Inter-Alkali-Metal Dative Bond in the MMN (M=Alkali Metal) Cluster.

Alkali metals are generally Lewis acids. On the contrary, Lewis basic character of alkali metals forming donor - acceptor complexes is a very rare phenomenon. In this contribution, I have theoretically designed an anionic cluster MMN (M=alkali metals) on the basis of experimentally known reagent, alkali salt of azide ion MN , which shows unprecedented M: →M donor-acceptor interaction. To the best of author's knowledge, the characterization of such donor-acceptor interaction among alkali metals is unprecedented. Formation of the 2c-2e donor-acceptor bonds have been confirmed by quantum theory of atoms in molecules and electron localization function analyses. The calculated bond dissociation energies are significant suggesting their possible spectroscopic identification.