Title of Invention	PROCESS FOR THE ISOMERIZATION OF METALLOCENE COMPOUNDS
Abstract	An isomerization process comprising the step of contacting a slurry or a solution comprising the meso or meso-like form of one or more bridged metallocene compounds of group 4 of the Periodic Table of the Elements having C2 or C2-like symmetry with an isomerization catalyst of formula (I) [R4W]<+>X<-> (I) wherein: W is a nitrogen or a phosphorus atom; R, equal to or different from each other, are C1-C40 hydrocarbon radicals and X<-> is an halide atom.

Title of Invention

PROCESS FOR THE ISOMERIZATION OF METALLOCENE COMPOUNDS

Abstract

An isomerization process comprising the step of contacting a slurry or a solution comprising the meso or meso-like form of one or more bridged metallocene compounds of group 4 of the Periodic Table of the Elements having C2 or C2-like symmetry with an isomerization catalyst of formula (I) [R4W]<+>X<-> (I) wherein: W is a nitrogen or a phosphorus atom; R, equal to or different from each other, are C1-C40 hydrocarbon radicals and X<-> is an halide atom.

Full Text	PROCESS FOR THE ISOMERIZATION OF METALLOCENE COMPOUNDS The present invention relates to a process for the conversion of the meso or meso-like form of a metallocene compound to the corresponding racemic or racemic-like form. The meso or the meso-like form to be subjected to the process of the invention can be admixed with the corresponding racemic (rac) or racemic-like form. Metallocene compounds are well known complexes, mainly used as catalyst components for the polymerization of olefins. Processes for the synthesis of such metallocene compounds tend to produce mixtures of racemic and meso form. Usually the racemic form produces stereoregular polymers while the meso form is inactive or produces low molecular weight atactic polymers. The racemic form is therefore the most used as polymerization catalyst component. Consequently it is desirable to obtain from the synthesis the racemic (rac) form or a mixture where the racemic form is predominant in order to reduce the work for the physical separation of the two isomers. EP 819 695 describes a process for the modification of the rac/meso ratio of a rac/meso mixture of a stereorigid bridged metallocene compounds by subjecting the mixture to a selective decomposition in the presence of compounds having either acidic hydrogen atoms or reactive halogen atoms, such as water, methanol, chlorotrimethylsilane. With this process, one isomeric form is decomposed with a consequently lowering of the overall yield of the process. WO 00/017213 describes an isomerization process in which the meso form or a mixture of racemic and meso form of a bridged metallocene compound is contacted with a Group 1 and/or 2 metal halide isomerization catalyst1 in a liquid medium. This process has the drawback that the elimination of the metal halide from the reaction mixture could be complicated. Organometallics 1998, 17, 1946-4958 describes a series of reactions in which rac-dimethylsilyl(l,3-diisopropylcyclopentadienyl)scandium allyl is isomerized to a rac/meso mixtures by using different isomerization catalysts. Among all (n-C7H15)4NCl and (n-C7H15)4NBr are used. This isomerization reaction is obviously not useful for an industrial process which target is to obtain the rac isomer. Moreover, on page 4953 of this document it is stated that the isomerization is discouraged for metallocenes of group 4, thus creating a prejudice in using this kind of reaction with metallocene compounds in which the central metal belongs to group 4 of the periodic table of the elements. The bridged metallocene compounds of group 4 of the Periodic Table of the Elements having C% or C2-Iike symmetry have two bridged cyclopentadienyl moieties linked to the central metal atom trough a n bond. The central metal atom is zirconium, titanium or hafnium, preferably zirconium. For the purpose of the present invention, the term "C2 symmetry" means that in the metallocene compound two isomeric forms are possible, the racemic and the meso forms. These isomeric forms are well known in the art for example they are cited in Chem. Rev. 2000,100, 1253-1345. For the purpose of the present invention, the term "C2-like symmetry" means that in the metallocene compound two isomeric forms are possible, the racemic-like and the meso- like form. "Racemic-like form" means that the bulkier substituents of the two cyclopentadienyl moieties on the metallocene compound are on the opposite sides with respect to the plane containing the zirconium and the centre of the cyclopentadienyl moieties as shown in the following compound.- racemic-like form Conversely meso-like form means that the bulkier substituents of the two cyclopentadienyl moieties on the metallocene compound axe on the same side with respect to the plane containing the zirconium and the centre of the cyclopentadienyl moieties as shown in the following compound. meso-Iike form With the process of the present invention the meso or meso-like form of one or more bridged metallocene compounds of group 4 of the Periodic Table of the Elements having C2 or C2-like symmetry can be used alone or in a mixture comprising the racemic or rac.emic-like form. According to a preferred embodiment, the process of the present invention is carried out in an aprotic solvent, either polar or apolar. Said aprotic solvent can be an aromatic or aliphatic hydrocarbon, optionally halogenated or optionally containing heteroatoms belonging to the group 16 of the periodic table, or an ether. Preferably it is selected from the group consisting of benzene, toluene, pentane, hexane, heptane, cyclohexane, dichloromethane, chlorobenzene, diethylether, tetrahydrofiiran, 1,2 dimethoxyethane N,N-dimethylformamide, dimethyl