Abstract: The invention generally relates to chain shuttling agents (CSAs), a process of preparing the CSAs, a composition comprising a CSA and a catalyst, a process of preparing the composition, a processes of preparing polyolefins, end functional polyolefins, and telechelic polyolefins with the composition, and the polyolefins, end functional polyolefins, and telechelic polyolefins prepared by the processes.

Abstract: The present invention provides a method for preparing a supported metallocene catalyst, a supported metallocene catalyst prepared by the method, and a method for preparing a polyolefin using the supported metallocene catalyst. The supported metallocene catalyst according to the present invention contains catalyst components uniformly distributed deep into the whole porous carrier particles to secure a high catalytic activity and facilitates polymerization of polyolefins with high bulk density.

Abstract: An imine phenol compound having Structure I: wherein O and N represent oxygen and nitrogen respectively; R comprises a halogen, a hydrocarbyl group, or a substituted hydrocarbyl group; R2 and R3 can each independently be hydrogen, a halogen, a hydrocarbyl group, or a substituted hydrocarbyl group; and Q is a donor group. A method comprising contacting a catalyst composition with a monomer under conditions suitable for the formation of a polymer wherein the catalyst composition comprises a metal salt complex of an imine (bis)phenolate compound, a solid oxide, and an optional metal alkyl and wherein the metal salt complex of an imine (bis)phenolate compound has Structure XIV where M is titanium, zirconium, or hafnium; OEt2 is ethoxide, R comprises a halogen, a hydrocarbyl group, or a substituted hydrocarbyl group; and R2 comprises hydrogen, a halogen, a hydrocarbyl group, or a substituted hydrocarbyl group.

Abstract: Modification of a unique supramolecular assembly of a pyridylphosphine ligand and a metal centered porphyrin complex is shown to give unprecedented selectivities to branched aldehydes via rhodium catalyzed hydroformylation of propylene and 1-octene. Use of magnesium in the porphyrin center provides the highest reported concentrations of iso-butyraldehyde and 2-methyl-octanal.

Abstract: A catalyst for NOx storage and reduction may include a carrier that contains alkali metal and Al, or alkali earth metal and Al, a NOx storage element of alkali metal, alkali earth metal or rare earth element, and one or more noble metals that are selected from the group consisting of Pt, Pd, Ru, Ag, Au and Rh. The catalyst for NOx storage and reduction shows excellent NOx storage and reduction capability, maintains excellent storage and reduction capability especially before and after deterioration and sulfation, and shows excellent catalytic activity under low temperature environment, while maintaining unusually high hydrophobicity.

Abstract: This invention relates to a process to make a multimodal polyolefin composition comprising: (i) contacting at least one first olefin monomer with a mixed catalyst system, under polymerization conditions, to produce at least a first polyolefin component having a Mw of 5,000 g/mol to 600,000 g/mol, wherein the mixed catalyst system comprises: (a) at least one polymerization catalyst comprising a Group 4 or Group 5 transition metal; (b) at least one organochromium polymerization catalyst; (c) an activator; and (d) a support material; (ii) thereafter, contacting the first polyolefin component/mixed catalyst system combination with a molecular switch; (iii) contacting the first polyolefin component/mixed catalyst system combination with at least one second olefin monomer, which may be the same or different, under polymerization conditions; and (iv) obtaining a multimodal polyolefin composition.

Abstract: The present invention relates to a novel metallocene compound, a catalyst composition comprising the same, and to olefinic polymers produced using the same. The metallocene compound according to the present invention and the catalyst composition comprising the same can be used when producing olefinic polymers, have outstanding copolymerization properties, and can produce olefinic polymers of high molecular weight. In particular, when the metallocene compound according to the present invention is employed, highly heat resistant block copolymers can be produced, and olefinic polymers can be produced which have a high melting point (Tm) even if the comonomer content is increased when producing the olefinic polymer.

Abstract: The present invention discloses catalyst compositions employing transition metal complexes with a thiolate ligand. Methods for making these transition metal complexes and for using such compounds in catalyst compositions for the polymerization of olefins also are provided.

Abstract: Process for supportation of a catalyst system comprising at least two different active catalyst components on a support wherein in an earlier supportation step a first active catalyst component is applied to the support at a first predetermined temperature and in a later supportation step a second active catalyst component is applied to the support at a temperature which is at least 20° C. lower than the first predetermined temperature.

