Alkali metal solutions comprising alkali metal anions, the ‘alkalides’, and complexed alkali cations side by side provide a large untapped potential with respect to future applications. This is due to their unique properties such as a strongly reducing nature and a high polarizability. The use of organic complexing agents such as crown ethers and cryptands allows for the stabilization of high concentrations of charge carriers in a weakly polar
medium. Nevertheless, the currently available knowledge about those solutions is very limited and their characterization is mostly centered around alkali metal NMR techniques. A significant upfield shift and exceptionally narrow width of the alkalide NMR signal were ascribed to the high shielding and high symmetry of an effectively unperturbed ‘gas-like’ anion in solution with little to no interaction with its local environment. Our investigations extend this traditional picture of the alkalide in solution and unveil the underlying effect of coulomb interactions on the properties of alkalides in low-polarity solvents by a comprehensive combination of spectroscopic methods. Concentration dependent measurement of both conductivity and permittivity of alkalide solutions revealed that ion pairing is a key factor in determining the kinetic properties and the stability of alkali metal solutions. Furthermore, the effect of dissolved metal on the mesoscopic structure of solutions of macrocyclic complexants was probed by small angle neutron scattering. Ultimately, we present a rationale for the rather obscure and unexpected temperature- and
concentration-dependence of alkali metal dissolution in organic media and provide a multi-facetted understanding of the remarkable preparatory and spectroscopic characteristics of alkalide solutions.
Finally, the synthesis of sterically congested amides and their unique fragmentation under dissolving metal reduction conditions are presented. Synthetic access to amide substrates was achieved by the use of highly electrophilic nitrimine precursors in the formation of
imine intermediates.Open Acces
