Metallocene compounds, process for their preparation, and their use in catalysts for the polymerization of olefins

Abstract

A class of metallocene compounds having two cyclopentadienyl rings bridged by an alkylidene group is disclosed. These metallocene compounds can be suitably used as catalyst components for the polymerization of olefins. In particular, by polymerising propylene in the presence of a catalyst based on these metallocene compounds, polymers having very high isotactic indexes, high molecular weights and narrow molecular weight distributions can be obtained in high yields.

1 . A metallocene compound of the formula (I):  
       
         
           
           
               
               
           
         
       
       wherein R 1 , R 2 , R 3  and R 4 , which can be identical or different, are hydrogen atoms or C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 2 -C 20 -alkenyl, C 6 -C 20 -aryl, C 7 -C 20 -alkylaryl or C 7 -C 20 -aryl-alkyl groups which can contain silicon or germanium atoms, R 3  being different from R 2  and from a hydrogen atom, and wherein 
 R 1  and R 2  on the same cyclopentadienyl ring can form a ring having 5 to 8 carbon atoms;  
 R 5  is a hydrogen atom or a —CHR 7 R 8  group;  
 R 6  is a C 6 -C 20 -aryl radical or a —CHR 9 R 10  group;  
 R 5  and R 6  can form a ring having 3 to 8 carbon atoms which can contain hetero atoms;  
 R 7 , R 8 , R 9  and R 10 , which can be identical or different, are hydrogen atoms or C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 2 -C 20 -alkenyl, C 6 -C 20 -aryl, C 7 -C 20 -alkylaryl or C 7 -C 20 -arylalkyl radicals which can contain hetero atoms such as nitrogen, phosphor, oxygen or sulphur, and two R 7 , R 8 , R 9  and R 10  substituents can form a ring having 3 to 8 carbon atoms which can contain hetero atoms;  
 M is an atom of a transition metal selected from those belonging to group 3, 4, 5, 6 or to the lanthanide or actinide groups in the Periodic Table of the Elements (new IUPAC version);  
 the X substituents, which can be identical or different, are hydrogen atoms, halogen atoms or R, OR, SR, NR 2  or PR 2  groups, wherein the R substituents are C 1 -C 20 -alkyl, C 3 -C 20 -cycloalkyl, C 2 -C 20 -alkenyl, C 6 -C 20 -aryl, C 7 -C 20 -alkylaryl or C 7 -C 20 -arylalkyl radicals which can contain silicon or germanium atoms;  
 with the proviso that, when the R 1 , R 2  and R 4  substituents are hydrogen atoms and the R 5  and the R 6  substituents are methyl groups, then the R 3  substituents are other than an isopropropyl or tertbutyl group.  
 
     
     
         2 . The metallocene compound according to  claim 1 , wherein the transition metal M is selected between titanium, zirconium and hafnium.  
     
     
         3 . The metallocene compound according to  claim 1  or  2 , wherein the X substituents are chlorine atoms or methyl groups.  
     
     
         4 . The metallocene compound according to any of  claims 1  to  3 , wherein the R 2  substituents are hydrogen atoms.  
     
     
         5 . The metallocene compound according to  claim 4 , wherein the R 1  substituents are different from hydrogen atoms.  
     
     
         6 . The metallocene compound according to  claim 4  or  5 , wherein the R 3  substituents are carbon, silicon or germanium atoms substituted with three alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl groups having 1 to 10 carbon atoms.  
     
     
         7 . The metallocene compound according to any of  claims 4  to  6 , wherein the R 4  substituents are hydrogen atoms.  
     
     
         8 . A metallocene compound of the formula (II):  
       
         
           
           
               
               
           
         
       
       and the corresponding bis-4,5,6,7-tetrahydroindenyl compound, wherein R 3 , R 4 , R 5 , R 6 , M and X are defined as in any of the preceding claims, the six-carbon-atom rings of the indenyl ligands being optionally substituted.  
     
     
         9 . The metallocene compound according to  claim 8 , wherein the R 3  substituents are carbon, silicon or germanium atoms substituted with three alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl groups having 1 to 10 carbon atoms.  
     