sulfoxide or mixtures thereof. Preferably the process of the present invention is carried out in the presence of one or more ethers such as tetrahydrofuran or 1,2 dimethoxyethane; more preferably the solvent contains at least 5% by volume of one or more ethers. The process of the present invention can be carried out at a temperature ranging from 0°C to a temperature below the temperature of decomposition of the bridged metallocene compound in the selected solvent, usually up to 180°C. Preferably the process of the present invention is carried out at a temperature ranging from 10°C to 150°C, more preferably from 30°C to 90°C, even more preferably from 40°C to 90°C. The reaction time depends on the temperature, on the wished degree of isomerization, on the metallocene to be used. Generally it ranges from 0.1 hour to 65 hours, preferably from 1 hour to 24 hours. The skilled in the art can easily select the reaction time in view of the results to be obtained. The process of the present invention can be advantageously carried out in an inert atmosphere, i.e. in the absence of oxygen, water or any other compounds able to decompose the metallocene. The molar ratio between the isomerization catalyst and the metal of the bridged metallocene compound is preferably comprised between 0.01 to 300; more preferably the ratio is from 0.01 to 100, even more preferably from 0.1 to 10; particularly preferred ratio range is from 0.2 to 5. With the process of the present invention it is possible to convert at least part of the meso or meso-like form to the racemic or racemic-like form of a bridged metallocene compound. This allows to improve the final yield in term of the racemic or racemic-like isomer of the whole process for synthesising the target metallocene compound. The removal of the isomerization catalyst and the final purification of the racemic or racemic like isomer can be carried out according to the procedure commonly used in the art. The process of the present invention can be used as such or it can be part of a one-pot process for obtaining metallocene compounds starting from the ligands, such as the processes described in EP 03101268.5; WO 03/057705; WO 99/36427 and WO 02/083699. Bridged metallocene compounds having C2 symmetry or C2-like symmetry that can be used in the process of the present invention are preferably compounds of formula (III) (HI) wherein: M is a transition metal belonging to group 4, preferably M is zirconium, or hafoium; the substituents Q, equal to or different from each other, are monoanionic sigma ligands selected from the group consisting of hydrogen, halogen, R8, OR8, OCOR8, SR8, NR82 and PR82, wherein R8 is a linear or branched, cyclic or acyclic, C1-C2o-alkyl, C2-C20 alkenyl, ■ C2-C20 alkynyl, C5-C20o-aryl, C7-C20-alkyteryl or C7-C2o-arylalkyl radical optionally containing one or more Si or Ge atoms; or two Q can optionally form a substituted or unsubstituted butadienyl radical or a OR O group wherein R is a divalent radical selected from C1-C20 aDcylidene, CVC40 arylidene, C7-C40 alkylarylidene and C7-C40 arylalkylidene radicals; the substituents Q are preferably the same and are preferably halogen atoms, R8, OR8 and NR82; wherein R8 is preferably a C1-C1o alkyl, C6-C20 aryl or C7-C20 arylalkyi group, optionally containing one or more Si or Ge atoms; more preferably, the substituents Q are selected from the group consisting of -Cl, -Br, -Me, -Et, -n-Bu, -sec-Bu, -Ph, -Bz, -CH2SiMe3, -OEt, -OPr, -OBu, -OBz and -NMe2; n is an integer equal to the oxidation state of the metal M minus 2; L is a divalent bridging group selected from Ci-C2o alkylidene, C3-C20 cycloalkylidene, Ce- C20 arylidene, C7-C20 alkylarylidene, or C7-C20 arylalkylidene radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements, and silylidene radical containing up to 5 silicon atoms such as SiMe2, SiPh2; preferably L is a divalent group (ZR9m)q; Z being C, Si, Ge, N or P, and the R9 groups, equal to or different from each other, being hydrogen or a linear or branched, cyclic or acyclic, C1-C20-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aryl, C7-C2o-alkylaryl or C7-C2o-aiylalkyl radical or two R9 can form a aliphatic or aromatic C4-C7 ring; preferably R9 is a hydrogen atom or a methyl or phenyl radical; preferably Z is Si or C; m is 1 or 2, and more specifically it is 1 when Z is N or P, and it is 2 when Z is C, Si or Ge; q is an integer ranging from 1 to 4; preferably q is 1 or 2; more preferably L is selected from Si(CH3)2, SiPfe, SiPhMe, SiMe(SiMe3), CHz, (CEb)2, (CH2)3 or C(CH3)2; R2, R3, equal to or different from each other, are hydrogen atoms, halogen atoms or linear or branched, cyclic or acyclic, C1-C1o-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aryl> C7-C2o-alkylaryl or C7-C2o-aryIalkyl radicals, optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; T, equal to or different from each other, is a moiety of formula (Ilia) or (nib): wherein: the atom marked with the symbol * bonds the atom marked with the same symbol in the compound of formula (HI); T1 is a sulphur atom, a oxygen atom or a CR102 or a NR12 group, wherein R10, equal to or different from each other, are hydrogen atoms, halogen atoms or linear or branched, cyclic or acyclic, Ci-C2o-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aryl, Cy^o-alkylaryl or C7-C2o-arylalkyl radicals, optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; and R is a or linear or branched, cyclic or acyclic, Ct-C2o-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aiyl, C7-C2o-alkylaryl or C7-C2o-arylalkyl radical, optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably Tl is sulphur. T2 is a CR10 group or a nitrogen atom; wherein R10 is a hydrogen atom, a halogen atom or linear or