Synthesis of a Ni Complex Chelated by a [2.2]Paracyclophane-Functionalized Diimine Ligand and Its Catalytic Activity for Olefin Oligomerization.

A diimine ligand having two [2.2]paracyclophanyl substituents at the N atoms () was prepared from the reaction of amino[2.2]paracyclophane with acenaphtenequinone. The ligand reacts with NiBr(dme) (dme: 1,2-dimethoxyethane) to form the dibromonickel complex with (,) and (,) configuration, NiBr(). The structure of the complex was confirmed by X-ray crystallography. NiBr() catalyzes oligomerization of ethylene in the presence of methylaluminoxane (MAO) co-catalyst at 10-50 °C to form a mixture of 1- and 2-butenes after 3 h. The reactions for 6 h and 8 h at 25 °C causes further increase of 2-butene formed via isomerization of 1-butene and formation of hexenes. Reaction of 1-hexene catalyzed by NiBr()-MAO produces 2-hexene via isomerization and C12 and C18 hydrocarbons via oligomerization. Consumption of 1-hexene of the reaction obeys first-order kinetics. The kinetic parameters were obtained to be Δ = 93.6 kJ mol, Δ = 63.0 kJ mol, and Δ = -112 J moldeg. NiBr() catalyzes co-dimerization of ethylene and 1-hexene to form C8 hydrocarbons with higher rate and selectivity than the tetramerization of ethylene.