Olefin metathesis, as a powerful metal-catalysed carbon–carbon bond-forming method, has achieved considerable progress in recent years. However, the complexity originating from multicomponent interactions has long impeded a complete mechanistic understanding of olefin metathesis, which hampers further optimization of the reaction. Here, we clarify both productive and hidden degenerate pathways of ring-closing metathesis by focusing on one individual catalyst, using a sensitive single-molecule electrical detection platform. In addition to visualizing the full pathway, we found that the conventionally unwanted degenerate pathways have an unexpected constructive coupling effect on the productive pathway, and both types of pathway can be regulated by an external electric field. We then pushed forward this ability to ring-opening metathesis polymerization involving more interactive components. With single-monomer-insertion-event resolution, precise on-device synthesis of a single polymer was achieved by online manipulation of monomer insertion dynamics, intramolecular chain transfer, stereoregularity, degree of polymerization and block copolymerization. These results offer a comprehensive mechanistic understanding of olefin metathesis, exemplifying infinite opportunities for practical precise manufacturing.

烯烃复分解作为一种强大的金属催化碳-碳键形成方法，近年来取得了长足的进展。然而，多组分相互作用带来的复杂性长期以来一直阻碍着对烯烃复分解的完整机理理解，这阻碍了反应的进一步优化。在这里，我们通过使用灵敏的单分子电检测平台专注于一种单独的催化剂，阐明了闭合环复分解的生产性和隐藏的简并途径。除了可视化完整途径外，我们还发现传统上不需要的简并途径对生产途径具有意想不到的建设性耦合效应，并且两种类型的途径都可以由外部电场调节。然后，我们将这种能力推进到涉及更多交互组分的开环复分解聚合。通过单体插入事件分辨率，通过在线操纵单体插入动力学、分子内链转移、立体规则性、聚合度和嵌段共聚，实现了单一聚合物的精确器件合成。这些结果提供了对烯烃复分解的综合机理理解，体现了实际精密制造的无限机会。