Visible-Light Photocatalysis of C(sp³)-H Fluorination by the Uranyl Ion: Mechanistic Insights

Abstract

© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim The uranyl dication shows photocatalytic activity towards C(sp3)−H bonds of aliphatic compounds, but not towards those of alkylbenzenes or cyclic ketones. Theoretical insights into the corresponding mechanisms are still limited. Multi-configurational ab initio calculations including relativistic effects reveal the inherent electron-transfer mechanism for the uranyl catalyzed C−H fluorination under blue light. Along the reaction path of the triplet state it was found that the hydrogen atom abstraction triggered by the electron-rich oxygen of the uranyl moiety is the rate-limiting step. The subsequent steps, that is, N−F and O−H bond breakage in a manner of concerted asynchronicity, generation of the targeted fluorinated product, and recovery of the photocatalyst are nearly barrierless. Moreover the single electron transfer between the reactive substrates plays a fundamental role during the whole photocatalytic cycle.