Evaluation of Bis(phosphine) Ligands for Ethylene Oligomerization: Discovery of Alkyl Phosphines as Effective Ligands for Ethylene Tri- and Tetramerization
Scott D. Boelter, Dan R. Davies, Kara A. Milbrandt, David R. Wilson, Molly Wiltzius, Mari S. Rosen, Jerzy Klosin
Abstract
Fifty-three bis(phosphines) were evaluated as ligands for chromium-catalyzed ethylene tetramerization in a high-throughput reactor. Selected ligands previously reported in the literature gave high activities with expected selectivities when evaluated under our reactor conditions. While the majority of ligands evaluated gave low activity catalysts that produced mostly high-density polyethylene (HDPE), alkyl phosphines were unexpectedly identified as a promising ligand class. In particular, the MeDuPhos ligand led to an active catalyst that produced 81.8 wt % α-olefins (50.0 wt % 1-octene, 31.8 wt % 1-hexene) and 3.5 wt % HDPE, approaching the selectivity of the state-of-the-art i-Pr-PNP ligand.