A new set of Cr(III) complexes, {L}CrCl3(THF), based on thiophene–imine (2a, L = PhOC6H4(N═CH)‐2‐SC4H3; 2b, L = PhOC2H4(N═CH)‐2‐SC4H3; 2c, L = Ph(NH)C2H4(N═CH)‐2‐SC4H3; 2d, L = PhOC6H4(N═CH)‐2‐SC4H2‐5‐Ph; 2e, L = Ph(NH)C2H4(N═CH)‐2‐SC4H2‐5‐Ph) have been prepared and characterized using elemental analysis and infrared spectroscopy. Upon activation with methylaluminoxane, all the chromium complexes generated active systems affording a nonselective distribution of α‐olefins with turnover frequencies in the range 9500–93 500 (mol ethylene) (mol Cr)−1 h−1, and producing mostly oligomers (95.0–99.3 wt% of total products). Small amounts of polymer were produced in these oligomerization reactions (0.8–8.2 wt%). The catalytic activities were quite sensitive to the ligand environment. Moreover, the effects of oligomerization parameters (temperature, [Al]/[Cr] molar ratio, time) on the activity and on the product distribution were examined.

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