C–H functionalisation reactions offer a sustainable method for molecular construction and diversification. These reactions however remain dominated by precious metal catalysis. While significant interest in iron-catalysed C–H activation reactions has emerged, the isolation, characterisation and mechanistic understanding of these processes remain lacking. Herein the iron-catalysed C(sp²)–H bond hydrogen/deuterium exchange reaction using CD₃OD is reported for both heterocycles and, for the first time, alkenes (38 examples). Isolation and characterisation, including by single-crystal X-ray diffraction, of the key iron-aryl and iron-alkenyl C–H metallation intermediates provided evidence for a reversible protonation of the active iron hydride catalyst. Good chemoselectivity was observed for both substrate classes. The developed procedure is orthogonal to previous iron-catalysed H/D exchange methods which used C₆D₆, D₂, or D₂O as the deuterium source, and uses only bench-stable reagents, including the iron(II) pre-catalyst. Further, a new mechanism of iron-hydride formation is reported in which β-hydride elimination from an alcohol generates the iron hydride. The ability to produce, isolate and characterise the organometallic products arising from C–H activation presents a basis for future discovery and development.

中文翻译：

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通过铁氢化物中间体的可逆质子化铁催化烯烃和杂芳烃 H/D 交换

C-H 官能化反应为分子构建和多样化提供了一种可持续的方法。然而，这些反应仍然以贵金属催化为主。虽然人们对铁催化的 C-H 活化反应产生了浓厚的兴趣，但仍然缺乏对这些过程的分离、表征和机理理解。_{在此，使用 CD 3}的铁催化的 C(sp ² )-H 键氢/氘交换反应OD 报道了杂环和烯烃的首次报道（38 个例子）。关键的铁芳基和铁烯基 C-H 金属化中间体的分离和表征，包括通过单晶 X 射线衍射，为活性氢化铁催化剂的可逆质子化提供了证据。对于两种底物类别都观察到良好的化学选择性。_{开发的程序与以前使用 C 6} D ₆、D ₂或 D ₂ O 作为氘源的铁催化 H/D 交换方法正交，并且仅使用工作稳定的试剂，包括铁 ( II) 预催化剂。此外，报道了一种新的氢化铁形成机制，其中β-氢化物从醇中消除产生氢化铁。生产、分离和表征由 C-H 活化产生的有机金属产品的能力为未来的发现和开发奠定了基础。