Catalytic Studies of VO(IV) Complexes in Alcohol Oligomerization and Ethylene/(Ethylene-1-octene) Polymerization: Structure-Activity and Mechanistic Insights.

Nowadays, new catalysts are being designed for polymerization of olefins and their derivatives containing functional groups, aiming to achieve higher reaction rates and improved selectivity by minimizing side reactions. Here, we present a vanadium(IV) catalyst with a novel N-oxide ligand, [VO(acac)2(4-phenylpyridine N-oxide)], synthesized in situ from a new ligand precursor, (N-OH)-4-phenylpyridine(Cl). We tested a new catalyst in the polymerization of ethylene, copolymerization of ethylene and 1-oxetane, and oligomerization of 2-chloro-2-propen-1-ol and 3-buten-1-ol. We optimized the reactions, e.g., the Al/V molar ratio using methylaluminoxane (MAO) as a cocatalyst during the oligomerization of 2-chloro-2-propen-1-ol. Density functional theory studies focused on the chain propagation step revealed key mechanistic differences between the olefin polymerization and oligomerization of polar monomers catalyzed by the vanadium complex. The active species, [VO(acac)(4-phenylpyridine N-oxide)]+, facilitates a stepwise mechanism involving two kinetic barriers: 8.0 and 4.7 kcal/mol for ethylene polymerization and 11.2 and 9.9 kcal/mol for 3-buten-1-ol oligomerization, corresponding to monomer coordination and insertion steps.