α-NH4Fe(HAsO4)2

Abstract

The title compound α-ammonium iron(III) bis[hydrogen arsenate(V)], α-NH4Fe(HAsO4)2(or poly[ammonium bis(μ-hydrogen arsenato)ferrate(III)], {NH4[Fe(HAsO4)2]}n), synthesized hydrothermally, is isostructural with NH4Fe(HPO4)2. Condensation of the hydrogen arsenate groups with FeO6coordination octahedraviacommon corners results in an overall three-dimensional framework containing interconnected channels parallel to thea-,b-andc-axis directions. The NH4+cations are located in three intersecting tunnels, which is promising as an ion exchange. Hydrogen bonding of the types O—H...O and N—H...O consolidates the packing of the structure. The distortion of the coordination polyhedra is analyzed by means of the effective coordination number and distortion indices. Structural relationships with other compounds of general formulaMIMIII[HXO4)]2(X= P, As) are discussed.