Late transition metal polymerization catalysts

Details Late transition metal polymerization catalysts Late transition metal polymerization catalysts

2002-03-04

2004-02-10

Harlan, Robert (Department: 1713)

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

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S133000, C526S134000, C526S161000, C526S172000, C502S155000, C502S167000

Reexamination Certificate

active

06689848

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a catalyst and its use in olefin polymerization. The catalyst comprises an activator and an inorganic compound that contains iron and a tridentate N-(2-ethylamino)-2-pyridylmethanimino or N,N-bis(2-pyridylmethyl)amino ligand.
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 active than conventional 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, and lower polymer density.
While traditional metallocenes commonly include one or more cyclopentadienyl groups, 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 heteroaromatic 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 (i.e., 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 their unusual ability 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. These catalysts are often less active than would otherwise be desirable.
Other late transition metal catalyst systems have also been disclosed. 2,6-bis(imino)pyridine complexes of iron and cobalt are disclosed in Gibson, et al.,
J. Am. Chem. Soc.
121 (1999) 8728 and in Brookhart, et al.,
J. Am. Chem. Soc.
120 (1998) 4049. These 2,6-bis(imino)pyridine complexes are shown to be active in ethylene polymerization. Chelating bis(amido) ligands have been described. See, for example, Cloke et al.,
J. Organomet. Chem.
506 (1996) 343, which discloses a ligand having secondary amine groups that chelate with a Group 4 transition metal. Similarly, Johnson et al. have described nickel-olefin pi-complexes in which two primary, secondary, or tertiary amine groups chelate the nickel atom (see, e.g., U.S. Pat. No. 5,714,556 at columns 4547). Tridentate complexes in which two secondary amine groups and a pyridinyl group bind to the transition metal are also known from McConville et al. (see, e.g.,
Organometallics
15 (1996) 5085, 5586). U.S. Pat. No. 3,651,065 describes a nickel catalyst that is active in the oligomerization of butadiene.
Improved single-site catalysts for olefin polymerization are still needed. Particularly valuable catalysts would be easy to synthesize and would have high activities.
SUMMARY OF THE INVENTION
The invention is a catalyst for polymerizing olefins. The catalyst comprises: (a) an activator; and (b) an inorganic compound comprising iron and a tridentate N-(2-ethylamino)-2-pyridylmethanimino or N,N-bis(2-pyridylmethyl)amino ligand. The tridentate ligand is easily prepared from inexpensive starting materials. The catalyst is useful in olefin polymerization.
DETAILED DESCRIPTION OF THE INVENTION
Catalysts of the invention comprise an activator and an inorganic compound comprising iron and a tridentate ligand.
The inorganic compound contains a tridentate ligand. The tridentate ligand is a substituted or unsubstituted N-(2-ethylamino)-2-pyridylmethanimino ligand or a substituted or unsubstituted N,N-bis(2-pyridylmethyl)amino ligand. Members of the N-(2-ethylamino)-2-pyridylmethanimino class of ligands have the basic chemical structure:
where any carbon and the primary nitrogen of the basic structure can be substituted or unsubstituted. Members of the of N,N-bis(2-pyridylmethyl)amino class of ligands have the basic chemical structure:
where any carbon and the secondary nitrogen of the basic structure can be substituted or unsubstituted.
Typical substituents on the carbon or nitrogen atoms of the basic structures include halogens, hydroxides, sulfoxides, C
1
-C
20
alkoxys, C
1
-C
20
siloxys, C
1
-C
20
sulfoxys, C
1
-C
20
hydrocarbyl, or a condensed ring attached to the pyridyl groups. These substituents replace the hydrogen atom of the unsubstituted structure.
Preferred tridentate ligands have the formula:
where
R
1
and R
9
, are the same or different, and are H, F, Cl, Br, I, C
1
-C
20
hydrocarbyl, or a condensed ring;
R
2
, R
3
, R
4
, R
5
, R
6
, R
7
, and R
8
, are the same or different, and are H or C
1
-C
20
hydrocarbyl; and
x=0-5.
The tridentate ligands are well known and easily prepared from known methods. In one convenient method described in Hinman, et. al.,
Organometallics,
2000, 19, 563, at 568, a pyridinecarboxaldehyde is reacted directly with a diamine, such as N,N-diethylethylenediamine, in an inert organic solvent. Stoichiometric quantities are typically used. The reactions are typically performed at room temperature, but temperatures of −20° C. to 150° C. can also be used. The solvent is typically removed by evaporation and the tridentate ligand is collected.
In the inorganic compound of the invention, the tridentate ligand is coordinated to iron such that iron is bound to the three nitrogen atoms of the ligand. The iron may also have other ligands. Suitable additional ligands include halides, nitrates, sulfates, carboxylates (e.g. acetate), acetylacetonates, and amines. Particularly preferred ligands are halides, such as chloride, bromide, and iodide.
A preferred catalyst comprises an activator and an inorganic compound of the formula:
where
R
10
and R
11
are the same or different, and are H or C
1
-C
20
hydrocarbyl; and
X is a halide.
The inorganic compound is prepared by any suitable method. In one convenient method, the inorganic compound is made by reacting a tridentate ligand with one equivalent of an iron complex such as iron dichloride in an inert organic solvent. Preferred solvents include diethyl ether, tetrahydrofuran, hexane, and toluene. The reactions typically occur at room temperature, but temperatures of −20° C. to 150° C. can also be used. The product can be used in polymerization without isolation from the solvent. However, the solvent can also be evaporated and the inorganic compound can be collected.
The inorganic compound is combined with an activator to give a catalyst of the invention. Suitable activators are well known in the art. They include alumoxanes. Preferred alumoxanes (methyl alumoxane (MAO), PMAO, ethyl alumoxane, and diisobutyl alumoxane), aluminum alkyls (e.g., triethyl aluminum, triisobutylaluminum), alkyl aluminum halides (e.g., diethylaluminum chloride), and the like. Suitable activators include acid salts that contain non-nucleophilic anions. These acid salts generally consist of bulky ligands attached to boron or aluminum. Examples include lithium tetrakis(pentafluorophenyl)borate, lithium tetrakis(pentafluorophenyl)aluminate, anilinium tetrakis(pentafluorophenyl)borate, and the like. Suitable activators also include organoboranes, which include boron and one or more alkyl, aryl, or aralkyl groups. Suitable activators include substituted and unsubstituted trialkyl and triarylboranes such as tris(pentafluorophenyl)borane, triphenylborane, tri-n-octylborane, and the like. These and other suitable boron-containing activators are described in U.S. Pat. Nos. 5,153,157, 5,198,401, and 5,241,025, the teachings of which are incorporated herein by reference.
The amount of activator needed relative to the amount of inorganic compound depends on many factors, including the nature of the inorganic compound and the activator, the desired reaction rate, the kind of polyolefin product, the reaction conditions, and other factors. Generally, however, when the activator is an alumox

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