Ammonium diphosphitoindate(III).

The crystal structure of the title compound, NH4[In(HPO3)2], is built up from In(III) cations (site symmetry 3m.) adopting an octa-hedral environment and two different phosphite anions (each with site symmetry 3m.) exhibiting a triangular-pyramidal geometry. Each InO6 octa-hedron shares its six apices with hydrogen phosphite groups. Reciprocally, each HPO3 group shares all its O atoms with three different metal cations, leading to In(HPO3)2 layers which propagate in the ab plane. The ammonium cation likewise has site symmetry 3m.. In the structure, the cations are located between the In(HPO3)2 layers of the host framework. The sheets are held together by hydrogen bonds formed between the NH4 (+) cations and the O atoms of the framework.