Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-04-18
2002-05-21
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...
C526S160000, C526S161000, C526S172000, C526S348600, C502S104000, C502S155000, C502S162000
Reexamination Certificate
active
06391988
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to anionic pyrazolyl, triazolyl, and tetraazolyl-containing ligands (“azacyclic” ligands) and transition metal complexes that contain them. The complexes are valuable pro-catalysts for organic reactions, particularly for olefin polymerizations.
2. Background Art
The chemical industry uses a wide variety of transition metal complexes as catalysts for organic reactions. Olefin polymerization is an important example of such a reaction. While conventional Ziegler-Natta catalysts continue to dominate the industry, highly active metallocene or single-site catalysts that give new polymers with narrow molecular weight distributions, low densities, and good comonomer incorporation are emerging.
Transition metal complexes used to polymerize olefins are normally non-zero-valent metals (e.g., Ti
4+
, Zr
4+
, Sc
3+
) surrounded by anionic ligands (e.g., chloride, alkyl, cyclopentadienyl) that satisfy the valency of the metal and often improve the solubility of the catalyst in the reaction medium. Anionic ligands can dramatically affect catalyst activity and polymer properties. Furthermore, the anionic ligand will affect the stability of the transition metal complexes.
Metallocene polymerization catalysts contain one or two cyclopentadienyl groups as anionic ligands. These serve to stabilize the active catalytic species, modulate the electronic and steric environment around the active metal center, and maintain the single-sited nature of the catalyst. Polymers with narrow molecular weight and composition distributions are formed from these metallocene catalysts.
Another class of anionic ligands is those which are isolobal to the cyclopentadienyl ring; that is, the orbital interaction of the metal with the ligand is similar in both cases. Examples of such ligands are pyrroyl anions, phospholyl anions, and tris(pyrazolyl)borate anions.
Catalysts containing anionic tris(pyrazolyl)borate ligands are known. For example, VOCl
3
reacts with potassium tris(pyrazolyl)borate to make a complex that polymerizes ethylene in the presence of an activator such as methyl alumoxane (MAO). Furthermore, the crystal structure of tris(3,5-dimethylpyrazolyl) methylsilane is known. Anionic multidentate ligand are particularly desirable because of the potential for these ligands to enhance the stability of transition metal complexes.
New anionic, multidentate ligands are needed. Particularly valuable ligands would be easy to synthesize from readily available starting materials and could be made in high yields. Such ligands would be valuable for making new transition metal complexes useful as pro-catalysts for olefin polymerization.
SUMMARY OF THE INVENTION
In one embodiment of the present invention, an anionic multidentate ligand is provided. This ligand includes a Group 14 element and at least one azacylic group. The anionic multidentate ligand is one component of a pro-catalyst suitable for catalyzing the olefin polymerization. The pro-catalyst of the present invention includes a Group 3 to 10 transition or lanthanide metal (M), one or more anionic or neutral ligands in an amount that satisfies the valency of the M, and at least one anionic multidentate ligand.
In another embodiment of the invention, a method for preparing a polymerization pro-catalyst is provided. The method comprises reacting an azacyclic compound having at least one nitrogen atom with a strong base to form an azacyclic salt. The azacyclic salt is reacted with a divalent Group 14 halide to form an anionic ligand. These negatively charged ligands are next reacted with a transition or lanthanide metal complex to form a pro-catalyst.
In yet another embodiment of the invention, a method for preparing a polymerization pro-catalyst is provided. The method comprises reacting an azacyclic compound with a strong base to form an azacyclic salt. The azacyclic salt is reacted with a Group 14 halide to form a substituted metal compound. The trisubstituted metal compound is reacted with a strong base to form an anionic ligand. The anionic ligand is reacted with a transition or lanthanide metal complex to form a procatalyst with at least one multidentate ligand.
In another embodiment of the invention, the procatalyst of the present invention is used to catalyze the polymerization of various olefins.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
Reference will now be made in detail to presently preferred embodiments and methods of the invention, which constitute the best modes of practicing the invention known to the inventor.
In one embodiment of the present invention, an anionic multidentate ligand is provided. The anionic multidentate ligand of the present invention has the following formula:
R
x
L
y
A (I)
where R is hydrogen, a C
1-30
alkyl, a C
1-30
aryl, or a C
1-30
aralkyl, A is a Group 14 element, L is a substituted or unsubstituted pyrazolyl, triazolyl, or tetrazolyl group, x is 0 to 2, y is 1 to 3 wherein the sum of x and y is equal to 3.
Preferred pyrazolyl groups have the following formula:
where R
1
, R
2
, and R
3
are independently hydrogen, a C
1-8
alkyl group, C
6-10
aryl group, C
7-15
aralkyl group, C
1-10
alkoxy group, C
6-14
aryloxy group, C
1-10
dialkylamino group, or C
6-15
diarylamino group, or any similar group. Such groups may be partially or full halogenated. Two adjacent groups may be joined to form a cyclic structure, as in indazole or tetrahydroindazole. The pyrazolyl groups are sigma-bonded to the Group 14 atom through the 1-nitrogen.
Preferred triazolyl groups are described by the following structures:
where R
1
and R
2
are as defined above.
Preferred tetraazolyl groups have the following formula:
where R
1
is defined above.
In another embodiment of the invention, a transition metal complex useful as a pro-catalyst is provided. The transition metal complex comprises a Group 3 to 10 transition or lanthanide metal (M), one or more anionic or neutral ligands, and the anionic multidentate ligand described above by structure I. Preferred Group 3 to 10 metals comprise Sc, Ti, Cr, Mn, Fe, Co, Ni, and elements directly below these in the Periodic Table. Preferred lanthanide metals include La, Ce, Pr, Eu, Yb, and the like. More preferably, the transition metal complex comprises a Group 3 to 6 transition or lanthanide metal, and most preferably, a Group 4 transition metal. The one or more anionic or neutral ligands are present in an amount such that the valency of M is satisfied. Examples include unsubstituted and substituted cyclopentadienyl, indenyl, fluorenyl, hydride, halide, alkyl, aryl, aralkyl, dialkylamino, siloxy, alkoxy, pyrrolyl, indolyl, carbazoyl, quinolinyl, pyridinyl, azaborolinyl, boraaryl groups, or the like, and combinations of these. Examples of neutral ligands are carbonyl, &eegr;
6
-aryl, &eegr;
4
-butadiene, &eegr;
4
-cyclobutadiene, &eegr;
4
-cyclooctatetraene, tertiary phosphine, and the like. Other examples of suitable anionic or neutral ligands appear in U.S. Pat. Nos. 5,756,611, 5,637,659, 5,637,660, 5,554,775, and 5,539,124, the teachings of which are incorporated herein by reference.
In another embodiment of the invention, the transition metal complex further comprises an activator. Generally, the activator converts the complex to a cationically active species. The catalysts are especially valuable for polymerizing olefins, such as ethylene, propylene, and/or other a-olefins such as 1-butene or 1-hexene. Suitable activators are well known in the art. Preferred activators include alumoxanes (e.g., methyl alumoxane (MAO), PMAO, ethyl alumoxane, diisobutyl alumoxane), alkylaluminum compounds (triethylaluminum, diethylaluminum chloride, trimethylaluminum), and the like. Such activators are generally used in an amount within the range of about 0.01 to about 100,000, preferably from about 1 to about 10,000, moles per mole of transition metal complex. Preferred activators also include acid salts that contain non-nucleophilic anions. These compounds generally consist of bulky ligands attached to
Brooks & Kushman P.C.
Equistar Chemicals L.P.
Harlan R.
Wu David W.
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