Abstract: The present invention relates to a process of preparing a double metal cyanide (DMC) complex catalyst with an improved catalytic activity useful for epoxide polymerization. It also relates to the DMC catalyst obtainable by said process, as well as to polyether polyols prepared by a polymerization reaction using said DMC catalyst.

Abstract: The present disclosure provides compositions for alkyne metathesis catalysts and methods for preparing enediynes and alkyne metathesis catalysts. The disclosure also provides methods for catalyzing alkyne metathesis reactions and polymerization of enediyne substrates to polydiacetylenes in solution-phase.

Abstract: This invention relates to a novel group 2, 3 or 4 transition metal metallocene catalyst compound having two indenyl ligands with identical substitution including, for example, cyclopropyl groups and substituted phenyl groups at the 2 and 4 positions of the catalyst, respectively, where the substituents are at the 3? and 5? positions of the phenyl groups.

Abstract: A composition is capable of curing via condensation reaction. The composition uses a new condensation reaction catalyst. The new condensation reaction catalyst is used to replace conventional tin catalysts. The composition can react to form a gum, gel, rubber, or resin.

Abstract: The present invention concerns the synthesis of dry powdered manganese complexes using spray-drying or freeze-drying methods.

Abstract: The invention relates to a process for the synthesis of spheroidal magnesium alkoxide having improved mechanical strength and narrow particle size distribution, the process comprising reacting magnesium metal, in the presence of iodine, with a mixture of alcohols by step-wise heating first in the range of 40° C. to 65° C. for a period of 2 hours and then in the range of 65° C. to 80° C. for a period of 1 hour, further by maintaining reaction temperature at 80° C. for a period of 6-10 hours, the vapors of the mixture produced during the reaction being condensed in an overhead condenser, hydrogen gas produced during the reaction being vented off and the mixture of alcohols left after the reaction being filtered and reused. The invention also relates to spheroidal magnesium alkoxide particles synthesized by the method, to the Ziegler natta procatalyst synthesized by using the alkoxide and to the polymer resin synthesized using the procatalyst.

Abstract: The invention provides: a polycondensation catalyst for polyester production, which contains titanium atoms, alkaline earth metal atoms and phosphorus atoms, has high reactivity and excellent long-term storage stability, can be easily produced industrially, and has an advantage in cost; a polyester resin obtained with the catalyst; and a molded article. These are: a polymerization catalyst for polyester production containing titanium atoms, alkaline earth metal atoms and phosphorus atoms and having a specific constitution; a polyester resin obtained with the catalyst; and a molded article.

Abstract: Organometallic compounds of the general formula (I), in which M=Mo, W, are claimed.

Abstract: A catalyst composition is provided, which may be used for ring closing metathesis. In the composition, a catalyst is immobilized on a siliceous mesocellular foam support. A suitable catalyst for use in the composition is a Grubbs-type catalyst or a Hoveyda-Grubbs-type catalyst.

Abstract: The present invention provides a catalyst composition and a method for producing an olefin polymer using the catalyst composition. The catalyst composition is prepared by bringing (A) a transition metal compound, (B) a solid boron compound capable of forming an ion pair with the component (A), (C) an organometallic compound and (D) a compound represented by the following general formula (XIV) and/or the following general formula (XV) into contact with each other in a hydrocarbon solvent, and enables a high catalyst concentration. Z5R14R15??(XIV) Z6R14R15R16??(XV) [In the formulae, Z5 represents an oxygen atom, etc.; Z6 represents a nitrogen atom, etc.; R14 to R16 each independently represent an organic group, and at least one of those organic groups is an organic group having at least 3 carbon atoms, and R14 to R16 may bond to each other to form a ring.

Abstract: The present invention provides polymerization catalyst compositions employing half-metallocene compounds with a heteroatom-containing ligand bound to the transition metal. Methods for making these hybrid metallocene compounds and for using such compounds in catalyst compositions for the polymerization of olefins also are provided.

