform comonomer incorporation.
The organometallic complex includes a Group 3 to 10 transition metal or lanthanide or actinide metal, M. More preferred complexes include a Group 4 to 8 transition metal. Particularly preferred complexes incorporate a “late” transition metal, i.e., a metal from Groups 6 to 8, i.e., chromium, manganese, iron, cobalt, nickel, and elements directly below these on the Periodic Table.
The complex includes a caged diimide ligand. “Caged” means that the ligand has a multicyclic structure that surrounds the imide groups and resembles a cage or container. “Cage compounds” are a well-known class of carbocyclic materials of interest to synthetic organic chemists. They include adamantanes, cubanes, polyquinanes, fullerenes (e.g., “Buckyballs”), and other interesting groups of compounds.
The caged diimide ligand typically features multiple five or six-membered rings. Preferred ligands are “diquinanes.” As used herein, “diquinane” refers to carbocyclic compounds that have at least two nonfused five-membered rings that share at least two carbon-carbon bonds and are oriented such that the five-membered rings occupy opposite “faces” in the structure, similar to the way in which the two-dotted and five-dotted sides occupy opposite faces on a six-sided die.
The caged ligand is a “diimide,” i.e., it is a diimine condensation product of a diketone and two equivalents of a primary amine or ammonia. Each imine has the general structure R
2
C═NR′ in which C and each R are part of one of a five or six-membered ring, and R′ is preferably hydrogen or a C
1
-C
30
alkyl, aryl, or aralkyl group.
Caged diimides useful as ligands for catalyst systems of the invention can be made by any desired method. One particularly valuable method involves the use of tandem Diels-Alder and photochemical [2+2] cycloaddition reactions starting with a diquinone, preferably p-benzoquinone or a halogenated p-benzoquinone such as 2,3,5,6-tetrachloro-p-benzoquinone. The resulting multicyclic dione is then reacted with two equivalents of ammonia or a primary amine to give the caged diimide ligand. The only requ

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