Ammonium Phosphinate

Ammonium phosphinate is a chemical compound with the chemical formula NH4PH2O2. This is a salt of ammonium and phosphinic acid. It is produced by neutralizing hypophosphorous acid with ammonia. Chemically it contains the hypophosphite (phosphinate) anion H₂PO₂⁻, a good mild reducing agent. It is typically produced by neutralising hypophosphorous acid (H₃PO₂) with ammonia (NH₃) to give NH₄H₂PO₂ (or by salt metathesis with other hypophosphite salts).

Synthesis

Synthesis of ammonium phosphinate may be achieved by the effect of ammonia solution on phosphinic acid solution:

HPH2O2 + NH3 → NH4PH2O2

Properties

Ammonium phosphonate forms colorless crystals of the orthorhombic system, space group Cmma, cell parameters a = 0.757 nm, b = 1.147 nm, c = 0.398 nm, Z = 4. The compound is soluble in water and ethanol, but insoluble in acetone.

Chemical formula: H6NO2P
Molar mass: 83.027 g·mol−1
Appearance: colorless crystals
Density: 1.634 g/cm3
Melting point: 200
Solubility in water: soluble

It is soluble in water, stable under normal conditions but slowly oxidizes to phosphates on prolonged exposure to air or heat. On strong acidification or severe decomposition it can release phosphine (PH₃) — a toxic, flammable gas — so acid contact and heating should be avoided.

Chemical behavior & reactivity

The hypophosphite anion (H₂PO₂⁻) is a strong reducing agent — it can reduce metal ions and organic substrates and is readily oxidized to phosphate species.
On strong acidification or heating, hypophosphites can generate phosphine (PH₃) and other phosphorus oxo-species (dangerous, toxic and flammable), so acid contact and high temperatures should be avoided.
The ammonium cation confers typical mild acidity/basicity behaviour (NH₄⁺ ↔ NH₃ + H⁺ under heating/basic conditions).

Uses

The compound is usually used as a catalyst for the production of polyamide. It is widely used in electroless metal plating (particularly as the reducing agent in electroless nickel–phosphorus baths), in some specialty chemical syntheses, and as a precursor in phosphorus-containing materials.

Hazards & handling

It is irritant to skin/eyes, harmful if swallowed; avoid inhalation and dust formation. Store in a cool, dry place away from oxidizers and acids. Dispose of per local hazardous-waste rules. Always consult Safety Data Sheets (SDS) for detailed protective measures before handling.