Silver hyponitrite
# Silver hyponitrite

Silver hyponitrite is an ionic compound with formula $Ag_2N_2O_2$ or $(Ag^+$ $)_2[ON=NO]^{2−},$ containing monovalent silver cations and hyponitrite anions. It is a bright canary yellow solid practically insoluble in water and most organic solvents, including DMF and DMSO.

## Preparation

The compound was described in 1848.

The salt can be precipitated from a solution of sodium hyponitrite in water by the addition of silver nitrate:

    Na $_2N$ $_2O$ $_2$ + 2 AgNO $_3$ → Ag $_2N$ $_2O$ $_2$ + 2 NaNO $_3$

Excess silver nitrate yields a brown or black precipitate.

Silver hyponitrite can be prepared also by reducing silver nitrate AgNO $_3$ with sodium amalgam.

## Properties and reactions

Silver hyponitrite is sparingly soluble in concentrated alkali hyponitrite solutions, but quite soluble in aqueous ammonia due to the formation of the complex cation [(NH $_3)_2Ag]^+.$ The compound is slowly decomposed by light.

The anhydrous compound decomposes in vacuum at 158 °C. The primary decomposition products are silver(I) oxide Ag $_2O$ and nitrous oxide N $_2O.$ However, these then react to form a variable mixture of nitrogen, metallic silver, and various oxides of the two elements and silver salts.

### Hyponitrous acid

Reaction of silver hyponitrite with anhydrous hydrogen chloride in ether is the standard way to prepare hyponitrous acid:

    Ag $_2N$ $_2O$ $_2$ + 2 HCl → H $_2N$ $_2O$ $_2$ + 2 AgCl

Spectroscopic data indicate a trans configuration for the resulting acid.

### Alkyl halides

Silver hyponitrite reacts with alkyl halides, to form alkyl hyponitrites. For example, reaction with methyl bromide yields the spontaneously explosive liquid dimethyl hyponitrite:

    2 CH $_3Br$ + Ag $_2N$ $_2O$ $_2$ → H $_3C-O-N=N-O-CH$ $_3$ + 2 AgBr

Other alkyl hyponitrites reported in the literature include those of ethyl, benzyl, and tert-butyl.