branched, cyclic or acyclic, C1-C2o-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aryl, C7-C2o-alkylaryl or C7-C2o-arylalkyl radical, optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably T2 is a CR10 group; with the proviso that if T2 is a nitrogen atom T1 is CRl02; R4, R5, R6, R7, and R11, equal to or different from each other, are hydrogen atoms, halogen atoms or linear or branched, cyclic or acyclic, Ci-C2o-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aryl, C7-C2o-aIkylaryl or C7-C2o-arylalkyl radicals, optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; or two adjacent R4, R5, R6, R7, R10 and R11 form one or more 3-7 membered ring optional containing heteroatoms belonging to groups 13-17 of the periodic table; preferably R2 and Ru, equal to or diflferent from each other, are linear or branched C1-C2o-alkyl radicals, such as methyl, ethyl or isopropyl radicals; preferably R4 and R10, equal to or different from each other, are hydrogen atoms ir C6-C2o-aryl,~or C7-C2o-arylalkyl radicals such as phenyl, 4-tert-butyl phenyl radicals. Non limiting examples of compounds belonging to formula (I) are the following compounds; dimethylsilanediylbis(indenyl)zirconiumdichloride, dimethylsilanediylbis(2-methyl-4-phenylindenyl)zirconiumdichloride, dimethylsilanediylbis(4-naphthylindenyl)zirconiumdichloride, dimethylsilanediylbis(2-methylindenyl)zirconiiundichloride, dimethylsilanediylbis(2-methyl-4-t-bu1ylindenyl)2irconiumdichloride, dimethylsilanediylbis(2-methyl-4-isopropylindenyl)zirconiumdichloride, dimethylsilanediylbis(2,4-dimethylindenyl)2irconiumdichloride, dimethylsilanediylbis(2-methyl-4,5-ben2oindenyl)zirconiumdichloride, dimethylsilanediylbis(2,4,7-trimethylindenyl)zirconiumdichloride, dimethylsilanediylbis(2)4)6-trimethylinderLyl)zirconiumdichloride, dimethylsilanediylbis(2,5,6-trimethylindenyl)zirconiumdichloride? methyl(phenyl)silanediylbis(2-methyl-4a6-diisopropylindenyl)-zirconiumdichloride, methyl(phenyl)silanediylbis(2-methyl-4-isopropylindenyl)-zirconiumdichloride, 1 s2-ethylenebis(indenyl)zirconium dichloride, 1,2-ethylenebis(4,7-dimethylindenyl)zirconium dichloride, 1,2-ethylenebis(2-methyl-4-phenylindenyl)zirconium dichloride, 1,4-butanediylbis(2-methyl-4-phenylindenyl)zirconium dichloride, 1,2- ethylenebis(2-methyl-4,6-diisopropylindenyI)zirconium dichloride, 1,4-butanediyIbis(2-methyl-4-isopropylindenyI)zirconiuni dichloride, 1 }4-butanediylbis(2-methyl»4,5-benzoindenyl)zirconium dichloride, 1,2- ethylenebis (2-methyl-4,5-benzoindenyl)zirconiuin dichloride, dimethylsilanediylbis-6-(3-methylcyclopentadienyl"[l,2-b]-thiophene) dichloride; dimethylsilanediylbis-6-(4-methylcyclopentad^ dichloride; dimethylsilanediylbis-6-(4-isopropylcyclopentadienyl-[l,2-b]-thiophene)zirconium dichloride; dimethylsilanediylbis-6-(4-ter-butylcyclopentadienyl-[l,2-b]-thiophene)zircoiiium dichloride; dimethylsilanediylbis-6-(3-isopropylcyclopentadienyl-[l,2-b]-thiophene)zirconixim dichloride; dimethylsilaaediylbis-6-(3-phenylcyclopentadienyl-[l,2-b]-tMophene)zkcoiuum dichloride; dimethylsilanediylbis-6-(2,5-dichloride-3-phenylcyclopentadienyl-[l,2-b]- thiophene)zirconium dimethyl; dimethylsilanediylbis-6-[2,5-dichloride-3-(2-methylphenyl)cyclopentadienyl--[lJ2-b]- thiophene]zirconium dichloride; dim'ethylsilanediylbis-6-[2,5-dichloride- thiophenejzirconium dichloride; dimethylsilanediylbis-e-6-[2,5-dichloride-S-mesitylenecyclopentadienyl-[1,2--b]- thiophenejzirconium dichloride; dimethylsilanediylbis-6-(2,435-trimethyl-3-phenylcyclopentadienyl-[l,2-b]- thiophene)zirconium dichloride; dimethylsilanediylbis-6-(235-diethyl-3-phenylcyclopentadienyl«[l,2-b]- thiophene)zirconium dichloride; dimethylsilanediylbis-6-(2,5-diisopropyl-3-phenylcyclopentadienyl-[l,2-b]- thiophene)zirconium dichloride; dimethylsilanediylbis-6-(2,5-diter-butyl-3-phenylcyclopentadienyl-[l,2-b]- thiophene)zirconium dichloride; dimethylsilanediylbis-6-(2,5-ditrimethylsilyl-3-phenylcyclopentadienyl-[l,2-b]- thiophene)zirconium dichloride; dimethylsilanediylbis-6-(3-methylcyclopentadienyl-[l,2--b]--siIoIe)zirconiiim dichloride; dimethylsilanediylbis-6-(3-isopropylcyclopentadienyl-[l,2-b]-silole)zirconium dichloride; sample of the resulting solution (or slurry) showed that the rac/meso ratio of the metallocene was substantially improved in favour of the rac isomer. The latter was also isolated in higher yields compared with the yields achieved by using standard procedures. The rac/meso ratios were determined by NMR analysis. The proton spectra of metallocenes were obtained on a Bruker DPX 200 spectrometer operating in the Fourier transform mode at room temperature at 200.13 MHz, The samples were dissolved in CD2C12 (Aldrich, 99.8 atom % D); preparation of the samples was carried out under nitrogen using standard inert atmosphere techniques. The residual peak of CHDCI2 in the !H spectra (5.35 ppm) was used as a reference. Proton spectra were acquired with a 15° pulse and 2 seconds of delay between pulses; 32 transients were stored for each spectrum. CLAIMS 1. An isomerization process comprising the step of contacting a slurry or a solution comprising the meso or meso-like form of one or more bridged metallocene compounds of group 4 of the Periodic Table of the Elements having C2 or C2-like symmetry with an isomerization catalyst of formula (I) wherein: W is a nitrogen or a phosphorus atom; R, equal to or different from each other, are C1-C40 hydrocarbon radicals optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; two R can also join to form a saturated or unsaturated C5-C6 membered cycle containing the atom W or two R can also join to form a radical of formula (II) (H) wherein R1, equal to or different from each other, are C1-C20 hydrocarbon radicals optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; P is a phosphorous atom bonded with a double bond to the atom W; and X' is an halide atom. 2. The isomerization process according to claim 1 wherein a mixture comprising the meso or meso-like form and the racemic or racemic-Iike form of one or more bridged metallocene compounds of group 4 of the Periodic Table of the Elements having C2 or C2-like symmetry is used. 3. The isomerization process according to claims 1-2 wherein R are linear or branched, cyclic or acyclic, C1-C40-alkyl, C2-C40 alkenyl, C2-C40 alkynyl, C6-C40-aryl, C7-C40to-alkylaryl or C7-C4o-arylalkyl radicals, optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; two R can also join to form a saturated or unsaturated Cs-C6 membered cycle containing the atom W; and X" is chloride (Cl") or bromide (Br). 