ansa-Metallocene derivatives

Abstract

The chiral ansa-zirconocene derivative ethylenebis(4,5,6, 7-tetrahydro-l-indenyl)zirconium(IV) dichloride has been prepared by reaction of dilithiobis(indenyl)ethane with ZrCl 4 and subsequent hydrogenation. The product has been shown to be the l-R,S rather than meso-metal-ring linkage stereoisomer by an X-ray determination of the molecular structure.

Syndiotactic Polypropylene: Discovery, Development, and Industrialization via Bridged Metallocene Catalysts

“…The importance of the bridge in ansa-metallocene catalysts was recognized early on during the development of chiral metallocene catalysts for olefin polymerization [43][44][45]. Its existence is the prerequisite for stereorigidity of the metallocene structure, designed to prevent the free rotation of the aromatic ring(s) and to maintain the appropriate chirality of the corresponding cationic active species during the initial stages and the entire process of the polymerization.…”

“…Also, the fact that homotopic metallocene/MAO catalysts polymerize propylene to stereoregular crystalline polypropylene was already known. In the mid-1980s, after the discovery of the bridged chiral ansabis-indenyl metallocene complexes [43][44][45], it was shown, in a series of polymerization tests, that MAO activation of C 2 symmetric chirotopic bis-indenyl-based metallocene complexes very efficiently promotes the isospecific polymerization of propylene to highly stereoregular i-PP [46][47][48][49][50][51][52][53][54][55]. In this case, the rationalization for the nature and behavior of catalytically active species and the formation of i-PP was again very similar to the activation processes and mechanistic routes that had been proposed, and generally accepted, for stereospecific polymerization of propylene with heterogeneous ZN catalyst systems [56][57][58][59][60][61][62][63].…”

Ethene/Propene Copolymerizations from Metallocene-Based Catalytic Systems: The Role of Comonomer Concentrations

“…[5] In this work, we have investigated the role of comonomer concentrations in ethene/propene (E/P) copolymerization. A catalytic system composed of a typical metallocene as rac-[ethylenebis(4,5,6,7-tetrahydro-1-indenyl)]-zirconium dichloride [6] (r-EBTHIZrCl 2 ) and by a newly developed aluminoxane such as tetraisooctylaluminoxane [7] (TIOAO) was employed. Hexane was used as a solvent or diluent.…”

Copolymerization of Ethylene and Cyclopentene with Zirconocene Catalysts: Effect of Ligand Structure of Zirconocenes

“…Scheme 3. [7] 6; a = 127.8 8, b = 60.2 8, c = 85.7 8, d = 2.46-2.66 , [8] where a, b, c and d are angle of cp-Zr-cp9 (cp,cp9 = centroids of the Cp rings, Cp = cyclopentadienyl moiety in the indenyl ligand), angle between Cp planes, angle between Cp plane and cp-Zr bond, and length of cp-Zr, respectively, as shown in Scheme 4. The catalyst 5 shows a somewhat smaller a angle and a larger c angle than those of the catalyst 6.…”