Abstract: This invention describes a process for the preparation of a catalytic composition that can be used for oligomerization, codimerization, or polymerization of olefins. This invention also describes the catalytic composition that can be obtained by said process for the preparation and its use for oligomerization, codimerization, or polymerization of olefins.

Abstract: A polymerization catalyst composition for preparing cis 1,4-polydienes is provided. The catalyst composition comprises (a) a metal-containing compound, said metal being a transition metal or a lanthanide metal; (b) a carbene, (c) an alkylating agent, and optionally (d) a halogen-containing compound with the proviso that the halogen-containing compound must be present when none of the metal-containing compound and the alkylating agent contain a labile halogen atom. Also provided is a process for producing a polydiene comprising reacting a conjugated diene in the presence of the polymerization catalyst composition.

Abstract: This invention relates to a method to polymerize olefins comprising contacting olefins with a catalyst system comprising a transition metal catalyst compound and: 1) at least two NCA activators represented by the formula: Zd+ (Ad-), where Z is a Bronsted acid or a reducible Lewis acid, Ad- is a boron containing NCA, d is 1, 2, or 3, and where Z is a Bronsted acid and Z is a reducible Lewis acid in the first and second NCA activators, respectively; or 2) at least two NCA activators, one as described in Formula I and one not as described in Formula I; or 3) two NCA activators as described in Formula I except that the N in the second NCA in the ArNHal is at a different position in the nitrogen containing aromatic ring than the N in the first NCA.

Abstract: The present invention relates to a process for the preparation of linear low molecular weight alpha-olefins having 4 to 24 carbon atoms, comprising oligomerizing ethylene in an inert solvent in the presence of a catalyst system comprising: (i) zirconium carboxylate of the formula (R1COO)mZrCl4-m, wherein R1 is saturated or unsaturated aliphatic C1-C10 hydrocarbon or aromatic C6-C14 hydrocarbon and m fulfills 1?m?4, (ii) at least one aluminum compound selected from organoaluminum compounds of the formula R2nAlX3-n, wherein R2 is C1-C20 alkyl, X is chlorine, bromine or iodine, and n fulfills 1?n?2, and/or aluminoxanes, and (iii) at least two different additives selected from the group consisting of hydrogen, esters, ketones, ethers, amines, anhydrides, phosphines and sulfur compounds; as well as to a catalyst used therein.

Abstract: The present invention describes a method for hydrocracking and/or hydrotreating hydrocarbon-containing feeds using a catalyst comprising at least one hydro-dehydrogenizing metal selected from the group made up of group VIB and non-noble group VIII metals of the periodic table and a support comprising at least one zeolite having at least pore openings containing 12 oxygen atoms, modified by a) at least a stage of introducing at least one alkaline cation belonging to groups IA or IIA of the periodic table, b) a stage of treating said zeolite in the presence of at least one molecular compound containing at least one silicon atom, c) at least one stage of partial exchange of said alkaline cations by NH4+ cations in such a way that the proportion of alkaline cations remaining in the modified zeolite at the end of stage c) is such that the alkaline cation/aluminum molar ratio ranges between 0.2:1 and 0.01:1, and d) at least one thermal treatment stage.

Abstract: Catalysts comprising a halogenated Salan ligand. Also disclosed are catalyst systems comprising the catalyst and an activator; methods to prepare the ligands, catalysts and catalyst systems; processes to polymerize olefins using the catalysts and/or catalyst systems; and the olefin polymers prepared according to the processes.

Abstract: Catalysts comprising salan ligands with carbazole moieties. Also, catalyst systems comprising the catalyst and an activator; methods to prepare the ligands, catalysts and catalyst systems; processes to polymerize olefins using the catalysts and/or catalyst systems; and the olefin polymers prepared according to the processes.

Abstract: The present invention discloses a catalyst system based on a metallocene catalyst component and a new single site catalyst component for the production in a single reactor of improved polyolefins having a bimodal molecular weight distribution.

Abstract: The present invention provides polymerization processes utilizing an ansa-metallocene catalyst system for the production of olefin polymers. Polymers produced from the polymerization processes have properties that vary based upon the presence or the absence of hydrogen and/or comonomer in the polymerization process.

