The cyclopentadienyl (Cp) ligand is a cornerstone of modern organometallic chemistry. Since the discovery of ferrocene, the Cp ligand and its various derivatives have become foundational motifs in catalysis, medicine and materials science. Although largely considered an ancillary ligand for altering the stereoelectronic properties of transition metal centres, there is mounting evidence that the core Cp ring structure also serves as a reservoir for reactive protons (H⁺), hydrides (H⁻) or radical hydrogen (H^•) atoms. This Review chronicles the field of Cp ring activation, highlighting the pivotal role that Cp ligands can have in electrocatalytic H₂ production, N₂ reduction, hydride transfer reactions and proton-coupled electron transfer.

环戊二烯基 (Cp) 配体是现代有机金属化学的基石。自从发现二茂铁以来，Cp 配体及其各种衍生物已成为催化、医学和材料科学的基础主题。尽管主要被认为是改变过渡金属中心立体电子特性的辅助配体，但越来越多的证据表明，核心 Cp 环结构也可作为活性质子 (H + )、氢化物 (H − ) 或^自由基氢⁽ H ^•）原子。本综述记录了 Cp 环活化领域，强调了 Cp 配体在电催化 H ₂生产、N ₂还原、氢化物转移反应和质子耦合电子转移中的关键作用。