title: New nickel(II) diimine complexes and the control of polyethylene microstructure by catalyst design.
abstract: Starting from differently substituted boronic acids as versatile building block, new "ortho-aryl" alpha-diimine ligands a-h were synthesized in an easy, high-yielding route. Reaction of the complex precursor diacetylacetonato-nickel(II) with a trityl salt, like [CPh3] [B(C6F5)4] or [CPh3] [SbCl6], in the presence of the diimine ligands afford the monocationic, square planar complexes 2a-g in almost quantitative yields. Suitable crystals (2d',e,f,g) were submitted for X-ray diffraction analysis. A geometry model was developed to describe the orientation of ligand fragments around the nickel(II) center that influence the polymer microstructure. At elevated reaction temperature and pressure, and in the presence of hydrogen, 2a-e catalyze the homopolymerization of ethylene to give branched PE products ranging from HD- to LLD-PE grades. The polymerization results indicate the possibility of precise microstructure control depending on the particular complex substitution. Preliminary investigations on material density and mechanical behavior by uniaxial stretching until failure point toward new material properties that can result from the simple ethylene monomer by catalyst design.
authors.affiliation: Institute of Inorganic Chemistry II, Ulm University, Albert-Einstein Allee 11, 89081 Ulm, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Meinhard
authors.forename: Marcus
authors.initials: M
authors.lastname: Wegner
authors.forename: Georgy
authors.initials: G
authors.lastname: Kipiani
authors.forename: Andrew
authors.initials: A
authors.lastname: Hearley
authors.forename: Peter
authors.initials: P
authors.lastname: Reuter
authors.forename: Stefan
authors.initials: S
authors.lastname: Fischer
authors.forename: Othmar
authors.initials: O
authors.lastname: Marti
authors.forename: Bernhard
authors.initials: B
authors.lastname: Rieger