Abstract: Provided are a solid titanium catalyst component for ethylene polymerization which can polymerize ethylene at a high activity and which can provide an ethylene polymer having an excellent particle property, an ethylene polymerization catalyst and an ethylene polymerization method in which the catalyst is used. The solid titanium catalyst component (I) for ethylene polymerization according to the present invention is obtained by bringing a liquid magnesium compound (A) including a magnesium compound, an electron donor (a) having 1 to 5 carbon atoms and an electron donor (b) having 6 to 30 carbon atoms into contact with a liquid titanium compound (C) under the presence of an electron donor (B) and includes titanium, magnesium and a halogen. The ethylene polymerization catalyst of the present invention includes the component (I) and an organic metal compound catalyst component (II).

Abstract: A low cost, viable and modular method to prepare new, highly selective catalytic materials, especially “catalytic membranes”, is described. A method for the engineering and use of various types of reactors based on these catalytic membranes, even in a one-pot procedure, is also disclosed. The catalytic membranes are versatile, in terms of variety of chemical reactions promoted, and can be easily reused with negligible catalysts leaching. They are particularly useful, but not limited to, the asymmetric hydrogenation of substituted ?,? unsaturated acids or esters.

Abstract: Process for the preparation of an unsupported, heterogeneous olefin polymerization catalyst system, comprising an organometallic compound of a transition metal of Group 3 to 10 of the Periodic Table (IUPAC 2007) in the form of solid particles comprising the steps of a) preparing a solution (A) comprising ai) an organometallic compound of a transition metal of Group 3 to 10 of the Periodic Table (IUPAC 2007) or of an actinide or lanthanide, a2) a cocatalyst comprising an element of group 13 of the Periodic Table (IUPAC 2007) and a3) a solvent (A-1), b) preparing a liquid/liquid emulsion system by dispersing the solution (A) in a solvent (B) essentially immiscible with said solution (A) in the presence of a polystyrene-b-fluoro polystyrene copolymer of the formula (I) in which n is a number from 10 to 100, m is a number from 1 to 40, x is a number from 5 to 16, y is a number from 11 to 33, provided that m, n, x and y are selected in a way that the block copolymer is soluble in the solvent B or the solution A in

Abstract: A polymerization catalyst system and polymerization processes using the catalyst systems are disclosed. The polymerization catalyst systems may include a) a first catalyst compound, and b) a second catalyst compound, wherein the first catalyst compound comprises a biphenyl phenol compound having essentially no hydrogen response.

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: This invention relates to a transition metal catalyst compound represented by the structure: wherein M is hafnium or zirconium; each X is, independently, selected from the group consisting of hydrocarbyl radicals having from 1 to 20 carbon atoms, hydrides, amides, alkoxides, sulfides, phosphides, halogens, dienes, amines, phosphines, ethers, or a combination thereof; each R1 and R3 are, independently, a C1 to C8 alkyl group; and each R2, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, and R14 are, independently, hydrogen, or a substituted or unsubstituted hydrocarbyl group having from 1 to 8 carbon atoms, provided however that at least three of the R10-R14 groups are not hydrogen, compositions thereof and methods of use thereof to prepare polymers.

Abstract: This invention relates to a homogenous process for making a vinyl terminated propylene polymer, wherein the process comprises: contacting, propylene, under polymerization conditions, with a catalyst system comprising an activator and at least one metallocene compound, where the metallocene compound is represented by the formula: where: M is hafnium or zirconium; each X is, independently, selected from the group consisting of hydrocarbyl radicals having from 1 to 20 carbon atoms, hydrides, amides, alkoxides, sulfides, phosphides, halides, dienes, amines, phosphines, ethers, and a combination thereof, (two X's may form a part of a fused ring or a ring system); each R1 is, independently, a C1 to C10 alkyl group; each R2 is, independently, a C1 to C10 alkyl group; each R3 is, independently, hydrogen; each R4, R5, and R6, is, independently, hydrogen or a substituted or unsubstituted hydrocarbyl group, a heteroatom or heteroatom containing group; T is a bridging group; each R7 is, independently, hydrogen, halog

Abstract: Disclosed is transition metal complex that serves as a catalytic component with which 1-hexene can be produced efficiently with excellent selectivity, even under high temperature conditions, by means of an ethylene trimerization reaction. Also disclosed is a method for economically preparing a butyl-branched ethylene polymer, even under high temperature conditions, by using said transition metal complex as an ethylene trimerization catalyst, and polymerizing ethylene in the presence of an olefin polymerization catalyst that is obtained by bringing an olefin copolymerization catalyst and an activating co-catalytic component into contact with one another. Said transition metal complex is represented by the following general formula (1), wherein M1 represents a Group 4 transition metal atom, and R1 through R11 and X1 through X3 each independently represent a hydrogen atom, a halogen atom, or a specific organic group.

