Abstract
A diimine ligand having two [2.2]paracyclophanyl substituents at the N atoms (L1) was prepared from the reaction of amino[2.2]paracyclophane with acenaphtenequinone. The ligand reacts with NiBr2(dme) (dme: 1,2-dimethoxyethane) to form the dibromonickel complex with (R,R) and (S,S) configuration, NiBr2(L1). The structure of the complex was confirmed by X-ray crystallography. NiBr2(L1) 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 NiBr2(L1)–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 ΔG‡ = 93.6 kJ mol−1, ΔH‡ = 63.0 kJ mol−1, and ΔS‡ = −112 J mol−1deg−1. NiBr2(L1) catalyzes co-dimerization of ethylene and 1-hexene to form C8 hydrocarbons with higher rate and selectivity than the tetramerization of ethylene.
Highlights
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The oligomerization of olefins catalyzed by transition metal complexes has attracted attention, as shown by many review articles on this topic over the last decades [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16] as well as recent original reports [17,18,19]
The mechanistic studies are of interest from the viewpoint of catalytic and organometallic chemistry
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Ni and Pd complexes with diimine ligands having bulky N-aryl substituents were found to catalyze high-mass polymerization of ethylene and 1-olefins as well as copolymerization of ethylene with acrylates [41]. Ni and Pd complexes with diimine ligands having bulky N-aryl substituents wer found to catalyze high-mass polymerization of ethylene and 1-olefins as well as copoly merization of ethylene with acrylates [41]. Ni center of intermediate (A) having the diimine ligand with 4-substituted N-ary is sterically less crowded, and undergoes associative coorindation of an ethylene monomer groups is sterically less crowded, and undergoes coorindation of an at the apical coordination site of square-planar. Further insertion complex withinto a diimine ligand having [2.2]paracyclophanyl substituents at the molecules the Ni–C bond provides new oligomer molecules. We report synthesis and structure of the new the sterically bulky N-cycloparaphenyl groups of the ligand We report synthesi structure of the new Ni-diimine complexes as well as its catalysis
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