4. The isomerization process according to anyone of claims 1-3 wherein W is a nitrogen atom. 5. The isomerization process according to anyone of claims 1-4 wherein the process is canied out in an aprotic solvent, either polar or apolar. 6. The isomerization process according to claim 5 wherein the aprotic solvent is an aromatic or aliphatic hydrocarbon, optionally halogenated or optionally containing heteroatoms belonging to the group 16 of the periodic table, or an ether, 7. The isomerization process according to claim 6 wherein the process is carried out in the presence of one or more ethers. 8. The isomerization process according to anyone of claims 1-7 wherein the process is carried out at a temperature ranging from 0 to a temperature below the temperature of decomposition of the bridged metallocene compound in the selected solvent. 9. The isomerization process according to anyone of claims 1-8 wherein the bridged metallocene compounds having C2 symmetry or C2-like symmetry has formula (ID) wherein: M is a transition metal belonging to group 4, the substituents Q, equal to or different from each other, are monoanionic sigma ligands selected from the group consisting of hydrogen, halogen, R8, OR8, OCOR8, SR, NR 2 and PR 2, wherein R is a linear or branched, cyclic or acyclic, Ct-C2o-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aryl, C7-C2o-alkylaryl or C7-C2o-arylalkyl radical optionally containing one or more Si or Ge atoms; or two Q can optionally form a substituted or unsubstituted butadienyl radical or a ORO group wherein R is a divalent radical selected from C1-C20 alkylidene, C6-C40 arylidene, C7-C40 alkylarylidene and C7-C40 arylalkylidene radicals; n is an integer equal to the oxidation state of the metal M minus 2; L is a divalent bridging group selected from C1-C20 alkylidene, C3-C20 cycloalkylidene, C6-C20 arylidene, C7-C20 alkylarylidene, or C7-C20 arylalkylidene radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements, and silylidene radical containing up to 5 silicon atoms; R2, R3, equal to or different from each other, are hydrogen atoms, halogen atoms or linear or branched, cyclic or acyclic, Ci-C2o-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aryl, C7-C2o-alkylaryl or C7-C2o-arylalkyl radicals, optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; T, equal to or different from each other, is a moiety of formula (Ilia) or (Hlb); (Ela) (IHb) wherein; the atom marked with the symbol * bonds the atom marked with the same symbol in the compound of formula (HI); T1 is a sulphur atom, a oxygen atom or a CRl02 or a NR12 group, wherein R10, equal to or different from each other, are hydrogen atoms, halogen atoms or linear or branched, cyclic or acyclic, Ci-C2o-aIkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aiyl, C7-C2o-alkylaryl or C7-C2o-arylalkyI radicals, optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; and R12 is a or linear or branched, cyclic or acyclic, Ci-C2o-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aryl, C7-C2o-alkylaryl or C7-C2o-arylalkyl radical, optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; T2 is a CR10 group or a nitrogen atom; wherein R10 is a hydrogen atom, a halogen atom or linear or branched, cyclic or acyclic, C1-C2o-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aryl, C7-C2o-alkylaiyl or C7-C2o-arylalkyl radical, optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; with the proviso that if T2 is a nitrogen atom T1 is CR102; R4, R5, R6, R7, and R11, equal to or different from each other, are hydrogen atoms, halogen atoms or linear or branched, cyclic or acyclic, C1-C20-ar-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aryl, C7-C2o-alkylaryl or C7-C2o-arylalkyl radicals, optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; or two adjacent R4, R5, R6, R7, R10 and R11 form one or more 3-7 membered ring optional containing heteroatoms belonging to groups 13-17 of the periodic table. 10. The isomerization process according to claim 9 wherein in the compound of formula (HI) M is zirconium, or hafoium; the substituents Q are the same and are halogen atoms, R8, OR8 and NR82; wherein R8 is preferably a C1-C10 alkyl, C6-C20 aryl or C7-C20 arylalkyl group, optionally containing one or more Si or Ge atoms; L is a divalent group (ZR9m)q; Z being C, Si, Ge, N or P, and the R9 groups, equal to or different from each other, being hydrogen or a linear or branched, cyclic or acyclic, C1-C2o-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aryl, C7-C2o-alkylaryl or C7-C2o-aryla3kyl radicals or two R9 can form a aliphatic or aromatic C4-C7 ring. 11. The isomerization process according to claims 9-10 wherein in the compound of formula (II) R2 and Ru, equal to or different from each other are linear or branched C1-C2o-alkyl radicals; R4 and R10, equal to or different from each other, are hydrogen atoms or C6-C2o-aryl, or C7-C2o-arylalkyl radicals; T1 is sulphur and T2 is a CR10 group.

