High active and selective 1–3 chromium catalysts based on the corresponding Ph₂PN(cyclopentyl)P (NR₂)₂-type L¹–L³ ligands (L¹: R = methyl, L²: R = ethyl, L³: R = isopropyl) have been explored for selective ethylene tri-/tetramerization. We found that the ligand substituents and the experimental conditions considerably influenced the catalytic performance of 1–3 based catalysts. Combining a higher ethylene pressure can elevate the selectivity of 1-octene (67.98%) of precatalyst 1 with high catalytic activity (9.3 × 10⁶ g/[molCr h]). Furthermore, precatalysts 2–3 efficiently offer selective ethylene trimerization and afforded 97.76% 1-hexene selectivity with 5.8 × 10⁶ g/(molCr h) catalytic activity (in case precatalyst 3). A relatively low catalyst mass, high Al/Cr molar ratio, and high ethylene pressure display excellent catalytic activity and selectivity for ethylene oligomerization.

中文翻译：

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基于 PNP(NR2)2 配体的铬催化剂用于选择性乙烯齐聚

基于相应的 Ph ₂ PN(环戊基)P (NR ₂ ) ₂型L ¹ - L ³配体 ( L ¹ : R = 甲基, L ² : R = 乙基, L ³ ) 的高活性和选择性1-3铬催化剂: R = 异丙基) 已被探索用于选择性乙烯三聚/四聚。我们发现配体取代基和实验条件显着影响了1-3基催化剂的催化性能。结合较高的乙烯压力可以提高前催化剂1的 1-辛烯 (67.98%) 的选择性具有高催化活性（9.3 × 10 ⁶  g/[mo​​lCr h]）。此外，预催化剂2-3有效地提供选择性乙烯三聚，并提供 97.76% 的 1-己烯选择性和 5.8 × 10 ⁶  g/(molCr h) 催化活性（在预催化剂3的情况下）。相对低的催化剂质量、高 Al/Cr 摩尔比和高乙烯压力显示出优异的催化活性和乙烯低聚选择性。