The known rac-[ethylenebis(4,7-dimethyl-eta(5)-1-indenyl)]ZrCl2(2r) and its meso isomer (2m) have been compared with the prototypal chiral isospecific rac-[ethylenebis(eta(5)-1-indenyl)]ZrCl2 (1r) and its aspecific meso isomer Im in terms of molecular structures, solution dynamics, and ligand substitution effect on polymerization performance. in Liquid propene at 50 degrees C, 2r/MAO produces iPP with appreciably higher isotacticity but lower molecular weight and regiospecificity than 1r/MAO. The lower molecular weight obtained with 2r in liquid monomer is due to predominant chain transfer to the monomer after a secondary propene insertion, producing >90% cis-2-butenyl- end groups. At lower propene concentration, 2r/MAO allows both beta-hydrogen transfer after a primary insertion and beta-methyl transfer, The low-activity 2m/MAO catalyst produces low molecular weight aPP. The diastereoselective synthesis of 2r,m via the corresponding rac- and meso-bis(4,7-dimethy-1-(trimethylsilyl)-3-indenyl)ethane,is reported. The crystal and molecular structures of meso-bis(4,7-dimethyl-1-(trimethylsilyl)-3-indenyl)ethane, 2r,m, have been determined.
Resconi, L., Piemontesi, F., Camurati, I., Balboni, D., Sironi, A., Moret, M., et al. (1996). Diastereoselective synthesis, molecular structure, and solution dynamics of meso- and rac-[ethylenebis(4,7-dimethyl-eta(5)-1-indenyl)]zirconium dichloride isomers and chain transfer reactions in propene polymerization with the rac isomer. ORGANOMETALLICS, 15(23), 5046-5059 [10.1021/om9604233].
Diastereoselective synthesis, molecular structure, and solution dynamics of meso- and rac-[ethylenebis(4,7-dimethyl-eta(5)-1-indenyl)]zirconium dichloride isomers and chain transfer reactions in propene polymerization with the rac isomer
MORET, MASSIMO;
1996
Abstract
The known rac-[ethylenebis(4,7-dimethyl-eta(5)-1-indenyl)]ZrCl2(2r) and its meso isomer (2m) have been compared with the prototypal chiral isospecific rac-[ethylenebis(eta(5)-1-indenyl)]ZrCl2 (1r) and its aspecific meso isomer Im in terms of molecular structures, solution dynamics, and ligand substitution effect on polymerization performance. in Liquid propene at 50 degrees C, 2r/MAO produces iPP with appreciably higher isotacticity but lower molecular weight and regiospecificity than 1r/MAO. The lower molecular weight obtained with 2r in liquid monomer is due to predominant chain transfer to the monomer after a secondary propene insertion, producing >90% cis-2-butenyl- end groups. At lower propene concentration, 2r/MAO allows both beta-hydrogen transfer after a primary insertion and beta-methyl transfer, The low-activity 2m/MAO catalyst produces low molecular weight aPP. The diastereoselective synthesis of 2r,m via the corresponding rac- and meso-bis(4,7-dimethy-1-(trimethylsilyl)-3-indenyl)ethane,is reported. The crystal and molecular structures of meso-bis(4,7-dimethyl-1-(trimethylsilyl)-3-indenyl)ethane, 2r,m, have been determined.
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