hydrazinium

{{Short description|Cation}}

{{Chembox

| ImageFile = File:N2H6++&N2H5+Redrawn.png

| ImageCaption = Structures of hydrazinium {{chem2|[N2H5]+}} and hydrazinediium {{chem2|[N2H6](2+)}}.

| OtherNames = Ammonia(+1) Dimer,

| Section1 = {{Chembox Identifiers

| CASNo = 18500-32-8

| ChEBI = 35324

| ChemSpiderID = 79101

| Gmelin = 183

| PubChem = 87681

| StdInChI=1S/H4N2/c1-2/h1-2H2/p+1

| StdInChIKey = OAKJQQAXSVQMHS-UHFFFAOYSA-O

| SMILES = [NH3+]N

}}

| Section2 = {{Chembox Properties

}}

| Section8 = {{Chembox Related

}}

}}

Hydrazinium is the cation with the formula {{chem2|[N2H5]+}}. This cation has a methylamine-like structure ({{chem2|[H2N\sNH3]+}}). It can be derived from hydrazine by protonation (treatment with a strong acid). Hydrazinium is a weak acid with pK_a = 8.1.

Salts of hydrazinium are common reagents in chemistry and are often used in certain industrial processes.Jean-Pierre Schirmann, Paul Bourdauducq "Hydrazine" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2002. {{doi|10.1002/14356007.a13_177}}. Notable examples are hydrazinium hydrogensulfate, {{chem2|N2H6SO4}} or {{chem2|[N2H5]+[HSO4]-}}, and hydrazinium azide, {{chem2|N5H5}} or {{chem2|[N2H5]+[N3]-}}. In the common names of such salts, the cation is often called "hydrazine", as in "hydrazine sulfate" for hydrazinium hydrogensulfate.

The terms "hydrazinium" and "hydrazine" may also be used for the doubly protonated cation {{chem2|[N2H6](2+)}}, more properly called hydrazinediium or hydrazinium(2+). This cation has an ethane-like structure ({{chem2|[H3N\sNH3](2+)}}). Salts of this cation include hydrazinediium sulfate {{chem2|[N2H6](2+)[SO4](2-)}}{{cite journal | last1 = Klapötke | first1 = T. | title = Reaction of hydrazinium azide with sulfuric acid: the X-ray structure of {{chem|[N|2|H|6|][SO|4|]}} | journal = Polyhedron | volume = 15 | issue = 15 | pages = 2579–2582 | year = 1996 | doi = 10.1016/0277-5387(95)00527-7 | author2 = Peter S. White | author3 = Inis C. Tornieporth-Oetting }} and hydrazinediium bis(6-carboxypyridazine-3-carboxylate), {{chem2|[N2H6](2+)([C6H3N2O4]-)2}}.W. Starosta and J. Leciejewicz (2008), "Hydrazinediium bis(6-carboxypyridazine-3-carboxylate) dihydrate". Acta Crystallographica, volume E64, article o461. {{doi|10.1107/S1600536808001037}}