A series of bulky unsymmetrical bis(imino)pyridyl iron(II) complexes 1-3 with different electronic effect substituents at the para-position of the N-aryl group have been synthesized and characterized. These highly robust thermostable iron(II) complexes display very high activity (up to 2.5 × 10⁷ g mol⁻¹ h⁻¹) in ethylene polymerization at high pressure, and can generate highly linear polyethylene (T_m = 131.6-138.8 °C) with high molecular weight (M_w up to 185.7 × 10⁴ g mol⁻¹) and broad molecular weight distributions (PDI: 2.34-13.68). The electronic effect and influence of polymerization conditions on activity and molecular weight of polyethylene are investigated in detail. The electronic perturbations show great influence on the activity and polyethylene molecular weight in ethylene polymerization. Compared with the classical isopropyl substituted iron(II) complex 4, the bulky iron(II) complexes 1-3 showed higher activity and thermal stability in ethylene polymerization at high temperature.

合成并表征了一系列大体积的不对称双（亚氨基）吡啶基铁（II）配合物1-3，其在N-芳基的对位具有不同的电子效应取代基。这些高度坚固的热稳定铁（II）配合物在高压下的乙烯聚合中显示出很高的活性（高达2.5×10 ⁷ g mol ^-1 h ^-1），并且可以生成高度线性的聚乙烯（T _m  = 131.6-138.8°C） ）具有高分子量（M_瓦特高达185.7×10 ⁴克摩尔^-1）和宽分子量分布（PDI：2.34-13.68）。详细研究了电子效应和聚合条件对聚乙烯活性和分子量的影响。电子扰动对乙烯聚合反应的活性和聚乙烯分子量影响很大。与经典的异丙基取代的铁（II）配合物4相比，大体积的铁（II）配合物1-3在高温乙烯聚合中显示出更高的活性和热稳定性。