C₁‐Symmetric Heterocyclic Zirconocenes as Catalysts for Propylene Polymerization, 2

Abstract

Summary: Sixteen C1‐symmetric zirconocene and one hafnocene complexes bearing the 2,5‐R2‐7H‐cyclopenta[1,2‐b:4,3‐b′]dithiophene ligand (R = H, Me, Et, Ph) linked to a substituted indenyl ligand have been synthesized and tested in propylene polymerization. Most of the C1‐symmetric zirconocenes of this type are highly active in propylene polymerization at low MAO/Zr ratios and produce poly(propylene)s (PP) in a broad range of isotacticity and melting points. The molecular weight and crystallinity of the PPs are strongly dependent upon the type of substituents on the indenyl moiety: PPs with Tm between 75 and 156 °C and viscosity average molecular weights between 100 000 and 400 000 have been obtained at 50–70 °C in liquid propylene.General formula of the indenyl‐based zirconocenes.magnified imageGeneral formula of the indenyl‐based zirconocenes.

The Deformability of Polymers: The Role of Disordered Mesomorphic Crystals and Stress‐Induced Phase Transformations

“…The concentrations of the rr triad stereodefects produced by each catalyst are indicated. [7,8] Figure 1. X-ray powder diffraction profiles (A) and stress-strain curves of samples of highly stereoregular iPP prepared with a Ziegler-Natta catalyst slowly crystallized from the melt in the a form (a) and in the mesophase by quenching the melt at 0 8C (b).…”

“…[6] iPP samples of different stereoregularity have been prepared with the metallocene catalysts shown in Scheme 1. These catalytic systems are able to produce iPP samples characterized by chains containing largely one type of stereoirregularity (rr triad defects), [6][7][8] the amount of which depends on the structure of the catalyst. Samples with concentration of rr defects ranging from 0.5 and 11 % and melting temperatures in the range of 160-80 8C have been analyzed and compared with a highly stereoregular iPP sample prepared with a conventional Zigler-Natta catalyst.…”

Comparing propene polymerization with 1-butene polymerization catalyzed by MAO-activated C2- and C1-symmetric zirconocenes: An experimental and computational study on the influence of olefin size on stereoselectivity

“…[7,8], we have produced and analyzed polypropene and polybutene samples with three additional C 1 -symmetric zirconocenes, namely Me 2 Si(2-MeInd)(9-Flu)ZrCl 2 (2) [9], Me 2 Si(2,4,6-Me 3 Ind)(9-Flu)ZrCl 2 (3) and Me 2 Si[2-Me-4-(a-naphthyl)Ind](BMTCp)ZrCl 2 (BMTCp = bis(2-methylthieno)cyclopentadienyl). The latter complex, for which only iPP results were previously presented [7], is the most stereoselective among the C 1 -symmetric structures also in 1-butene polymerization, producing iPB with the highest stereoregularity (mmmm = 98%), and a consequently high melting point (T m = 109°C for the crystalline form II), values almost identical to those obtained with the most isoselective C 2 -symmetric complex rac-H 2 C-(3-t BuInd) 2 ZrCl 2 [8]. We also prepared and tested Me 2 Si(2,4,6-Me 3 Ind)(9-Flu)ZrMe 2 (3a), the dimethyl derivative of 3 [10].…”

“…Selected literature polypropene [7] and polybutene [8] characterization data from known complexes are compared in Table 1. In addition to the data already presented in Refs.…”

“…We have recently reported on the polymerization of propene [7] and 1-butene [8] with a series of C 1 -symmetric and C 2 -symmetric zirconocenes. Possibly, the most striking feature of the C 1 -symmetric catalysts is the strong increase in catalyst selectivity on going from propene to 1-butene.…”