Fluorine- and Trifluoromethyl-Substituted Iminopyridinenickel(II) Complexes Immobilized into Fluorotetrasilicic Mica Interlayers as Ethylene Oligomerization Catalysts

Heterogeneous catalysts comprising immobilized nickel(II) complexes bearing a fluorine- or trifluoromethyl-substituted iminopyridine ligand (Xn-C6H5–n-N=C (CH3)-C5H5N, X = F or CF3) in fluorotetrasilicic mica interlayers were prepared by reacting Ni2+-exchange fluorotetrasilicic mica with the appropriate ligand. Upon activating the precatalyst with triethylaluminum or triisobutylaluminum, the generated active species showed catalytic activity for ethylene oligomerization, yielding low-molecular-weight polyethylene (PE), ethylene oligomers, and wax-like PE. The oligomer distribution almost agreed with what we expected according to the Schultz–Flory distribution. However, the amount of solid products was much higher than the theoretical value, indicating that at least two active species were formed, i.e., the oligomer and low-molecular-weight PE. The precatalyst with a 2,4-F2C6H3 group on the imino nitrogen atom activated by triethylaluminum showed the highest catalytic activity for ethylene oligomerization (408 g-C2 g-cat−1 h−1), with selectivities to the liquid and solid products of 51.0% and 11.5%, respectively, with the rest of the product corresponding to wax-like PE. Meanwhile, the highest selectivity to the liquid product (66.7% at 233 g-C2 g-cat−1 h−1) was obtained using the precatalyst with a 2-FPh group on the imino nitrogen atom activated by triisobutylaluminum.