Abstract: A coordination polymer includes a plurality of metal atoms or metal clusters linked together by a plurality of organic linking ligands. Each linking ligand comprises a residue of a negatively charged polydentate ligand. Characteristically, the plurality of multidentate ligands include a first linking ligand having first hydrocarbon backbone and a second ligand having a second hydrocarbon backbone. The first hydrocarbon backbone is different than the second hydrocarbon backbone.

Abstract: The present invention relates to a composition including a dialkyl tin oxide, such as DBTO, which can be used as a transesterification catalyst for the synthesis of (meth)acrylic esters. The invention also relates to a method for the synthesis of (meth)acrylic esters by transesterification in the presence of said composition.

Abstract: La present invention relates to a multi-component catalytic system that can be used for the cis-1,4 stereospecific polymerization of conjugated dienes. The system is based on: (i) a rare-earth complex of Formula (II) Ln(A)3(B)n, Ln being a rare-earth metal, A a ligand, B a Lewis base or a solvent molecule and n a number from 0 to 3; (ii) an alkylating agent; (iii) a compound based on an aromatic ring and having at least two heteroatoms chosen from the elements O, N, S, P, and corresponding to the Formula (III): in which the R groups each denote hydrogen, an alkyl radical optionally comprising one or more heteroatoms (N, O, P, S, Si) or one or more halogen atoms, a halogen atom, a group based on one or more heteroatoms (N, O, P, S, Si); x and y are integers from 0 to 6; D is a group having a chemical function, one of the atoms of which has a non-bonding pair; L being an atom from column 1 of the Periodic Table.

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 copolymerisation 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 disclosure provides for a process and polymerization system to produce isoolefin polymers (72) utilizing polymorphogenates (16, 26) in the catalyst system to control polydispersity (MWD). The disclosure also provides a catalyst system (20) comprising a plurality of active catalyst complex species (34) formed by combination of a Lewis acid (24), an initiator (22) and a polymorphogenate (26), as well as polymers made using the catalyst system or process. The polymorphogenate (16, 26) can promote or mimic the formation of different active catalyst complex species (34) having different polymerization rates, i.e. different rates of propagation, chain transfer, or termination, as observed by different polydispersities resulting from the presence of relatively different proportions of the polymorphogenate.

Abstract: The present invention relates to a binuclear metallocene compound having a new structure that is able to offer various selectivities and activities for copolymers, a preparation method thereof, and a method for preparing a polyolefin using the binuclear metallocene compound.

Abstract: The present invention provides a novel catalyst composition comprising a metallocene complex, and a novel producing method for various polymer compounds. Preferably, the invention provides a novel polymer compound, and a producing method thereof. Specifically, the invention provides a polymerization catalyst composition, comprising: (1) a metallocene complex represented by the general formula (I), including: a central metal M which is a group III metal atom or a lanthanoid metal atom; a ligand Cp* bound to the central metal and including a substituted or unsubstituted cyclopentadienyl derivative; monoanionic ligands Q1 and Q2; and w neutral Lewis base L; and (2) an ionic compound composed of a non-ligand anion and a cation: where w represents an integer of 0 to 3.

Abstract: A catalyst component comprising Ti, Mg, Al, Cl, and optionally ORI groups in which RI is a C1-C20 hydrocarbon group, optionally containing heteroatoms, up to an amount such as to give a molar ORI/Ti ratio lower than 0.5, characterized by the fact that substantially all the titanium atoms are in valence state of 4, that the porosity (PF), measured by the mercury method and due to pores with radius equal to or lower than 1 ?m, is at least 0.3 cm3/g, and by the fact that the Cl/Ti molar ratio is lower than 29. The said catalysts are characterized by high morphological stability under the low molecular weight ethylene polymerization conditions while at the same time maintaining characteristics of high activity.

