Titanium and zirconium complexes for polymerization of propylene and cyclic esters

TY - JOUR

T1 - Titanium and zirconium complexes for polymerization of propylene and cyclic esters

AU - Gornshtein, Florina

AU - Kapon, Moshe

AU - Botoshansky, Mark

AU - Eisen, Moris S.

PY - 2007/1/29

Y1 - 2007/1/29

N2 - The new group IV complexes ((CH3)3CCOCHCONEt 2)2Ti(OMe)2 (3), ((CH3) 3CCOCHCONMe2)2Ti(OMe)2 (4), (CH 3COCHCONMe2)2Ti(OC(CH3) 3)2 (5), and ((CH3)3CCOCHCONEt 2)2ZrCl2 (6) were synthesized and characterized. The titanium dialkoxide complexes 3 - 5 were produced during the attempts to synthesize the corresponding titanium diamido complexes via an intramolecular metathesis. A mechanism for the intramolecular metathesis is presented. Complexes 3 and 4 exhibit dynamic behavior in solution as a function of temperature. This dynamic behavior is due to a disconnection and recoordination of the β-ketoamidate chelating ligands through the weaker Ti-O bond, resulting in the formation of different octahedral stereoisomers in solution. Complexes 3-6, activated with MAO, were found to be active in the polymerization of propylene, producing elastomeric polypropylene. The elastomeric properties of the polymers obtained using complex 3 as catalyst are due to a dynamic interconversion between two C2-symmetric enantiomeric structures via an open C2v-symmetric intermediate complex. Additionally, complexes 3-6 were found to be active in the polymerization of ε-caprolactone and rac-lactide. The activity of the zirconium dichloride complex 6 is higher than the activities of any of the titanium dialkoxide complexes 3-5 both in ε-caprolactone and in rac-lactide polymerizations.

AB - The new group IV complexes ((CH3)3CCOCHCONEt 2)2Ti(OMe)2 (3), ((CH3) 3CCOCHCONMe2)2Ti(OMe)2 (4), (CH 3COCHCONMe2)2Ti(OC(CH3) 3)2 (5), and ((CH3)3CCOCHCONEt 2)2ZrCl2 (6) were synthesized and characterized. The titanium dialkoxide complexes 3 - 5 were produced during the attempts to synthesize the corresponding titanium diamido complexes via an intramolecular metathesis. A mechanism for the intramolecular metathesis is presented. Complexes 3 and 4 exhibit dynamic behavior in solution as a function of temperature. This dynamic behavior is due to a disconnection and recoordination of the β-ketoamidate chelating ligands through the weaker Ti-O bond, resulting in the formation of different octahedral stereoisomers in solution. Complexes 3-6, activated with MAO, were found to be active in the polymerization of propylene, producing elastomeric polypropylene. The elastomeric properties of the polymers obtained using complex 3 as catalyst are due to a dynamic interconversion between two C2-symmetric enantiomeric structures via an open C2v-symmetric intermediate complex. Additionally, complexes 3-6 were found to be active in the polymerization of ε-caprolactone and rac-lactide. The activity of the zirconium dichloride complex 6 is higher than the activities of any of the titanium dialkoxide complexes 3-5 both in ε-caprolactone and in rac-lactide polymerizations.

UR - http://www.scopus.com/inward/record.url?scp=33847194660&partnerID=8YFLogxK

U2 - 10.1021/om060723c

DO - 10.1021/om060723c

M3 - 文章

AN - SCOPUS:33847194660

SN - 0276-7333

VL - 26

SP - 497

EP - 507

JO - Organometallics

JF - Organometallics

IS - 3

ER -