Bis-cycloheptyl-fused bis(imino)pyridine-cobalt catalysts for PE wax formation: positive effects of fluoride substitution on catalytic performance and thermal stability. Issue 27 (26th June 2020)

• Record Type: Journal Article
• Authors: Zhang, Qiuyue; Wu, Ningning; Xiang, Junfeng; Solan, Gregory A.; Suo, Hongyi; Ma, Yanping; Liang, Tongling; Sun, Wen-Hua
• Is Part Of: Dalton transactions. Volume 49:Issue 27(2020)
• Page Start: 9425
• Page End: 9437
• Publication Date: 2020-06-26
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/d0dt01876g
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : The depicted ethylene polymerization catalysts exhibited optimal activities at 60 °C forming low molecular weight PE waxes; ortho -F substitution proved beneficial. Abstract : The α, α′-bis(imino)-2, 3:5, 6-bis(pentamethylene)pyridyl-cobalt(ii ) chlorides, [2, 3:5, 6-{C4 H8 C(N(2-R 1 -4-R 3 -6-R 2 C6 H2 ))}2 C5 HN] CoCl2 (R 1 = Me, R 2 = R 3 = CH( p -FPh)2 Co1 ; R 1 = Et, R 2 = R 3 = CH( p -FPh)2 Co2 ; R 1 = i-Pr, R 2 = R 3 = CH( p -FPh)2 Co3 ; R 1 = Cl, R 2 = R 3 = CH( p -FPh)2 Co4 ; R 1 = F, R 2 = R 3 = CH( p -FPh)2 Co5 ; R 1 = F, R 2 = R 3 = CHPh2 Co5′′, R 1 = R 2 = Me, R 3 = CH( p -FPh)2 Co6 ; R 1 = R 3 = Me, R 2 = CH( p -FPh)2 Co7 ), have been synthesized by a one-pot template reaction of α, α′-dioxo-2, 3:5, 6-bis(pentamethylene)pyridine, cobalt(ii ) chloride and the respective aniline in n -butanol. By contrast, the mixed cobalt(ii ) chloride/acetate complex, [2, 3:5, 6-{C4 H8 C(N(2-F-4, 6-(CH( p -FPh)2 )2 C6 H2 ))}2 C5 HN]CoCl(OAc) (Co5′ ), was isolated when the corresponding template reaction was carried out in acetic acid. Structural characterization of Co4, Co5 and Co5′′ revealed distorted square pyramidal geometries while six-coordinate Co5′, incorporating a chelating acetate ligand, exhibited a distorted octahedral geometry. On activation with either MAO or MMAO, 2-fluoride-4, 6-bis{di( p -fluorophenyl)methyl}-substituted Co5 showed maximum catalytic activity for ethylene polymerization at a high operating temperature of 60 °C (up to 2.1 × 10 7 g (PE) mol −1 (Co) h −1 ), producing highly linear ( T m s > 121 °C), low molecular weight polyethylene waxes ( M w range: 1.5–5.0 kg mol −1 ) with narrow dispersity ( M w / M n range: 1.7–2.9). End-group analysis of the waxes reveals β-H elimination as the dominant chain transfer process.