Abstract: The invention relates to a multinuclear metallocene catalyst of general formula (1); wherein Y and Y? are the same or different and independently selected from a C1-20 linear hydrocarbyl group; C1-20 branched hydrocarbyl group; C1-20 cyclic hydrocarbyl group; a C1-30 aryl group and a C1-30 substituted aryl group; L and L? are the same or different and each is an electron-donating group independently selected from the elements of Group 15 of the Periodic Table; Q and Q? are the same or different and independently selected from hydrogen, a C1-30 alkyl group and a C1-30 aryl group; M? is a metal selected from Group 3, 4, 5, 6, 7, 8, 9 and 10 elements and from lanthanide series elements of the Periodic Table; Z is selected from the group consisting of hydrogen; a halogen element; a C1-20 hydrocarbyl group; C1-20 alkoxy group and a C1-20 aryloxy group; B and B? are the same or different and each is a half sandwich metallocene compound, with B being represented by Formula 2 and B? being represented by Formula 3: W-

Abstract: A silicon-bridged Cp-Ar transition metal complex is provided that serves as a catalytic component capable of efficiently and highly selectively producing 1-hexene through the trimerization reaction of ethylene. The transition metal complex is represented by formula (1): wherein M1 represents a transition metal atom of Group 4 of the Periodic Table of the Elements; Ar1 is an aryl group represented by formula (2), Ar2 is an aryl group represented by formula (3) and Ar3 is an aryl group represented by formula (4) (not all of the three aryl groups Ar1, Ar2 and Ar3 are the same at the same time), Wherein each of the X and R groups represents hydrogen or the like.

Abstract: A silicon-bridged Cp-Ar transition metal complex serves as a catalytic component capable of efficiently and highly selectively producing 1-hexene through trimerization reaction of ethylene. The transition metal complex is represented by formula (1): wherein M represents a transition metal atom of Group 4 of the Periodic Table of the Elements; X1, X2, X3, R1, R2, R3, R4, R5, R6, R7, R8, and R9 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, and an aralkyloxy group having 7 to 20 carbon atoms, and wherein each of the groups may have a halogen atom as a substituent.

Abstract: The invention describes a process for the selective dimerization of ethylene to but-1-ene using a catalytic composition comprising at least one organometallic titanium complex, said organometallic complex containing at least one alkoxy type ligand functionalized by a heteroatom selected from nitrogen, oxygen, phosphorus, sulphur, arsenic and antimony or by an aromatic group.

Abstract: The present invention discloses catalyst compositions employing transition metal complexes with a thiolate ligand. Methods for making these transition metal complexes and for using such compounds in catalyst compositions for the polymerization of olefins also are provided.

Abstract: A metallocene compound is represented by the following formula, (4HInd)(Cp?)MX2 wherein 4HInd is a group having tetrahydroindenyl nucleus, Cp? is a group having cyclopentadienyl nucleus, and 4HInd and Cp? are unsubstituted/substituted by one or more substituents of radicals from group of an alkyl, alkoxy, alkylsilyl, alkylsiloxy, alkylamino or haloalkyl group of 1 to 20 carbon atoms, a cycloalkyl group of 3 to 20 carbon atoms, an aryl, arylalkyl, arylsilyl, alkylaryl or aryloxy group of 6 to 20 carbon atoms, a dialkylamino group of 2 to 20 carbon atoms, a halogen atom, and an amino group, and M is a Group IV, V or VI transition metal, and X is radical from the group of a halogen atom, an alkyl or alkoxy group of 1 to 20 carbon atoms, an alkenyl group of 2 to 20 carbon atoms, aryl, alkylaryl, arylalkyl, aryloxy group of 6 to 20 carbon atoms.

Abstract: The present invention generally relates to a process that selectively polymerizes ethylene in the presence of an alpha-olefin, and to a metal-ligand complex (precatalyst) and catalyst useful in such processes, and to related compositions. The present invention also generally relates to ligands and intermediates useful for preparing the metal-ligand complex and to processes of their preparation.

