دراسة نظرية لبلمرة الإتيلين المحفزة بوساطة معقدات النيكل (II) الألكيلية مع مرتبطات α-ثنائي إيمين متنوعة.

Abstract

The mechanism of alkyl nickel(II)-catalyzed ethylene polymerization and chain branching with various α-diimine ligands of the N^ÇN type has been studied for the first time using the M06-2X functional with 6-31+G(d) basis sets for the main elements and LANL2DZl for the nickel atom. Alkyl nickel(II) complexes with all studied ligands exhibit significant activity towards ethylene polymerization except for ligand L2. The nickel complex with ligand L5 ligand is the most active toward polymerization compared to the other ligands. The presence of the 2-methylpyrrole (ligand L4) instead of the methylbenzene (ligand L3) increased the free energy barrier for ethylene polymerization by about 3.4 kcal/mol. However, when the methyl substituent is added orthogonally to the α-diimine structure (ligand L5), the nickel complex with this ligand becomes more active for polymerization. This result is consistent with experimental observations in terms of activity.