Co-oligomerization of ethylene and higher linear alpha olefins. II. Olefin reactivities in various reaction steps of co-oligomerization with nickel ylide-based system

Part I described co-oligomerization reactions of ethylene and various linear α-olefins (propylene, 1-butene, 1-hexene, 1-heptene, 1-octene, and 1-decene) in the presence of the homogeneous catalyst consisting of sulfonated nickel ylide and diethylaluminum ethoxide. The present article analyzes olefin reactivities in various reaction steps of the co-oligomerization reactions as well as reactivities of various catalytic species. Chain propagation reactions (insertion into the Ni? C bonds) with participation of α-olefins exhibit poor regioselectivity, primary insertion being ca. 60% more probable than the secondary insertion. Ethylene is significantly more reactive in chain propagation reactions: 50–70 times compared to olefin primary insertion and 100–120 times compared to olefin secondary insertion. Reactivities of α-olefins in chain propagation reactions decrease slightly for higher olefin alkyl groups. Reactivities of Ni? C bonds in chain propagation and chain termination reactions strongly depend on the structure of the alkyl group attached to the nickel atom. The Ni? CHR? CH₂? R bond has very low reactivity in ethylene insertion reaction and usually decomposes in the α-hydrogen elimination process. Kinetic analysis of olefin co-oligomerization reactions provides numerous analogies with olefin copolymerization reactions in the presence of Ziegler–Natta catalysts.