Phospholane-Based Ligands for Chromium-Catalyzed Ethylene Tri- and Tetramerization

Chromium complexes with bis(phospholane) ligands were synthesized and evaluated for ethylene tetramerization in a high-throughput reactor. Three ligand parameters—the phospholane substituent, the ligand backbone, and the type of phosphine (cyclic vs acyclic)—were investigated. The size of the phospholane substituent was found to impact the selectivity of the resulting catalysts, with smaller substituents leading to the production of larger proportions of 1-octene. Changing the ligand backbone from 1,2-phenylene to ethylene did not impact catalysis, but the use of acyclic phosphines in place of the cyclic phospholanes had a detrimental effect on catalytic activity. Selected phospholane-chromium complexes were evaluated in a 300 mL Parr reactor at 70 °C and 700 psi of ethylene pressure, and the ethylene oligomerization performance was consistent with that observed in the smaller, high-throughput reactor. MeDuPhos-CrCl3(THF) (MeDuPhos = 1,2-bis(2,5-dimethylphospholano)benzene; THF = tetrahydrofuran) gave act...