Iminohydroxamato Early and Late Transition Metal Halide Complexes − New Precatalysts for Aluminoxane-Cocatalyzed Olefin Insertion Polymerization
✍ Scribed by Alexander Krajete; Georg Steiner; Holger Kopacka; Karl-Hans Ongania; Klaus Wurst; Marc O. Kristen; Peter Preishuber-Pflügl; Benno Bildstein
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 276 KB
- Volume
- 2004
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
Abstract
We report on new families of non‐metallocene metal precatalysts for olefin polymerization with titanium, zirconium, vanadium and nickel as the active metal sites. The novel ligand design concept is based on iminohydroxamic acids and their derivatives as the principal chelating units. Various anionic and neutral [N,O] and [N,N] ligand systems are easily accessible by a modular synthetic sequence of imidoyl chlorides with substituted hydroxylamines or hydrazines, respectively. Steric protection of the metal coordination site, a necessary requirement for suppression of chain termination pathways of non‐metallocene catalysts, is brought about by bulky aryl substituents on the imino nitrogen atoms. Crystal structures of some of the hydroxamato ligands reveal interesting intermolecular hydrogen‐bridged structures, whereas in the solid‐state structure of one titanium precatalyst a five‐membered chelate was observed, in line with the design principle of these systems. Preliminary ethylene polymerization studies with methylaluminoxane‐activated metal complexes (M = Ti, Zr, V, Ni) show that the most active systems are [N,O]NiBr~2~ catalysts containing neutral O‐alkyl iminohydroxamate ligands. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)