LAUSR

Abstract Two Ni-diimine catalysts were synthesized in which the sterics of the imine-aryl groups were adjusted, and their reactivities towards 1-pentene and 2-pentene were studied. When the aryl groups are o-isopropyl-phenyl, oligomeric products are formed from 1-pentene and trans-2-pentene, but cis-2-pentene is unreactive under the reaction conditions. Characterization of the oligomers demonstrate that they form from a chain-walking mechanism, consistent with previous work on similar Ni-diimine catalysts used for polymerization. When the aryl groups are phenyl, pentene dimerization becomes dominant, and all three linear pentenes are reactive. These results show that decreasing the ligand sterics give increased rates of associative olefin substitution, thereby decreasing the size of the oligomeric products formed, consistent with previous work. Analysis of the products helps to determine the mechanisms by which the Ni-diimines react with linear olefins, demonstrating that in addition to olefin oligomerization via insertion into primary Ni–C bonds, both olefin isomerization and olefin insertion into secondary Ni–C bonds occurs. Due to chain-walking catalysts giving more linear, less branched products, the hydrogenated products can be desirable for lubricant and diesel fuel applications, depending on the size of the oligomers formed.