Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Plural component system comprising a - group i to iv metal...
Reexamination Certificate
2001-07-17
2003-04-08
Nazario-Gonzalez, Porfirio (Department: 1621)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Plural component system comprising a - group i to iv metal...
C502S117000, C502S155000, C502S158000, C526S160000, C526S352000, C556S012000, C556S022000, C556S023000, C556S052000
Reexamination Certificate
active
06544918
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to catalysts useful for olefin polymerization. In particular, the invention relates to transition metal polymerization catalysts that incorporate a chelating dianionic ligand.
BACKGROUND OF THE INVENTION
While Ziegler-Natta catalysts are a mainstay for polyolefin manufacture, single-site (metallocene and non-metallocene) catalysts represent the industry's future. These catalysts are often 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 incorporate one or more cyclopentadienyl (Cp) or Cp-like anionic ligands such as indenyl, fluorenyl, or the like, that donate pi-electrons to the transition metal. Non-metallocene single-site catalysts have evolved more recently. Some of these include pi-donor heterocyclic ligands that are isolobal to the cyclopentadienide anion, such as boraaryl (see U.S. Pat. No. 5,554,775) or azaborolinyl (U.S. Pat. No. 5,902,866). A different type of non-metallocene single-site catalyst capitalizes on the chelating effect. Two or more n-donor atoms coordinate to a transition metal in these complexes. Examples are 8-quinolinoxy or 2-pyridinoxy ligands (see U.S. Pat. No. 5,637,660) and the bidentate bisimines of Brookhart (see
Chem. Rev.
100 (2000) 1169). “Constrained geometry” or “open architecture” catalysts (see, for example, U.S. Pat. Nos. 5,132,380 and 5,350,723) are now well known. They are valuable for their ability to incorporate comonomers such as 1-butene, 1-hexene, or 1-octene into polyolefins. Bridging in these complexes is thought to expose the catalytically active site, thereby facilitating monomer complexation and promoting polymer chain growth. In these complexes, the metal is usually sigma-bonded to a linking group that is attached to a cyclopentadienyl ring. The cyclopentadienyl ring, a 6-pi electron donor, complexes with the metal to complete the bridge.
U.S. Pat. No. 5,959,132 describes olefin polymerization catalysts that incorporate a dianionic pentalene ligand. The observed bent geometry of this ligand is not consistent with an aromatic 10-pi electron system, which must be substantially planar, but instead suggests two separate pi-electron donors: (1) an allylic anion (a 4-pi electron donor) that is fused to (2) a cyclopentadienyl anion (a 6-pi electron donor).
A conceptually different approach would utilize a bicyclic ligand to expose the active site, but with pi bonding from two separate allylic anion donor groups. While such an approach has not been explored, the ready availability of suitable ligand precursors makes it an attractive option. Many bicyclic bis(allyl) compounds, such as bicyclic[3.3.1]nona-2,6-dienes, are available commercially or are easily prepared. In spite of their availability, bicyclic bis(allyl) compounds have not been used to produce dianionic transition metal complexes. In contrast, acyclic bis(allyl) dianions are known as ligands for transition metal complexes (see
Organometallics
4 (1985) 2001). However, these complexes have not been used to polymerize olefins.
The ease with which a variety of interesting acyclic and bicyclic bis(allyl) or bis(benzyl) ligands can be prepared suggests that catalysts with advantages such as higher activity and better control over polyolefin properties are within reach. Ideally, these catalysts would avoid the all-too-common, multi-step syntheses from expensive, hard-to-handle starting materials and reagents.
SUMMARY OF THE INVENTION
The invention is a catalyst system useful for polymerizing olefins. The catalyst system comprises an activator and an organometallic complex. The complex incorporates a Group 3 to 10 transition metal and a chelating bis(allyl) or bis(benzyl) dianionic ligand that is pi-bonded to the metal. The dianionic ligands are often easy to make, and they are readily incorporated into transition metal complexes. By modifying the structure of the chelating dianion, polyolefin makers can control catalyst activity, comonomer incorporation, and polymer properties.
