Solvation of Na^– in the Sodide Solution, LiNa·10MeNH₂

Abstract

Alkalides, the alkali metals in their −1 oxidation state, represent some of the largest and most polarizable atomic species in condensed phases. This study determines the solvation environment around the sodide anion, Na–, in a system of co-solvated Li+. We present isotopically varied total neutron scattering experiments alongside empirical potential structure refinement and ab initio molecular dynamics simulations for the alkali–alkalide system, LiNa·10MeNH2. Both local coordination modes and the intermediate range liquid structure are determined, which demonstrate that distinct structural correlations between cation and anion in the liquid phase extend beyond 8.6 Å. Indeed, the local solvation around Na– is surprisingly well defined with strong solvent orientational order, in contrast to the classical description of alkalide anions not interacting with their environment. The ion-paired Li­(MeNH2)4 +·Na– species appears to be the dominant alkali–alkalide environment in these liquids, whereby Li+ and Na– share a MeNH2 molecule through the amine group in their primary solvation spheres.

Intermediate Range Order in Metal–Ammonia Solutions: Pure and Na-Doped Ca-NH3

“…As we have previously noted, this structuring in the liquid state seems to be a feature of metal–amine systems, which undergo crystallization at their concentration limit, and is significantly reduced or absent in those which do not. 24 …”

“…As we have previously noted, this structuring in the liquid state seems to be a feature of metal−amine systems, which undergo crystallization at their concentration limit, and is significantly reduced or absent in those which do not. 24 Furthermore, we have showed the miscibility of Na− and Ca−NH 3 enables the local and intermediate structure of the bulk liquid to be controlled as a function of the conduction electron density. Sequential disruption of the primary solvation environment upon incorporation of Na is evident from the neutron scattering data, which in turn is reflected in the intermediate range, ion−ion correlations being reduced.…”

Mechanochemical Synthesis of a Sodium Anion Complex [Na+(2,2,2-cryptand)Na–] and Studies of Its Reactivity: Two-Electron and One-Electron Reductions

“…Since the first reports in the 1970s by the group of the late James Dye, − alkalides appear in every inorganic chemistry textbook . Discussions about the nature of the exotic −1 oxidation-state alkali metal anions have continued until today, , along with several in silico theoretical studies from the physics and physical chemistry communities. − Nonetheless, from a synthetic chemistry perspective, the reactivity of alkalides, including their potential in two-electron redox chemistry, has never been properly studied apart from a few decomposition studies. , This status quo is due to their formidable synthetic hurdles.…”