Abstract: A catalyst system obtainable by the process comprising the steps of contacting an adduct of formula (I) MgT2.yAlQj(OR?)3-j??(I) wherein T is chlorine, bromine, or iodine; R? is a linear or branched C1-C10 alkyl radical; y ranges from 1.00 to 0.05; and j ranges from 0.01 to 3.00; with at least one metallocene compound having titanium as central metal and at least one ligand having a cyclopentadienyl skeleton.

Abstract: The invention provides: a polycondensation catalyst for polyester production, which contains titanium atoms, alkaline earth metal atoms and phosphorus atoms, has high reactivity and excellent long-term storage stability, can be easily produced industrially, and has an advantage in cost; a polyester resin obtained with the catalyst; and a molded article. These are: a polymerization catalyst for polyester production containing titanium atoms, alkaline earth metal atoms and phosphorus atoms and having a specific constitution; a polyester resin obtained with the catalyst; and a molded article.

Abstract: The invention relates to a liquid catalyst solution containing a polycondensation catalyst for polyester production, which contains titanium atoms, alkaline earth metal atoms and phosphorus atoms, has high reactivity and excellent long-term storage stability, can be easily produced industrially, and has an advantage in cost.

Abstract: A catalyst component for the polymerization of olefins comprises Mg, Ti, halogen, and an alpha-omega-diether represented by the general formula: (RO)—(CR1R2)n—(OR), wherein the number of n is from 5 to 10, R is an alkyl, cycloalkyl or aryl radical containing 1 to 12 carbons, and R1 and R2 are independently from each other hydrogen, an alkyl, cycloalkyl or aryl radical containing 1 to 12 carbons. The catalysts prepared with such component provide a high mileage for the production of polyolefins with a high bulk density of the polymer produced in gas-phase polymerization process or in slurry polymerization process. Such catalyst produces narrower MWD PE, if compared with other catalyst systems.

Abstract: Disclosed are solid titanium catalyst components, catalyst systems containing solid titanium catalyst components, and methods of making solid titanium catalyst components. The solid titanium catalyst components contain an internal electron donor compound containing at least one ether group and at least one ketone group. The catalyst system can contain a solid titanium catalyst component, an organoaluminum compound, and an organosilicon compound. Also disclosed are methods of polymerizing or copolymerizing an alpha-olefin. The methods involve contacting an olefin with a catalyst system containing the solid titanium catalyst component.

Abstract: Provided are transition metal catalytic systems for preparing ethylene homopolymers or copolymers of ethylene with ?-olefins. More specifically, provided are Group 4 transition metal catalysts, which is characterized in that the Group 4 transition metal catalyst comprises around the Group 4 transition metal a cyclopentadiene derivative, and at least one naphthoxide ligand(s) having aryl substituent(s) that function(s) as an electron donor and serve(s) to stabilize the catalyst system by surrounding an oxygen atom that links the ligand to the transition metal at 2-position, and there is no cross-linkage between the ligands; catalytic systems comprising such transition metal catalyst and aluminoxane cocatalyst or boron compound cocatalyst; and processes for preparing ethylene homopolymers or copolymers of ethylene with ?-olefins by using the same.

Abstract: A solid, hydrocarbon-insoluble, catalyst component useful in polymerizing olefins, said catalyst component containing magnesium, titanium, and halogen, and further containing an internal electron donor having a structure: [R1—O—C(O)—O—]xR2 wherein R1 is independently at each occurrence, an aliphatic or aromatic hydrocarbon, or substituted hydrocarbon group containing from 1 to 20 carbon atoms; x is 2-4; and R2 is an aliphatic or aromatic hydrocarbon, or substituted hydrocarbon group containing from 1 to 20 carbon atoms, provided that there are 2 atoms in the shortest chain connecting a first R1—O—C(O)—O— group and a second R1—O—C(O)—O— group.

