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The hypophosphite ion is H2PO2, hypophosphorous acid minus one hydrogen ion.

Hypophosphites are the compounds containing this ion, with phosphorus in oxidation state +1, or similar covalent ones.

Two hydrogens are attached directly to the phosphorus atom.

The IUPAC (mostly organic) name for the same ion is phosphinate. This is virtually not used for hypophosphite ion itself, with both hydrogens remaining, but for substituted ions. For example, "dimethylphosphinate" ion would be (CH3)2PO2.

Hypophosphites can be made by heating white phosphorus in warm aqueous alkali:[1]

P4 + 3 OH + 3 H2O → 3 H2PO2 + PH3

Hypophosphites are reducing agents:[1]

H2PO2 +3OH → HPO32− + 2H2O + 2e

Hypophosphites are used in electroless nickel plating as the reducing agent to deposit for example Ni metal from Ni salts.[1] The hypophosphite ion is thermodynamically unstable, and disproportionates on heating to phosphine gas and phosphate salts:

2 H2PO2PH3 + HPO42−


  1. ^ a b c Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0080379419.