Post-functionalization of narrowly dispersed PE waxes generated using tuned N,N,N′-cobalt ethylene polymerization catalysts substituted with ortho-cycloalkyl groups

Abstract

Six structurally related bis(arylimino)trihydroquinolyl-cobalt (II) chloride complexes [2-(ArNCCH3)-8-(ArN)-5,6,7-C9H8N]CoCl2 (Ar = 2-(C5H9)-6-MeC6H3Co1, 2-(C6H11)-6-MeC6H3Co2, 2-(C8H15)-6-MeC6H3Co3, 2-(C5H9)-4,6-Me2C6H2Co4, 2-(C6H11)-4,6-Me2C6H2Co5, 2-(C8H15)-4,6-Me2C6H2Co6), distinguishable by the ring size of the ortho-cycloalkyl substituent and type of para-R group, have been synthesized and characterized. A distorted square pyramidal geometry is a feature of the molecular structure of Co4 with the two ortho-cyclopentyl groups located on neighboring N-aryl groups trans-configured. Compounds Co1 – Co6, on activation with methylaluminoxane (MAO) or modified MAO (MMAO), proved highly productive catalysts for ethylene polymerization at 60 °C [up to 17.1 × 106 g (PE) mol−1(Co) h−1 for cyclopentyl-containing Co4/MAO]; even at 90 °C significant activity was attainable (up to 6.75 × 106 g (PE) mol−1(Co) h−1). Strictly linear polyethylene waxes of low molecular weight (ca. 1.50 kg mol−1), narrow dispersity (Mw/Mn range: 1.1–2.4) and incorporating high levels of vinyl end-groups were generated. Post-functionalization of these PE waxes by epoxidation, thiol-ene addition and cross-olefin metathesis to form e-PE, PE-S-CH2CH2NH2·HCl and PE-MMA, respectively, has been demonstrated. For comparative purposes, [2-(ArNCCH3)-8-ArN-5,6,7-C9H8N]CoCl2 (Ar = 2,4,6-Me3C6H2Coo-Me, 2-(Ph2CH)-4,6-Me2C6H2Coo-CHPh2) have also been prepared and evaluated as polymerization catalysts.