The impact of P substituents on the oligomerization of ethylene with nickel 2-diphenyl and 2-dicyclohexylphosphinophenolate phosphine catalysts

Solutions of 2-diphenyl- or 2-dicyclohexylphosphinophenol, nickel bis(1,5-cyclooctadiene), and a tertiary phosphine R3P in toluene oligomerize ethylene in most cases with high selectivity to linear α-olefins. The molecular weights can be tuned by the catalyst composition. Molecular weights are generally lower with Ph2P∩ONi than with cHex2P∩ONi catalysts and in the presence of R3P additives, but basicity-dependent effects of various triarylphosphine additives on the molecular weights and relative reaction rates, displayed by pressure-time plots, are rather different or opposite for Ph2P∩ONi and cHex2P∩ONi catalysts.