Crystal structure of (NH4)2FeII5(HPO3)6 a new open-framework phosphite

摘要

Di­ammonium hexa­phosphito­penta­ferrate(II), (NH4)2[Fe5(HPO3)6], was synthesized under mild hydro­thermal conditions and autogeneous pressure, yielding twinned crystals. The crystal structure exhibits an [Fe^II 5(HPO3)6]²⁻ open framework with NH4 ⁺ groups as counter-cations. The anionic skeleton is based on (001) sheets of [FeO6] octa­hedra (one with point-group symmetry 3.. and one with .2.) linked along [001] through [HPO3]²⁻ oxoanions. Each sheet is constructed from 12-membered rings of edge-sharing [FeO6] octa­hedra, giving rise to channels with a radius of ca 3.1 Å in which the disordered NH4 ⁺ cations are located. The IR spectrum shows vibrational bands typical for phosphite and ammonium groups.