Diverse stereocontrol effects induced by weakly coordinating anions. Stereospecific olefin polymerization pathways at archetypal Cs- and C1-symmetric metallocenium catalysts using mono- and polynuclear halo-perfluoroarylmetalates as cocatalysts

John A.S. Roberts, Ming Chou Chen, Afif M. Seyam, Ting Li, Cristiano Zuccaccia, Nicholas G. Stahl, Tobin J. Marks

Research output: Contribution to journalArticle

51 Citations (Scopus)

Abstract

Counteranion effects on propylene polymerization rates and stereoselectivities are compared using Cs-symmetric Me 2C(Cp)(Flu)ZrMe2 (1; Cp = C5H 45-cyclopentadienyl; Flu = C13H 8, η5-fluorenyl) and C1-symmetric Me 2Si(OHF)(CpR*)ZrMe2 (2; OHF = C13H 16, η5-octahydrofluorenyl; CpR* = η5-3-(-)-menthylcyclopentadienyl) precatalysts activated with the mononuclear and polynuclear perfluoroarylborate, -aluminate, and -gallate cocatalysts/activators B(C6F5)3 (3), B(o-C 6F5C6F4)3 (4), AI(C 6F5)3 (5), Ph3C+B(C 6F5)4- (6) Ph3C +FAI(o-C6F5C6F4) 3- (7), Ga(C6F5)3 (8), and recently reported mono- and polymetallic trityl perfluoroarylhalometalates Ph3C+FB(C6F5)3 - (9), Ph3C+FB(o-C6F 5C6F4)3- (10), (Ph 3C-)xF x[AI(C6F 5)3]yx- (x = 1, y = 1, 11; X = 1, y = 2, 12; x = 2, y = 3, 13), Ph3C+(C6F 5)3AIFAI(o-C6F5C6F 4)3- (14), Ph3C +XAI(C6F5)3- (X = Cl, 15; X = Br, 16), and Ph3C+F[Ga(C6F 5)3]2- (17). Temperature, propylene concentration, and solvent polarity dependence are surveyed in polymerizations catalyzed by 1 activated with cocatalysts 3-16 and with a 1:2 ratio of Ph 3CCI and 5, and with a 1:2 ratio of Ph3CBr and 5, and by 2 activated with 3, 6, 7, 12, and 14. Remarkable stereocontrol with high activities is observed for 1 + 12 and 1 + 14. Polypropylene samples produced using C1-symmetric precatalyst 2 are subjected to microstructural analyses using stochastic models describing the relative contributions of enantiofacial misinsertion and backskip processes. A powerful technique is introduced for calculating interparametric correlation matrices for these nonlinear stochastic models. The collected results significantly extend what is known about ion-pairing effects in the case of Cs-symmetric precatalyst 1 and allow these findings to be applied to the case of C 1-symmetric precatalyst 2 as an agent of isospecific propylene polymerization.

Original languageEnglish
Pages (from-to)12713-12733
Number of pages21
JournalJournal of the American Chemical Society
Volume129
Issue number42
DOIs
Publication statusPublished - Oct 24 2007

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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