Special hydrogen bonds observed in two monovalent metal carboxylate–phosphinates: {NaH(PhPO2C2H4COOH)2}∞ and {[KH(PhPO2C2H4COOH)2]·H2O}∞

The addition of strong base such as sodium hydroxide or potassium hydroxide to the aqueous solution of (2-carboxyethyl)(phenyl)phosphinic acid afforded two novel monovalent metal carboxylate–phosphinates, namely, {NaH(PhPO2C2H4COOH)2}∞ (1) and {[KH(PhPO2C2H4COOH)2]·H2O}∞ (2). They represent the first examples of phosphinate containing short, symmetric or almost symmetric O⋯H⋯O hydrogen bonds.