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.

o‐Amine‐Assisted Cannizzaro Reaction of Glyoxal with New 2,6‐Diaminoanilines

“…Several studies on nucleophilic substitution of glyoxal with 2,6-substituted anilines to form only diimines have been reported previously. [2][3] So, we attribute these abnormal reactions to some specific reactivity of the o-aminesubstituted anilines as mentioned in the Introduction of this article. We were interested to see which rôle tertiary alkylamines like 3a-c and 3g could play in the Cannizzaro reaction.…”

“…In a typical example, to a 100 mL Schlenk flask were added 2,6-dichloro nitrobenzene (3.00 g, 15.6 mmol), IPr (273 mg, 0.702 mmol), Pd(OAc) 2 (105 mg, 0.468 mmol), Cs 2 CO 3 (14.2 g, 43.7 mmol), aniline (4.3 mL, 46.8 mmol), and toluene (32 mL), and the mixture was stirred at 100°C for 48 h. After the resulting suspension was cooled to room temperature, the precipitate in the reaction mixture was removed by filtration and washing with CH 2 Cl 2 . After the solvent was evaporated, the residual black solid was dissolved in CH 2 Cl 2 and crystallized.…”

“…[1] However, studies on versatile, substituted primary anilines at the aromatic ring are not so numerous. For example, the substituents introduced into anilines were isopropyl groups, aromatic groups, [2] and alkyne groups [3] at the o-positions, which were used as building units of specific metal ligands for sterically demanding metal catalysts.…”

(1E,2E)-N1,N2-Bis(5′-methyl-[1,1′:3′,1′′-terphenyl]-4′-yl)acenaphthylene-1,2-diimine unknown solvent

“…The catalytic activity and properties of the resulting data reports polymers are greatly dependent on the reaction conditions (Helldö rfer et al, 2003) and ligand structures (Meinhard et al, 2007;Popeney et al, 2011;Yuan et al, 2005;2013). Nickel and palladium metal complex catalysts have a high catalytic activity for ethylene polymerization which gives high branched polyethylene, and the copolymerization of ethylene and polar monomers have also high catalytic activity.…”

Homo-Polymerization of 1-Hexene Catalysed by O^N^N (Salicylaldimine)Iron(III) Pre-Catalysts to Branched Poly(1-hexene)

“…Brookhart and co-workers [11,17,[19][20][21][22] and others [23][24][25] have investigated extensively the polymerisation of ethylene with nickel(II) and palladium(II) catalysts. The type of polyethylenes produced by these nickel and palladium catalysts range from highly branched, amorphous materials to semi crystalline high density materials.…”