Full Text

PROCESS FOR THE ISOMERIZATION OF METALLOCENE COMPOUNDS
The present invention relates to a process for the conversion of the meso or meso-like form of a metallocene compound to the corresponding racemic or racemic-like form. The meso or the meso-like form to be subjected to the process of the invention can be admixed with the corresponding racemic (rac) or racemic-like form.
Metallocene compounds are well known complexes, mainly used as catalyst components for the polymerization of olefins. Processes for the synthesis of such metallocene compounds tend to produce mixtures of racemic and meso form. Usually the racemic form produces stereoregular polymers while the meso form is inactive or produces low molecular weight atactic polymers. The racemic form is therefore the most used as polymerization catalyst component. Consequently it is desirable to obtain from the synthesis the racemic (rac) form or a mixture where the racemic form is predominant in order to reduce the work for the physical separation of the two isomers. EP 819 695 describes a process for the modification of the rac/meso ratio of a rac/meso mixture of a stereorigid bridged metallocene compounds by subjecting the mixture to a selective decomposition in the presence of compounds having either acidic hydrogen atoms or reactive halogen atoms, such as water, methanol, chlorotrimethylsilane. With this process, one isomeric form is decomposed with a consequently lowering of the overall yield of the process.
WO 00/017213 describes an isomerization process in which the meso form or a mixture of racemic and meso form of a bridged metallocene compound is contacted with a Group 1 and/or 2 metal halide isomerization catalyst1 in a liquid medium. This process has the drawback that the elimination of the metal halide from the reaction mixture could be complicated.
Organometallics 1998, 17, 1946-4958 describes a series of reactions in which rac-dimethylsilyl(l,3-diisopropylcyclopentadienyl)scandium allyl is isomerized to a rac/meso mixtures by using different isomerization catalysts. Among all (n-C7H15)4NCl and (n-C7H15)4NBr are used. This isomerization reaction is obviously not useful for an industrial process which target is to obtain the rac isomer. Moreover, on page 4953 of this document it is stated that the isomerization is discouraged for metallocenes of group 4, thus creating a prejudice in using this kind of reaction with metallocene compounds in which the central metal belongs to group 4 of the periodic table of the elements.

The bridged metallocene compounds of group 4 of the Periodic Table of the Elements
having C% or C2-Iike symmetry have two bridged cyclopentadienyl moieties linked to the
central metal atom trough a n bond. The central metal atom is zirconium, titanium or
hafnium, preferably zirconium.
For the purpose of the present invention, the term "C2 symmetry" means that in the
metallocene compound two isomeric forms are possible, the racemic and the meso forms.
These isomeric forms are well known in the art for example they are cited in Chem. Rev.
2000,100, 1253-1345.
For the purpose of the present invention, the term "C2-like symmetry" means that in the
metallocene compound two isomeric forms are possible, the racemic-like and the meso-
like form.
"Racemic-like form" means that the bulkier substituents of the two cyclopentadienyl
moieties on the metallocene compound are on the opposite sides with respect to the plane
containing the zirconium and the centre of the cyclopentadienyl moieties as shown in the
following compound.-

racemic-like form
Conversely meso-like form means that the bulkier substituents of the two cyclopentadienyl moieties on the metallocene compound axe on the same side with respect to the plane containing the zirconium and the centre of the cyclopentadienyl moieties as shown in the following compound.

meso-Iike form
With the process of the present invention the meso or meso-like form of one or more bridged metallocene compounds of group 4 of the Periodic Table of the Elements having C2 or C2-like symmetry can be used alone or in a mixture comprising the racemic or rac.emic-like form.
According to a preferred embodiment, the process of the present invention is carried out in an aprotic solvent, either polar or apolar. Said aprotic solvent can be an aromatic or aliphatic hydrocarbon, optionally halogenated or optionally containing heteroatoms belonging to the group 16 of the periodic table, or an ether. Preferably it is selected from the group consisting of benzene, toluene, pentane, hexane, heptane, cyclohexane, dichloromethane, chlorobenzene, diethylether, tetrahydrofiiran, 1,2 dimethoxyethane N,N-dimethylformamide, dimethyl sulfoxide or mixtures thereof. Preferably the process of the present invention is carried out in the presence of one or more ethers such as tetrahydrofuran or 1,2 dimethoxyethane; more preferably the solvent contains at least 5% by volume of one or more ethers.
The process of the present invention can be carried out at a temperature ranging from 0°C to a temperature below the temperature of decomposition of the bridged metallocene

compound in the selected solvent, usually up to 180°C. Preferably the process of the
present invention is carried out at a temperature ranging from 10°C to 150°C, more
preferably from 30°C to 90°C, even more preferably from 40°C to 90°C.
The reaction time depends on the temperature, on the wished degree of isomerization, on
the metallocene to be used. Generally it ranges from 0.1 hour to 65 hours, preferably from
1 hour to 24 hours. The skilled in the art can easily select the reaction time in view of the
results to be obtained.
The process of the present invention can be advantageously carried out in an inert
atmosphere, i.e. in the absence of oxygen, water or any other compounds able to
decompose the metallocene.
The molar ratio between the isomerization catalyst and the metal of the bridged
metallocene compound is preferably comprised between 0.01 to 300; more preferably the
ratio is from 0.01 to 100, even more preferably from 0.1 to 10; particularly preferred ratio
range is from 0.2 to 5.
With the process of the present invention it is possible to convert at least part of the meso
or meso-like form to the racemic or racemic-like form of a bridged metallocene compound.
This allows to improve the final yield in term of the racemic or racemic-like isomer of the
whole process for synthesising the target metallocene compound. The removal of the
isomerization catalyst and the final purification of the racemic or racemic like isomer can
be carried out according to the procedure commonly used in the art.
The process of the present invention can be used as such or it can be part of a one-pot
process for obtaining metallocene compounds starting from the ligands, such as the
processes described in EP 03101268.5; WO 03/057705; WO 99/36427 and WO
02/083699.
Bridged metallocene compounds having C2 symmetry or C2-like symmetry that can be
used in the process of the present invention are preferably compounds of formula (III)

