Hydrazinium

Hydrazinium is the name given to the positively charged nitrogens species with formula N2H5+, the conjugate acid of hydrazine (N2H4). It is most commonly encountered as salts formed by protonation of hydrazine in acid solution. In such salts the hydrazinium cation pairs with various anions, producing compounds such as hydrazinium chloride, hydrazinium sulfate, or hydrazinium nitrate.

Structurally, the cation consists of two nitrogen atoms linked by a single N–N bond. One nitrogen bears three hydrogens and the other two, giving an overall +1 charge. Protonation can occur on either nitrogen, and the cation is often represented as [H3N-NH2]+ with the positive charge delocalized over the two nitrogens.

Preparation and occurrence: Hydrazinium salts are prepared by reacting hydrazine with an appropriate acid, or by exchanging partners in metathesis reactions to form a desired salt. They are typically white crystalline solids or water-soluble liquids.

Properties: Hydrazinium salts are usually stable under ambient conditions but can decompose on heating or in strongly oxidizing environments, potentially releasing hydrazine or nitrogen-containing volatiles. They are generally hygroscopic and water-soluble.

Applications and safety: Hydrazinium salts are used as reagents in organic synthesis and as precursors to other nitrogen-rich compounds; some salts have been explored as energetic materials. Hydrazine and its salts are toxic and potentially carcinogenic; they should be handled in a fume hood with appropriate PPE, and kept away from strong oxidizers and heat.