The trianionic hydrazido radical (N2)3−: a promising platform for transforming N2

Abstract

A quintessential approach to activate and functionalize the exceptionally stable diatomic nitrogen (N₂) consists of its coordination to transition metal complexes. Accordingly, coordinated N₂ can undergo reduction steps to deliver a variety of anionic species such as (N₂)¹⁻, (N₂)²⁻, (N₂)³⁻ and (N₂)⁴⁻. In this context, trianionic hydrazido radicals (N₂)³⁻ seem to possess atypical reactivity which can be harnessed to forge unprecedented nitrogen-element functionalities (N–E) (E = element). In spite of these promising characteristics, the reaction chemistry of metal-coordinated (N₂)³⁻ ligands remains considerably scarce in the literature. In this article, we have surveyed the limited reports related to (N₂)³⁻ species and performed preliminary DFT calculations on the known scandium–(N₂)³⁻ complex [(η⁵-C₅Me₅){ⁿBuC(NⁱPr)₂}Sc]₂(μ²–η²:η²-N₂)[{K(2.2.2)cryptand}] (1). We have emphasized the future study of the coordinated trianionic hydrazido radical (N₂)³⁻ by proposing reaction intermediates and possible reaction pathways as well as radical coupling strategies. These ideas represent an effort to stimulate alternative perspectives on the activation and transformation of N₂ into N-containing compounds.