Abstract: A production process of a polymerization catalyst of an alkylene oxide, comprising a step of contacting an alumoxane compound with a compound having a hydroxyl group; a production process of a pre-polymerized polymerization catalyst thereof, comprising a step of pre-polymerizing an alkylene oxide in the presence of the above polymerization catalyst; and a production process of a poly(alkylene oxide), comprising a step of polymerizing an alkylene oxide in the presence of the above polymerization catalyst or pre-polymerized polymerization catalyst.

Abstract: The disclosure provides for a process and polymerization system to produce isoolefin polymers (72) utilizing polymorphogenates (16, 26) in the catalyst system to control polydispersity (MWD). The disclosure also provides a catalyst system (20) comprising a plurality of active catalyst complex species (34) formed by combination of a Lewis acid (24), an initiator (22) and a polymorphogenate (26), as well as polymers made using the catalyst system or process. The polymorphogenate (16, 26) can promote or mimic the formation of different active catalyst complex species (34) having different polymerization rates, i.e. different rates of propagation, chain transfer, or termination, as observed by different polydispersities resulting from the presence of relatively different proportions of the polymorphogenate.

Abstract: This invention relates to Group 4 catalyst compounds containing di-anionic tridentate nitrogen/oxygen based ligands. The catalyst compounds are useful, with or without activators, to polymerize olefins, particularly a-olefins, or other unsaturated monomers. Systems and processes to oligomerize and/or polymerize one or more unsaturated monomers using the catalyst compound, as well as the oligomers and/or polymers produced therefrom are also provided.

Abstract: Compositions useful for activating catalysts for olefin polymerization are-provided. The compositions are derived from at least: a) compound derived from at least (i) carrier having at least one pair of hydrogen bonded hydroxyl groups, (ii) organoaluminum compound, and (iii) Lewis base, such that each of a majority of aluminum atoms in the organoaluminum compound forms chemical bonds with at least two oxygen atoms from the at least one pair of hydrogen bonded hydroxyl groups; and b) Bronsted acid, wherein the molar ratio of the Bronsted acid to the organoaluminum compound is less than or equal to about 2:1.

Abstract: The present invention relates to a process for the polymerization of olefins, comprising the steps of introducing at least one olefin, at least one polymerization catalyst, at least one cocatalyst and at least one cocatalyst aid, and optionally a scavenger, into a polymerization reactor, and polymerizing the olefin, wherein the cocatalyst aid is a reaction product prepared separately prior to the introduction into the reactor by reacting at least one metal alkyl compound of group IIA or IIIA of the periodic system of elements and at least one compound (A) of the formula RmXR?n, wherein R is a branched, straight, or cyclic, substituted or unsubstituted, hydrocarbon group having 1 to 30 carbon atoms, R? is hydrogen or any functional group with at least one active hydrogen, X is at least one heteroatom selected from the group of O, N, P or S or a combination thereof, and wherein n and m are each at least 1 and are such that the formula has no net charge.

Abstract: This invention relates to an organotin-based catalyst system for polyurethane synthesis that is useful in coatings applications. The catalyst has low activity in the absence of oxygen. When a coating mixture comprising the catalyst is sprayed and/or applied to a substrate as a thin film in air, the catalyst is activated. For solvent-based refinish systems comprising hydroxyl and isocyanate species at high solids levels, the catalyst system therefore provides extended viscosity stability, i.e., pot life.

Abstract: A composition useful for activating catalysts for olefin polymerization Is provided. The composition is derived from at least: carrier; treated organoaluminoxy compound: and ionic compound having at feast one active proton.

Abstract: The present invention provides a catalyst complex or ligand, and compositions thereof, for use in a variety of organic reactions having high reactivity and enantioselectivity. The catalyst is a N-heterocyclic carbene having three fused rings with first and second rings being six-membered rings and the third being a five-membered ring. The first ring is fused to the second and has four substituents. The second ring has two nitrogens flanking a carbene atom with one nitrogen bound to a substituent. The carbene atom may optionally be bonded to a metal. The third ring is fused to the second ring and contains two nitrogens. The third ring of the catalyst has a double bond and two substituents on adjacent non-fused carbons. A non-fused nitrogen of the third ring is partially bonded to another substituent. Methods for the synthesis and use of the catalyst embodiments of the present invention are also provided.