     
         10 . The metallocene compound according to  claim 8  or  9 , wherein the R 4  substituents are hydrogen atoms.  
     
     
         11 . A process for the preparation of a metallocene compound as claimed in any of  claims 1  to  10 , comprising the reaction of the corresponding bis-cyclopentadienyl ligands of the formula (III):  
       
         
           
           
               
               
           
         
       
       wherein R 1 , R 2 , R 3 , R 4 , R 5  and R 6  are defined as above, and A is a suitable leaving group, with a compound of the formula MX 4  wherein M and X are defined as in any of the preceding claims.  
     
     
         12 . A catalyst for the polymerization of olefins, consisting of the product of the reaction between: 
 (a) a metallocene compound as claimed in any of  claims 1  to  10 , and    (b) an alumoxane or a compound able to form an alkyl-metallocene cation.    
     
     
         13 . A process for the polymerization of olefins, said process comprising the polymerization reaction of an olefin monomer in the presence of a catalyst as claimed in  claim 12 .  
     
     
         14 . The process for the polymerization of olefins according to  claim 13 , wherein the olefin monomer is propylene.  
     
     
         15 . The process for the polymerization of propylene according to  claim 14 , wherein propylene is polymerized in the presence of a metallocene compound of the formula (II), wherein the R 3  substituents are carbon, silicon or germanium atoms substituted with three alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl groups having 1 to 10 carbon atoms, and wherein R 4 , R 5 , R 6 , M and X are defined as above, the R 4  substituents being preferably hydrogen atoms.  
     
     
         16 . The process for the polymerization of propylene according to  claim 15 , wherein the metallocene compound of the formula (II) is selected between: 
 isopropylidene-bis(3-t-butyl-indenyl)zirconium dichloride,    isopropylidene-bis(3-trimethylsilyl-indenyl)zirconium dichloride, and    isopropylidene-bis (3-trimethylgermyl-indenyl)zirconium dichloride.    
     
     
         17 . The process for the polymerization of propylene according to  claim 14 , wherein propylene is polymerized in the presence of a metallocene compound of the formula (I) in which the R 2  substituents are hydrogen atoms and the R 3  substituents are carbon, silicon or germanium atoms substituted with three alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl groups having 1 to 10 carbon atoms, the R 4  substituents being preferably hydrogen atoms.  
     
     
         18 . The process for the polymerization of propylene according to  claim 17 , wherein in the metallocene compound of the formula (I) the R 1  substituents are different from hydrogen atoms.  
     
     
         19 . The process for the polymerization of propylene according to  claim 18 , which is carried out at a temperature of at least 50° C.  
     
     
         20 . The process for the polymerization of propylene according to  claim 17 , wherein the metallocene compound of the formula (II) is selected between: 
 isopropylidene-bis(3-t-butyl-cyclopentadienyl)zirconium dichloride, and    isopropylidene-bis (2-methyl-4-t-butyl-cyclopentadienyl)zirconium dichloride.    
     
     
         21 . A propylene homopolymer having the following characteristics: 
 molecular weight distribution (Mw/Mn) lower than 4,    isotactic (mmmm), as determined by  13 C-NMR analyses, pentads higher than 70%,    no structural units due to regioirregular insertions detectable at the  13 C-NMR analysis carried out with a 300 MHz instrument.    
     
     
         22 . A propylene homopolymer having the following characteristics: 
 molecular weight distribution (Mw/Mn) lower than 4,    isotactic (m) diads, as determined by  13 C-NMR analyses, higher than 99%.    
     
     
         23 . A propylene copolymer with 0.1-10% by moles of a C 4 -C 10  α-olefin comonomer, having the following characteristics: 
 isotactic (m) diads, as determined by  13 C-NMR analyses, higher than 70%,  
 molecular weight distribution (Mw/Mn) lower than 4,  
 xylene-soluble fractions lower than 3% by weight.  
 
     
     
         24 . The propylene copolymer according to  claim 23 , wherein the α-olefin comonomer is 1-butene.