hydrogen natride

Other names: hydrogen sodide, inverse sodium hydride, hydrogen-incar-[³6]adamanzane natride

HNa·Adz

39/50 uncommon

Hydrogen natride (HNa·Adz) represents an extraordinary reversal of the traditional sodium hydride (NaH) structure, featuring a hydridic sodium atom (Na^-) bonded to a proton (H⁺). This "inverse salt" configuration fundamentally challenges conventional understanding of electronegativity and bonding. First reported in 1974 and further characterized in 2002, the compound's stability depends on encapsulation within a [³6]adamanzane cage (Adz), which isolates the reactive hydrogen-sodium pair from the environment. The cage's interior provides an electronic environment that inverts the normal polarity of the Na-H bond, essentially forcing sodium to act as the more electronegative element. Crystallographic studies confirm this unusual bonding arrangement, with the proton positioned between sodium and a nitrogen atom of the cage. This remarkable compound demonstrates how confinement can dramatically alter electronic structure and chemical behavior, providing new insights into the fundamental nature of chemical bonding and expanding the possibilities for designing materials with counterintuitive properties.