Abstract: This invention relates to a Salen type ligand including three or more quaternary ammonium salts of nitrate anions, to a trivalent metal complex compound prepared from this ligand and a method of preparing the same, to a method of preparing polycarbonate by copolymerizing an epoxide compound and carbon dioxide using the complex compound as a catalyst, and to a method of separating and collecting the catalyst from the copolymer after copolymerization. This catalyst used to copolymerize an epoxide compound and carbon dioxide can be more simply prepared, and has lower catalyst preparation and recovery costs, and higher activity, compared to conventional catalysts.

Abstract: A catalyst for a polymerization of norbornene monomers includes a transition metal complex represented by a formula (1). A method for producing a norbornene copolymer includes copolymerizing first norbornene monomers corresponding to a first monomer unit represented by a formula (2) and second norbornene monomers corresponding to a second monomer unit represented by a formula (3) in a presence of the catalyst. The transition metal complex is preferably (?-allyl) {2-[N-(2,6-diisopropylphenyl) iminomethyl]phenolate}palladium, (?-allyl) {2-[N-(2,6-diisopropylphenyl)iminomethyl]-4-fluorophenolate}palladium, (?-allyl)[2-(N-phenyliminomethyl) phenolate]palladium or (?-allyl){2-[N-(2,6-diisopropylphenyl) iminomethyl]-6-methylphenolate}palladium.

Abstract: The present invention is directed to a process for the production of high density polyethylene by polymerisation of ethylene in the presence of a supported chromium oxide based catalyst which is modified with an organic compound comprising oxygen and a nitrogen atom which is selected from the group consisting of saturated heterocyclic organic compounds with a five or six membered ring, amino esters and amino alcohols. Such organic compounds allow manufacturing of HDPE with increases molecular weight distribution and increased molecular weight.

Abstract: Olefin polymerization catalyst systems including a high molecular weight catalyst compound and a low molecular weight catalyst compound, and methods of making same are provided. High molecular weight catalysts include metallocene catalysts and low molecular weight catalysts include non-metallocene compounds including biphenyl phenol compounds. Generally catalyst systems may include less than about 5.0 mol % of the high molecular weight catalyst compound relative to said low molecular weight catalyst. Methods for olefin polymerization including the aforementioned catalyst systems, and polyolefins and products made therefrom.

Abstract: A solid catalyst component for the (co)polymerization of ?-olefins having general formula (I): ZrnMAlxClMgp (I) wherein: M represents titanium (Ti), vanadium (V), or mixtures thereof; n is a number ranging from 0.01 to 2; x is a number ranging from 0.1 to 4; y is a number ranging from 5 to 53; p is a number ranging from 0 to 15; obtained by means of a process comprising putting at least one zirconium arene in contact with at least one metal compound and, optionally, with at least one compound of magnesium. Said solid catalyst component can be advantageously used as a solid component in a catalyst for the (co)polymerization of ?-olefins. Said catalyst can be advantageously used in a process for the (co)polymerization of ?-olefins.

Abstract: Compositions useful for activating catalysts for olefin polymerization, and methods for making same, are provided. Such compositions can be derived from at least: an organoaluminum compound, a carrier, an oxygen source, and, optionally, a Lewis base.

Abstract: The present invention describes a method of preparing a catalytic composition used for oligomerization, co-dimerization or polymerization of olefins, wherein the compound obtained upon contacting at least one iron compound with at least one nitrogen-containing compound is subjected to an oxidation stage prior to being mixed with an activating agent and optionally with a solvent. The present invention also describes the catalytic composition obtained by means of said preparation method and the use thereof for oligomerization, co-dimerization or polymerization of olefins.

Abstract: A complex containing a ligand of formula (I): useful in the formation of olefin polymerization catalysts and their use in olefin polymerization.

Abstract: Method employing a supported metallocene catalyst composition in the production of an isotactic ethylene propylene co-polymer. The composition comprises a metallocene component supported on a particulate silica support having average particle size of 10-40 microns, a pore volume of 1.3-1.6 ml/g, a surface area of 200-400 m2/g. An alkylalumoxane cocatalyst component is incorporated on the support. The isospecific metallocene is characterized by the formula: B(CpRaRb)(FlR?2)MQn??(1) or by the formula: B?(Cp?R?aR?b)(Fl?)M?Q?n???(2) In the formulas Cp and Cp? are substituted cyclopentadienyl groups, Fl and Fl? are fluorenyl groups, and B and B? are structural bridges. R? are substituents at the 2 and 7 positions, Ra and R?a are substituents distal to the bridge, and Rb and R?b are proximal to the bridge. M and M? are transition metals, Q? is a halogen or a C1-C4 alkyl group; and n? is an integer of from 0-4.

