Nickel(II) Complex Bearing Fluorine-substituted [alpha]-Diimine Ligand Immobilized in Fluorotetrasilicic Mica Interlayer as Heterogeneous Catalysts for Ethylene Oligomerization

• Published in: Journal of the Japan Petroleum Institute Vol. 57; no. 3; p. 146
• Main Authors: Kurokawa, Hideki, Ogawa, Ryota, Yamamoto, Kazuhiro, Sakuragi, Tsutomu, Ohshima, Masa-aki, Miura, Hiroshi
• Format: Journal Article
• Language: English
• Published: Tokyo Japan Science and Technology Agency 01.05.2014
• ISSN: 1346-8804; 1349-273X
• DOI: 10.1627/jpi.57.146

Heterogeneous α-diiminenickel(II) catalysts were prepared by the direct reaction between nickel(II) ion-exchanged fluorotetrasilicic mica and the ligand [Ph'-N = C(Me)-C(Me) = N-Ph' Ph' = C6H5-, 2-FC6H4-, 4-FC6H4-, 2,4-F2C6H3-, and 2,4,6-F3C6H2-]. When the prepared procatalysts were activated by a conventional alkyl aluminum compound, such as triethylaluminum or triisobutylaluminum, the high activity for ethylene oligomerization was readily obtained with the formation of linear α-olefins. The activity of the catalysts increased with the addition of fluorine atoms on the phenyl groups in the ligand, and the maximum activity (420 g-C2 g-cat-1 h-1 at 0.7 MPa and 50 °C) was obtained by the catalysts containing 2,4-difluorophenyl groups, because fluorine atoms decreased the electron density of the nickel center. The oligomers were formed in good accordance with the Schulz-Flory distribution, and the values of the distribution constant were within 0.53-0.65. The selectivities of the linear α-olefins were not less than 90 mol% in all the runs. During all the oligomerization runs, long induction periods were clearly observed, but the period was shortened when the reaction temperature was raised. It seemed that the characteristic catalytic behavior was due to a complicated activation mechanism derived from the specific layered structure of the procatalysts.