Catalytic Oligomerization of Ethylene to Higher Linear α-Olefins Promoted by Cationic Group 4 Cyclopentadienyl-Arene Active Catalysts: A DFT Investigation Exploring the Influence of Electronic Factors on the Catalytic Properties by Modification of the Hemilabile Arene Functionality

Abstract

Hessen and co-workers described Ti-based precatalysts of the title class bearing a hemilabile ancillary arene functionality for ethylene trimerization. The analogues with the heavier group 4 metals Zr and Hf as the active center have been recently explored computationally. This study suggested the Zr-based system as a promising catalyst for production of an oligomer mixture containing 1-octene besides the prevalent 1-hexene. Herein, we have presented a detailed computational analysis of the influence of modifications of the hemilabile arene functionality on the catalytic abilities of cationic group 4 [(η5-Cp-(CMe2R‘-bridge)-C6HyRx)MII(C2H4)2]+ active species (M = Zr, Hf) for linear ethylene oligomerization, employing a gradient-corrected DFT method. This comprised the arene substitution with prototypical electron-releasing (R = Me) and electron-withdrawing (R = F, CF3) groups in various combinations and also the enlargement of the Cp-arene connecting bridge by an additional methylene group (R‘ = CH2). The...