Abstract: A solid catalyst component for olefin polymerization in which the molar ratio of residual alkoxy groups to supported titanium is 0.60 or less is obtained by reacting the following compound (a1) with the following compound (b1) at a hydroxyl group/magnesium molar ratio of 1.0 or more, reacting the reaction mixture with the following compound (c1) at a halogen/magnesium molar ratio of 0.20 or more, reacting the resultant reaction mixture with the following compounds (d1) and (e) at a temperature of 120° C. or higher but 150° C.

Abstract: The present invention relates to a preparation method of a metallocene catalyst. More particularly, the present invention relates to a preparation method of a supported hybrid metallocene catalyst, including the steps of treating a support having a water content of 4 to 7% by weight with trialkyl aluminum at a predetermined temperature; supporting alkyl aluminoxane on the support; and supporting a metallocene compound on the alkyl aluminoxane-supported support. According to the present invention, it is possible to prepare a supported hybrid metallocene catalyst which shows a high activity in the polymerization of olefins and enables the preparation of polyolefins having a high bulk density, by a simple process.

Abstract: Supported catalyst system for the polymerization of olefins, having at least two different monocyclopentadienyl transition metal compounds, one or more activators including an ionic compound having (i) a cation and (ii) an anion having up to 100 non-hydrogen atoms and the anion containing at least one substituent comprising a moiety having an active hydrogen, and one or more support materials. The supported “mixed or dual site” catalyst systems having different monocyclopentadienyl catalysts when activated by specific ionic activators lead to catalyst systems showing an improved balance of properties which may be used to prepare LLDPE polymers having broad melt flow ratios.

Abstract: A process for removing metal species from a composition comprising contacting: a. an oligomer mixture stream comprising the monomers of a partially aromatic polyester polymer and at least one metal species, or b. a molten polyester polymer stream comprising partially aromatic polyester polymers and at least one metal species, with a non-catalytic porous material in the presence of hydrogen to produce a treated stream containing a reduced amount of at least one metal species. There are provided compositions comprising a partially aromatic polyester polymer having an It.V. of at least 0.50 produced in a direct esterification melt phase process, from greater than 0 to less than 50 ppm antimony, and less than 40 ppm cobalt, or produced in an ester exchange melt phase process, having from greater than zero to less than 5 ppm titanium and less than 10 ppm manganese.

Abstract: The present invention relates to a process for preparing an activating support for metallocene complexes in the polymerization of olefins comprising the steps of: I) providing a support consisting in particles formed from at least one porous mineral oxide; II) optionally fixing the rate of silanols on the surface of the support; III) functionalizing the support with a solution containing a metallic salt; IV) heating the functionalized support of step c) under an inert gas or hydrogen; V) oxidizing the support of step IV by treatment under N2O and then under oxygen; VI) retrieving an active support having a controlled number of OH groups. That activating support is used to activate a metallocene catalyst component for the polymerization of olefins.

Abstract: Trianionic ligand precursor compounds, catalyst systems containing the precursor compounds, and uses of the precursor compounds are described. The present invention also provides constrained geometry catalysts, methods to make the constrained geometry catalysts and methods to use the constrained geometry catalysts in various reaction systems, including polymerization, metathesis reactions, and hydroamination reactions.

Abstract: The present invention provides polymerization catalyst compositions employing novel dinuclear metallocene compounds. Methods for making these new dinuclear metallocene compounds and for using such compounds in catalyst compositions for the polymerization and copolymerization of olefins are also provided.

Abstract: The present invention relates to a supported catalyst for olefin polymerization to which a novel transition metal compound and a co-catalyst compound are bound, and a preparation method for polyolefin using the supported catalyst. The transition metal compound bound to the catalyst of the present invention provides high activity for olefin-based monomers in heterogeneous reaction as well as in homogeneous system. Particularly, a polyolefin with higher molecular weight can be prepared by using the supported catalyst containing the transition metal compound bound to a support, rather than using the novel transition metal compound in a non-supported status, or the conventional transition metal compound in a supported or non-supported status.

