Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2001-08-15
2003-05-13
Nazario-Gonzalez, Porfirio (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C546S002000, C502S167000, C556S137000, C556S138000
Reexamination Certificate
active
06562973
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for making olefin polymerization catalysts. In particular, the invention relates to a high-yield method for making late transition metal complexes in a single reactor.
BACKGROUND OF THE INVENTION
“Single-site” catalysts, which include metallocenes, actively polymerize olefins to give polymers with valuable properties such as narrow molecular weight distribution and uniform comonomer distribution. While traditional metallocenes have cyclopentadienyl (Cp) ligands and/or Cp-like ligands (e.g., iridenyl, fluorenyl), a variety of non-metallocene, single-site catalysts having heteroatomic ring ligands have also been developed (see, e.g., U.S. Pat. Nos. 5,554,775 and 5,539,124).
Since the late 1990s, olefin polymerization catalysts that incorporate late transition metals (especially iron, nickel, or cobalt) and bulky &agr;-diimine ligands (hereinafter also called “bis(imine) ligands” or “bis(imines)”) have been extensively studied and described by scientists at DuPont, the University of North Carolina at Chapel Hill, and BP Chemicals. For a few examples, see
Chem. & Eng. News
, Apr. 13, 1998, p. 11;
Chemtech
, July 1999, p. 24;
Chem. Commun
. (1998) 849;
J. Am. Chem. Soc.
120 (1998) 4049;
Chem. Rev.
100 (2000) 1169; PCT Int. Publ. WO 99/12981; and U.S. Pat. Nos. 5,866,663 and 5,955,555. Similar complexes have been known much longer (see, e.g.,
J. Chem. Soc., Part A
(1968) 1510), but olefin polymerizations with the complexes are a recent phenomenon.
Late transition metal catalysts are of interest because they can be highly active and, unlike traditional early transition metal-based metallocenes, they can tolerate and incorporate polar comonomers. The most widely studied late transition metal catalysts incorporate bis(imine) ligands produced by reacting 2,6-diacylpyridines and anilines. The ligand is then combined in a separate reaction step with a suitable transition metal source to give the desired complex. The two-step preparation of a tridentate complex from 2,6-diacetylpyridine, 2,4,6-trimethylaniline, and FeCl
2
is typical:
The two reaction steps are normally performed separately. The bis(imine) is prepared in one flask and is isolated. Subsequently, the bis(imine) is combined in another reaction vessel with the transition metal source to give the desired complex. For typical preparations, see U.S. Pat. No. 5,955,555 (Examples 1 and 11) and PCT Int. Appl. WO 99/12981 (Examples 4.1, 4.2, 9.1, and 9.2).
A drawback of the current methods for making these complexes is that the overall yield for the two-step process is often less than 50%. See, e.g., WO 99/12981, examples 9.1 and 9.2, where the overall yield from the two steps is 60%×64%=38.4%. Our own comparisons using the published two-step procedures (see Comparative Examples 7 and 9 below), gave results consistent with the published yields, and the results did not change significantly by changing the reaction solvent, catalyst, or reaction conditions (temperature, time). For example, we obtained about a 40% yield when using either the two-step, two-reactor procedure of the '555 patent (imine preparation in methanol using catalytic formic acid, complex preparation in THF, both at room temperature) or the two-step, two-reactor procedure of WO 99/12981 (acetic acid, refluxing ethanol for imine preparation; complex made in refluxing 1-butanol).
In view of the accelerating importance of highly active Group VIII metal bis(imine) complexes to polyolefin makers, finding ways to produce them in high yields (e.g., greater than 90%) is crucial.
SUMMARY OF THE INVENTION
The invention is a one-reactor method for making late transition metal bis(imine) complexes useful for catalyzing olefin polymerizations.
