Olefin oligomerization by main group Ga and Zn single site catalysts on SiO.

In heterogeneous catalysis, olefin oligomerization is typically performed on immobilized transition metal ions, such as Ni and Cr. Here we report that silica-supported, single site catalysts containing immobilized, main group Zn and Ga ion sites catalyze ethylene and propylene oligomerization to an equilibrium distribution of linear olefins with rates similar to that of Ni. The molecular weight distribution of products formed on Zn is similar to Ni, while Ga forms higher molecular weight olefins. In situ spectroscopic and computational studies suggest that oligomerization unexpectedly occurs by the Cossee-Arlman mechanism via metal hydride and metal alkyl intermediates formed during olefin insertion and β-hydride elimination elementary steps. Initiation of the catalytic cycle is proposed to occur by heterolytic C-H dissociation of ethylene, which occurs at about 250 °C where oligomerization is catalytically relevant. This work illuminates new chemistry for main group metal catalysts with potential for development of new oligomerization processes.