Synthesis Of Novel Diphosphine Ligands And Other Nitrogen And Phosphine Ligands And Their Application In Cr-catalyzed Selective Ethylene Oligomerization

Linear a-olefins, particularly the1-hexene and1-octene, play an important role in the polyethylene industry. The polyethylene produced from1-hexene or1-octene as co-monomer has improved product performance compared with ones from1-butene as co-monomer. In the perspective of atomic economics, the most efficient way to obtain these a-olefin is selective oligomerization of ethylene. Cr-based catalysts are prominent in the ethylene oligomerization catalyst system. This paper contains the following two parts:1. To sum up the related literatures, we present the type and mechanism of ethylene oligomerization, and especially introduce the highly selective ethylene trimerization and tetramerization catalyst systems.2. Based on others and our previous work, we have developed a class of the asymmetric carbon-bridged diphosphine ligands. Cr complexes bearing these diphosphine ligands exhibit very high activity and high selectivity in ethylene trim/tetramerization, which is very important not only in academic but also in industrial communities. The ligand scaffold of this type is finely tunable. Based on the X-ray diffraction data of the representative Cr complex, we try to explain the mechanism.3. We continue to tentative exploration in the NP and PP bidendate ligands and some other tridendate ligands in the Cr-catalyzed ethylene oligmerization...