In one aspect, the invention is a one-reactor method for making the complexes in a s3ingle reaction step. In this method, a 2,6-diacylpyridine, an aniline, and a Group VIII metal compound are combined and reacted in a single reaction step in a reactor that is equipped with an internal filter to give a Group VIII metal bis(imine) complex. The complex is preferably washed in the same vessel, and the wash solvent is removed through the internal filter.
In a second aspect of the invention, a one-reactor method is used to make the complexes in two reaction steps. In this method, the bis(imine) ligand is prepared first. The ligand is then reacted in the same reactor with a Group VIII transition metal compound to give the desired complex, which is preferably washed in the same vessel.
I surprisingly found that the use of a single reactor to prepare Group VIII metal bis(imine) complexes and the use of an in-reactor filter for washing the ligands and/or complexes greatly enhances the yield of complex compared with the conventional two-reactor, two-step approach in which ligand and complex are purified outside the reactor. Catalyst activity remains high. Moreover, active complexes can be made in high yield even in a single reaction step when the complex is prepared and purified in the same reactor according to the method of the invention. The method enables the efficient preparation of exceptionally high (>90%) yields of desirable Group VIII metal bis(imine) complexes.
DETAILED DESCRIPTION OF THE INVENTION
The invention provides one-reactor methods for making late transition metal complex(es. In one of these methods, the complex is made in a single reaction step. Hereinafter, this method is sometimes called the “one-reactor, one-reaction-step method.” In contrast, prior-art methods are normally “two-reactor, two-reaction-step” methods. In the one-reactor methods of the invention, the bis(imine) ligand, the Group VIII metal bis(imine) complex, or both, are produced in the same reaction vessel in either one or two reaction steps. This is also known as a “one-pot” method.
In each method of the invention, a 2,6-diacylpyridine reacts with an aniline and a Group VIII metal compound to give a Group VIII metal bis(imine) complex. In the “one-reactor, one-reaction-step” method, the complex is generated in a single step, and no attempt is made to prepare or isolate a bis(imine) ligand. In the “one-reactor, two-reaction-step” method, a bis(imine) ligand is prepared first by reacting the aniline and the 2,6-diacylpyridine in the absence of the Group VIII metal compound. After the bis(imine) is prepared (and usually purified), the Group VIII metal compound is introduced, and the desired Group VIII metal bis(imine) complex is generated.
Suitable 2,6-diacylpyridines are well known. The pyridine ring can be unsubstituted or substituted with hydrocarbyl, halogen, alkoxy, aryloxy, or other functional groups that do not interfere with imine preparation, Group VIII metal complex formation, or olefin polymerization reactions. The carbonyl groups, which are attached to the 2- and 6-positions of the pyridine ring, are also attached to a hydrogen, hydrocarbyl, or substituted hydrocarbyl (e.g., haloalkyl or alkoxyalkyl) group. Preferred 2,6-diacylpyridines are 2,6-diacetylpyridine and substituted 2,6-diacetylpyridines. More examples of suitable 2,6-diacylpyridines appear in U.S. Pat. No. 5,955,555, the teachings of which are incorporated herein by reference.
Suitable anilinees are also well known. They have the general structure Ar-NH
2
, wherein Ar is an aryl or substituted aryl group. As with the pyridines, the aniline can be substituted with hydrocarbyl, halogen, alkoxy, aryloxy, or other functional groups that do not interfere with imine preparation, Group VIII metal complex formation, or olefin polymerization reactions. Aniline and alkyl-substituted anilines, such as 2,4,6-trimethylaniline and 2,6-diethylaniline, are preferred.
The Group VIII metal compound contains a Group VIII metal in a 2+ or 3+ oxidation state. Preferred Group VIII metal compounds include iron(II), iron(III), nickel(II), cobalt(II), or the like. Suitable Group VIII metal compounds also incorporate anionic organic or inorganic groups such as halides, acetates, acetylacetonates, amides, thiocyanates, pho
Equistar Chemicals LP
Nazario-Gonzalez Porfirio
Schuchardt Jonathan L.
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