Phosphinite-Ligand-Assisted Chromium Pre-catalysts and their Ethylene Oligomerization Properties

Phosphinite based ligands with or without a secondary nitrogen binding site have been evaluated for the first time towards chromium catalyzed ethylene oligomerization using modified aluminoxane (MMAO-12) as an activator. Through systematic optimization of the reaction parameters specifically the reaction temperature, olefin selectivity up to 92 wt % could be achieved. In particular, at higher temperature (~75 °C), the rate of β-hydrogen elimination leading to the formation of olefinic products, is relatively more favorable over the rate of propagation which produces polyethylene. Overall, the present study reveals that the phosphinite type ligands could promote ethylene oligomerization, although nonselective way to yield olefin products with carbon number ranging from C₆−C₁₄ while yielding highest productivity up to 12517 g/gCr.h.