Unveiling <i>meta</i>-Alkyloxy/-Silyloxy-Substituted <i>N</i>-Aryl PNP Ligands for Efficient Cr-Catalyzed Ethylene Tetramerization

Novel N-aryl-functionalized PNP ligands (1–4) bearing m-alkyloxy/-silyloxy substituents were prepared and evaluated for chromium-catalyzed ethylene oligomerization using MMAO-3A as an activator. The selected Cr/PNP system under optimized condition exhibited high 1-octene-selective (up to 70 wt %) tetramerization at a remarkable rate (over 3000 kg gCr–1 h–1). More importantly, the undesirable polyethylene selectivity was restricted minimum level of ∼1–2 % pre-catalysts derived with 1 2. Employing chlorobenzene reaction medium yielded best productivity in conjunction total α-olefin (1-C6 + 1-C8) (∼88 %). N-aryl (3 4) incorporating m-silyloxy phenyl ring relatively poorer performance while yielding higher PE fraction compared their m-alkyloxy derivatives. A detailed molecular structure best-performing pre-catalyst 1-Cr established by single-crystal X-ray diffraction analysis. stability 1/Cr-based catalyst investigated time up 2 h condition.