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Article Abstract
A series of novel diphosphinoamine (PNP) ligands bearing a -alkenyl group were synthesized and applied in chromium-catalyzed selective ethylene tri-/tetramerization by combination of Cr(acac) and modified methylalumoxane (MMAO-3A). The ligand substitution and oligomerization conditions have a remarkable influence on the catalytic activity and controllable selectivity. Most of these PNP ligands are highly active for ethylene tri-/tetramerization with considerable selectivity. An asymmetric diisopropenylphosphanyl ligand with an -cyclohexyl group achieved the highest activity of 2036 kg (g Cr h) with a high total selectivity of 81.1 wt% toward valuable 1-hexene (43.0 wt%) and 1-octene (38.1 wt%) at 40 bar ethylene and 60 °C. An asymmetric mixed isopropenyl/ethylphosphanyl ligand with an -isopropyl group exhibited a high 1-octene selectivity of 65.5 wt% and a high total 1-hexene/1-octene selectivity (91.5 wt%) with a high activity of 1256 kg (g Cr h).
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Highly active chromium-based selective ethylene tri-/tetramerization catalysts supported by alkenylphosphanyl PNP ligands.
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