Abstract: Certain metallocene compounds are provided that, when used as a component in a supported polymerization catalyst under industrially relevant polymerization conditions, afford high molar mass homo polymers or copolymers like polypropylene or propylene/ethylene copolymers without the need for any ?-branched substituent in either of the two available 2-positions of the indenyl ligands. The substituent in the 2-position of one indenyl ligand can be any radical comprising hydrogen, methyl, or any other C2-C40 hydrocarbon which is not branched in the ?-position, and the substituent in the 2-position of the other indenyl ligand can be any C4-C40 hydrocarbon radical with the proviso that this hydrocarbon radical is branched in the ?-position. This metallocene topology affords high melting point, very high molar mass homo polypropylene and very high molar mass propylene-based copolymers. The activity/productivity levels of catalysts including the metallocenes of the present invention are exceptionally high.

Abstract: The present invention relates to the field of single site catalyst systems based on pyrrol-iminophenol, pyrrol-iminoalcohol or pyrrol-iminoamine complexes and suitable for oligomerising or homo- or co-polymerising ethylene and alpha-olefins.

Abstract: A solid catalyst component comprising Ti, Mg, halogen and a couple of monofunctional electron donor compounds MD1 and MD2 selected from esters and ethers, said donors being present in amounts such that the molar ratio MD1/MD2 ranges from 20 to 800. The so obtained catalyst component when converted into a catalyst is able to produce ethylene polymers with good morphological properties even under drastic polymerization conditions.

Abstract: Catalyst composition for the oligomerization of ethylene, comprising (i) an at least partially hydrolyzed transition metal compound, obtainable by controlled addition of water to a transition metal compound having the general formula MXm(OR?)4-m or MXm(OOCR?)4-m, wherein R? is an alkyl, alkenyl, aryl, aralkyl or cycloalkyl group, X is halogen, preferably Cl or Br, and m is from 0 to 4; preferably 0-3; and (ii) an organoaluminum compound as a cocatalyst, wherein the molar ratio of water and transition metal compound is within a range of between about (0.01-3):1; a process for oligomerization of ethylene and a method for preparing the catalyst composition.

Abstract: The present invention relates to a polypropylene composition comprising a propylene homopolymer or a propylene random copolymer having at least one comonomer selected from alpha-olefins with 2 or 4-8 carbon atoms and a comonomer content of not more than 8.0 wt %, wherein the propylene homo- or copolymer is polymerized in the presence of a Ziegler-Natta catalyst, and the polypropylene composition has a MWD of 2.0 to 6.0 and an MFR (2.16 kg/230° C.) of 4.0 g/10 min to 20.0 g/10 min, characterized in that the polypropylene composition has not been subjected to a vis-breaking step, the use of the inventive polypropylene composition for the production of a film and/or injection molded articles, a process for preparing a film wherein the inventive polypropylene composition is formed into a film, and wherein the polypropylene composition has not been subjected to a vis-breaking step and a film comprising the inventive polypropylene composition.

Abstract: Among other things, this disclosure provides an olefin oligomerization system and process, the system comprising: a) a transition metal compound; b) a pyrrole compound having a hydrogen atom on at the 5-position or the 2- and 5-position of a pyrrole compound and having a bulky substituent located on each carbon atom adjacent to the carbon atom bearing a hydrogen atom at the 5-position or the 2- and 5-position of a pyrrole compound. These catalyst system have significantly improved productivities, selectivities to 1-hexene, and provides higher purity 1-hexene within the C6 fraction than catalyst systems using 2,4-dimethyl pyrrole.

Abstract: Novel group 4 organometallic compounds, supported on anions by means of at least one covalent metal-oxygen bond, are obtained by reaction of at least one borate or aluminum comprising at least one hydroxy group with at least one group 4 transition metal compound. These compounds are used in a catalytic composition implemented in an olefin oligomerization or polymerization method.

Abstract: The present invention relates to non-symmetrical organometallic transition metal compounds of the compound of the formula (I) where R8 and R9 are identical or different and each an substituted or unsubstituted organic radical having from 1 to 40 carbon atoms, catalyst systems comprising at least one of the organometallic transition metal compounds of the present invention and a process for preparing polyolefins by polymerization or copolymerization of at least one olefin in the presence of one of the catalyst systems of the present invention.