Steric reduction principles were applied in N-phosphinoamidine ligand (PN) design to significantly improve 1-octene selectivity in ethylene tri-/tetramerization chromium catalysis. Novel phospholeand phospholane-based PN-ligands were prepared and used to synthesize discrete chromium complexes which were fully characterized. The highest 1-octene producing Cr/PN/MMAO catalyst system compares favorably with the benchmark Cr/PNP/MMAO system generating a higher overall product selectivity at equivalent yields. Characterization of the structurally related cyclic phosphine-based Cr/PN pre catalysts revealed that 1-octene selectivity varied inversely with the ligand bite angle, albeit over a small range. In contrast, the acyclic phosphine-based catalyst produces significantly less 1-octene than expected based on its small bite angle. This disparity signals a breakdown of bite angle as the main 1octene selectivity geometric descriptor and suggests that the key selectivity driver occurs further away from the metal center requiring more sophisticated modeling efforts to properly account for the differences. (c) 2020 Elsevier Inc. All rights reserved.