(HI)
wherein:
M is a transition metal belonging to group 4, preferably M is zirconium, or hafoium;
the substituents Q, equal to or different from each other, are monoanionic sigma ligands
selected from the group consisting of hydrogen, halogen, R8, OR8, OCOR8, SR8, NR82 and
PR82, wherein R8 is a linear or branched, cyclic or acyclic, C1-C2o-alkyl, C2-C20 alkenyl, ■
C2-C20 alkynyl, C5-C20o-aryl, C7-C20-alkyteryl or C7-C2o-arylalkyl radical optionally
containing one or more Si or Ge atoms;
or two Q can optionally form a substituted or unsubstituted butadienyl radical or a OR O
group wherein R is a divalent radical selected from C1-C20 aDcylidene, CVC40 arylidene,
C7-C40 alkylarylidene and C7-C40 arylalkylidene radicals;
the substituents Q are preferably the same and are preferably halogen atoms, R8, OR8 and
NR82; wherein R8 is preferably a C1-C1o alkyl, C6-C20 aryl or C7-C20 arylalkyi group,
optionally containing one or more Si or Ge atoms; more preferably, the substituents Q are
selected from the group consisting of -Cl, -Br, -Me, -Et, -n-Bu, -sec-Bu, -Ph, -Bz, -CH2SiMe3,
-OEt, -OPr, -OBu, -OBz and -NMe2;
n is an integer equal to the oxidation state of the metal M minus 2;
L is a divalent bridging group selected from Ci-C2o alkylidene, C3-C20 cycloalkylidene, Ce-
C20 arylidene, C7-C20 alkylarylidene, or C7-C20 arylalkylidene radicals optionally containing
heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements, and silylidene
radical containing up to 5 silicon atoms such as SiMe2, SiPh2; preferably L is a divalent group
(ZR9m)q; Z being C, Si, Ge, N or P, and the R9 groups, equal to or different from each other,
being hydrogen or a linear or branched, cyclic or acyclic, C1-C20-alkyl, C2-C20 alkenyl,
C2-C20 alkynyl, C6-C2o-aryl, C7-C2o-alkylaryl or C7-C2o-aiylalkyl radical or two R9 can form a

aliphatic or aromatic C4-C7 ring; preferably R9 is a hydrogen atom or a methyl or phenyl
radical; preferably Z is Si or C;
m is 1 or 2, and more specifically it is 1 when Z is N or P, and it is 2 when Z is C, Si or Ge; q
is an integer ranging from 1 to 4; preferably q is 1 or 2;
more preferably L is selected from Si(CH3)2, SiPfe, SiPhMe, SiMe(SiMe3), CHz, (CEb)2,
(CH2)3 or C(CH3)2;
R2, R3, equal to or different from each other, are hydrogen atoms, halogen atoms or linear or
branched, cyclic or acyclic, C1-C1o-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aryl>
C7-C2o-alkylaryl or C7-C2o-aryIalkyl radicals, optionally containing one or more heteroatoms
belonging to groups 13-17 of the Periodic Table of the Elements;
T, equal to or different from each other, is a moiety of formula (Ilia) or (nib):
wherein:
the atom marked with the symbol * bonds the atom marked with the same symbol in the
compound of formula (HI);
T1 is a sulphur atom, a oxygen atom or a CR102 or a NR12 group, wherein R10, equal to or
different from each other, are hydrogen atoms, halogen atoms or linear or branched, cyclic
or acyclic, Ci-C2o-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aryl, Cy^o-alkylaryl or
C7-C2o-arylalkyl radicals, optionally containing one or more heteroatoms belonging to groups
13-17 of the Periodic Table of the Elements; and R is a or linear or branched, cyclic or
acyclic, Ct-C2o-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aiyl, C7-C2o-alkylaryl or
C7-C2o-arylalkyl radical, optionally containing one or more heteroatoms belonging to groups
13-17 of the Periodic Table of the Elements; preferably Tl is sulphur.
T2 is a CR10 group or a nitrogen atom; wherein R10 is a hydrogen atom, a halogen atom or
linear or branched, cyclic or acyclic, C1-C2o-alkyl, C2-C20 alkenyl, C2-C20 alkynyl,
C6-C2o-aryl, C7-C2o-alkylaryl or C7-C2o-arylalkyl radical, optionally containing one or more

heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably T2 is
a CR10 group;
with the proviso that if T2 is a nitrogen atom T1 is CRl02;
R4, R5, R6, R7, and R11, equal to or different from each other, are hydrogen atoms, halogen
atoms or linear or branched, cyclic or acyclic, Ci-C2o-alkyl, C2-C20 alkenyl, C2-C20 alkynyl,
C6-C2o-aryl, C7-C2o-aIkylaryl or C7-C2o-arylalkyl radicals, optionally containing one or more
heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; or two adjacent
R4, R5, R6, R7, R10 and R11 form one or more 3-7 membered ring optional containing
heteroatoms belonging to groups 13-17 of the periodic table;
preferably R2 and Ru, equal to or diflferent from each other, are linear or branched
C1-C2o-alkyl radicals, such as methyl, ethyl or isopropyl radicals;
preferably R4 and R10, equal to or different from each other, are hydrogen atoms ir
C6-C2o-aryl,~or C7-C2o-arylalkyl radicals such as phenyl, 4-tert-butyl phenyl radicals.
Non limiting examples of compounds belonging to formula (I) are the following compounds;
dimethylsilanediylbis(indenyl)zirconiumdichloride,
dimethylsilanediylbis(2-methyl-4-phenylindenyl)zirconiumdichloride,
dimethylsilanediylbis(4-naphthylindenyl)zirconiumdichloride,
dimethylsilanediylbis(2-methylindenyl)zirconiiundichloride,
dimethylsilanediylbis(2-methyl-4-t-bu1ylindenyl)2irconiumdichloride,
dimethylsilanediylbis(2-methyl-4-isopropylindenyl)zirconiumdichloride,
dimethylsilanediylbis(2,4-dimethylindenyl)2irconiumdichloride,
dimethylsilanediylbis(2-methyl-4,5-ben2oindenyl)zirconiumdichloride,
dimethylsilanediylbis(2,4,7-trimethylindenyl)zirconiumdichloride,
dimethylsilanediylbis(2)4)6-trimethylinderLyl)zirconiumdichloride,
dimethylsilanediylbis(2,5,6-trimethylindenyl)zirconiumdichloride?
methyl(phenyl)silanediylbis(2-methyl-4a6-diisopropylindenyl)-zirconiumdichloride,
methyl(phenyl)silanediylbis(2-methyl-4-isopropylindenyl)-zirconiumdichloride,
1 s2-ethylenebis(indenyl)zirconium dichloride,
1,2-ethylenebis(4,7-dimethylindenyl)zirconium dichloride,
1,2-ethylenebis(2-methyl-4-phenylindenyl)zirconium dichloride,
1,4-butanediylbis(2-methyl-4-phenylindenyl)zirconium dichloride,
1,2- ethylenebis(2-methyl-4,6-diisopropylindenyI)zirconium dichloride,
1,4-butanediyIbis(2-methyl-4-isopropylindenyI)zirconiuni dichloride,

1 }4-butanediylbis(2-methyl»4,5-benzoindenyl)zirconium dichloride,
1,2- ethylenebis (2-methyl-4,5-benzoindenyl)zirconiuin dichloride,
dimethylsilanediylbis-6-(3-methylcyclopentadienyl"[l,2-b]-thiophene) dichloride;
dimethylsilanediylbis-6-(4-methylcyclopentad^
dichloride;
dimethylsilanediylbis-6-(4-isopropylcyclopentadienyl-[l,2-b]-thiophene)zirconium
dichloride;
dimethylsilanediylbis-6-(4-ter-butylcyclopentadienyl-[l,2-b]-thiophene)zircoiiium
dichloride;
dimethylsilanediylbis-6-(3-isopropylcyclopentadienyl-[l,2-b]-thiophene)zirconixim
dichloride;
dimethylsilaaediylbis-6-(3-phenylcyclopentadienyl-[l,2-b]-tMophene)zkcoiuum
dichloride;
dimethylsilanediylbis-6-(2,5-dichloride-3-phenylcyclopentadienyl-[l,2-b]-
thiophene)zirconium dimethyl;
dimethylsilanediylbis-6-[2,5-dichloride-3-(2-methylphenyl)cyclopentadienyl--[lJ2-b]-
thiophene]zirconium dichloride;
dim'ethylsilanediylbis-6-[2,5-dichloride-
thiophenejzirconium dichloride;
dimethylsilanediylbis-e-6-[2,5-dichloride-S-mesitylenecyclopentadienyl-[1,2--b]-
thiophenejzirconium dichloride;
dimethylsilanediylbis-6-(2,435-trimethyl-3-phenylcyclopentadienyl-[l,2-b]-
thiophene)zirconium dichloride;
dimethylsilanediylbis-6-(235-diethyl-3-phenylcyclopentadienyl«[l,2-b]-
thiophene)zirconium dichloride;
dimethylsilanediylbis-6-(2,5-diisopropyl-3-phenylcyclopentadienyl-[l,2-b]-
thiophene)zirconium dichloride;
dimethylsilanediylbis-6-(2,5-diter-butyl-3-phenylcyclopentadienyl-[l,2-b]-
thiophene)zirconium dichloride;
dimethylsilanediylbis-6-(2,5-ditrimethylsilyl-3-phenylcyclopentadienyl-[l,2-b]-
thiophene)zirconium dichloride;
dimethylsilanediylbis-6-(3-methylcyclopentadienyl-[l,2--b]--siIoIe)zirconiiim dichloride;
dimethylsilanediylbis-6-(3-isopropylcyclopentadienyl-[l,2-b]-silole)zirconium dichloride;

sample of the resulting solution (or slurry) showed that the rac/meso ratio of the metallocene was substantially improved in favour of the rac isomer. The latter was also isolated in higher yields compared with the yields achieved by using standard procedures. The rac/meso ratios were determined by NMR analysis. The proton spectra of metallocenes were obtained on a Bruker DPX 200 spectrometer operating in the Fourier transform mode at room temperature at 200.13 MHz, The samples were dissolved in CD2C12 (Aldrich, 99.8 atom % D); preparation of the samples was carried out under nitrogen using standard inert atmosphere techniques. The residual peak of CHDCI2 in the !H spectra (5.35 ppm) was used as a reference. Proton spectra were acquired with a 15° pulse and 2 seconds of delay between pulses; 32 transients were stored for each spectrum.

