Basic Properties and Structure of Sodium Hydride

Sodium Hydride(NaH) is a silver gray highly flammable and corrosive particle. It is a strong base; dangerous when wet. It reacts violently with water forming flammable/explosive gas (hydrogen). Sodium hydride is sold in commerce as a 60% w/w dispersion form in mineral oil for safe handling. The solubility in organic solvents is very poor. It is dispersed in an inert solvents.NaH is produced by the direct reaction of hydrogen and liquid sodium. Pure NaH is colorless, although samples generally appear grey. NaH is ca. 40% denser than Na (0.968 g/cm³).

NaH, like LiH, KH, RbH, and CsH, adopts the NaCl crystal structure. In this motif, each Na+ ion is surrounded by six H− centers in an octahedral geometry. The ionic radii of H− (146 pm in NaH) and F− (133 pm) are comparable, as judged by the Na−H and Na−F distances.\

A very unusual situation occurs in a compound dubbed "inverse sodium hydride", which contains Na- and H+ ions. Na- is an alkalide, and this compound differs from ordinary sodium hydride in having a much higher energy content due to the net displacement of two electrons from hydrogen to sodium. Despite the name, the experimentally observed "inverse sodium hydride" requires the presence of a third molecule, 36 adamanzane, which irreversibly encapsulates the H+ and makes it kinetically inert to interaction with the alkalide.Further theoretical work has suggested that even an unprotected protonated tertiary amine complexed with the sodium alkalide might be metastable under certain solvent conditions, though the barrier to reaction would be small and finding a suitable solvent might be difficult.

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