The olefin metathesis reaction is among the most widely applicable catalytic reactions for carbon–carbon double bond formation. Currently, Mo– and Ru–carbene catalysts are the most common choices for this reaction. It has been suggested that an iron-based catalyst would be a desirable economical and biocompatible substitute of the Ru catalysts; however, practical solutions in this regard are still lacking. Here, we report the discovery and mechanistic studies of three-coordinate iron(II) catalysts for ring-opening metathesis polymerization of olefins. Remarkably, their reactivity enabled the formation of polynorbornene with stereoregularity and high molecular weight (>10⁷ g mol^–1). The polymerization in the presence of styrene revealed cross metathesis reactivity with iron catalysts. Mechanistic studies suggest the possible role of metal–ligand cooperation in formation of the productive catalyst. This work opens the door to the development of iron complexes that can be economical and biocompatible catalysts for olefin metathesis reactions.

烯烃复分解反应是碳-碳双键形成中应用最广泛的催化反应之一。目前，Mo-和Ru-卡宾催化剂是该反应最常见的选择。有人提出，铁基催化剂将是 Ru 催化剂的理想经济和生物相容性替代品；然而，仍然缺乏这方面的实际解决办法。在这里，我们报告了用于烯烃开环复分解聚合的三配位铁 (II) 催化剂的发现和机理研究。值得注意的是，它们的反应性使得能够形成具有立体规整性和高分子量 (>10 ⁷  g mol ^{–1 ) 的聚降冰片烯}）。在苯乙烯存在下的聚合揭示了与铁催化剂的交叉复分解反应。机理研究表明金属-配体合作在生产催化剂的形成中可能发挥的作用。这项工作为开发铁络合物打开了大门，铁络合物可以成为烯烃复分解反应的经济且生物相容的催化剂。