CLAIMS
1. An isomerization process comprising the step of contacting a slurry or a solution comprising the meso or meso-like form of one or more bridged metallocene compounds of group 4 of the Periodic Table of the Elements having C2 or C2-like symmetry with an isomerization catalyst of formula (I)
wherein:
W is a nitrogen or a phosphorus atom;
R, equal to or different from each other, are C1-C40 hydrocarbon radicals optionally
containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of
the Elements; two R can also join to form a saturated or unsaturated C5-C6 membered
cycle containing the atom W or two R can also join to form a radical of formula (II)

(H)
wherein R1, equal to or different from each other, are C1-C20 hydrocarbon radicals optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; P is a phosphorous atom bonded with a double bond to the atom W; and X' is an halide atom.
2. The isomerization process according to claim 1 wherein a mixture comprising the
meso or meso-like form and the racemic or racemic-Iike form of one or more bridged
metallocene compounds of group 4 of the Periodic Table of the Elements having C2
or C2-like symmetry is used.
3. The isomerization process according to claims 1-2 wherein R are linear or branched,
cyclic or acyclic, C1-C40-alkyl, C2-C40 alkenyl, C2-C40 alkynyl, C6-C40-aryl,
C7-C40to-alkylaryl or C7-C4o-arylalkyl radicals, optionally containing one or more
heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; two R
can also join to form a saturated or unsaturated Cs-C6 membered cycle containing the
atom W; and X" is chloride (Cl") or bromide (Br).
4. The isomerization process according to anyone of claims 1-3 wherein W is a nitrogen
atom.

5. The isomerization process according to anyone of claims 1-4 wherein the process is
canied out in an aprotic solvent, either polar or apolar.
6. The isomerization process according to claim 5 wherein the aprotic solvent is an
aromatic or aliphatic hydrocarbon, optionally halogenated or optionally containing
heteroatoms belonging to the group 16 of the periodic table, or an ether,
7. The isomerization process according to claim 6 wherein the process is carried out in
the presence of one or more ethers.
8. The isomerization process according to anyone of claims 1-7 wherein the process is
carried out at a temperature ranging from 0 to a temperature below the temperature of
decomposition of the bridged metallocene compound in the selected solvent.
9. The isomerization process according to anyone of claims 1-8 wherein the bridged
metallocene compounds having C2 symmetry or C2-like symmetry has formula (ID)
wherein:
M is a transition metal belonging to group 4,
the substituents Q, equal to or different from each other, are monoanionic sigma
ligands selected from the group consisting of hydrogen, halogen, R8, OR8, OCOR8,
SR, NR 2 and PR 2, wherein R is a linear or branched, cyclic or acyclic,
Ct-C2o-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aryl, C7-C2o-alkylaryl or
C7-C2o-arylalkyl radical optionally containing one or more Si or Ge atoms;
or two Q can optionally form a substituted or unsubstituted butadienyl radical or a
ORO group wherein R is a divalent radical selected from C1-C20 alkylidene, C6-C40
arylidene, C7-C40 alkylarylidene and C7-C40 arylalkylidene radicals;
n is an integer equal to the oxidation state of the metal M minus 2;
L is a divalent bridging group selected from C1-C20 alkylidene, C3-C20 cycloalkylidene,

C6-C20 arylidene, C7-C20 alkylarylidene, or C7-C20 arylalkylidene radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements, and silylidene radical containing up to 5 silicon atoms; R2, R3, equal to or different from each other, are hydrogen atoms, halogen atoms or linear or branched, cyclic or acyclic, Ci-C2o-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aryl, C7-C2o-alkylaryl or C7-C2o-arylalkyl radicals, optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; T, equal to or different from each other, is a moiety of formula (Ilia) or (Hlb);

(Ela) (IHb)
wherein;
the atom marked with the symbol * bonds the atom marked with the same symbol in the compound of formula (HI);
T1 is a sulphur atom, a oxygen atom or a CRl02 or a NR12 group, wherein R10, equal to or different from each other, are hydrogen atoms, halogen atoms or linear or branched, cyclic or acyclic, Ci-C2o-aIkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aiyl, C7-C2o-alkylaryl or C7-C2o-arylalkyI radicals, optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; and R12 is a or linear or branched, cyclic or acyclic, Ci-C2o-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aryl, C7-C2o-alkylaryl or C7-C2o-arylalkyl radical, optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements;
T2 is a CR10 group or a nitrogen atom; wherein R10 is a hydrogen atom, a halogen atom or linear or branched, cyclic or acyclic, C1-C2o-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aryl, C7-C2o-alkylaiyl or C7-C2o-arylalkyl radical, optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements;

with the proviso that if T2 is a nitrogen atom T1 is CR102;
R4, R5, R6, R7, and R11, equal to or different from each other, are hydrogen atoms, halogen atoms or linear or branched, cyclic or acyclic, C1-C20-ar-alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C6-C2o-aryl, C7-C2o-alkylaryl or C7-C2o-arylalkyl radicals, optionally containing one or more heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; or two adjacent R4, R5, R6, R7, R10 and R11 form one or more 3-7 membered ring optional containing heteroatoms belonging to groups 13-17 of the periodic table.
10. The isomerization process according to claim 9 wherein in the compound of formula
(HI) M is zirconium, or hafoium; the substituents Q are the same and are halogen
atoms, R8, OR8 and NR82; wherein R8 is preferably a C1-C10 alkyl, C6-C20 aryl or C7-C20
arylalkyl group, optionally containing one or more Si or Ge atoms; L is a divalent group
(ZR9m)q; Z being C, Si, Ge, N or P, and the R9 groups, equal to or different from each
other, being hydrogen or a linear or branched, cyclic or acyclic, C1-C2o-alkyl, C2-C20
alkenyl, C2-C20 alkynyl, C6-C2o-aryl, C7-C2o-alkylaryl or C7-C2o-aryla3kyl radicals or
two R9 can form a aliphatic or aromatic C4-C7 ring.
11. The isomerization process according to claims 9-10 wherein in the compound of
formula (II) R2 and Ru, equal to or different from each other are linear or branched
C1-C2o-alkyl radicals; R4 and R10, equal to or different from each other, are hydrogen
atoms or C6-C2o-aryl, or C7-C2o-arylalkyl radicals; T1 is sulphur and T2 is a CR10
group.