Zhang Qiuyue, Wu Ningning, Xiang Junfeng, Solan Gregory A, Suo Hongyi, Ma Yanping, Liang Tongling, Sun Wen-Hua
Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
Dalton Trans. 2020 Jul 17;49(27):9425-9437. doi: 10.1039/d0dt01876g.
The α,α'-bis(imino)-2,3:5,6-bis(pentamethylene)pyridyl-cobalt(ii) chlorides, [2,3:5,6-{C4H8C(N(2-R1-4-R3-6-R2C6H2))}2C5HN] CoCl2 (R1 = Me, R2 = R3 = CH(p-FPh)2Co1; R1 = Et, R2 = R3 = CH(p-FPh)2Co2; R1 = i-Pr, R2 = R3 = CH(p-FPh)2Co3; R1 = Cl, R2 = R3 = CH(p-FPh)2Co4; R1 = F, R2 = R3 = CH(p-FPh)2Co5; R1 = F, R2 = R3 = CHPh2Co5'', R1 = R2 = Me, R3 = CH(p-FPh)2Co6; R1 = R3 = Me, R2 = CH(p-FPh)2Co7), 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-{C4H8C(N(2-F-4,6-(CH(p-FPh)2)2C6H2))}2C5HN]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 × 107 g (PE) mol-1 (Co) h-1), producing highly linear (Tms > 121 °C), low molecular weight polyethylene waxes (Mw range: 1.5-5.0 kg mol-1) with narrow dispersity (Mw/Mn range: 1.7-2.9). End-group analysis of the waxes reveals β-H elimination as the dominant chain transfer process.
α,α'-双（亚氨基）-2,3:5,6-双（亚戊基）吡啶基氯化钴（II），[2,3:5,6-{C4H8C(N(2-R1-4-R3-6-R2C6H2))}2C5HN] CoCl2（R1 = 甲基，R2 = R3 = CH(p-FPh)2Co1；R1 = 乙基，R2 = R3 = CH(p-FPh)2Co2；R1 = 异丙基，R2 = R3 = CH(p-FPh)2Co3；R1 = 氯，R2 = R3 = CH(p-FPh)2Co4；R1 = 氟，R2 = R3 = CH(p-FPh)2Co5；R1 = 氟，R2 = R3 = CHPh2Co5''，R1 = R2 = 甲基，R3 = CH(p-FPh)2Co6；R1 = R3 = 甲基，R2 = CH(p-FPh)2Co7），是通过α,α'-二氧代-2,3:5,6-双（亚戊基）吡啶、氯化钴（II）和相应的苯胺在正丁醇中进行一锅法模板反应合成的。相比之下，当在乙酸中进行相应的模板反应时，分离得到了混合的氯化钴（II）/乙酸盐配合物，[2,3:5,6-{C4H8C(N(2-F-4,6-(CH(p-FPh)2)2C6H2))}2C5HN]CoCl(OAc)（Co5'）。Co4、Co5和Co5''的结构表征显示为扭曲的四方锥几何构型，而包含螯合乙酸盐配体的六配位Co5'则呈现出扭曲的八面体几何构型。用MAO或MMAO活化后，2-氟-4,6-双{二（对氟苯基）甲基}取代的Co5在60°C的高操作温度下对乙烯聚合表现出最大催化活性（高达2.1×107 g（PE）mol-1（Co）h-1），生成高度线性（熔点>121°C）、低分子量的聚乙烯蜡（Mw范围：1.5 - 5.0 kg mol-1），且分散度窄（Mw/Mn范围：1.7 - 2.9）。蜡的端基分析表明β-H消除是主要的链转移过程。
