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The sustainable fixation of atmospheric N₂ and its conversion into industrially relevant molecules is one of the major current challenges in chemistry. Besides nitrogen activation with transition metal complexes, a "push‐pull" approach that fine‐tunes electron density along the N−N bond has shown success recently. The "pushing" is performed by an electron rich entity such as a transition metal complex, and the "pulling" is achieved with an electron acceptor such as a Lewis acid. In this contribution, we explore the electronic structure implications of this approach using the complex trans‐[ReᴵCl(N₂)(PMe₂Ph)₄] as a starting point. We show that borane Lewis acids exert a pull‐effect of increasing strength with increased Lewis acidity via a π‐pathway. Furthermore, the ligand trans to dinitrogen can weaken the dinitrogen bond via a σ‐pathway. Binding a strong Lewis acid is found to have electronic structure effects potentially relevant for electrochemistry: dinitrogen‐dominated molecular orbitals are shifted into advantageous energetic positions for redox activation of the dinitrogen bond. We show how these electronic structure design principles are rooted in cooperative effects of a transition metal complex and a Lewis acid, and that they can be exploited to tailor a complex towards the desired thermal, electrochemical or photochemical reactivity.

This article also appears in: Inorganic Reaction Mechanisms