rac-[Methylene(3-tert-butyl-1-indenyl)₂]ZrCl₂:  A Simple, High-Performance Zirconocene Catalyst for Isotactic Polypropene

Abstract

The synthesis and propene polymerization performance of the novel rac-[CH 2 (3-tert-butyl-1-indenyl) 2 ]ZrCl 2 (2) and rac-[CH 2 (3-tert-butyl-1-indenyl) 2 ]ZrMe 2 (2-Me 2 ) are described. The ligand precursor, bis(1-tert-butyl-3-indenyl)methane (L2), is obtained in ca. 80% conversion from the condensation of 3-tert-butylindene and formaldehyde in DMF at room temperature and is isolated as a yellow powder by washing with pentane. Red 2 is obtained in 50-60% yield and free from its meso stereoisomer by reacting an Et 2 O solution of the ligand dianion, (L2)Li 2 (Et 2 O) x , with a slurry of ZrCl 4 in either pentane or toluene. Yellow 2-Me 2 is prepared in 90% yield by reaction of 2 with excess MeMgCl in toluene. Alternatively, 2-Me 2 (contaminated with about 5% of its meso isomer) can be obtained directly from the ligand L2, by reacting L2 in Et 2 O with 4 equiv of MeLi and then 1 equiv of ZrCl 4 in toluene. Both 2 and 2-Me 2 are remarkably soluble in pentane (2, ca. 1.7 g/L; 2-Me 2 , ca. 13 g/L) and toluene (2, ca. 50 g/L). 2/MAO and 2-Me 2 /MAO polymerize liquid propene with good activities to highly isotactic (mmmm ) 95-98%), fully regioregular polypropene with medium-high molecular weights (M h w ) 70 000-780 000) and high melting points (T m ) 154-163 °C) in the T p range 30-70 °C. The behavior of 2 is compared to that of the prototypical Montell zirconocene rac-[Me 2 C(3-t-Bu-Ind) 2 ]ZrCl 2 (1). 2 is the first example of a highly efficient and at the same time simple and inexpensive zirconocene catalyst for isotactic polypropene. The molecular structures of 2 and its Hf analogue (Hf-2) have been determined and compared to that of 1.

Highly Isospecific Styrene Polymerization Catalyzed by Single‐Component Bridged Bis(indenyl) Allyl Yttrium and Neodymium Complexes

“…[15] and a solution structure similar to that observed in the solid state. [16] The allyl moiety appears as a triplet at d = 7.00 ppm for the central hydrogen and two doublets of doublets at d = 3.85 and 1.19 ppm for the nonequivalent terminal hydrogen atoms.…”

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.…”

Isospecific Propylene Polymerization Behavior of Lewis Base Functionalized Unbridged Zirconocences under Bulk Conditions

“…The M w of polypropylenes decreases with increasing polymerization temperature for all zirconocenes probably due to the increased rate of chain transfer reaction at high temperature. 26,27 At the same temperature, the M w of polypropylenes from meta-di-functionalized zirconocenes was higher than that from both meta-and para-mono-functionalized ones (mZrN2 > mZrN1 > pZrN1 and mZrO2 > pZrO1 > mZrO1). This result could also be explained by steric effect of functional groups.…”