Abstract: A composition useful for activating catalysts for olefin polymerization is provided. The composition is derived from at least: carrier; organoaluminoxy compound; N,N-dimethylaniline and pentaflurophenol in amounts such that them are at least two equivalents of pentafluorophenol per equivalent of the N,N-dimethylaniline.

Abstract: The invention relates to soluble metal oxides and mixed metal oxides and to solutions comprising metal oxides and mixed metal oxides. The invention further relates to a process for preparing a soluble metal oxide and a soluble mixed metal oxide and additionally relates to a process for modifying the solubility of a soluble metal oxide. The metal oxides, mixed metal oxides and solutions thereof have a number of applications and in particular are suitable for use as catalysts and also as precursors for the formation of metal films.

Abstract: A rare earth metal complex represented by the formula (1): in which A represents a Group 14 element of the periodic table, Cp represents a group having a substituted or unsubstituted cyclopentadienyl anion moiety, Ln represents a Group 3 metal atom or a lanthanoid metal atom, R1 to R6 are the same or different, and represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, a silyl group substituted with a hydrocarbon group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, R7 represents an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, Xs represent a monoanionic ligand, Ys represent a neutral ligand, m represents an integer of 1 to 3, and n represents an integer of 0 to 3. The rare earth metal complex is useful as, for example, a catalyst for polymerization reaction of olefins.

Abstract: Catalyst compositions are disclosed exhibiting activity for dehydrating an alcohol, the composition comprising a source of a Group VIII transition metal, an organic salt, an acid and/or a compound consisting of a conjugate base of an acid bonded to a radical of the alcohol to be dehydrated and, optionally, a ligand. Also disclosed are methods of converting an alcohol into a product using the catalyst composition. The product of the methods may be predominately alkene or ether depending on the method. In some embodiments of the method a second catalyst for converting a product into a further product may be present.

Abstract: Processes are provided for producing activators, wherein the processes comprise use of borane compositions that are at least 95 mol % pure and trialkylsilyl halides such as R2R3R4SiX2, where R2 is ethyl (Et), isopropyl (iPr), or phenyl (Ph), R3 is methyl (Me), ethyl (Et), or phenyl (Ph), and R4 is methyl (Me) or ethyl (Et), Si is silicon, and X is a suitable halide, such as Cl (chloride), F (fluoride), B (bromide), or I (iodide).

Abstract: The present invention provides a novel transesterification catalyst having the general formula: Zn3M2(CN)n(ROH).xZnCl2.yH2O wherein R is tertiary-butyl and M is a transition metal ion selected from Fe, Co and Cr, x varies from 0 to 0.5, y varies from 3-5 and n is 10 or 12. The above said catalyst is useful for an efficient transesterification of glycerides, fatty acid esters and cyclic carbonates on reactions with alcohols.

Abstract: This invention relates to an organotin-based catalyst system for polyurethane synthesis that is useful in coatings applications. The catalyst has low activity in the absence of oxygen. When a coating mixture comprising the catalyst is sprayed and/or applied to a substrate as a thin film in air, the catalyst is activated. For solvent-based refinish systems comprising hydroxyl and isocyanate species at high solids levels, the catalyst system therefore provides extended viscosity stability, i.e., pot life.

Abstract: Provided are transition metal catalytic systems for preparing ethylene homopolymers or copolymers of ethylene with ?-olefins. More specifically, provided are Group 4 transition metal catalysts, which is characterized in that the catalyst comprises around the Group 4 transition metal a cyclopentadiene derivative, and at least one aryloxide ligand(s) having a fluorenyl group or a derivative thereof (which is ready to be substituted at 9-position) that functions as an electron donor and serves to stabilize the catalytic system by surrounding an oxygen atom that links the ligand to the transition metal at ortho-position, and there is no cross-linkage between the ligands; catalytic systems comprising such transition metal catalyst and aluminoxane cocatalyst or boron compound cocatalyst; and processes for preparing ethylene homopolymers or copolymers of ethylene with ?-olefins by using the same.