Trapping the Short-Chain Odd Carbon Number Olefins Using Nickel(II)-catalyzed Tandem Ethylene Oligomerization and Friedel-Crafts Alkylation of Toluene

Abstract

<div>Nickel(II) complexes with pyrazole-based ligands are widely employed in catalysis of ethylene</div><div>oligomerization and subsequent Friedel-Crafts alkylation of toluene. We have prepared ten new</div><div>nickel(II) dibromide complexes with various substituted bis(azolyl)methanes. They have been</div><div>characterized using <sup>1</sup>H NMR, IR, MALDI-TOF and elemental analysis. The structures of three</div><div>complexes have been unambiguously established using X-ray diffraction. It was found that these</div><div>complexes in the presence of Et<sub>2</sub>AlCl or Et<sub>3</sub>Al<sub>2</sub>Cl<sub>3</sub> are active both in ethylene oligomerization and</div><div>Friedel-Crafts alkylation processes (activity up to 3720 kgoligomer·mol[Ni]<sup>−1</sup>·h<sup>−1</sup>). The use of Et<sub>3</sub>Al<sub>2</sub>Cl<sub>3</sub></div><div>results in the higher share of alkylated products (up to 60%). Moreover, catalytic systems activated with</div><div>Et<sub>3</sub>Al<sub>2</sub>Cl<sub>3</sub> produced small amounts of odd carbon number olefins (up to 0.8%). The Friedel-Crafts</div><div>alkylation was used as a trap for previously undetected short-chain odd carbon number olefins (C<sub>3</sub> and</div><div>C<sub>5</sub>).</div>