Polymerization of Ethylene Catalyzed by a Nickel(+2) Anilinotropone-Based Catalyst: DFT and Stochastic Studies on the Elementary Reactions and the Mechanism of Polyethylene Branching

Abstract

The results of combined DFT/stochastic studies on the mechanism of ethylene polymerization catalyzed by a neutral Ni-anilinotropone complex are presented. The generation of active species by phosphine dissociation and chain propagation and chain isomerization reactions have been investigated. The alternative methyl acrylate binding modes have also been studied. Further, the DFT-calculated energetics of the elementary reactions have been used to model the influence of the reaction conditions (T, P) on the branching/microstructure of polyethylenes produced in this process. The model and real catalysts (N∧O−Ni; N∧O = −N(Ar)−(C7H5)−O−, with Ar = H and Ar = C6H3(i-Pr)2, respectively) have been considered to account for the electronic and steric effects. The presence of two cis/trans isomers for all the reactions has been considered. The results indicate that for the real anilinotropone catalyst the phosphine dissocciation is less endothermic (22 kcal/mol) than for the corresponding salicylaldiminato system (29...