DETAILED DESCRIPTION OF THE INVENTION
Catalyst systems of the invention include an organometallic complex that contains a Group 3-10 transition metal. “Transition metal” as used herein includes, in addition to the main transition group elements, elements of the lanthanide and actinide series. More preferred complexes include a Group 4 or a Group 8 to 10 transition metal.
The organometallic complex includes at least one chelating dianionic ligand. The ligand “chelates” with the transition metal by bonding to it with two separate allylic or benzylic bonds, each of which is a 4-pi electron donor. The ligand is “dianionic,” i.e., it has a net charge of −2; each of two electron pairs generated by deprotonation is conjugated with a carbon-carbon double bond.
Suitable chelating ligands include acyclic bis(allyl) and bis(benzyl) dianions. These are generally produced by deprotonating an acyclic diene having allylic and/or benzylic hydrogens. Proton removal generates a resonance-stabilized dianion. “Acyclic” means that the allylic or benzylic anions reside in an open chain of atoms. Preferred acyclic dienes contain two carbon-carbon double bonds that are separated by at least three carbons. Some exemplary acyclic dienes and corresponding dianions:
Preferred chelating ligands are bicyclic. “Bicyclic” means that the ligand contains two alicyclic rings that share two bridgehead atoms and from 0 to 3 bridging atoms. In a bicyclic structure, breaking any bond in the main carbon skeleton yields a monocyclic fragment.
The bicyclic dianionic ligands also generally derive from dienes. Each carbon-carbon double bond of the diene is attached to a non-bridgehead carbon that has at least one hydrogen atom attached to it. Proton removal generates a resonance-stabilized allylic or benzylic anion.
Preferred bicyclic dianions originate from a diene having a bicyclic framework of 8 to 15 atoms. The framework includes two bridgehead atoms, which are preferably carbons. The bridgehead atoms are connected to each other through two primary chains, which have x and y atoms, respectively. A bridge of z atoms joins the bridgehead atoms to complete the bicyclic system. Preferably, each of x and y is independently 3 to 5, and z is 0 to 3. The diene groups, which are present within the two longer atom chains, are separated by the bridgehead atoms. Either diene can be part of a benzo-fused system. Thus, the total number of atoms in the bicyclic framework is preferably x+y+z, plus 2 bridgehead atoms, or a maximum of 5+5+3+2=15.
The framework can be substituted with other atoms that do not interfere with formation of the allylic or benzylic dianion or incorporation of the dianion into a transition metal complex. Preferably, the framework is hydrocarbyl.
In an [x.y.0] system, there is no bridging group; the bridgehead atoms are bonded directly to each other. When a bridging group is present (i.e., when z is 1, 2, or 3), it is preferably O, S, NR, PR, SiR
2
, CR
2
, CR
2
CR
2
, CR═CR, 1,2-aryl, or CR
2
CR
2
CR
2
, in which each R is independently hydrogen or a C
1
-C
30
hydrocarbyl group.
The bicyclic framework is preferably fused together such that the hydrogens attached to the bridgehead carbons are “cis” to each other. Generally, an allylic or benzylic dianion produced by deprotonating a “trans”-fused bicyclic diene will lack the ability to chelate to a transition metal.
Preferred bicyclic dianionic ligands have the general structure:
wherein X represents a first chain of 3 to 5 atoms, Y represents a second chain of 3 to 5 atoms, Z represents an optional bridge of 0 to 3 atoms, and each Q is a bridgehead atom. Each of the X and Y chains includ
Nagy Sandor
Neal-Hawkins Karen L.
Schuchardt Jonathan L.
Equistar Chemicals LP
Nazario-Gonzalez Porfirio
Schuchardt Jonathan L.
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