The Role of Co-Activation and Ligand Functionalization in Neutral Methallyl Nickel(II) Catalysts for Ethylene Oligomerization and Polymerization

作者：Ortega Daniela E; Cortes Arriagada Diego; Trofymchuk Oleksandra S; Yepes Diana; Gutierrez Oliva Soledad; Rojas Rene S; Toro Labbe Alejandro

来源：Chemistry - A European Journal, 2017, 23(42): 10167-10176.

DOI：10.1002/chem.201701571

• boron
• ethylene
• polymerization
• ligand effects
• nickel complexes

A detailed quantum chemical study that analyzed the mechanism of ethylene oligomerization and polymerization by means of a family of four neutral methallyl Ni-II catalysts is presented. The role of the boron co-activators, BF3 and B(C6F5)(3), and the position of ligand functionalization (ortho or para position of the N-arylcyano moiety of the catalysts) were investigated to explain the chain length of the obtained polymers. The chain initialization proceeded with higher activation barriers for the ortho-functionalized complexes (approximate to 19 kcal mol(-1)) than the para-substituted isomers (17-18 kcal mol(-1)). Two main pathways were revealed for the chain propagation: The first pathway was favored when using the B(C6F5)(3) co-activated catalyst, and it produced long-chain polymers. A second pathway led to the -hydrogen complexes, which resulted in chain oligomerization; this pathway was preferred when the BF3 co-activated catalysts were used. Otherwise, the termination of longer chains occurred via a stable hydride intermediate, which was formed with an energy barrier of about 14 kcal mol(-1) for the B(C6F5)(3) co-activated catalysts. Significant new insights were made into the reaction mechanism, whereby neutral methallyl Ni-II catalysts act in oligomerization and polymerization processes. Specifically, the role of co-activation and ligand functionalization, which are key information for the further design of related catalysts, were revealed.

• 出版日期2017-7-26